WorldWideScience

Sample records for antibiotics microstructure mechanical

  1. Fracture mechanics and microstructures

    International Nuclear Information System (INIS)

    Gee, M.G.; Morrell, R.

    1986-01-01

    The influence of microstructure on defects in ceramics, and the consequences of their presence for the application of fracture mechanics theories are reviewed. The complexities of microstructures, especially the multiphase nature, the crystallographic anisotropy and the resultant anisotropic physical properties, and the variation of microstructure and surface finish from point to point in real components, all lead to considerable uncertainties in the actual performance of any particular component. It is concluded that although the concepts of fracture mechanics have been and will continue to be most useful for the qualitative explanation of fracture phenomena, the usefulness as a predictive tool with respect to most existing types of material is limited by the interrelation between material microstructure and mechanical properties. At present, the only method of eliminating components with unsatisfactory mechanical properties is to proof-test them, despite the fact that proof-testing itself is limited in ability to cope with changes to the component in service. The aim of the manufacturer must be to improve quality and consistency within individual components, from component to component, and from batch to batch. The aim of the fracture specialist must be to study longer-term properties to improve the accuracy of behaviour predictions with a stronger data base. Materials development needs to concentrate on obtaining defect-free materials that can be translated into more-reliable products, using our present understanding of the influence of microstructure on strength and toughness

  2. Mechanisms of Antibiotic Resistance

    Science.gov (United States)

    Munita, Jose M.; Arias, Cesar A.

    2015-01-01

    Emergence of resistance among the most important bacterial pathogens is recognized as a major public health threat affecting humans worldwide. Multidrug-resistant organisms have emerged not only in the hospital environment but are now often identified in community settings, suggesting that reservoirs of antibiotic-resistant bacteria are present outside the hospital. The bacterial response to the antibiotic “attack” is the prime example of bacterial adaptation and the pinnacle of evolution. “Survival of the fittest” is a consequence of an immense genetic plasticity of bacterial pathogens that trigger specific responses that result in mutational adaptations, acquisition of genetic material or alteration of gene expression producing resistance to virtually all antibiotics currently available in clinical practice. Therefore, understanding the biochemical and genetic basis of resistance is of paramount importance to design strategies to curtail the emergence and spread of resistance and devise innovative therapeutic approaches against multidrug-resistant organisms. In this chapter, we will describe in detail the major mechanisms of antibiotic resistance encountered in clinical practice providing specific examples in relevant bacterial pathogens. PMID:27227291

  3. Inventory of alloy composition, microstructures and mechanical ...

    African Journals Online (AJOL)

    Inventory of alloy composition, microstructures and mechanical properties of automobile engine parts. ... Journal of Applied Science, Engineering and Technology ... This research work investigated the chemical compositions, microstructures and mechanical properties of the ferrous and non-ferrous auto engine parts such ...

  4. Microstructures and mechanical properties of aging materials

    International Nuclear Information System (INIS)

    Liaw, P.K.; Viswanathan, R.; Murty, K.L.; Simonen, E.P.; Frear, D.

    1993-01-01

    This book contains a collection of papers presented at the symposium on ''Microstructures and Mechanical Properties of Aging Materials,'' that was held in Chicago, IL. November 2-5, 1992 in conjunction with the Fall Meeting of The Minerals, Metals and Materials Society (TMS). The subjects of interest in the symposium included: (1) mechanisms of microstructural degradation, (2) effects of microstructural degradation on mechanical behavior, (3) development of life prediction methodology for in-service structural and electronic components, (4) experimental techniques to monitor degradation of microstructures and mechanical properties, and (5) effects of environment on microstructural degradation and mechanical properties. Individual papers have been processed separately for inclusion in the appropriate data bases

  5. Mechanisms of antibiotic resistance in Staphylococcus aureus.

    Science.gov (United States)

    Pantosti, Annalisa; Sanchini, Andrea; Monaco, Monica

    2007-06-01

    Staphylococcus aureus can exemplify better than any other human pathogen the adaptive evolution of bacteria in the antibiotic era, as it has demonstrated a unique ability to quickly respond to each new antibiotic with the development of a resistance mechanism, starting with penicillin and methicillin, until the most recent, linezolid and daptomycin. Resistance mechanisms include enzymatic inactivation of the antibiotic (penicillinase and aminoglycoside-modification enzymes), alteration of the target with decreased affinity for the antibiotic (notable examples being penicillin-binding protein 2a of methicillin-resistant S. aureus and D-Ala-D-Lac of peptidoglycan precursors of vancomycin-resistant strains), trapping of the antibiotic (for vancomycin and possibly daptomycin) and efflux pumps (fluoroquinolones and tetracycline). Complex genetic arrays (staphylococcal chromosomal cassette mec elements or the vanA operon) have been acquired by S. aureus through horizontal gene transfer, while resistance to other antibiotics, including some of the most recent ones (e.g., fluoroquinolones, linezolid and daptomycin) have developed through spontaneous mutations and positive selection. Detection of the resistance mechanisms and their genetic basis is an important support to antibiotic susceptibility surveillance in S. aureus.

  6. Investigations on the microstructure and mechanical properties

    Indian Academy of Sciences (India)

    This paper addresses the weldability, microstructure and mechanical properties of the multi-pass welding of super-duplex stainless steel (SDSS). Pulsed current gas tungsten arc welding (PCGTAW) was carried out employing ER2553 and ERNiCrMo-4 fillers. Microstructure examination showed the presence of austenite in ...

  7. Pharmaceutical Approaches to Target Antibiotic Resistance Mechanisms.

    Science.gov (United States)

    Schillaci, Domenico; Spanò, Virginia; Parrino, Barbara; Carbone, Anna; Montalbano, Alessandra; Barraja, Paola; Diana, Patrizia; Cirrincione, Girolamo; Cascioferro, Stella

    2017-10-26

    There is urgent need for new therapeutic strategies to fight the global threat of antibiotic resistance. The focus of this Perspective is on chemical agents that target the most common mechanisms of antibiotic resistance such as enzymatic inactivation of antibiotics, changes in cell permeability, and induction/activation of efflux pumps. Here we assess the current landscape and challenges in the treatment of antibiotic resistance mechanisms at both bacterial cell and community levels. We also discuss the potential clinical application of chemical inhibitors of antibiotic resistance mechanisms as add-on treatments for serious drug-resistant infections. Enzymatic inhibitors, such as the derivatives of the β-lactamase inhibitor avibactam, are closer to the clinic than other molecules. For example, MK-7655, in combination with imipenem, is in clinical development for the treatment of infections caused by carbapenem-resistant Enterobacteriaceae and Pseudomonas aeruginosa, which are difficult to treat. In addition, other molecules targeting multidrug-resistance mechanisms, such as efflux pumps, are under development and hold promise for the treatment of multidrug resistant infections.

  8. Microstructure mechanical properties relationship in bainitic structures

    International Nuclear Information System (INIS)

    Altuna, M. A.; Gutierrez, I.

    2005-01-01

    In the present work, the microstructures and their mechanical properties have been studies in different bainitic structures. therefore, different bainitic morphologies have been produced by isothermal treatments carried out at different temperatures. For these steels, 400-450 degree centigree is the optimum range of temperatures in order to obtain bainitic structures. If the Temperature is higher, perlite is also formed and if it is lower, martensite is obtained during quenching. SEM and EBSD/OIM techniques were applied in order to study the microstructure. Tensile tests were carried out for mechanical characterization. (Author) 20 refs

  9. Vancomycin Molecular Interactions: Antibiotic and Enantioselective Mechanisms

    Science.gov (United States)

    Ward, Timothy J.; Gilmore, Aprile; Ward, Karen; Vowell, Courtney

    Medical studies established that vancomycin and other related macrocyclic antibiotics have an enhanced antimicrobial activity when they are associated as dimers. The carbohydrate units attached to the vancomycin basket have an essential role in the dimerization reaction. Covalently synthesized dimers were found active against vancomycin-resistant bacterial strains. A great similarity between antibiotic potential and enantioselectivity was established. A covalent vancomycin dimer was studied in capillary electrophoresis producing excellent chiral separation of dansyl amino acids. Balhimycin is a macrocyclic glycopeptide structurally similar to vancomycin. The small differences are, however, responsible for drastic differences in enantioselectivity in the same experimental conditions. Contributions from studies examining vancomycin's mechanism for antimicrobial activity have substantially aided our understanding of its mechanism in chiral recognition.

  10. Microstructure and Mechanical Properties of Porous Mullite

    Science.gov (United States)

    Hsiung, Chwan-Hai Harold

    Mullite (3 Al2O3 : 2 SiO2) is a technologically important ceramic due to its thermal stability, corrosion resistance, and mechanical robustness. One variant, porous acicular mullite (ACM), has a unique needle-like microstructure and is the material platform for The Dow Chemical Company's diesel particulate filter AERIFY(TM). The investigation described herein focuses on the microstructure-mechanical property relationships in acicular mullites as well as those with traditional porous microstructures with the goal of illuminating the critical factors in determining their modulus, strength, and toughness. Mullites with traditional pore morphologies were made to serve as references via slipcasting of a kaolinite-alumina-starch slurry. The starch was burned out to leave behind a pore network, and the calcined body was then reaction-sintered at 1600C to form mullite. The samples had porosities of approximately 60%. Pore size and shape were altered by using different starch templates, and pore size was found to influence the stiffness and toughness. The ACM microstructure was varied along three parameters: total porosity, pore size, and needle size. Total porosity was found to dominate the mechanical behavior of ACM, while increases in needle and pore size increased the toughness at lower porosities. ACM was found to have much improved (˜130%) mechanical properties relative to its non-acicular counterpart at the same porosity. A second set of investigations studied the role of the intergranular glassy phase which wets the needle intersections of ACM. Removal of the glassy phase via an HF etch reduced the mechanical properties by ˜30%, highlighting the intergranular phase's importance to the enhanced mechanical properties of ACM. The composition of the glassy phase was altered by doping the ACM precursor with magnesium and neodymium. Magnesium doping resulted in ACM with greatly reduced fracture strength and toughness. Studies showed that the mechanical properties of the

  11. Zirconium diselenite microstructures, formation and mechanism

    Science.gov (United States)

    Naik, Chandan C.; Salker, A. V.

    2018-04-01

    In this work, a series of microstructures of zirconium diselenite (Zr(SeO3)2) has been prepared via a simple precipitation method at room temperature without adding any organic surfactants. Phase purity of the sample has been checked by X-ray Diffraction. From the SEM, FESEM, and TEM images spheroid nanoparticles to the starfish-like structure of zirconium diselenite are detected. The morphological evolution processes were investigated carefully following time-dependent experiments and a growth mechanism has been proposed. Two different crystal growth processes, the oriented attachment process accompanying the Ostwald ripening process were held responsible for the formation of a structure resembling starfish having four arms.

  12. Genetic Mechanisms of Antibiotic Resistance and the Role of Antibiotic Adjuvants.

    Science.gov (United States)

    Pontes, Daniela Santos; de Araujo, Rodrigo Santos Aquino; Dantas, Natalina; Scotti, Luciana; Scotti, Marcus Tullius; de Moura, Ricardo Olimpio; Mendonca-Junior, Francisco Jaime Bezerra

    2018-01-01

    The ever increasing number of multidrug-resistant microorganism pathogens has become a great and global public health threat. Antibiotic mechanisms of action and the opposing mechanisms of resistance are intimately associated, but comprehension of the biochemical and molecular functions of such drugs is not a simple exercise. Both the environment, and genetic settings contribute to alterations in phenotypic resistance (natural bacterial evolution), and make it difficult to control the emergence and impacts of antibiotic resistance. Under such circumstances, comprehension of how bacteria develop and/or acquire antibiotic resistance genes (ARG) has a critical role in developing propositions to fight against these superbugs, and to search for new drugs. In this review, we present and discuss both general information and examples of common genetic and molecular mechanisms related to antibiotic resistance, as well as how the expression and interactions of ARGs are important to drug resistance. At the same time, we focus on the recent achievements in the search for antibiotic adjuvants, which help combat antibiotic resistance through deactivation of bacterial mechanisms of action such as β-lactamases. Recent advances involving the use of anti-resistance drugs such as: efflux pump inhibitors; anti-virulence drugs; drugs against quorum sensing; and against type II/III secretion systems are revealed. Such antibiotic adjuvants (as explored herein) collaborate against the problems of antibiotic resistance, and may restore or prolong the therapeutic activity of known antibiotics. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

  13. Action and resistance mechanisms of antibiotics: A guide for clinicians

    Directory of Open Access Journals (Sweden)

    Garima Kapoor

    2017-01-01

    Full Text Available Infections account for a major cause of death throughout the developing world. This is mainly due to the emergence of newer infectious agents and more specifically due to the appearance of antimicrobial resistance. With time, the bacteria have become smarter and along with it, massive imprudent usage of antibiotics in clinical practice has resulted in resistance of bacteria to antimicrobial agents. The antimicrobial resistance is recognized as a major problem in the treatment of microbial infections. The biochemical resistance mechanisms used by bacteria include the following: antibiotic inactivation, target modification, altered permeability, and “bypass” of metabolic pathway. Determination of bacterial resistance to antibiotics of all classes (phenotypes and mutations that are responsible for bacterial resistance to antibiotics (genetic analysis are helpful. Better understanding of the mechanisms of antibiotic resistance will help clinicians regarding usage of antibiotics in different situations. This review discusses the mechanism of action and resistance development in commonly used antimicrobials.

  14. Immunomodulatory Effects of Macrolide Antibiotics - Part 1 : Biological Mechanisms

    NARCIS (Netherlands)

    Altenburg, J.; de Graaff, C. S.; van der Werf, T. S.; Boersma, W. G.

    2011-01-01

    Macrolide antibiotics are well known for their antibacterial and anti-inflammatory properties. This article provides an overview of the biological mechanisms through which macrolides exert this 'double effect'. Their antibacterial effect consists of the inhibition of bacterial protein synthesis,

  15. Effect of initial microstructure on the microstructural evolution and mechanical properties of Ti during cold rolling

    International Nuclear Information System (INIS)

    Stolyarov, V.V.; Zhu, Y.T.; Raab, G.I.; Zharikov, A.I.; Valiev, R.Z.

    2004-01-01

    Ultrafine-grained (UFG) Ti rods were produced via cold rolling UFG and coarse-grained (CG) Ti stocks. The initial UFG stock was produced via equal channel angular pressing. It was found that the initial UFG structure had beneficial influence on the mechanical properties of the cold-rolled Ti rods. Compared with Ti rods with initial CG microstructure, the Ti rods with the initial UFG microstructure have both higher strength and higher ductility after being cold rolled to varying strains. Transmission electron microscopy revealed that the Ti rods with the initial UFG microstructure had finer, more homogeneous microstructures after cold rolling. This study demonstrates the merit of UFG Ti processed by ECAP for further shaping and forming into structural components with superior mechanical properties

  16. Microstructure evolution and microstructure/mechanical properties relationships in alpha+beta titanium alloys

    Science.gov (United States)

    Lee, Eunha

    In this study, the microstructural evolution of Timetal 550 was investigated. Timetal 550 showed two types of phase transformations (martensitic and nucleation and growth) depending on the cooling rate from the beta region. The alpha phase initially precipitated at the prior beta grain boundaries, and it had a Burgers OR with one of the adjacent grains. It was found that colonies could grow, even in the fast-cooled Timetal 550 sample, from the grain boundary alpha into the prior beta grain with which it exhibited the Burgers OR. Three orientation relationships were also found between alpha laths in the basketweave microstructure. Microhardness testing demonstrated that fast-cooled Timetal 550 samples with basketweave microstructure were harder than slowly-cooled samples with colony microstructure. Orientation-dependent deformation was found in the colony microstructure. Specifically, when the surface normal is perpendicular to the [0001] of alpha, the material deforms easily in the direction perpendicular to the [0001] of alpha. Fuzzy logic and Bayesian neural network models were developed to predict the room temperature tensile properties of Timetal 550. This involved the development of a database relating microstructural features to mechanical properties. A Gleeble 3800 thermal-mechanical simulator was used to develop various microstructures. Microstructural features of tensile-tested samples were quantified using stereological procedures. The quantified microstructural features and the tensile properties were used as inputs and outputs, respectively, for modeling the relationships between them. The individual influence of five microstructural features on tensile properties was determined using the established models. The microstructural features having the greatest impact on UTS and YS were the thickness of alpha laths and the width of grain boundary alpha layer, and the microstructural features having the greatest impact on elongation were the thickness of

  17. Nebulized antibiotics in mechanically ventilated patients: roadmap and challenges.

    Science.gov (United States)

    Poulakou, G; Siakallis, G; Tsiodras, S; Arfaras-Melainis, A; Dimopoulos, G

    2017-03-01

    Nebulized antibiotics use has become common practice in the therapeutics of pneumonia in cystic fibrosis patients. There is an increasing interest in their use for respiratory infections in mechanically ventilated (MV) patients in order to a) overcome pharmacokinetic issues in the lung compartment with traditional systemic antibiotic use and b) prevent the emergence of multi-drug-resistant (MDR) pathogens. Areas covered: The beneficial effects of antibiotic nebulization in MV patients e.g. increasing efficacy, reduced toxicity and prevention of resistance are described. Physicochemical parameters of optimal lung deposition, characteristics of currently available nebulizers, practical aspects of the procedure, including drug preparation and adjustments of ventilator and circuit parameter are presented. Antibiotics used in nebulized route, along with efficacy in various clinical indications and safety issues are reviewed. Expert commentary: The safety of nebulization of antibiotics has been proven in numerous studies; efficacy as adjunctive treatment to intravenous regimens or as monotherapy has been demonstrated in ventilator-associated pneumonia or ventilator-associated tracheobronchitis due to MDR or susceptible pathogens. However, due to the heterogeneity of studies, multiple meta-analyses fail to demonstrate a clear effect. Clarification of indications, standardization of technique and implementation of clinical practice guidelines, based on new large-scale trials will lead to the optimal use of nebulized antibiotics.

  18. Unique microstructure and excellent mechanical properties of ADI

    Directory of Open Access Journals (Sweden)

    Jincheng Liu

    2006-11-01

    Full Text Available Amongst the cast iron family, ADI has a unique microstructure and an excellent, optimised combination of mechanical properties. The main microstructure of ADI is ausferrite, which is a mixture ofextremely fine acicular ferrite and stable, high carbon austenite. There are two types of austenite in ADI:(1 the coarser and more equiaxed blocks of austenite between non-parallel acicular structures, which exist mainly in the last solidified area, and (2 the thin films of ustenite between the individual ferriteplatelets in the acicular structure. It is this unique microstructure, which gives ADI its excellent static and dynamic properties, and good low temperature impact toughness. The effect of microstructure on the mechanical properties is explained in more detail by examining the microstructure at the atomic scale. Considering the nanometer grain sizes, the unique microstructure, the excellent mechanical properties,good castability, (which enables near net shape components to be produced economically and in large volumes, and the fact that it can be 100% recycled, it is not overemphasized to call ADI a high-tech,nanometer and “green” material. ADI still has the potential to be further improved and its production and the number of applications for ADI will continue to grow, driven by the resultant cost savings over alternative materials.

  19. Microstructures and mechanical properties of an Osprey aluminium 7000 alloy

    International Nuclear Information System (INIS)

    Cottignies, L.; Brechet, Y.; Audier, M.; Livet, F.; Louchet, F.; Sainfort, P.

    1993-01-01

    An alloy from the 7000 serie obtained by the Osprey process has been studied both from the microstructural (TEM, SAXS) and from the mechanical viewpoint. The modelling of the mechanical properties and of their anisotropy was performed using both models from physical metallurgy and a self consistent elastoplastic model. (orig.)

  20. Microstructure and Mechanical Properties of a Laser Treated Al Alloy

    NARCIS (Netherlands)

    Noordhuis, J.; Hosson, J.Th.M. De

    An Al-Cu-Mg alloy, Al 2024-T3, was exposed to laser treatments at various scan velocities. In this paper the microstructural features and mechanical properties are reported. As far as the mechanical property is concerned a striking observation is a minimum in the hardness value at a laser scan

  1. Microstructure and mechanical properties of laser treated aluminium alloys

    NARCIS (Netherlands)

    deHosson, JTM; vanOtterloo, LDM; Noordhuis, J; Mazumder, J; Conde, O; Villar, R; Steen, W

    1996-01-01

    Al-Cu alloys and an Al-Cu-Mg alloy, Al 2024-T3, were exposed to laser treatments at various scan velocities. In this paper the microstructural features and mechanical properties are reported. As far as the mechanical property of the Al-Cu-Mg alloy is concerned a striking observation is a minimum in

  2. Effect of curing time on microstructure and mechanical strength ...

    Indian Academy of Sciences (India)

    The aim of this paper is to study the influence of curing time on the microstructure and mechanical strength development of alkali activated binders based on vitreous calcium aluminosilicate (VCAS). Mechanical strength of alkali activated mortars cured at 65 °C was assessed for different curing times (4–168 h) using 10 ...

  3. Antibiotics

    Science.gov (United States)

    Antibiotics are powerful medicines that fight bacterial infections. Used properly, antibiotics can save lives. They either kill bacteria or ... natural defenses can usually take it from there. Antibiotics do not fight infections caused by viruses, such ...

  4. ODS steel fabrication: relationships between process, microstructure and mechanical properties

    International Nuclear Information System (INIS)

    Couvrat, M.

    2011-01-01

    Oxide Dispersion Strengthened (ODS) steels are promising candidate materials for generation IV and fusion nuclear energy systems thanks to their excellent thermal stability, high-temperature creep strength and good irradiation resistance. Their superior properties are attributed both to their nano-structured matrix and to a high density of Y-Ti-O nano-scale clusters (NCs). ODS steels are generally prepared by Mechanical Alloying of a pre-alloyed Fe-Cr-W-Ti powder with Y 2 O 3 powder. A fully dense bar or tube is then produced from this nano-structured powder by the mean of hot extrusion. The aim of this work was to determine the main parameters of the process of hot extrusion and to understand the link between the fabrication process, the microstructure and the mechanical properties. The material microstructure was characterized at each step of the process and bars were extruded with varying hot extrusion parameters so as to identify the impact of these parameters. Temperature then appeared to be the main parameter having a great impact on microstructure and mechanical properties of the extruded material. We then proposed a cartography giving the microstructure versus the process parameters. Based on these results, it is possible to control very accurately the obtained material microstructure and mechanical properties setting the extrusion parameters. (author) [fr

  5. Nucleation mechanisms of refined alpha microstructure in beta titanium alloys

    Science.gov (United States)

    Zheng, Yufeng

    Due to a great combination of physical and mechanical properties, beta titanium alloys have become promising candidates in the field of chemical industry, aerospace and biomedical materials. The microstructure of beta titanium alloys is the governing factor that determines their properties and performances, especially the size scale, distribution and volume fraction of precipitate phase in parent phase matrix. Therefore in order to enhance the performance of beta titanium alloys, it is critical to obtain a thorough understanding of microstructural evolution in beta titanium alloys upon various thermal and/or mechanical processes. The present work is focusing on the study of nucleation mechanisms of refined alpha microstructure and super-refined alpha microstructure in beta titanium alloys in order to study the influence of instabilities within parent phase matrix on precipitates nucleation, including compositional instabilities and/or structural instabilities. The current study is primarily conducted in Ti-5Al-5Mo-5V-3Cr (wt%, Ti-5553), a commercial material for aerospace application. Refined and super-refined precipitates microstructure in Ti-5553 are obtained under specific accurate temperature controlled heat treatments. The characteristics of either microstructure are investigated in details using various characterization techniques, such as SEM, TEM, STEM, HRSTEM and 3D atom probe to describe the features of microstructure in the aspect of morphology, distribution, structure and composition. Nucleation mechanisms of refined and super-refined precipitates are proposed in order to fully explain the features of different precipitates microstructure in Ti-5553. The necessary thermodynamic conditions and detailed process of phase transformations are introduced. In order to verify the reliability of proposed nucleation mechanisms, thermodynamic calculation and phase field modeling simulation are accomplished using the database of simple binary Ti-Mo system

  6. The factors influencing microstructure and mechanical properties of ADI

    Directory of Open Access Journals (Sweden)

    A. Vaško

    2009-01-01

    Full Text Available The paper deals with the influence of different conditions of isothermal heat treatment on microstructure and mechanical properties of austempered ductile iron (ADI. Different temperature of isothermal transformation of austenite and different holding time at this temperature were used for heat treatment of specimens. The microstructure of specimens after casting and after heat treatment was evaluated by STN EN ISO 945 and by image analysis (using Lucia software. Mechanical properties were evaluated by the tensile test, the Rockwell hardness test and fatigue tests.

  7. Microstructure and mechanical properties of SiC materials

    International Nuclear Information System (INIS)

    Yarahmadi, M.

    1985-01-01

    The effect of the microstructure on the mechanical properties of SiC materials of different chemical composition (SSiC, SiSiC, and RSiC) was investigated. Furthermore, the creep strength was determined on oxidized samples and on non-pretreated samples. (HSCH)

  8. Microstructures and mechanical properties of Mg–Zn–Zr–Dy ...

    Indian Academy of Sciences (India)

    Microstructures and phase compositions of as-cast and extruded ZK60–Dy ( = 0–5) alloys were analysed by optical microscope, scanning electron microscope, X-ray diffraction and differential scanning calorimetry. Meanwhile, the tensile mechanical property was tested.With increasing Dy content, Mg–Zn–Dy new phase ...

  9. Synthesis, microstructure and mechanical properties of ceria ...

    Indian Academy of Sciences (India)

    Unknown

    ceria stabilized zirconia powders with improved mechanical properties. Ce–ZrO2 with 20 wt% ... structural ceramic materials (Garvie et al 1975; Evans and. Cannon 1986) ... thermal expansion matching with that of iron alloys. (Tsukuma and ...

  10. Phase transformations in nickel sulphide: Microstructures and mechanisms

    International Nuclear Information System (INIS)

    Yousfi, Oussama; Donnadieu, Patricia; Brechet, Yves; Robaut, Florence; Charlot, Frederic; Kasper, Andreas; Serruys, Francis

    2010-01-01

    Nickel sulphide inclusions are known to be responsible for delayed fracture in tempered glasses due to phase transformation within the inclusion. Microstructural identification of the phase transformation mechanisms in the Ni-S system close to the NiS composition were carried out on a series of partially transformed states. Observations allow to investigate the morphological evolution during transformation, the phase orientation relationships and the first stages of the transformation were investigated by optical microscopy, electron backscatter diffraction, and scanning and transmission electron microscopy. The transformation mechanisms change significantly with the change in sulphur content of the α-NiS phase. Massive transformation is observed for near-stoichiometric composition. For overstoichiometric composition, the transformation is controlled by a long-range diffusion mechanism. The influence of stoichiometry and impurities (Fe) on the microstructural evolution and transformation mechanisms has also been studied.

  11. Microstructure and mechanical properties of selective laser melted magnesium

    International Nuclear Information System (INIS)

    Ng, C.C.; Savalani, M.M.; Lau, M.L.; Man, H.C.

    2011-01-01

    The effects of laser processing parameters on the microstructure and mechanical properties of selective laser-melted magnesium were investigated. The results show that the microstructure characteristics of the laser-melted samples are dependent on the grain size of SLM magnesium. The grains in the molten zone coarsen as the laser energy density increases. In addition, the average hardness values of the molten zone decreases significantly with an increase of the laser energy densities and then decreased slowly at a relatively high laser energy density irrespective of mode of irradiation. The hardness value was obtained from 0.59 to 0.95 GPa and corresponding elastic modulus ranging from 27 to 33 GPa. The present selective laser-melted magnesium parts are promising for biomedical applications since the mechanical properties are more closely matched with human bone than other metallic biomaterials.

  12. Microstructural and mechanical characterization of injection molded 718 superalloy powders

    Energy Technology Data Exchange (ETDEWEB)

    Özgün, Özgür [Bingol University, Faculty of Engineering and Architecture, Mechanical Eng. Dep., 12000 Bingol (Turkey); Gülsoy, H. Özkan, E-mail: ogulsoy@marmara.edu.tr [Marmara University, Technology Faculty, Metallurgy and Materials Eng. Dep., 34722 Istanbul (Turkey); Yılmaz, Ramazan [Sakarya University, Technology Faculty, Metallurgy and Materials Eng. Dep., 54187 Sakarya (Turkey); Fındık, Fehim [Sakarya University, Technology Faculty, Metallurgy and Materials Eng. Dep., 54187 Sakarya (Turkey) and International University of Sarajevo, Faculty of Engineering and Natural Sciences, Department of Mechanical Engineering, 71000 Sarajevo, Bosnia and Herzegovina (Bosnia and Herzegowina)

    2013-11-05

    Highlights: •Microstructural and mechanical properties of injection molded Nickel 718 superalloy were studied. •The maximum sintered density achieved this study was 97.3% at 1290 °C for 3 hours. •Tensile strength of 1022 MPa and elongation of 5.3% were achieved for sintered-heat treated samples. -- Abstract: This study concerns with the determination of optimum production parameters for injection molding 718 superalloy parts. And at the same time, microstructural and mechanical characterization of these produced parts was also carried out. At the initial stage, 718 superalloy powders were mixed with a multi-component binder system for preparing feedstock. Then the prepared feedstock was granulated and shaped by injection molding. Following this operation, the shaped samples were subjected to the debinding process. These samples were sintered at different temperatures for various times. Samples sintered under the condition that gave way to the highest relative density (3 h at 1290 °C) were solution treated and aged respectively. Sintered, solution treated and aged samples were separately subjected to microstructural and mechanical characterization. Microstructural characterization operations such as X-ray diffraction, optical microscope (OM), scanning electron microscope (SEM), transmission electron microscope (TEM) and elemental analysis showed that using polymeric binder system led to plentiful carbide precipitates to be occurred in the injection molded samples. It is also observed that the volume fractions of the intermetallic phases (γ′ and γ″) obtained by aging treatment were decreased due to the plentiful carbide precipitation in the samples. Mechanical characterization was performed by hardness measurements and tensile tests.

  13. Surface modification, microstructure and mechanical properties of investment cast superalloy

    OpenAIRE

    M. Zielińska; K. Kubiak; J. Sieniawski

    2009-01-01

    Purpose: The aim of this work is to determine physical and chemical properties of cobalt aluminate (CoAl2O4) modifiers produced by different companies and the influence of different types of modifiers on the grain size, the microstructure and mechanical properties of high temperature creep resisting superalloy René 77.Design/methodology/approach: The first stage of the research work took over the investigations of physical and chemical properties of cobalt aluminate manufactured by three diff...

  14. Microstructure and mechanical properties of AC AlSi9CuX alloys

    OpenAIRE

    L.A. Dobrzański; R. Maniara; M. Krupiński; J.H. Sokołowski

    2007-01-01

    Purpose: In order to gain a better understanding of how to control the as-cast microstructure, it is important to understand the evaluation of microstructure during solidification and understanding how influence the changes of chemical concentration on this microstructure and mechanical properties. In this research, the effect of Cu content on the microstructure and mechanical properties of AC AlSi9CuX series alloys has been investigated.Design/methodology/approach: The experimental alloy ...

  15. Microstructural and mechanical characterization of Al–Zn–Si nanocomposites

    Energy Technology Data Exchange (ETDEWEB)

    García-Villarreal, S. [Centro de Investigación en Materiales Avanzados S.C. Monterrey, 66600, Alianza Nte. 202, Parque PIIT, Apodaca, N.L. (Mexico); Chávez-Valdez, A. [Katcon Institute for Innovation and Technology KIIT, 66629, Alianza Sur 200, Apodaca, N.L. (Mexico); Moreno, K.J. [Instituto Tecnológico de Celaya, Apartado Postal 57, 38010 Celaya, Guanajuato (Mexico); Leyva, C.; Aguilar-Martínez, J.A. [Centro de Investigación en Materiales Avanzados S.C. Monterrey, 66600, Alianza Nte. 202, Parque PIIT, Apodaca, N.L. (Mexico); Hurtado, A. [Centro de Investigación en Materiales Avanzados S.C., 31109, Miguel de Cervantes 120, Chih., Chih. (Mexico); Arizmendi-Morquecho, A., E-mail: ana.arizmendi@cimav.edu.mx [Centro de Investigación en Materiales Avanzados S.C. Monterrey, 66600, Alianza Nte. 202, Parque PIIT, Apodaca, N.L. (Mexico)

    2013-09-15

    In this paper the addition of silicon nanoparticles into Al–Zn alloys to form metallic matrix nanocomposites by mechanical alloying process was investigated. The influence of various process parameters such as milling time and Si concentration in the Al–Zn matrix has an interesting effect on the microstructure and mechanical properties of the synthesized nanocomposites. The microstructural characterization of the nanocomposites was evaluated by transmission electron microscopy and energy dispersive X-ray spectroscopy (TEM–EDXS) and the mechanical properties were measured by nanoindentation and micro-hardness tests. The results showed that during mechanical milling Si is added to the Al–Zn matrix achieving a uniform and homogeneous dispersion. After solidification, it forms small particles of AlZnSi with blocky morphology in interdendritic regions. The nanoindentation profiles showed that the elastic modulus and hardness properties increase with increasing milling time. However, a high concentration of Si (> 1.2 wt.%) results in a saturation of Si in the Al–Zn matrix, which adversely affects the mechanical properties. Thus, it is important to tune the milling time and concentration of Si added to the Al–Zn alloys to control the growth of brittle phases that result in reduction of the mechanical properties of the material. - Highlights: • A novel technique for addition of Si nanocomposites into Al–Zn liquid alloy is reported. • Good dispersion and homogeneity of Si in the Al–Zn matrix are obtained. • Increasing Si content above 1.2 wt.% decreases the mechanical properties of Al–Zn alloy. • The saturation point of Si in 1.2 wt.% differs from Galvalume® composition. • The Al–Zn–1.5Si alloy with addition of nanocomposite shows 5.7 GPa of hardness.

  16. Microstructure and mechanical properties of neutron irradiated beryllium

    Energy Technology Data Exchange (ETDEWEB)

    Ishitsuka, E.; Kawamura, H. [Japan Atomic Energy Research Inst., Oarai, Ibaraki (Japan). Oarai Research Establishment; Terai, T.; Tanaka, S.

    1998-01-01

    Microstructure and mechanical properties of the neutron irradiated beryllium with total fast neutron fluences of 1.3 - 4.3 x 10{sup 21} n/cm{sup 2} (E>1 MeV) at 327 - 616degC were studied. Swelling increased by high irradiation temperature, high fluence, and by the small grain size and high impurity. Obvious decreasing of the fracture stress was observed in the bending test and in small grain specimens which had many helium bubbles on the grain boundary. Decreasing of the fracture stress for small grain specimens was presumably caused by crack propagation on the grain boundaries which weekend by helium bubbles. (author)

  17. Mechanical properties and microstructure of nano grain nickel alloy deposit

    International Nuclear Information System (INIS)

    Seo, Moo Hong; Kim, Jung Su; Kim, Seung Ho; Jung, Hyun Kyu; Wyi, Jung Il; Hwang, Woon Suk; Jang, Si Sung; Chun, Byung Sun

    2003-01-01

    In this study, Ni-P layers were electroplated on the surface of stainless steel in order to investigate the effects of an additive and agitation on their mechanical properties and microstructure. The concentration of the additive in the plating solution increased, the pores formed in the layer decreased, while the residual stress developed in the layers during electroplating increased. Agitation of the solution during electroplating was observed to force to increase local pores in the layer which lowers its tensile properties. Grain growth was suppressed due to very fine Ni 3 P precipitates formed at its grain boundaries during heat treatment at 343 .deg. C for 1 hr in air

  18. Microstructure and mechanical properties of molybdenum silicides with Al additions

    International Nuclear Information System (INIS)

    Rosales, I.; Bahena, D.; Colin, J.

    2007-01-01

    Several molybdenum silicides alloys with different aluminum additions were produced by the arc-cast method. Microstructure observed in the alloys presented a variation of the precipitated second phase respect to the aluminum content. Evaluation of the compressive behavior at high temperature of the alloys shows an important improvement in its ductility, approximately of 20%. Fracture toughness was increased proportionally with Al content. In addition at room temperature the alloys show a better mechanical behavior in comparison with the sample unalloyed. In general, Al additions result to be a good alternative to improve the resistance of these intermetallic alloys. The results are interpreted on the base of the analysis of second phase strengthening

  19. Mechanical bowel preparation and oral antibiotic prophylaxis in colorectal surgery: Analysis of evidence and narrative review.

    Science.gov (United States)

    Badia, Josep M; Arroyo-García, Nares

    2018-05-14

    The role of oral antibiotic prophylaxis and mechanical bowel preparation in colorectal surgery remains controversial. The lack of efficacy of mechanical preparation to improve infection rates, its adverse effects, and multimodal rehabilitation programs have led to a decline in its use. This review aims to evaluate current evidence on antegrade colonic cleansing combined with oral antibiotics for the prevention of surgical site infections. In experimental studies, oral antibiotics decrease the bacterial inoculum, both in the bowel lumen and surgical field. Clinical studies have shown a reduction in infection rates when oral antibiotic prophylaxis is combined with mechanical preparation. Oral antibiotics alone seem to be effective in reducing infection in observational studies, but their effect is inferior to the combined preparation. In conclusion, the combination of oral antibiotics and mechanical preparation should be considered the gold standard for the prophylaxis of postoperative infections in colorectal surgery. Copyright © 2018 AEC. Publicado por Elsevier España, S.L.U. All rights reserved.

  20. Microstructure and Mechanical Behavior of Deep Drawing DC04 Steel at Different Length Scales

    OpenAIRE

    Schreijäg, Simone

    2013-01-01

    The deformation behavior of steels is strongly influenced by their microstructure which is a result of the alloying elements and thermal treatments. In this work, the microstructure and the deformation behavior of a non-alloyed deep drawing DC04 steel was investigated. The microstructure was analyzed during heat treatment by EBSD, then microcompression experiments were performed on selected microstructural units and then bulk steel samples were mechanically tested by tensile experiments.

  1. Microstructure and mechanical behavior of Al-Li-Zr alloys

    International Nuclear Information System (INIS)

    Wang, Wego; Wells, M.G.H.

    1991-01-01

    The mechanical properties of two Al-Li-Zr alloys, A and B, are determined at various heat treatment conditions. Alloy B was found to have superior mechanical properties. It shows improvements in yield strength by 31.2-56.2 MPa and in ultimate tensile strength by 14.7-40.7 MPa, and yet still has a 20-25 percent better elongation value. The microstructure and fracture surface were studied by SEM and TEM. A fracture surface with mixed ductile samples and brittle facets was observed in both tensile and notch tensile samples. The fracture was more localized in alloy A than alloy B. Both alloys exhibited good notch toughness with a notch tensile strength to yield a strength ratio larger than one for all heat treatment conditions. 32 refs

  2. Mechanical And Microstructural Evaluation Of A Wear Resistant Steel

    International Nuclear Information System (INIS)

    Santos, F.L.F. dos; Vieira, A.G.; Correa, E.C.S.; Pinheiro, I.P.

    2010-01-01

    In the present work, the analysis of the mechanical properties and the microstructural features of a high strength low alloy steel, containing chromium, molybdenum and boron, subjected to different heat treatments, was conducted. After austenitizing at 910 deg C for 10 minutes, three operations were carried out: oil quenching, oil quenching followed by tempering at 200 deg C for 120 minutes and austempering at 400 deg C for 5 minutes followed by water cooling. The analysis was performed through tensile and hardness tests, optical microscopy and X-ray diffraction. The bainitic structure led to high strength and toughness, both essential mechanical properties for wear resistant steels. The occurrence of allotriomorphic ferrite and retained austenite in the samples also increased the wear resistance. This phenomenon is related to the fact that both structures are able to be deformed and, in the case of the retained austenite, the transformation induced plasticity TRIP effect may take place as the material is used. (author)

  3. Microstructure and Mechanical Properties of Graphene Oxide/Copper Composites

    Directory of Open Access Journals (Sweden)

    HONG Qi-hu

    2016-09-01

    Full Text Available Graphene oxide/copper (GO/Cu composites were successfully synthesized through the ball milling and vacuum hot press sintering process. The morphologies of the mixture powders, and the microstructure and mechanical properties of GO/Cu composites were investigated by OM, SEM, XRD, hardness tester and electronic universal testing machine, respectively. The results show that the GO/Cu composites are compact. Graphene oxide with flake morphology is uniformly dispersed and well consolidated with copper matrix. When the mass fraction of graphene oxide is 0.5%, the microhardness and compress strength at RT reach up to 63HV and 276MPa, increased by 8.6% and 28%, respectively. The strengthening mechanism is load transfer effect, dislocation strengthening and fine crystal reinforcing.

  4. Microstructure and Mechanical Property of Aluminum Alloy Plate AA 7055

    Directory of Open Access Journals (Sweden)

    CHEN Junzhou

    2017-10-01

    Full Text Available Through-thickness microstructure and mechanical property of AA 7055-T7751 aluminum alloy plate were investigated by using electron backscattered diffraction (EBSD, transmission electron microscope (TEM and small angle X-ray scattering(SAXS. The results indicate an inhomogeneous distribution of microstructure through the thickness. The degree of recrystallization decreases gradually from 69% to 19.1%, as deepening from the surface to the center of the plate. The size of subgrains decreases from 10 μm at the surface to around 2 μm at the center. Strong texture of rolling type is observed near the center but the intensity decreases gradually as nearing the surface and the shear texture becomes the dominant. High density of plate-like η' phases are observed in the alloy, indicating the sufficient precipitation. η' precipitates of this condition are around 3.7 nm in radius, 1-3 nm in thickness and are found coherent with the Al matrix with a coherent strain of 0.0133, showing a strong strengthening effect. The heterogeneity in grain scale does not influence the distribution and the morphology of precipitates. The yield strength (L direction varies linearly along the thickness direction of the plate, fitting an equation of σy=-38.7S+604.8 (0≤S≤1. The variation of yield strength is related to the heterogeneity of grain structure.

  5. Microstructure and Mechanical Behavior of High-Entropy Alloys

    Science.gov (United States)

    Licavoli, Joseph J.; Gao, Michael C.; Sears, John S.; Jablonski, Paul D.; Hawk, Jeffrey A.

    2015-10-01

    High-entropy alloys (HEAs) have generated interest in recent years due to their unique positioning within the alloy world. By incorporating a number of elements in high proportion, usually of equal atomic percent, they have high configurational entropy, and thus, they hold the promise of interesting and useful properties such as enhanced strength and alloy stability. The present study investigates the mechanical behavior, fracture characteristics, and microstructure of two single-phase FCC HEAs CoCrFeNi and CoCrFeNiMn with some detailed attention given to melting, homogenization, and thermo-mechanical processing. Ingots approaching 8 kg in mass were made by vacuum induction melting to avoid the extrinsic factors inherent to small-scale laboratory button samples. A computationally based homogenization heat treatment was given to both alloys in order to eliminate any solidification segregation. The alloys were then fabricated in the usual way (forging, followed by hot rolling) with typical thermo-mechanical processing parameters employed. Transmission electron microscopy was subsequently used to assess the single-phase nature of the alloys prior to mechanical testing. Tensile specimens (ASTM E8) were prepared with tensile mechanical properties obtained from room temperature through 800 °C. Material from the gage section of selected tensile specimens was extracted to document room and elevated temperature deformation within the HEAs. Fracture surfaces were also examined to note fracture failure modes. The tensile behavior and selected tensile properties were compared with results in the literature for similar alloys.

  6. Enhancing Microstructure and Mechanical Properties of AZ31-MWCNT Nanocomposites through Mechanical Alloying

    Directory of Open Access Journals (Sweden)

    J. Jayakumar

    2013-01-01

    Full Text Available Multiwall carbon nanotubes (MWCNTs reinforced Mg alloy AZ31 nanocomposites were fabricated by mechanical alloying and powder metallurgy technique. The reinforcement material MWCNTs were blended in three weight fractions (0.33%, 0.66%, and 1% with the matrix material AZ31 (Al-3%, zinc-1% rest Mg and blended through mechanical alloying using a high energy planetary ball mill. Specimens of monolithic AZ31 and AZ31-MWCNT composites were fabricated through powder metallurgy technique. The microstructure, density, hardness, porosity, ductility, and tensile properties of monolithic AZ31 and AZ31-MWCNT nano composites were characterized and compared. The characterization reveals significant reduction in CNT (carbon nanoTube agglomeration and enhancement in microstructure and mechanical properties due to mechanical alloying through ball milling.

  7. Mechanical and Microstructural Evaluation of DMAG Welding of Structural Steel

    Directory of Open Access Journals (Sweden)

    Tolga Mert

    2015-01-01

    Full Text Available Double channel torch, which allows concentric flow of two different shielding gases, was designed and manufactured in order to pursue double channel torch gas metal arc welding of unalloyed structural steel S235JR (EN 10025-2 with fourteen passes. Tensile and Charpy V-notch tests were realized and the results were compared with those of conventional gas metal arc welding. In order to evaluate mechanical testing results, microstructural analyses were conducted. It was found that the increase with double channel gas metal arc welding process in yield and tensile strengths as well as in toughness tests, especially in subzero temperatures, compared with conventional gas metal arc welding was due to longer columnar grains and finer tempered zone grain structure between passes and due to solidification and less dendritic structure formation in all-weld metal in double channel gas metal arc welding.

  8. Microstructure and mechanical properties of Cu-Ni-Si alloys

    International Nuclear Information System (INIS)

    Monzen, Ryoichi; Watanabe, Chihiro

    2008-01-01

    The microstructure and mechanical properties of 0.1 wt.% Mg-added and Mg-free Cu-2.0 wt.% Ni-0.5 wt.% Si alloys aged at 400 deg. C have been examined. The addition of Mg promotes the formation of disk-shaped Ni 2 Si precipitates. The Cu-Ni-Si-Mg alloy exhibits higher strength and resistance to stress relaxation than the Cu-Ni-Si alloy. The higher strength or stress relaxation resistance is attributable to the reduction in inter-precipitate spacing by the Mg addition or the drag effect of Mg atoms on dislocation motion. The Cu-Ni-Si alloy with a large grain size of 150 μm shows higher stress relaxation resistance than the alloy with a small grain size of 10 μm because of a lower density of mobile dislocations in the former alloy

  9. Microstructure and mechanical properties of Cu-Ni-Si alloys

    Energy Technology Data Exchange (ETDEWEB)

    Monzen, Ryoichi [Division of Innovative Technology and Science, Graduate School of Natural Science and Technology, Kanzawa University, Kakuma-machi, Kanazawa 920-1192 (Japan)], E-mail: monzen@t.kanazawa-u.ac.jp; Watanabe, Chihiro [Division of Innovative Technology and Science, Graduate School of Natural Science and Technology, Kanzawa University, Kakuma-machi, Kanazawa 920-1192 (Japan)

    2008-06-15

    The microstructure and mechanical properties of 0.1 wt.% Mg-added and Mg-free Cu-2.0 wt.% Ni-0.5 wt.% Si alloys aged at 400 deg. C have been examined. The addition of Mg promotes the formation of disk-shaped Ni{sub 2}Si precipitates. The Cu-Ni-Si-Mg alloy exhibits higher strength and resistance to stress relaxation than the Cu-Ni-Si alloy. The higher strength or stress relaxation resistance is attributable to the reduction in inter-precipitate spacing by the Mg addition or the drag effect of Mg atoms on dislocation motion. The Cu-Ni-Si alloy with a large grain size of 150 {mu}m shows higher stress relaxation resistance than the alloy with a small grain size of 10 {mu}m because of a lower density of mobile dislocations in the former alloy.

  10. The microstructure of mechanically alloyed nanocrystalline aluminium-magnesium

    Energy Technology Data Exchange (ETDEWEB)

    Gubicza, J. [Dept. of General Physics, Eoetvoes Univ., Budapest (Hungary); Dept. of Solid State Physics, Eoetvoes Univ., Budapest (Hungary); Kassem, M. [Dept. of Materials Science and Engineering, Faculty of Petroleum and Mining, Suez Canal Univ., Suez (Egypt); Ungar, T. [Dept. of General Physics, Eoetvoes Univ., Budapest (Hungary)

    2004-07-01

    The effect of the nominal Mg content and the milling time on the microstructure of mechanically alloyed Al(Mg) solid solutions is studied. The crystallite size distribution and the dislocation structure are determined by X-ray diffraction peak profile analysis. Magnesium gradually goes into solid solution during ball milling and after 3 h almost all of the Mg atoms are soluted into the Al matrix. With increasing milling time the Mg content in solid solution, the dislocation density as well as the hardness are increasing, whereas the crystallite size is decreasing. A similar tendency of these parameters is observed at a particular duration of ball milling with increasing of the nominal Mg content. At the same time for a long milling period the dislocation density slightly decreases together with a slight reduction of the hardness. (orig.)

  11. Microstructure and surface mechanical properties of pulse electrodeposited nickel

    Energy Technology Data Exchange (ETDEWEB)

    Ul-Hamid, A., E-mail: anwar@kfupm.edu.sa [Center of Research Excellence in Corrosion (CoRE-C), Research Institute, King Fahd University of Petroleum and Minerals, P.O. Box 1073, Dhahran 31261 (Saudi Arabia); Dafalla, H.; Quddus, A.; Saricimen, H.; Al-Hadhrami, L.M. [Center of Research Excellence in Corrosion (CoRE-C), Research Institute, King Fahd University of Petroleum and Minerals, P.O. Box 1073, Dhahran 31261 (Saudi Arabia)

    2011-09-01

    The surface of carbon steel was modified by electrochemical deposition of Ni in a standard Watt's bath using dc and pulse plating electrodeposition. The aim was to compare the microstructure and surface mechanical properties of the deposit obtained by both techniques. Materials characterization was conducted using field emission scanning electron microscope fitted with scanning transmission electron detector, atomic force microscope and X-ray diffractometer. Nanoindentation hardness, elastic modulus, adhesion, coefficients of friction and wear rates were determined for both dc and pulse electrodeposits. Experimental results indicate that pulse electrodeposition produced finer Ni grains compared to dc plating. Size of Ni grains increased with deposition. Both dc and pulse deposition resulted in grain growth in preferred (2 0 0) orientation. However, presence of Ni (1 1 1) grains increased in deposits produced by pulse deposition. Pulse plated Ni exhibited higher hardness, creep and coefficient of friction and lower modulus of elasticity compared to dc plated Ni.

  12. Microstructure and mechanical properties of thixoformed A319 aluminium alloy

    International Nuclear Information System (INIS)

    Salleh, M.S.; Omar, M.Z.; Syarif, J.; Alhawari, K.S.; Mohammed, M.N.

    2014-01-01

    Highlights: • A319 was successfully thixoformed at 50% liquid, i.e. at 571 °C. • T6 heat treatment has increased the strength and hardness of the thixoformed alloy. • The elongation after T6 heat treatment is even significantly improved. • The iron-rich intermetallic phase reduces the strength of the thixoformed alloy. - Abstract: Thixoforming is a viable technology for forming alloys in a semisolid state into near net-shaped products. In the present study, the effect of a thixoforming process on the microstructure and mechanical properties of A319 aluminium alloy was investigated. The ingots obtained from the cooling slope were thixoformed in a press after they remained at 571 °C for 5 min, yielding a microstructure predominantly composed of α-Al globules and inter-globular Si particles. Some of the thixoformed samples were treated with an ageing process (T6) and then, hardness and tensile samples were prepared from the as-cast, as-thixoformed and thixoformed T6. All the thixoformed samples were characterised using optical microscopy, scanning electron microscopy (SEM), energy dispersive X-ray (EDX) and X-ray diffraction (XRD) as well as hardness measurements and tensile tests. The results indicate that the mechanical properties of the thixoformed A319 alloy increased after the T6 heat treatment (hardness of 124.2 ± 3.2 HV, tensile strength of 298 ± 3.0 MPa, yield strength of 201 ± 2.6 MPa and elongation to fracture of 4.5 ± 0.3%). The fracture samples from the tensile test were analysed, revealing that the iron-rich intermetallic observed in the samples reduced the tensile strength and ductility of the thixoformed A319 alloys

  13. Genomic sequencing of a strain of Acinetobacter baumannii and potential mechanisms to antibiotics resistance.

    Science.gov (United States)

    Zhao, Lei; Li, Hongru; Zhu, Ziwen; Wakefield, Mark R; Fang, Yujiang; Ye, Ying

    2017-06-01

    Acinetobacter baumannii has been becoming a great challenge to clinicians due to their resistance to almost all available antibiotics. In this study, we sequenced the genome from a multiple antibiotics resistant Acinetobacter baumannii stain which was named A. baumannii-1isolated from China by SMRT sequencing technology to explore its potential mechanisms to antibiotic resistance. We found that several mechanisms might contribute to the antibiotic resistance of Acinetobacter baumannii. Specifically, we found that SNP in genes associated with nucleotide excision repair and ABC transporter might contribute to its resistance to multiple antibiotics; we also found that specific genes associated with bacterial DNA integration and recombination, DNA-mediated transposition and response to antibiotics might contribute to its resistance to multiple antibiotics; Furthermore, specific genes associated with penicillin and cephalosporin biosynthetic pathway and specific genes associated with CHDL and MBL β-lactamase genes might contribute to its resistance to multiple antibiotics. Thus, the detailed mechanisms by which Acinetobacter baumannii show extensive resistance to multiple antibiotics are very complicated. Such a study might be helpful to develop new strategies to control Acinetobacter baumannii infection. Copyright © 2017 Elsevier B.V. All rights reserved.

  14. Relationships among the Microstructure, Mechanical Properties, and Fatigue Behavior in Thin Ti6Al4V

    Directory of Open Access Journals (Sweden)

    Y. Fan

    2016-01-01

    Full Text Available The microstructures of Ti6Al4V are complex and strongly affect its mechanical properties and fatigue behavior. This paper investigates the role of microstructure on mechanical and fatigue properties of thin-section Ti6Al4V sheets, with the aim of reviewing the effects of microstructure on fatigue properties where suboptimal microstructures might result following heat treatment of assemblies that may not be suited to further annealing, for example, following laser welding. Samples of Ti6Al4V sheet were subjected to a range of heat treatments, including annealing and water quenching from temperatures ranging from 650°C to 1050°C. Micrographs of these samples were inspected for microstructure, and hardness, 0.2% proof stress, elongation, and fracture strength were measured and attributed back to microstructure. Fractography was used to support the findings from microstructure and mechanical analyses. The strength ranking from high to low for the microstructures of thin Ti6Al4V sheets observed in this study is as follows: acicular α′ martensite, Widmanstätten, bimodal, and equiaxed microstructure. The fatigue strength ranking from high to low is as follows: equiaxed, bimodal, Widmanstätten, and acicular α′ martensite microstructure.

  15. The microstructural mechanism for mechanical property of LY2 aluminum alloy after laser shock processing

    International Nuclear Information System (INIS)

    Luo, Kai-yu; Lu, Jin-zhong; Zhang, Ling-feng; Zhong, Jun-wei; Guan, Hai-bing; Qian, Xiao-ming

    2010-01-01

    This paper described nanoindentation techniques for measuring thin films mechanical properties, including elastic modulus and nano-hardness. The effects of laser shock processing (LSP) on elastic modulus and nano-hardness of the sample manufactured by LY2 aluminum alloy were experimentally investigated by nanoindentation techniques. Transmission electron microscope (TEM) observations of the microstructures in different regions after LSP are carried out. Experimental results showed that the values of nano-hardness and elastic modulus in the laser-shocked region were obviously increased by 58.13% and 61.74% compared to those in the non-shocked region, respectively. The influences of LSP on microstructure and grain size of LY2 aluminum alloy were discussed, and the enhancement mechanism of LSP on nano-hardness and elastic modulus was also addressed.

  16. Mechanical Properties and Microstructure of Dissimilar Material Welded Joints

    Directory of Open Access Journals (Sweden)

    Ziewiec A.

    2014-10-01

    Full Text Available The paper presents results of the mechanical testing and the microstructure analysis of dissimilar welded joint of the R350HT steel and the high-manganese (Hadfield cast steel using Cr-Ni cast steel spacer. The simulation tests of the welded joint surface deformation were carried out. The macroscopic and microscopic investigation were made using light microscopy (LM and scanning electron microscopy (SEM. Content of the magnetic phase was measured using magnetoscope. The quantitative metallographic investigation was used for assessment of ferrite and martensite contents and X-ray diffraction phase analysis was carried out. The results showed that during cooling of the spacer after welding, the transformation of metastable austenite into martensite proceeded. In addition to work hardening, the phase transformation of austenite into martensite occurs during the process of the superficial deformation of the spacer while simulated exploitation. This leads to a substantial increase of hardness, and at the same time, causes the increase of wear resistance of the welded joints of crossovers.

  17. Microstructural and mechanical characterization of laser deposited advanced materials

    Science.gov (United States)

    Sistla, Harihar Rakshit

    Additive manufacturing in the form of laser deposition is a unique way to manufacture near net shape metallic components from advanced materials. Rapid solidification facilitates the extension of solid solubility, compositional flexibility and decrease in micro-segregation in the melt among other advantages. The current work investigates the employment of laser deposition to fabricate the following: 1. Functionally gradient materials: This allows grading dissimilar materials compositionally to tailor specific properties of both these materials into a single component. Specific compositions of the candidate materials (SS 316, Inconel 625 and Ti64) were blended and deposited to study the brittle intermetallics reported in these systems. 2. High entropy alloys: These are multi- component alloys with equiatomic compositions of 5 or more elements. The ratio of Al to Ni was decreased to observe the transition of solid solution from a BCC to an FCC crystal structure in the AlFeCoCrNi system. 3. Structurally amorphous alloys: Zr-based metallic glasses have been reported to have high glass forming ability. These alloys have been laser deposited so as to rapidly cool them from the melt into an amorphous state. Microstructural analysis and X-ray diffraction were used to study the phase formation, and hardness was measured to estimate the mechanical properties.

  18. Microstructure and mechanical properties of lost foam cast 356 alloys

    Directory of Open Access Journals (Sweden)

    Qi-gui Wang

    2015-05-01

    Full Text Available Microstructure and mechanical properties of lost foam cast aluminum alloys have been investigated in both primary A356 (0.13% Fe and secondary 356 (0.47%. As expected, secondary 356 shows much higher content of Fe-rich intermetallic phases, and in particular the porosity in comparison with primary A356. The average area percent and size (length of Fe-rich intermetallics change from about 0.5% and 6 祄 in A356 to 2% and 25 祄 in 356 alloy. The average area percent and maximum size of porosity also increase from about 0.4% and 420 祄 to 1.4% and 600 祄, respectively. As a result, tensile ductility decreases about 60% and ultimate tensile strength declines about 8%. Lower fatigue strength was also experienced in the secondary 356 alloy. Low cycle fatigue (LCF strength decreased from 187 MPa in A356 to 159 MPa in 356 and high cycle fatigue (HCF strength also declined slightly from 68 MPa to 64 MPa.

  19. Hexagonal OsB2: Sintering, microstructure and mechanical properties

    International Nuclear Information System (INIS)

    Xie, Zhilin; Lugovy, Mykola; Orlovskaya, Nina; Graule, Thomas; Kuebler, Jakob; Mueller, Martin; Gao, Huili; Radovic, Miladin; Cullen, David A.

    2015-01-01

    Highlights: • ReB 2 -type hexagonal OsB 2 powder has been densified by spark plasma sintering. • The sintered OsB 2 contains ∼80 wt.% hexagonal and ∼20 wt.% orthorhombic phases. • The average grain size of the sintered OsB 2 sample was 0.56 ± 0.26 μm. • H = 31 ± 9 GPa and E = 574 ± 112 GPa measured by nanoindentation. - Abstract: The metastable high pressure ReB 2 -type hexagonal OsB 2 bulk ceramics was produced by spark plasma sintering. The phase composition, microstructure, and mechanical behavior of the sintered OsB 2 were studied by X-ray diffraction, optical microscopy, TEM, SEM, EDS, and nanoindentation. The produced ceramics was rather porous and contained a mixture of hexagonal (∼80 wt.%) and orthorhombic (∼20 wt.%) phases as identified by X-ray diffraction and EBSD analysis. Two boron-rich phases, which do not contain Os, were also identified by TEM and SEM/EDS analysis. Nanoindentation measurements yielded a hardness of 31 ± 9 GPa and Young’s modulus of 574 ± 112 GPa, indicating that the material is rather hard and very stiff; however, it is very prone to crack formation and propagation, which is indicative of a very brittle nature of this material. Improvements in the sintering regime are required in order to produce dense, homogeneous and single phase hexagonal OsB 2 bulk ceramics

  20. Mechanical properties and antibiotic release characteristics of poly(methyl methacrylate)-based bone cement formulated with mesoporous silica nanoparticles.

    Science.gov (United States)

    Letchmanan, Kumaran; Shen, Shou-Cang; Ng, Wai Kiong; Kingshuk, Poddar; Shi, Zhilong; Wang, Wilson; Tan, Reginald B H

    2017-08-01

    The influence of mesoporous silica nanoparticles (MSNs) loaded with antibiotics on the mechanical properties of functional poly(methyl methacrylate)-(PMMA) based bone cements is investigated. The incorporation of MSNs to the bone cements (8.15wt%) shows no detrimental effects on the biomechanical properties of the freshly solidified bone cements. Importantly, there are no significant changes in the compression strength and bending modulus up to 6 months of aging in PBS buffer solution. The preserved mechanical properties of MSN-functionalized bone cements is attributed to the unchanged microstructures of the cements, as more than 96% of MSNs remains in the bone cement matrix to support the cement structures after 6 months of aging. In addition, the MSN-functionalized bone cements are able to increase the drug release of gentamicin (GTMC) significantly as compared with commercially available antibiotic-loaded bone cements. It can be attributed to the loaded nano-sized MSNs with uniform pore channels which build up an effective nano-network path enable the diffusion and extended release of GTMC. The combination of excellent mechanical properties and sustainable drug delivery efficiency demonstrates the potential applicability of MSN-functionalized PMMA bone cements for orthopedic surgery to prevent post-surgery infection. Copyright © 2017 Elsevier Ltd. All rights reserved.

  1. SAFOD Brittle Microstructure and Mechanics Knowledge Base (BM2KB)

    Science.gov (United States)

    Babaie, Hassan A.; Broda Cindi, M.; Hadizadeh, Jafar; Kumar, Anuj

    2013-07-01

    Scientific drilling near Parkfield, California has established the San Andreas Fault Observatory at Depth (SAFOD), which provides the solid earth community with short range geophysical and fault zone material data. The BM2KB ontology was developed in order to formalize the knowledge about brittle microstructures in the fault rocks sampled from the SAFOD cores. A knowledge base, instantiated from this domain ontology, stores and presents the observed microstructural and analytical data with respect to implications for brittle deformation and mechanics of faulting. These data can be searched on the knowledge base‧s Web interface by selecting a set of terms (classes, properties) from different drop-down lists that are dynamically populated from the ontology. In addition to this general search, a query can also be conducted to view data contributed by a specific investigator. A search by sample is done using the EarthScope SAFOD Core Viewer that allows a user to locate samples on high resolution images of core sections belonging to different runs and holes. The class hierarchy of the BM2KB ontology was initially designed using the Unified Modeling Language (UML), which was used as a visual guide to develop the ontology in OWL applying the Protégé ontology editor. Various Semantic Web technologies such as the RDF, RDFS, and OWL ontology languages, SPARQL query language, and Pellet reasoning engine, were used to develop the ontology. An interactive Web application interface was developed through Jena, a java based framework, with AJAX technology, jsp pages, and java servlets, and deployed via an Apache tomcat server. The interface allows the registered user to submit data related to their research on a sample of the SAFOD core. The submitted data, after initial review by the knowledge base administrator, are added to the extensible knowledge base and become available in subsequent queries to all types of users. The interface facilitates inference capabilities in the

  2. Microstructure and mechanical properties of bulk highly faulted fcc/hcp nanostructured cobalt microstructures

    Energy Technology Data Exchange (ETDEWEB)

    Barry, Aliou Hamady [Université Paris 13, Sorbonne Paris Cité, LSPM CNRS UPR 3407, 93430 Villetaneuse (France); Laboratoire Chimie des Matériaux, Département de Chimie, Faculté des Sciences et Technique, Université de Nouakchott (Mauritania, Islamic Republic of); Dirras, Guy, E-mail: dirras@unv-paris13.fr [Université Paris 13, Sorbonne Paris Cité, LSPM CNRS UPR 3407, 93430 Villetaneuse (France); Schoenstein, Frederic; Tétard, Florent; Jouini, Noureddine [Université Paris 13, Sorbonne Paris Cité, LSPM CNRS UPR 3407, 93430 Villetaneuse (France)

    2014-05-01

    Nanostructured cobalt powders with an average particle size of 50 nm were synthesized using a polyol method and subsequently consolidated by spark plasma sintering (SPS). SPS experiments performed at 650 °C with sintering times ranging from 5 to 45 min under a pressure of 100 MPa, yielded to dense bulk nanostructured cobalt (relative density greater than 97%). X-ray diffraction patterns of the as-prepared powders showed only a face centered cubic (fcc) crystalline phase, whereas the consolidated samples exhibited a mixture of both fcc and hexagonal close packed (hcp) phases. Transmission electron microscopy observations revealed a lamellar substructure with a high density of nanotwins and stacking faults in every grain of the sintered samples. Room temperature compression tests, carried out at a strain rate of 10{sup −3} s{sup −1}, yielded to highest strain to fracture values of up to 5% for sample of holding time of 15 min, which exhibited a yield strength of 1440 MPa, an ultimate strength as high as 1740 MPa and a Young's modulus of 205 GPa. The modulus of elasticity obtained from the nanoindentation tests, ranges from 181 to 218 GPa. The lowest modulus value of 181 GPa was obtained for the sample with the highest sintering time (45 min), which could be related to mass density loss as a consequence of trapped gases releasing. - Highlights: • Co nanopowder (50 nm) was prepared by reduction in polyol medium. • SPS was used to process bulk nanostructured Co specimens. • Microstructures were made of intricate fcc/hcp, along with nanotwins and SFs. • High strengths and moderate compressive ductility were obtained. • Deformation mechanisms related to complex interplay of different length scales.

  3. Molecular Mechanisms of Antibiotic Resistance in Helicobacter pylori

    NARCIS (Netherlands)

    M.M. Gerrits (Monique)

    2004-01-01

    textabstractAn estimated 4 to 5 million individuals in the Netherlands are actively infected with Helicobacter pylori. Eradication of this bacterium becomes more difficult as the prevalence of antibiotic resistance is increasing worldwide. Most H. pylori infections are now diagnosed by

  4. Development of microstructure to optimise mechanical performance of power generation equipment

    International Nuclear Information System (INIS)

    Marshall, P.

    1986-11-01

    The factors responsible for the development of microstructure in CEGB construction ceramics and steels is assessed as a function of composition, thermomechanical treatment, thermal ageing and environmental degradation. The relationships between microstructure and mechanical properties (tensile, toughness, creep and fatigue) of relevance to structures operating in power generation equipment is then developed in quantitative terms. The conclusions from the assessment are as follows: 1 The relationship between microstructure and mechanical properties of construction ceramics and steels used in the power generation industry has been assessed. 2 Factors which significantly influence microstructure and thus mechanical properties are chemical composition, thermomechanical treatment, ageing and environmental degradation. The influence of such microstructural changes in tensile, toughness, fatigue and creep properties of ceramics and steels is assessed. 3 The benefits arising from an understanding of materials behaviour are discussed in terms of improved materials and the assessment of plant performance. (author)

  5. The relationship of microstructure and temperature to fracture mechanics parameters in reaction bonded silicon nitride

    International Nuclear Information System (INIS)

    Jennings, H.M.; Dalgleish, B.J.; Pratt, P.L.

    1978-01-01

    The development of physical properties in reaction bonded silicon nitride has been investigated over a range of temperatures and correlated with microstructure. Fracture mechanics parameters, elastic moduli, strength and critical defect size have been determined. The nitrided microstructure is shown to be directly related to these observed properties and these basic relationships can be used to produce material with improved properties. (orig.) [de

  6. Mechanisms of microstructural changes of fuel under irradiation

    International Nuclear Information System (INIS)

    Garcia, P.; Carlot, G.; Dorado, B.; Maillard, S.; Sabathier, C.; Martin, G.; Oh, J.Y.; Welland, M.J.

    2015-01-01

    Nuclear fuels are subjected to high levels of radiation damage mainly due to the slowing of fission fragments, which results in substantial modifications of the initial fuel microstructure. Microstructure changes alter practically all engineering fuel properties such as atomic transport or thermomechanical properties so understanding these changes is essential to predicting the performance of fuel elements. Also, with increasing burn-up, the fuel drifts away from its initial composition as the fission process produces new chemical elements. Because nuclear fuels operate at high temperature and usually under high-temperature gradients, damage annealing, foreign atom or defect clustering and migration occur on multiple time and length scales, which make long-term predictions difficult. The end result is a fuel microstructure which may show extensive differences on the scale of a single fuel pellet. The main challenge we are faced with is, therefore, to identify the phenomena occurring on the atom scale that are liable to have macroscopic effects that will determine the microstructure changes and ultimately the life-span of a fuel element. One step towards meeting this challenge is to develop and apply experimental or modelling methods capable of connecting events that occur over very short length and timescales to changes in the fuel microstructure over engineering length and timescales. In the first part of this chapter, we provide an overview of some of the more important microstructure modifications observed in nuclear fuels. The emphasis is placed on oxide fuels because of the extensive amount of data available in relation to these materials under neutron or ion irradiation. When possible and relevant, the specifics of other types of fuels such as metallic or carbide fuels are alluded to. Throughout this chapter but more specifically in the latter part, we attempt to give examples of how modelling and experimentation at various scales can provide us with

  7. Microstructure and Mechanical Properties of High Copper HSLA-100 Steel in 2-inch Plate Form

    Science.gov (United States)

    1992-06-01

    CCT diagram . Increasing copper in HSLA-100 steel also increases the toughness as well as the strength, though the dynamics of this process are not clear. Steel, High Copper HSLA-100 Steel, mechanical property, microstructure.

  8. Mechanical properties and microstructure of laser treated Al-Cu-Mg alloys

    OpenAIRE

    De Hosson , J.; Noordhuis , J.

    1993-01-01

    The mechanical properties and microstructural features of Al-Cu-Mg alloys were investigated, as exposed to laser treatments at various scan velocities. As far as the mechanical property is concerned a striking observation is a minimum in the hardness value at a laser scan velocity of 1/2 cm/s. Usually an increasing hardness with increasing laser scan velocities is reported in the literature. This remarkable property could be explained based on the microstructural features observed by transmis...

  9. Influence of electropulsing globularization on the microstructure and mechanical properties of Ti–6Al–4V alloy strip with lamellar microstructure

    Energy Technology Data Exchange (ETDEWEB)

    Ye, Xiaoxin, E-mail: xiaoxinye905@gmail.com [Advanced Materials Institute, Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055 (China); Key Laboratory for Advanced Materials of Ministry of Education, Department of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China); Tse, Zion T.H. [College of Engineering, The University of Georgia, Athens, GA 30602 (United States); Tang, Guoyi, E-mail: tanggy@mails.tsinghua.edu.cn [Advanced Materials Institute, Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055 (China); Key Laboratory for Advanced Materials of Ministry of Education, Department of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China); Geng, Yubo [Advanced Materials Institute, Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055 (China); Key Laboratory for Advanced Materials of Ministry of Education, Department of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China); Song, Guolin [Advanced Materials Institute, Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055 (China)

    2015-01-12

    The effect of high-energy electropulsing treatment (EPT) on the microstructure and mechanical properties of Ti–6Al–4V alloy strip with initial lamellar microstructure was investigated. The results indicated that EPT accelerated the phase change process tremendously inducing equiaxed microstructure in titanium alloy. The EPT-induced microstructural change resulted in remarkably increasing elongation-to-failure while the tensile strength remained unchanged. A mechanism for rapid phase change in low temperature during EPT was proposed based on the reduction of nucleation thermodynamic barrier and enhancement of atomic diffusion. A medium migration model was utilized for discussing the globularization process.

  10. Influence of electropulsing globularization on the microstructure and mechanical properties of Ti–6Al–4V alloy strip with lamellar microstructure

    International Nuclear Information System (INIS)

    Ye, Xiaoxin; Tse, Zion T.H.; Tang, Guoyi; Geng, Yubo; Song, Guolin

    2015-01-01

    The effect of high-energy electropulsing treatment (EPT) on the microstructure and mechanical properties of Ti–6Al–4V alloy strip with initial lamellar microstructure was investigated. The results indicated that EPT accelerated the phase change process tremendously inducing equiaxed microstructure in titanium alloy. The EPT-induced microstructural change resulted in remarkably increasing elongation-to-failure while the tensile strength remained unchanged. A mechanism for rapid phase change in low temperature during EPT was proposed based on the reduction of nucleation thermodynamic barrier and enhancement of atomic diffusion. A medium migration model was utilized for discussing the globularization process

  11. The temperature-dependent microstructure of PEDOT/PSS films: insights from morphological, mechanical and electrical analyses

    KAUST Repository

    Zhou, Jian; Anjum, Dalaver H.; Chen, Long; Xu, Xuezhu; Ventura, Isaac Aguilar; Jiang, Long; Lubineau, Gilles

    2014-01-01

    microstructure changes at different temperatures and correlates the microstructure with its physical properties (mechanical and electrical). We used High-Angle Annular Dark-Field Scanning Electron Microscopy (HAADF-STEM) combined with electron energy loss

  12. Microstructure and Mechanical Properties of HSLA-100 Steel

    Science.gov (United States)

    1990-12-01

    hardenability of HSLA-100 steel through the shifting of the nose of the CCT diagram to the right (Figure 2 from Ref. 10) and lowering the B, temperature as seen...of the CCT diagram by increasing the hardenability of the alloy and quenching. The object of the quench is to produce a finely-grained microstructure

  13. Mechanical, microstructure and electrical properties of ternary ZnO ...

    Indian Academy of Sciences (India)

    V2O5–Mn3O4 (ZVM)-based varis- tors were investigated at different sintering temperatures of 825–950◦C. The microstructure of the samples consists mainly of ZnO grains with Zn3(VO4)2, ZnV2O4 and VO2 as minor secondary phases.

  14. Mechanisms of microstructure formation under the influence of ultrasonic vibrations

    Science.gov (United States)

    Rakita, Milan

    Positive effects of ultrasound on crystallization have been known for almost 90 years. Application of ultrasound has been very successful in many industries, most notably in chemistry, creating a new branch of science - sonochemistry. However, ultrasonication has not found wide commercial application in the solidification processing. The reason for that is the complexity of underlying phenomena and the lack of predicting models which correlate processing parameters with the properties of a product. The purpose of this study is to give some contribution toward better understanding of mechanisms that lead to changes in the solidifying microstructure. It has been found that, under experimental conditions used in this work, cavitation-induced nucleation is the major contributor to the grain refinement. Ultrasonication at minimal supercoolings is expected to give maximal grain refinement. Dendrite fragmentation has not shown to be a significant contributor to the grain refinement. Dendrite fragmentation is maximal if done by bubbles that come in contact with the solidifying phase, or that are created there. Alloys/solutions with long solidification interval, or wide mushy zone, are expected to exhibit more dendrite fragmentation. Bubbles are recognized as a crucial feature in ultrasonication. Their size distribution in the liquid phase prior to ultrasonication dictates the cavitation threshold and intensity of cavitation. For the first time, radiation pressure has been recognized as potentially significant factor in grain refinement. In the experimental setup used in this study, acoustic pressure at the main (driving) frequency is not substantial to cause significant fragmentation, and only dendrites close to the sonotrode were fragmented. However, application of ultrasound with frequencies that are several times higher than the current industrial practice could substantially increase dendrite fragmentation. Appearance of fractional harmonics has also been recognized

  15. Microstructure and mechanical properties of Al-3Fe alloy processed by equal channel angular extrusion

    International Nuclear Information System (INIS)

    Fuxiao, Yu; Fang, Liu; Dazhi, Zhao; Toth, Laszlo S

    2014-01-01

    Al-Fe alloys are attractive for applications at temperatures beyond those normally associated with the conventional aluminum alloys. Under proper solidification condition, a full eutectic microstructure can be generated in Al-Fe alloys at Fe concentration well in excess of the eutectic composition of 1.8 wt.% Fe. The microstructure in this case is characterized by the metastable regular eutectic Al-Al 6 Fe fibers of nano-scale in diameter, instead of the equilibrium eutectic Al-Al 3 Fe phase. In this study, the microstructure and mechanical properties of the Al-3Fe alloy with metastable Al 6 Fe particles deformed by equal channel angular extrusion were investigated. Severe plastic deformation results in a microstructure consisting of submicron equiaxed Al grains with a uniform distribution of submicron Al 6 Fe particles on the grain boundaries. The room temperature tensile properties of the alloy with this microstructure will be presented

  16. Antibiotics Resistance in Rhizobium: Type, Process, Mechanism and Benefit for Agriculture.

    Science.gov (United States)

    Naamala, Judith; Jaiswal, Sanjay K; Dakora, Felix D

    2016-06-01

    The use of high-quality rhizobial inoculants on agricultural legumes has contributed substantially to the N economy of farming systems through inputs from biological nitrogen fixation (BNF). Large populations of symbiotically effective rhizobia should be available in the rhizosphere for symbiotic BNF with host plants. The rhizobial populations should also be able to compete and infect host plants. However, the rhizosphere comprises large populations of different microorganisms. Some of these microorganisms naturally produce antibiotics which are lethal to susceptible rhizobial populations in the soil. Therefore, intrinsic resistance to antibiotics is a desirable trait for the rhizobial population. It increases the rhizobia's chances of growth, multiplication and persistence in the soil. With a large population of rhizobia in the soil, infectivity of host plants and the subsequent BNF efficiency can be guaranteed. This review, therefore, puts together findings by various researchers on antibiotic resistance in bacteria with the main emphasis on rhizobia. It describes the different modes of action of different antibiotics, the types of antibiotic resistance exhibited by rhizobia, the mechanisms of acquisition of antibiotic resistance in rhizobia and the levels of tolerance of different rhizobial species to different antibiotics.

  17. Mechanical behaviour of Zn–Al–Cu–Mg alloys: Deformation mechanisms of as-cast microstructures

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Zhicheng; Sandlöbes, Stefanie; Wu, Liang; Hu, Weiping; Gottstein, Günter; Korte-Kerzel, Sandra, E-mail: Korte-Kerzel@imm.rwth-aachen.de

    2016-01-10

    We study the effects of dilute Mg addition on the microstructure formation and mechanical properties of a ZnAl4Cu1 alloy. On the basis of the composition of the commercial alloy Z410 (4 wt% Al, 1 wt% Cu, and 0.04 wt% Mg), three laboratory alloys with different Mg contents (0.04 wt%, 0.21 wt% and 0.31 wt%) are characterised in terms of their mechanical properties and microstructures using ex-situ and in-situ tensile tests in conjunction with scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). Increasing Mg content causes the precipitation of Mg{sub 2}Zn{sub 11} phase precipitates and refined lamellar spacings in the eutectoid phase. The alloy with a medium Mg content (0.21 wt%) exhibits the highest yield strength both at room temperature and at elevated temperatures. Further, we show that dilute Mg alloying causes an improvement of the ductility of ZnAl4Cu1 base-alloys, especially at elevated temperatures. In addition, the alloys reveal two distinct deformation regimes distinguishable close to room temperature and at commonly employed strain rates, with work hardening and brittle fracture exhibited at room temperature and/or elevated strain rate (5×10{sup −4} s{sup −1}), and work softening and ductile fracture at elevated temperature and/or low strain rate (6×10{sup −6} s{sup −1}). The deformation mechanisms and fracture behaviour in both regimes are investigated and the underlying physical mechanisms of the observed phenomena are discussed.

  18. Mechanical behaviour of Zn–Al–Cu–Mg alloys: Deformation mechanisms of as-cast microstructures

    International Nuclear Information System (INIS)

    Wu, Zhicheng; Sandlöbes, Stefanie; Wu, Liang; Hu, Weiping; Gottstein, Günter; Korte-Kerzel, Sandra

    2016-01-01

    We study the effects of dilute Mg addition on the microstructure formation and mechanical properties of a ZnAl4Cu1 alloy. On the basis of the composition of the commercial alloy Z410 (4 wt% Al, 1 wt% Cu, and 0.04 wt% Mg), three laboratory alloys with different Mg contents (0.04 wt%, 0.21 wt% and 0.31 wt%) are characterised in terms of their mechanical properties and microstructures using ex-situ and in-situ tensile tests in conjunction with scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). Increasing Mg content causes the precipitation of Mg_2Zn_1_1 phase precipitates and refined lamellar spacings in the eutectoid phase. The alloy with a medium Mg content (0.21 wt%) exhibits the highest yield strength both at room temperature and at elevated temperatures. Further, we show that dilute Mg alloying causes an improvement of the ductility of ZnAl4Cu1 base-alloys, especially at elevated temperatures. In addition, the alloys reveal two distinct deformation regimes distinguishable close to room temperature and at commonly employed strain rates, with work hardening and brittle fracture exhibited at room temperature and/or elevated strain rate (5×10"−"4 s"−"1), and work softening and ductile fracture at elevated temperature and/or low strain rate (6×10"−"6 s"−"1). The deformation mechanisms and fracture behaviour in both regimes are investigated and the underlying physical mechanisms of the observed phenomena are discussed.

  19. Fuel relocation mechanism based on microstructures of debris

    International Nuclear Information System (INIS)

    Strain, R.V.; Neimark, L.A.; Sanecki, J.E.

    1988-05-01

    Argonne National Laboratory (ANL) has performed a number of examinations to determine the microstructure and micro-chemistry of samples of debris from the TMI-2 reactor. These examinations have been a small part of the overall effort to gain an understanding of the TMI-2 accident. As a result of these overall efforts, a general scenario of the response of the core components has been established. In this paper we will describe the microstructure and micro-chemistry of debris from the lower plenum of the reactor and relate these data to a segment of the general scenario dealing with the relocation of this material. The primary tools used at ANL for the examination of material from the TMI-2 core were optical microscopy, scanning electron microscopy and Energy Dispersive X-Ray Spectroscopy, and Scanning Auger Spectroscopy. In some cases these techniques were augmented by the use of gamma spectroscopy, autoradiography, and X-ray diffraction analysis

  20. Microstructure and mechanical properties in TIG welding of CLAM steel

    International Nuclear Information System (INIS)

    Zhu Qiang; Lei Yucheng; Chen Xizhang; Ren Wenjie; Ju Xin; Ye Yimin

    2011-01-01

    Tungsten insert gas (TIG) welding on China low activation martensitic (CLAM) steel under identical conditions was performed. Microhardness test, tensile test, Charpy impact test and microstructure measurements were carried out on TIG welded joints after post weld heat-treatment. Hardening at WM and softening in HAZ is detected in the TIG weld joint. Microhardness in WM decreased when the temperature of PWHT increased. The ultimate tensile stress of weld metal is higher than that of HAZ and BM. Absorbed energy increased with PWHT temperature rising, until PWHT was done at 760 deg. C/30 min, the specimen ductile fractured in local area. The microstructure of the weld metal for every specimen was found to be tempered martensite with a little of delta ferrite. M 23 C 6 particles are the predominant type of carbides. Oxide precipitate phases appeared in WM, which are the primary crack initiation sites and it is critically important minimize their formation.

  1. Identification of microstructural mechanisms during densification of a TiAl alloy by spark plasma sintering

    Energy Technology Data Exchange (ETDEWEB)

    Jabbar, Houria; Couret, Alain; Durand, Lise [CNRS, CEMES-UPR 8011, Centre d' Elaboration de Materiaux et d' Etudes Structurales, BP 94347, 29 rue J. Marvig, F-31055 Toulouse (France); Universite de Toulouse, UPS, F-31055 Toulouse (France); Monchoux, Jean-Philippe, E-mail: monchoux@cemes.fr [CNRS, CEMES-UPR 8011, Centre d' Elaboration de Materiaux et d' Etudes Structurales, BP 94347, 29 rue J. Marvig, F-31055 Toulouse (France); Universite de Toulouse, UPS, F-31055 Toulouse (France)

    2011-10-13

    Graphical abstract: Highlights: > Mechanisms of a TiAl alloy powder densified by spark plasma sintering are identified. > Microstructure evolution of the powder is followed during the sintering cycle. > As-atomized supersaturated powder comes back to equilibrium. > Densification occurs by plastification of the particles at high temperature. > No mechanisms related to electric current are observed. - Abstract: This work aims at identifying, by coupled scanning and transmission electron microscopy (SEM and TEM) observations, the densification mechanisms occurring when an atomized Ti-47Al-1W-1Re-0.2Si powder is densified by spark plasma sintering (SPS). For this purpose, interruptions of the SPS cycle have been performed to follow the evolution of the microstructure step by step. The powder particles exhibit a classical dendritic microstructure containing a large amount of out-of-equilibrium {alpha} phase. During heating-up, the microstructure undergoes successive transformations. At T = 525-875 deg. C the {alpha} phase transforms into {gamma}. The {gamma} phase formed is supersaturated in W and Re. It de-saturates for T above 875 deg. C by discontinuous precipitation of W and Re-rich B2 phase. Densification takes place for T between 900 deg. C and 1150 deg. C by plastic deformation of the powder particles. TEM observations show that the repartition of the plastic deformation is correlated to the dendritic microstructure, and that dynamic recrystallization mechanisms occur. Microstructural phenomena directly resulting from the high currents involved in the SPS process have not been observed.

  2. Microstructures and mechanical properties of two-phase alloys based on NbCr{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Chen, K.C.; Kotula, P.G.; Cady, C.M.; Mauro, M.E.; Thoma, D.J.

    1999-07-01

    A two-phase, NbCrTi alloy (bcc + C15 Laves phase) has been developed using several alloy design methodologies. In efforts to understand processing-microstructure-property relationships, different processing routes were employed. The resulting microstructures and mechanical properties are discussed and compared. Plasma arc melted (PAM) samples served to establish baseline, as-cast properties. In addition, a novel processing technique, involving decomposition of a supersaturated and metastable precursor phase during hot isostatic pressing (HIP), was used to produce a refined, equilibrium two-phase microstructure. Quasi-static compression tests as a function of temperature were performed on both alloy types. Different deformation mechanisms were encountered based upon temperature and microstructure.

  3. Microstructure and mechanical properties after annealing of equal-channel angular pressed interstitial-free steel

    International Nuclear Information System (INIS)

    Hazra, Sujoy S.; Pereloma, Elena V.; Gazder, Azdiar A.

    2011-01-01

    The evolution of microstructure, microtexture and mechanical properties during isothermal annealing of an ultrafine-grained interstitial-free steel after eight passes of route B C room temperature equal-channel angular pressing (ECAP) was studied. The microstructure and microtexture were characterized by electron back-scattering diffraction, and mechanical properties were assessed by shear punch and uniaxial tensile testing. Homogeneous coarsening via continuous recrystallization of the ECAP microstructure is accompanied by minor changes in the ∼63% high-angle boundary population and a sharpening of the original ECAP texture. This is followed by abnormal growth during the final stages of softening due to local growth advantages. Linear correlations between shear and tensile data were established for yield, ultimate strength and total elongation. After yield, the changes in uniaxial tensile behaviour from geometrical softening after ECAP to load drop, Lueders banding and continuous yielding after annealing is attributable to a coarsening of the microstructure.

  4. Effects of Static Magnetic Fields on the Physical, Mechanical, and Microstructural Properties of Cement Pastes

    OpenAIRE

    Soto-Bernal, Juan J.; Gonzalez-Mota, Rosario; Rosales-Candelas, Iliana; Ortiz-Lozano, Jose A.

    2015-01-01

    This paper presents the results of an experimental study carried out to comprehend the physical, mechanical, and microstructural behavior of cement pastes subjected to static magnetic fields while hydrating and setting. The experimental methodology consisted in exposing fresh cement pastes to static magnetic fields at three different magnetic induction strengths: 19.07, 22.22, and 25.37 Gauss. The microstructural characterization makes evident that there are differences in relation to amount ...

  5. Functional Characterization of Bacteria Isolated from Ancient Arctic Soil Exposes Diverse Resistance Mechanisms to Modern Antibiotics

    Science.gov (United States)

    Perron, Gabriel G.; Whyte, Lyle; Turnbaugh, Peter J.; Goordial, Jacqueline; Hanage, William P.; Dantas, Gautam; Desai, Michael M.

    2015-01-01

    Using functional metagenomics to study the resistomes of bacterial communities isolated from different layers of the Canadian high Arctic permafrost, we show that microbial communities harbored diverse resistance mechanisms at least 5,000 years ago. Among bacteria sampled from the ancient layers of a permafrost core, we isolated eight genes conferring clinical levels of resistance against aminoglycoside, β-lactam and tetracycline antibiotics that are naturally produced by microorganisms. Among these resistance genes, four also conferred resistance against amikacin, a modern semi-synthetic antibiotic that does not naturally occur in microorganisms. In bacteria sampled from the overlaying active layer, we isolated ten different genes conferring resistance to all six antibiotics tested in this study, including aminoglycoside, β-lactam and tetracycline variants that are naturally produced by microorganisms as well as semi-synthetic variants produced in the laboratory. On average, we found that resistance genes found in permafrost bacteria conferred lower levels of resistance against clinically relevant antibiotics than resistance genes sampled from the active layer. Our results demonstrate that antibiotic resistance genes were functionally diverse prior to the anthropogenic use of antibiotics, contributing to the evolution of natural reservoirs of resistance genes. PMID:25807523

  6. Microstructure evaluation and mechanical behavior of high-niobium containing titanium aluminides

    Science.gov (United States)

    Bean, Glenn Estep, Jr.

    Ti-Al-Nb-based alloys with gamma(TiAl)+sigma(Nb2Al) microstructure have shown promise for potential high temperature applications due to their high specific strength. Recent research has been aimed towards increasing strength and operating temperatures through microstructural refinement and control. Alloys with 10 - 30% sigma-phase have been investigated, exploring relationships between chemistry, microstructure development, and flow behavior. Alloys with composition Ti-45Al-xNb-5Cr-1Mo (where x = 15, 20, 25 at%) have been produced, characterized, and tested at high temperature under compression. Processing, microstructure and mechanical property relationships are thoroughly investigated to reveal a significant connection between phase stability, morphology and their resultant effects on mechanical properties. Phase transformation temperatures and stability ranges were predicted using the ThermoCalc software program and a titanium aluminide database, investigated through thermal analysis, and alloys were heat treated to develop an ultrafine gamma+sigma microstructure. It has been demonstrated that microstructural development in these alloys is sensitive to composition and processing parameters, and heating and cooling rates are vital to the modification of gamma+sigma microstructure in these alloys. Towards the goal of designing a high-Nb titanium aluminide with ultrafine, disconnected gamma+sigma morphology, it has been established that microstructural control can be accomplished in alloys containing 15-25at% Nb through targeted chemistry and processing controls. The strength and flow softening characteristics show strain rate sensitivity that is also affected by temperature. From the standpoint of microstructure development and mechanical behavior at elevated temperature, the most favorable results are obtained with the 20 at% Nb alloy, which produces a combination of high strength and fine disconnected gamma+sigma microstructure. Microstructural analysis reveals

  7. Effect of pH on the microstructure of β-Ga2O3 and its enhanced photocatalytic activity for antibiotic degradation.

    Science.gov (United States)

    Liu, Jin; Lu, Wei; Zhong, Qian; Wu, Hongzhang; Li, Yunlin; Li, Lili; Wang, Zhenling

    2018-06-01

    Semiconductor photocatalysis has become the focus of recent research on antibiotic treatment because it is a green and efficient technology. In this study, α-GaOOH with several novel microstructures has been synthesized at a low temperature and its subsequent thermal transformation. The influence of pH on the synthesis of α-GaOOH is studied, and the results indicate that pH played an important role in the microstructures of α-GaOOH and β-Ga 2 O 3 . All Ga 2 O 3 samples possess macro-mesoporous network structures and exhibits a remarkable photocatalytic activity for antibiotic degradation. The photoelectron chemical tests show that the separation efficiency of photogenerated charge carriers of Ga 2 O 3 -7.0 is higher than that of other Ga 2 O 3 . The enhanced photocatalytic activity of Ga 2 O 3 -7.0 is mainly ascribed to its morphology and oxygen vacancy. The active species trapping and photoluminescence measurement experiments indicate that OH and O 2 - are the major active species contributing to the photocatalytic process. This study will bring about the potential application in treatment of the antibiotic pollutants. Copyright © 2018 Elsevier Inc. All rights reserved.

  8. Effects of β treatments on microstructures and mechanical properties of TC4-DT titanium alloy

    International Nuclear Information System (INIS)

    Peng Xiaona; Guo Hongzhen; Wang Tao; Yao Zekun

    2012-01-01

    Highlights: ► Effects of β treatments on microstructures and mechanical properties of TC4-DT alloy were studied. ► The microstructure evolutions at each condition were analyzed. ► Influence of microstructures on tensile properties and fracture toughness were studied. ► Relationships among processing parameters–microstructures–properties were determined. - Abstract: β Processing (deformation in β phase field followed by heat treatment in α + β phase field) and β annealing (deformation in α + β phase field followed by annealing in β phase field) were carried out to research their influence on microstructures and mechanical properties including fracture toughness of TC4-DT titanium alloy. The tensile properties at room and high temperature as well as fracture toughness were tested for all the experiment conditions. The microstructure evolution and fracture surfaces were researched by optical microscope and scanning electronic microscope (SEM) and the microstructure features were measured by means of image analysis software. Results showed that the microstructures were lamellar in β processing and acicular Widmanstatten in β annealing respectively. Spheroidization of α lamellar was found in the microstructures of β processing. SEM observation showed that the fracture mechanism changed from transcrystalline in the β processing conditions to a mixture of intercrystalline and transcrystalline at the β annealing conditions. The tensile strength and plasticity did not change much under the β processing conditions. While at β annealing conditions, the strength and plasticity varied with the temperature in a reverse trend. The biggest fracture toughness was obtained at β annealing conditions. It was found that β annealing was preferable to β processing with regard to obtaining high fracture toughness and tensile properties with a little sacrifice of plasticity which does not affect its practice use.

  9. Nanocrystalline-grained tungsten prepared by surface mechanical attrition treatment: Microstructure and mechanical properties

    International Nuclear Information System (INIS)

    Guo, Hong-Yan; Xia, Min; Wu, Zheng-Tao; Chan, Lap-Chung; Dai, Yong; Wang, Kun; Yan, Qing-Zhi; He, Man-Chao; Ge, Chang-Chun; Lu, Jian

    2016-01-01

    A nanostructured surface layer was fabricated on commercial pure tungsten using the method of surface mechanical attrition treatment (SMAT). The microstructure evolution of the surface layer was characterized by using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) and its formation mechanism was discussed as well. Both refinement and elongation of the brittle W grains were confirmed. The elongated SMATed W was heavily strained, the maximum value of the strain at the grain boundaries reaches as high as 3–5%. Dislocation density in the SMATed W nanograins was found to be 5 × 10 12  cm −2 . The formation of the nanograins in the top surface layer of the W was ascribed to the extremely high strain and strain rate, as well as the multidirectional repetitive loading. Bending strength of commercial W could be improved from 825 MPa to 1850 MPa by SMAT process. Microhardness results indicated the strain range in SMATed W can reach up to 220 μm beneath the top surface. The notched Charpy testing results demonstrated that SMATed W possess higher ductility than that of commercial W. The top surface of the W plates with and without SMATe processing possesses residual compressive stress of about −881 MPa and −234 MPa in y direction, and −872 MPa and −879 MPa in x direction respectively. The improvement of toughness (DBTT shift) of SMATed W may be the synergistic effect of residual compressive stress, dislocation density improvement and microstructure refinement induced by SMAT processing. SMAT processing could be a complementary method to further decrease the DBTT value of tungsten based materials.

  10. Nanocrystalline-grained tungsten prepared by surface mechanical attrition treatment: Microstructure and mechanical properties

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Hong-Yan [State Key Laboratory for GeoMechanics and Deep Underground Engineering, China University of Mining and Technology, Beijing 100083 (China); Institute of Nuclear Materials, University of Science & Technology Beijing, Beijing 100083 (China); Department of Mechanical and Biomedical Engineering, City University of Hong Kong, Tae Chee Avenue Kowloon, Hong Kong 999077 (China); Xia, Min, E-mail: xmdsg@ustb.edu.cn [Institute of Nuclear Materials, University of Science & Technology Beijing, Beijing 100083 (China); Wu, Zheng-Tao [College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005 (China); Chan, Lap-Chung [Department of Mechanical and Biomedical Engineering, City University of Hong Kong, Tae Chee Avenue Kowloon, Hong Kong 999077 (China); Dai, Yong; Wang, Kun [Laboratory for Nuclear Materials, Paul Scherrer Institut, 5323 Villigen PSI (Switzerland); Yan, Qing-Zhi [Institute of Nuclear Materials, University of Science & Technology Beijing, Beijing 100083 (China); He, Man-Chao [State Key Laboratory for GeoMechanics and Deep Underground Engineering, China University of Mining and Technology, Beijing 100083 (China); Ge, Chang-Chun, E-mail: ccge@mater.ustb.edu.cn [Institute of Nuclear Materials, University of Science & Technology Beijing, Beijing 100083 (China); Lu, Jian, E-mail: jianlu@cityu.edu.hk [Department of Mechanical and Biomedical Engineering, City University of Hong Kong, Tae Chee Avenue Kowloon, Hong Kong 999077 (China)

    2016-11-15

    A nanostructured surface layer was fabricated on commercial pure tungsten using the method of surface mechanical attrition treatment (SMAT). The microstructure evolution of the surface layer was characterized by using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) and its formation mechanism was discussed as well. Both refinement and elongation of the brittle W grains were confirmed. The elongated SMATed W was heavily strained, the maximum value of the strain at the grain boundaries reaches as high as 3–5%. Dislocation density in the SMATed W nanograins was found to be 5 × 10{sup 12} cm{sup −2}. The formation of the nanograins in the top surface layer of the W was ascribed to the extremely high strain and strain rate, as well as the multidirectional repetitive loading. Bending strength of commercial W could be improved from 825 MPa to 1850 MPa by SMAT process. Microhardness results indicated the strain range in SMATed W can reach up to 220 μm beneath the top surface. The notched Charpy testing results demonstrated that SMATed W possess higher ductility than that of commercial W. The top surface of the W plates with and without SMATe processing possesses residual compressive stress of about −881 MPa and −234 MPa in y direction, and −872 MPa and −879 MPa in x direction respectively. The improvement of toughness (DBTT shift) of SMATed W may be the synergistic effect of residual compressive stress, dislocation density improvement and microstructure refinement induced by SMAT processing. SMAT processing could be a complementary method to further decrease the DBTT value of tungsten based materials.

  11. Local microstructures, Hardness and mechanical properties of a stainless steel pipe-welded joint

    International Nuclear Information System (INIS)

    Zhao Yongxiang; Gao Qing; Cai Lixun

    2000-01-01

    An experimental investigation is carefully performed into the local microstructures, hardness values and monotonic mechanical properties of the three zones (the base metal, heat affecting zone and weld metal) of 1Cr18Ni9Ti stainless steel pipe-welded joint. The local microstructures are observed by a metallurgical test and a surface replica technology, the local hardness values are measures by a random Vickers hardness test, and the local mechanical properties are characterized by the Ramberg-Osgood and modified Ramberg-Osgood stress-stain relations. The investigation reveals that there are significant differences of the three zones in the local microstructures, hardness values and monotonic mechanical properties, especially of the three zones in the local microstructure, hardness values and monotonic mechanical properties, especially of the weld metal. The weld metal exhibits the largest heterogeneity of local microstructures and monotonic mechanical properties, and the largest scatter of local hardness values. It is necessary to consider these difference and introduce the reliability method to model the scatter in the pipe analysis. In addition, it is verified that a columnar grain structure, which is made up of matrix-rich δ ferrite bands, can characterize the weld metal and the distance between the neighboring rich δ ferrite bands is an appropriate measurement of the columnar grain structure. This measurement is in accordance with the transition point between the microstructural short crack and physical small crack stages, which are generally used for characterizing the short fatigue crack behavior of materials. This indicates that the microstructure controls the fatigue damage character of the present material

  12. Biology of Acinetobacter baumannii: Pathogenesis, Antibiotic Resistance Mechanisms, and Prospective Treatment Options

    Science.gov (United States)

    Lee, Chang-Ro; Lee, Jung Hun; Park, Moonhee; Park, Kwang Seung; Bae, Il Kwon; Kim, Young Bae; Cha, Chang-Jun; Jeong, Byeong Chul; Lee, Sang Hee

    2017-01-01

    Acinetobacter baumannii is undoubtedly one of the most successful pathogens responsible for hospital-acquired nosocomial infections in the modern healthcare system. Due to the prevalence of infections and outbreaks caused by multi-drug resistant A. baumannii, few antibiotics are effective for treating infections caused by this pathogen. To overcome this problem, knowledge of the pathogenesis and antibiotic resistance mechanisms of A. baumannii is important. In this review, we summarize current studies on the virulence factors that contribute to A. baumannii pathogenesis, including porins, capsular polysaccharides, lipopolysaccharides, phospholipases, outer membrane vesicles, metal acquisition systems, and protein secretion systems. Mechanisms of antibiotic resistance of this organism, including acquirement of β-lactamases, up-regulation of multidrug efflux pumps, modification of aminoglycosides, permeability defects, and alteration of target sites, are also discussed. Lastly, novel prospective treatment options for infections caused by multi-drug resistant A. baumannii are summarized. PMID:28348979

  13. Microstructures and mechanical properties of duplex low carbon steel

    Science.gov (United States)

    Alfirano; Eben, U. S.; Hidayat, M.

    2018-04-01

    The microstructures behavior of duplex cold-rolled low carbon steel for automotive applications has been investigated. Intercritical annealing treatment is commonly used to develop a duplex low carbon steel containing ferrite and martensite. To get a duplex phase ferrite and martensite, the specimens were heated at inter-critical annealing temperature of 775°C - 825°C, for heating time up to 20 minutes, followed by water-quenched. The hardness of specimens was studied. The optical microscopy was used to analyze the microstructures. The optimal annealing conditions (martensite volume fraction approaching 20%) at 775°C with a heating time of 10 minutes was achieved. The highest hardness value was obtained in cold-rolled specimens of 41% in size reduction for intercritical annealing temperature of 825°C. In this condition, the hardness value was 373 HVN. The correlation between intercritical annealing temperature and time can be expressed in the transformation kinetics as fγ/fe = 1-exp(-Ktn) wherein K and n are grain growth rate constant and Avrami’s exponent, respectively. From experiment, the value of K = 0.15 and n = 0.461. Using the relationship between temperatures and heating time, activation energy (Q) can be calculated that is 267 kJ/mol.

  14. ON MODELLING OF MICROSTRUCTURE FORMATION, LOCAL MECHANICAL PROPERTIES AND STRESS – STRAIN DEVELOPMENT IN ALUMINIUM CASTINGS

    DEFF Research Database (Denmark)

    Svensson, Ingvar; Seifeddine, Salem; Kotas, Petr

    2009-01-01

    , related to mechanical properties as elastic modulus, yield stress, ultimate strength and elongation. In the present work, a test case of a complex casting in an aluminium alloy is considered including simulation of the entire casting process with focus on of microstructure formation, related to mechanical...

  15. Mechanical properties and microstructure of laser treated Al-Cu-Mg alloys

    NARCIS (Netherlands)

    Hosson, J.Th.M. De; Noordhuis, J.

    1993-01-01

    The mechanical properties and microstructural features of Al-Cu-Mg alloys were investigated, as exposed to laser treatments at various scan velocities. As far as the mechanical property is concerned a striking observation is a minimum in the hardness value at a laser scan velocity of 1/2 cm/s.

  16. EFFECTS OF MO ADDITION ON THE MICROSTRUCTURE AND MECHANICAL PROPERTIES OF CAST MICROALLOYED STEEL

    Directory of Open Access Journals (Sweden)

    H. Torkamani

    2017-09-01

    Full Text Available In industry, the cost of production is an important factor and it is preferred to use conventional and low cost procedures for producing the parts. Heat treatment cycles and alloying additions are the key factors affecting the microstructure and mechanical properties of the cast steels. In this study an attempt was made to evaluate the influence of minor Mo addition on the microstructure and mechanical properties of conventionally heat treated cast micro-alloyed steels. The results of Jominy and dilatometry tests and also microstructural examinations revealed that Mo could effectively increase the hardenability of the investigated steel and change the microstructure features of the air-cooled samples. Acicular microstructure was the consequence of increasing the hardenability in Mo-added steel. Besides, it was found that Mo could greatly affect the isothermal bainitic transformation and higher fraction of martensite after cooling (from isothermal temperature was due to the Mo addition. The results of impact test indicated that the microstructure obtained in air-cooled Mo-added steel led to better impact toughness (28J in comparison with the base steel (23J. Moreover, Mo-added steel possessed higher hardness (291HV, yield (524MPa and tensile (1108MPa strengths compared to the base one.

  17. Concurrent multiscale modeling of microstructural effects on localization behavior in finite deformation solid mechanics

    Science.gov (United States)

    Alleman, Coleman N.; Foulk, James W.; Mota, Alejandro; Lim, Hojun; Littlewood, David J.

    2018-02-01

    The heterogeneity in mechanical fields introduced by microstructure plays a critical role in the localization of deformation. To resolve this incipient stage of failure, it is therefore necessary to incorporate microstructure with sufficient resolution. On the other hand, computational limitations make it infeasible to represent the microstructure in the entire domain at the component scale. In this study, the authors demonstrate the use of concurrent multiscale modeling to incorporate explicit, finely resolved microstructure in a critical region while resolving the smoother mechanical fields outside this region with a coarser discretization to limit computational cost. The microstructural physics is modeled with a high-fidelity model that incorporates anisotropic crystal elasticity and rate-dependent crystal plasticity to simulate the behavior of a stainless steel alloy. The component-scale material behavior is treated with a lower fidelity model incorporating isotropic linear elasticity and rate-independent J2 plasticity. The microstructural and component scale subdomains are modeled concurrently, with coupling via the Schwarz alternating method, which solves boundary-value problems in each subdomain separately and transfers solution information between subdomains via Dirichlet boundary conditions. In this study, the framework is applied to model incipient localization in tensile specimens during necking.

  18. Effects of high pressure on microstructure evolution and crystallization mechanisms during solidification of nickel

    Science.gov (United States)

    Zhang, Hai-Tao; Mo, Yun-Fei; Liu, Rang-Su; Tian, Ze-An; Liu, Hai-Rong; Hou, Zhao-Yang; Zhou, Li-Li; Liang, Yong-Chao; Peng, Ping

    2018-03-01

    To deeply understand the effects of high pressure on microstructural evolutions and crystallization mechanisms of liquid metal Ni during solidification process, MD simulation studies have been performed under 7 pressures of 0 ˜ 30 GPa, at cooling rate of 1.0 × 1011 K s-1. Adopting several microstructural analyzing methods, especially the cluster-type index method (CTIM-2) to analyze the local microstructures in the system. It is found that the pressure has important influence on the formation and evolution of microstructures, especially of the main basic clusters in the system. All the simulation systems are directly solidified into crystal structures, and the 1421, 1422, 1441 and 1661 bond-types, as well the FCC (12 0 0 0 12 0), HCP (12 0 0 0 6 6) and BCC (14 6 0 8 0 0) clusters play a key role in the microstructure transitions from liquid to crystal structures. The crystallization temperature T c is enhanced almost linearly with the increase of pressure. Highly interesting, it is found for the first time that there is an important phase transformation point from FCC to BCC structures between 20 ˜ 22.5 GPa during the solidification processes from the same initial liquid system at the same cooling rate. And the effect of increasing pressure is similar to that of decreasing cooling rate for the phase transformation of microstructures during solidification process of liquid metal Ni system, though they have different concrete effecting mechanisms.

  19. Microstructure and mechanical properties of a novel β titanium metallic composite by selective laser melting

    International Nuclear Information System (INIS)

    Vrancken, B.; Thijs, L.; Kruth, J.-P.; Van Humbeeck, J.

    2014-01-01

    Selective laser melting (SLM) is an additive manufacturing process in which functional, complex parts are produced by selectively melting consecutive layers of powder with a laser beam. This flexibility enables the exploration of a wide spectrum of possibilities in creating novel alloys or even metal–metal composites with unique microstructures. In this research, Ti6Al4V-ELI powder was mixed with 10 wt.% Mo powder. In contrast to the fully α′ microstructure of Ti6Al4V after SLM, the novel microstructure consists of a β titanium matrix with randomly dispersed pure Mo particles, as observed by light optical microscopy, scanning electron microscopy and X-ray diffraction. Most importantly, the solidification mechanism changes from planar to cellular mode. Microstructures after heat treatment indicate that the β phase is metastable and locate the β transus at ∼900 °C, and tensile properties are equal to or better than conventional β titanium alloys

  20. Effect of process parameters on microstructure and mechanical properties of friction stir welded joints: A review

    Science.gov (United States)

    Wanare, S. P.; Kalyankar, V. D.

    2018-04-01

    Friction stir welding is emerging as a promising technique for joining of lighter metal alloys due to its several advantages over conventional fusion welding processes such as low thermal distortion, good mechanical properties, fine weld joint microstructure, etc. This review article mainly focuses on analysis of microstructure and mechanical properties of friction stir welded joints. Various microstructure characterization techniques used by previous researchers such as optical microscopes, x-ray diffraction, electron probe microscope, transmission electron microscope, scanning electron microscopes with electron back scattered diffraction, electron dispersive microscopy, etc. are thoroughly overviewed and their results are discussed. The effects of friction stir welding process parameters such as tool rotational speed, welding speed, tool plunge depth, axial force, tool shoulder diameter to tool pin diameter ratio, tool geometry etc. on microstructure and mechanical properties of welded joints are studied and critical observations are noted down. The microstructure examination carried out by previous researchers on various zones of welded joints such as weld zone, heat affected zone and base metal are studied and critical remarks have been presented. Mechanical performances of friction stir welded joints based on tensile test, micro-hardness test, etc. are discussed. This article includes exhaustive literature review of standard research articles which may become ready information for subsequent researchers to establish their line of action.

  1. Microstructure, Mechanical Properties, and Toughening Mechanisms of a New Hot Stamping-Bake Toughening Steel

    Science.gov (United States)

    Lin, Tao; Song, Hong-Wu; Zhang, Shi-Hong; Cheng, Ming; Liu, Wei-Jie; Chen, Yun

    2015-09-01

    In this article, the hot stamping-bake toughening process has been proposed following the well-known concept of bake hardening. The influences of the bake time on the microstructure and the mechanical properties of the hot stamped-baked part were studied by means of scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and mechanical tests at room temperature. The results show that the amount of the retained austenite was nearly not changed by the bake process. Also observed were spherical Cu-rich precipitates of about 15 nm in martensite laths. According to the Orowan mechanism, their contribution of the Cu-rich precipitates to the strength is approximately 245 MPa. With the increase of the bake time, the tensile strength of the part was decreased, whereas both the ductility and the product of the tensile strength and ductility were increased then decreased. The tensile strength and ductility product and the tensile strength are as high as 21.9 GPa pct, 2086 MPa, respectively. The excellent combined properties are due to the transformation-induced plasticity effect caused by retained austenite.

  2. Influence of scandium on the microstructure and mechanical properties of A319 alloy

    International Nuclear Information System (INIS)

    Emadi, Daryoush; Rao, A.K. Prasada; Mahfoud, Musbah

    2010-01-01

    Recycling of aluminum scrap alloys by melting is gaining its importance in foundry sector. During recycling, some of the alloying elements present in scrap alloys eventually become trace/tramp impurities in the recycled alloy. These elements could potentially affect the alloy's microstructure and hence its mechanical properties. In the present work, an attempt has been made to investigate the effect of one of such trace elements on the microstructure and mechanical properties of A319 alloy. The element chosen for the present investigation is scandium (Sc). This paper discusses the effects of the additions of trace amount of Sc on the microstructure and mechanical properties of A319 alloy in as-cast, T6 and T7 heat treated conditions.

  3. The effect of simulating porcelain firing on the elemental composition, microstructure, and mechanical properties of electroformed gold restorations

    Directory of Open Access Journals (Sweden)

    Youssef S. Al Jabbari

    2016-09-01

    Conclusion: Although microstructure and elemental composition of electroformed Au crowns remain unchanged, the mechanical properties are significantly affected by the thermal treatment of porcelain firing.

  4. Synthesis, Properties, and Mechanism of Action of New Generation of Polycyclic Glycopeptide Antibiotics.

    Science.gov (United States)

    Olsufyeva, Eugenia N; Tevyashova, Anna N

    2017-01-01

    The increased resistance of glycopeptide based antibiotics has become a serious problem for the chemotherapy of infections triggered by resistant Gram-positive bacteria. This has motivated the urgent sincere efforts to develop potent glycopeptide-based antibiotics in both academy and industry research laboratories. Understanding of the mechanism of action of natural and modified glycopeptides is considered as the basis for the rational design of compounds with valuable properties to achieve the fundamental results. Several hydrophobic glycopeptide analogues active against resistant strains were developed during the last two decades. Three drugs, namely, oritavancin, telavancin and dalbavancin were approved by FDA in 2013-2014. It was found that hydrophobic derivatives act through different mechanisms without binding with the modified target of resistant bacteria. Types: Different types of chemical modifications led to several glycopeptide analogues active against Gram-negative bacteria as advocated by in vitro studies or demonstrating potent antiviral activity in the cell models. A new class of glycopeptide antibiotics with potent activity against sensitive and resistant bacterial strains has been recently reported with the aim to overcome the resistance, however, there are a lot of obscure problems in the complete understanding of their mechanisms of actions. In this review, we summarized the achievements of synthetic methods devoted to the construction of new polycyclic glycopeptide antibiotics and described the studies related to their mechanism of actions. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

  5. Microstructure And Mechanical Properties Of Lead Oxide- Thermoplastic Elas Tomer Composite

    International Nuclear Information System (INIS)

    Sudirman; Handayani, Ari; Darwinto, Tri; Teguh, Yulius S.P.P.; Sunarni, Anik; Marlijanti, Isni

    2000-01-01

    Research on microstructure and mechanical properties of lead oxide-thermoplastic elastomer composite with Pb 3 O 4 as lead oxide. Thermoplastic elastomer synthesized from natural rubber as the elastomer and methyl metacrilate as the thermoplastic and irradiated simultaneously with optimum gamma ray. Thermoplastic elastomer (NR-PMMA) grind in a laboplastomill and Pb 3 O 4 was added in varied amount of 10%. 30%. 40% and 50%wt.The results showed that mechanical properties (tensile strength and elongation break) decreased as the Pb 3 O 4 composition increased. Microstructure from SEM observation showed that Pb 3 O 4 distributed evenly and having function as filler in composite

  6. Microstructural and mechanical properties of pure aluminum, 5083 and 7075 alloys joined by friction stir welding

    Energy Technology Data Exchange (ETDEWEB)

    Yilmaz, Selim Sarper [Celal Bayar Univ., Manisa, Muradiye (Turkey)

    2012-07-01

    In this study, microstructural and mechanical properties of pure aluminum, 5083 and 7075 alloys joined by friction stir welding were investigated. Hardness, tensile, bending and impact tests were applied to the welded samples. In addition, optical and SEM tests were carried out. The effects of welding speed on microstructure and mechanical properties were investigated in these materials. Then, the optimal conditions for friction stir welding were determined for pure aluminum, 5083 and 7075 alloys. The maximum hardness was observed for 7075 while the minimum hardness was observed for pure aluminum. (orig.)

  7. Microstructure and Mechanical Properties of Graphene-Reinforced Titanium Matrix/Nano-Hydroxyapatite Nanocomposites.

    Science.gov (United States)

    Li, Feng; Jiang, Xiaosong; Shao, Zhenyi; Zhu, Degui; Zhu, Minhao

    2018-04-16

    Biomaterial composites made of titanium and hydroxyapatite (HA) powder are among the most important biomedicalmaterials due to their good mechanical properties and biocompatibility. In this work, graphene-reinforced titanium matrix/nano-hydroxyapatite nanocomposites were prepared by vacuum hot-pressing sintering. The microstructure and mechanical properties of graphene-reinforced titanium matrix/nano-hydroxyapatite nanocomposites with different graphene content were systematically investigated. Microstructures of the nanocomposites were examined by X-ray diffraction (XRD), back scattered electron imaging (BSE), scanning electron microscope (SEM) equipped with energy dispersive spectrometer (EDS), electron probe microanalyzer (EPMA), and transmission electron microscope (TEM). The mechanical properties were determined from microhardness, shear strength, and compressive strength. Results showed that during the high-temperature sintering process, complex chemical reactions occurred, resulting in new phases of nucleation such as Ca₃(PO₄)₂, Ti x P y , and Ti₃O.The new phases, which easily dropped off under the action of external force, could hinder the densification of sintering and increase the brittleness of the nanocomposites. Results demonstrated that graphene had an impact on the microstructure and mechanical properties of the nanocomposites. Based on the mechanical properties and microstructure of the nanocomposites, the strengthening and fracture mechanisms of the graphene-reinforced titanium matrix/nano-hydroxyapatite nanocomposites with different graphene content were analyzed.

  8. Microstructure and Mechanical Properties of Graphene-Reinforced Titanium Matrix/Nano-Hydroxyapatite Nanocomposites

    Directory of Open Access Journals (Sweden)

    Feng Li

    2018-04-01

    Full Text Available Biomaterial composites made of titanium and hydroxyapatite (HA powder are among the most important biomedicalmaterials due to their good mechanical properties and biocompatibility. In this work, graphene-reinforced titanium matrix/nano-hydroxyapatite nanocomposites were prepared by vacuum hot-pressing sintering. The microstructure and mechanical properties of graphene-reinforced titanium matrix/nano-hydroxyapatite nanocomposites with different graphene content were systematically investigated. Microstructures of the nanocomposites were examined by X-ray diffraction (XRD, back scattered electron imaging (BSE, scanning electron microscope (SEM equipped with energy dispersive spectrometer (EDS, electron probe microanalyzer (EPMA, and transmission electron microscope (TEM. The mechanical properties were determined from microhardness, shear strength, and compressive strength. Results showed that during the high-temperature sintering process, complex chemical reactions occurred, resulting in new phases of nucleation such as Ca3(PO42, TixPy, and Ti3O.The new phases, which easily dropped off under the action of external force, could hinder the densification of sintering and increase the brittleness of the nanocomposites. Results demonstrated that graphene had an impact on the microstructure and mechanical properties of the nanocomposites. Based on the mechanical properties and microstructure of the nanocomposites, the strengthening and fracture mechanisms of the graphene-reinforced titanium matrix/nano-hydroxyapatite nanocomposites with different graphene content were analyzed.

  9. Menadione (vitamin K enhances the antibiotic activity of drugs by cell membrane permeabilization mechanism

    Directory of Open Access Journals (Sweden)

    Jacqueline C. Andrade

    2017-01-01

    Full Text Available Menadione, vitamin K3, belongs to the class of lipid-soluble vitamins and lipophilic substances as menadione cause disturbances in the bacterial membrane, resulting in damage to the fundamental elements for the integrity of the membrane, thus allowing increased permeability. Accordingly, the aim of this study was to evaluate in vitro the antibiotic-modifying activity of menadione in multiresistant strains of Staphylococcus aureus, Pseudomonas aeruginosa and Escherichia coli, with a gradual increase in its subinhibitory concentration. In addition, menadione was compared with cholesterol and ergosterol for similarity in mechanism of drug modulatory action. Antibiotic-modifying activity and antibacterial effect were determined by the broth microdilution assay. Menadione, cholesterol and ergosterol showed modulatory activity at clinically relevant concentrations, characterizing them as modifiers of bacterial drug resistance, since they lowered the MIC of the antibiotics tested. This is the first report of the antibacterial activity of menadione and its potentiation of aminoglycosides against multiresistant bacteria.

  10. Microstructural evolution and mechanical properties of Ti–Zr beta titanium alloy after laser surface remelting

    International Nuclear Information System (INIS)

    Yao, Y.; Li, X.; Wang, Y.Y.; Zhao, W.; Li, G.; Liu, R.P.

    2014-01-01

    Highlights: • The surface mechanical properties of the alloy have been greatly improved. • Its grain size was decreased from 100 μm to 10 μm. • The metastable ω with the size of 20–50 nm was observed in the alloy after LSR. • The strengthening effect is mainly due to fine microstructure and strengthened phase. -- Abstract: The effects of laser surface remelting (LSR) on the microstructural evolution and surface mechanical properties of Ti–Zr beta titanium alloy were investigated. The surfaces of the Ti–Zr alloy was re-melted using a CO 2 laser. X-ray diffraction, Scanning electron microscope, Transmission electron microscope, nanoindentation, and microhardness analyses were performed to evaluate the microstructural and mechanical properties of the alloy. The results showed that the alloy microstructure in the remelting region was greatly refined and homogeneous compared with that in the base material because of the rapid remelting and resolidifying. Meanwhile, the metastable hexagonal ω phases with the size of 20–50 nm was found and uniformly distributed throughout the β matrix after LSR. Phase transformation and microstructural refinement were the major microstructural changes in the alloys after LSR. The microhardness and elastic modulus in the remelted region clearly increased by 92.9% and 21.78%, respectively, compared with those in the region without laser processing. The strengthening effect of LSR on the mechanical properties of the Ti–Zr alloy was also addressed. Our results indicated that LSR was an effective method of improving the surface mechanical properties of alloys

  11. The effect of thermal processing on microstructure and mechanical properties in a nickel-iron alloy

    Science.gov (United States)

    Yang, Ling

    The correlation between processing conditions, resulted microstructure and mechanical properties is of interest in the field of metallurgy for centuries. In this work, we investigated the effect of thermal processing parameters on microstructure, and key mechanical properties to turbine rotor design: tensile yield strength and crack growth resistance, for a nickel-iron based superalloy Inconel 706. The first step of the designing of experiments is to find parameter ranges for thermal processing. Physical metallurgy on superalloys was combined with finite element analysis to estimate variations in thermal histories for a large Alloy 706 forging, and the results were adopted for designing of experiments. Through the systematic study, correlation was found between the processing parameters and the microstructure. Five different types of grain boundaries were identified by optical metallography, fractography, and transmission electron microscopy, and they were found to be associated with eta precipitation at the grain boundaries. Proportions of types of boundaries, eta size, spacing and angle respect to the grain boundary were found to be dependent on processing parameters. Differences in grain interior precipitates were also identified, and correlated with processing conditions. Further, a strong correlation between microstructure and mechanical properties was identified. The grain boundary precipitates affect the time dependent crack propagation resistance, and different types of boundaries have different levels of resistance. Grain interior precipitates were correlated with tensile yield strength. It was also found that there is a strong environmental effect on time dependent crack propagation resistance, and the sensitivity to environmental damage is microstructure dependent. The microstructure with eta decorated on grain boundaries by controlled processing parameters is more resistant to environmental damage through oxygen embrittlement than material without eta

  12. Microstructure Deformation and Fracture Mechanism of Highly Filled Polymer Composites under Large Tensile Deformation

    International Nuclear Information System (INIS)

    Tao Zhangjiang; Ping Songdan; Mei Zhang; Cheng Zhaipeng

    2013-01-01

    The microstructure deformation and fracture mechanisms of particulate-filled polymer composites were studied based on microstructure observations in this paper. By using in-situ tensile test system under scanning electron microscopy, three different composites composed of polymer binder filled by three different types of particles, namely Al particles, AP particles and HMX particles, with the same total filler content were tested. The roles of initial microstructure damage and particle type on the microstructure deformation and damage are highlighted. The results show that microstructure damage starts with the growth of the initial microvoids within the binders or along the binder/particle interfaces. With the increase of strain, the microstructure damages including debonding at the particle/binder interface and tearing of the binder lead to microvoid coalescence, and finally cause an abrupt fracture of the samples. Coarse particles lead to an increase of debonding at the particle/binder interface both in the initial state and during the loading process, and angular particles promote interface debonding during the loading process.

  13. Molecular Level Investigation of Staphylococci’s Resistance Mechanisms to Antibiotics

    Directory of Open Access Journals (Sweden)

    Lavinia Lorena PRUTEANU

    2017-09-01

    Full Text Available Polymerase chain reaction (PCR techniques development allows elaboration of many assays for identification of bacteria’s resistance mechanisms to antibiotics. Following this idea, the results of molecular level investigation of bacteria’s resistance mechanisms to antibiotics may give many opportunities to find more rapid methods for identifying the genes which are responsible for antibiotic resistance induction. The aim of this study was to investigate antibiotic resistance genes in Staphylococcus bacteria on molecular level. As classes of antibiotics it was used macrolides-lincosamides-streptogramin B (MLSB and beta-lactams. In the proposed study the bacterial strains are represented by 50 isolates of Staphylococcus. The bacterial strains were analyzed using polymerase chain reaction to identify the nuc, tuf, tst, sea, pathogenic activity genes. After this, the bacteria were tested for ermA, ermB, ermC genes and for mecA, femA which are involved in resistance to macrolides, lincosamides, streptogramin B and to beta-lactams, respectively. The presence or the absence of these genes confirms that tested strains are resistant to specific antibiotic or not. Bacteria pathogenic activity was emphasized by genes as follows: sea (enterotoxin which was found at all isolates, tst (toxic shock toxin gene was not detected in any of isolates and tuf gene (elongation factor was obtained with one pair of primers. Resistance to beta-lactams was evidenced by the presence of mecA in all isolates and femA in some strains. Each of ermC, ermA and ermB, macrolides-lincosamides-streptogramin B resistance genes, were detected.

  14. Microstructure evolution and mechanical properties of a particulate reinforced magnesium matrix composites forged at elevated temperatures

    International Nuclear Information System (INIS)

    Deng, K.K.; Wu, K.; Wang, X.J.; Wu, Y.W.; Hu, X.S.; Zheng, M.Y.; Gan, W.M.; Brokmeier, H.G.

    2010-01-01

    SiCp/AZ91 magnesium matrix composite was fabricated by stir casting. The as-cast ingots were cut into cylindrical billets, and then forged at different temperatures (320, 370, 420, 470 and 520 deg. C) at a constant RAM speed of 15 mm/s with 50% reduction. The microstructure evolution of the composites during forging was investigated by optical microscope, scanning electron microscope, and transmission electron microscope. The texture of the forged composites was measured by neutron diffraction. Mechanical properties of the composite at different forging temperatures were tested by tensile tests at room temperature. It was found that a strong basal plane texture formed during forging, and the intensity of basal plane texture weakened as forging temperatures increased. The particle distribution in the composite was significantly improved by hot forging. Typical microstructures were obtained after forging at different temperatures and the composite with different microstructures offered different mechanical properties during tensile test.

  15. Effect of graphene orientation on microstructure and mechanical properties of silicon nitride ceramics

    Directory of Open Access Journals (Sweden)

    Yubing Zhang

    2018-03-01

    Full Text Available Mechanical properties and microstructure of graphene platelets reinforced Si3N4 composites have been investigated and compared to monolithic Si3N4. The microstructure shows that graphene platelets are parallel to each other and perpendicular to the hot pressing direction. Fracture toughness and flexural strength of composite with 1 wt.% graphene measured on polished surface perpendicular to hot pressing direction are 8.7 MPa·m1/2 and 892 MPa, respectively, which are increased about 14.5% and 20.2% compared with that parallel to hot pressing direction. The anisotropy of microstructure and mechanical properties of composites can be explained by the intrinsic anisotropy of graphene as well as the crack deflection energy release rate and the weak boundary bonding between graphene and Si3N4 caused by the thermal expansion mismatch.

  16. Effects of Static Magnetic Fields on the Physical, Mechanical, and Microstructural Properties of Cement Pastes

    Directory of Open Access Journals (Sweden)

    Juan J. Soto-Bernal

    2015-01-01

    Full Text Available This paper presents the results of an experimental study carried out to comprehend the physical, mechanical, and microstructural behavior of cement pastes subjected to static magnetic fields while hydrating and setting. The experimental methodology consisted in exposing fresh cement pastes to static magnetic fields at three different magnetic induction strengths: 19.07, 22.22, and 25.37 Gauss. The microstructural characterization makes evident that there are differences in relation to amount and morphology of CSH gel; the amount of CSH is larger and its morphology becomes denser and less porous with higher magnetostatic induction strengths; it also shows the evidence of changes in the mineralogical composition of the hydrated cement pastes. The temperature increasing has no negative effects over the cement paste compressive strength since the magnetostatic field affects the process of hydration through a molecular restructuring process, which makes cement pastes improve microstructurally, with a reduced porosity and a higher mechanical strength.

  17. Influence of cobalt, tantalum, and tungsten on the microstructure and mechanical properties of superalloy single crystals

    International Nuclear Information System (INIS)

    Nathal, M.V.; Ebert, L.J.

    1982-01-01

    The influence of Co, Ta, and W on the microstructure and mechanical properties of nickel base super-alloy single crystals was investigated. A matrix of alloys was based on Mar-M 247 stripped of C, B, Zr, and Hf. The microstructures of the alloys were examined using optical and electron microscopy, phase extraction, X-ray diffraction, and differential thermal analysis. Tensile and creep-rupture tests were performed at 1000 C. An increase in tensile and creep strength resulted when Co was removed from alloys containing high refractory metal contents, but Co effects were negligible for alloys with lower refractory metal levels. In the composition range studied, W was more effective than Ta in increasing the creep resistance. The mechanical properties are discussed in relation to the microstructures of the alloys

  18. Influence of cobalt, tantalum, and tungsten on the microstructure and mechanical properties of superalloy single crystals

    Science.gov (United States)

    Nathal, M. V.; Ebert, L. J.

    1982-01-01

    The influence of Co, Ta, and W on the microstructure and mechanical properties of nickel base super-alloy single crystals was investigated. A matrix of alloys was based on Mar-M 247 stripped of C, B, Zr, and Hf. The microstructures of the alloys were examined using optical and electron microscopy, phase extraction, X-ray diffraction, and differential thermal analysis. Tensile and creep-rupture tests were performed at 1000 C. An increase in tensile and creep strength resulted when Co was removed from alloys containing high refractory metal contents, but Co effects were negligible for alloys with lower refractory metal levels. In the composition range studied, W was more effective than Ta in increasing the creep resistance. The mechanical properties are discussed in relation to the microstructures of the alloys.

  19. Evolution of microstructure and mechanical properties in naturally aged 7050 and 7075 Al friction stir welds

    Energy Technology Data Exchange (ETDEWEB)

    Fuller, Christian B., E-mail: christian.fuller@yahoo.com [Rockwell Scientific, 1049 Camino Dos Rios, Thousand Oaks, CA 93021 (United States); Mahoney, Murray W., E-mail: murraymahoney@comcast.net [Rockwell Scientific, 1049 Camino Dos Rios, Thousand Oaks, CA 93021 (United States); Calabrese, Mike [Rockwell Scientific, 1049 Camino Dos Rios, Thousand Oaks, CA 93021 (United States); Micona, Leanna [The Boeing Company, P.O. Box 3707 MC 19-HP, Seattle, WA 98124 (United States)

    2010-04-15

    The microstructural and mechanical property evolution of friction stir welded 7050-T7651 and 7075-T651 Al alloys were examined as a function of room temperature (natural) aging for up to 67,920 h. During the range of aging times studied, transverse tensile strengths continuously increased, and are still increasing, with improvements of 24% and 29% measured for the 7050-T7651 and 7075-T651 Al alloy friction stir welds, respectively. Microstructural evolution within the weld nugget and heat-affected zone was evaluated with both transmission electron microscopy (TEM) and differential scanning calorimetry (DSC). Formation of a high volume fraction of GP(II) zones produced a majority of the strength improvement within the weld nugget and HAZ regions. The rational for the microstructural changes are discussed in light of the mechanical properties.

  20. The microstructure and mechanical properties of a welded molybdenum alloy

    International Nuclear Information System (INIS)

    Wadsworth, J.; Morse, G.R.; Chewey, P.M.

    1983-01-01

    Wrought Ti-Zr-Mo (TZM) alloy has been welded using electron beam, laser and tungsten-inert gas welding techniques. The microstructure, tensile properties and fracture surfaces of these welded samples have been examined. Although the welds have been found to be defect free, a disparity in grain size leading to large strength differences exists between the weld and parent metal. Tensile tests have revealed that fusion zone strengths are typical of those expected for the grain size in the weld metal. However, brittle behavior is also always observed, with fracture initiating at grain boundaries and propagating by intergranular and cleavage modes. Auger electron spectroscopy analysis has eliminated oxygen or other interstitial elements as sources of grain boundary embrittlement. It is proposed that brittle behavior is a result of local high strain rates in the weld zone. These local high strain rates arise from the strength difference between the wrought parent metal and the weld metal as a result of the strong grain size dependence of TZM. It is shown that, either by reducing the strain rate of testing or by removing the grain size difference between the parent and weld metals by heat treatment, significant ductility can in fact be achieved in tensile-tested butt-welded TZM. Thus, it is proposed that TZM welds are not inherently brittle as had commonly been believed. (Auth.)

  1. Microstructural Architecture, Microstructures, and Mechanical Properties for a Nickel-Base Superalloy Fabricated by Electron Beam Melting

    Science.gov (United States)

    Murr, L. E.; Martinez, E.; Gaytan, S. M.; Ramirez, D. A.; Machado, B. I.; Shindo, P. W.; Martinez, J. L.; Medina, F.; Wooten, J.; Ciscel, D.; Ackelid, U.; Wicker, R. B.

    2011-11-01

    Microstructures and a microstructural, columnar architecture as well as mechanical behavior of as-fabricated and processed INCONEL alloy 625 components produced by additive manufacturing using electron beam melting (EBM) of prealloyed precursor powder are examined in this study. As-fabricated and hot-isostatically pressed ("hipped") [at 1393 K (1120 °C)] cylinders examined by optical metallography (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive (X-ray) spectrometry (EDS), and X-ray diffraction (XRD) exhibited an initial EBM-developed γ″ (bct) Ni3Nb precipitate platelet columnar architecture within columnar [200] textured γ (fcc) Ni-Cr grains aligned in the cylinder axis, parallel to the EBM build direction. Upon annealing at 1393 K (1120 °C) (hot-isostatic press (HIP)), these precipitate columns dissolve and the columnar, γ, grains recrystallized forming generally equiaxed grains (with coherent {111} annealing twins), containing NbCr2 laves precipitates. Microindentation hardnesses decreased from 2.7 to 2.2 GPa following hot-isostatic pressing ("hipping"), and the corresponding engineering (0.2 pct) offset yield stress decreased from 0.41 to 0.33 GPa, while the UTS increased from 0.75 to 0.77 GPa. However, the corresponding elongation increased from 44 to 69 pct for the hipped components.

  2. Microstructure and mechanical properties of laminated Al–Cu–Mg ...

    Indian Academy of Sciences (India)

    2017-11-29

    Nov 29, 2017 ... Initially, aluminium, copper and magnesium strips were alternatively stacked together. Then these ... These differences in mechanical behaviour have been attributed to ... hand, Cu has a good formability and a good corrosion resis- tance [16]. .... Under ideal conditions, for two layers with the same mechan-.

  3. Mutual associations among microstructural, physical and mechanical properties of human cancellous bone

    DEFF Research Database (Denmark)

    Ding, Ming; Odgaard, A; Danielsen, CC

    2002-01-01

    structure and mechanical properties. In this study, 160 cancellous bone specimens were produced from 40 normal human tibiae aged from 16 to 85 years at post-mortem. The specimens underwent micro-CT and the microstructural properties were calculated using unbiased three-dimensional methods. The specimens...... were tested to determine the mechanical properties and the physical/compositional properties were evaluated. The type of structure together with anisotropy correlated well with Young's modulus of human tibial cancellous bone. The plate-like structure reflected high mechanical stress and the rod......-like structure low mechanical stress. There was a strong correlation between the type of trabecular structure and the bone-volume fraction. The most effective microstructural properties for predicting the mechanical properties of cancellous bone seem to differ with age....

  4. Influence of solution annealing on microstructure and mechanical properties of Maraging 300 steel

    Energy Technology Data Exchange (ETDEWEB)

    Lima Filho, Venceslau Xavier; Barros, Isabel Ferreira; Abreu, Hamilton Ferreira Gomes de, E-mail: venceslau@ifce.edu.br [Universidade Federal do Ceara (UFC), Fortaleza, CE (Brazil). Departamento de Engenharia Metalurgica e Materiais. Laboratorio de Caracterizacao de Materiais, Metalurgia Fisica e Grupo de Pesquisa de Transformacao de Fase

    2017-01-15

    Maraging 300 belongs to a family of metallic materials with extremely high mechanical strength and good toughness. Some works have been published about aging temperatures that improve ultimate strength resistance with acceptable toughness levels in this steel family, where the prior austenite grain size obtained by different solution annealing temperature influence in the final mechanical properties. Solution annealing temperatures ranging from 860 °C to 1150 deg C and were kept constant until the aging temperature. These treatments were used in order to investigate their influence on the microstructure and mechanical properties of maraging steel 300, especially with regard to toughness. The characterization of the microstructure was performed by optical microscopy, scanning electron microscope (SEM) and X-ray diffraction (XRD). Mechanical properties were evaluated by Rockwell C hardness and Charpy impact tests. The results showed that there is a temperature range where one can get some improvement in toughness without a large loss of mechanical strength. (author)

  5. Bacillus subtilis as a Platform for Molecular Characterisation of Regulatory Mechanisms of Enterococcus faecalis Resistance against Cell Wall Antibiotics

    OpenAIRE

    Fang, Chong; Stiegeler, Emanuel; Cook, Gregory M.; Mascher, Thorsten; Gebhard, Susanne

    2014-01-01

    To combat antibiotic resistance of Enterococcus faecalis, a better understanding of the molecular mechanisms, particularly of antibiotic detection, signal transduction and gene regulation is needed. Because molecular studies in this bacterium can be challenging, we aimed at exploiting the genetically highly tractable Gram-positive model organism Bacillus subtilis as a heterologous host. Two fundamentally different regulators of E. faecalis resistance against cell wall antibiotics, the bacitra...

  6. An investigation of deformed microstructure and mechanical properties of Zircaloy-4 processed through multiaxial forging

    Energy Technology Data Exchange (ETDEWEB)

    Fuloria, Devasri; Nageswararao, P. [Department of Metallurgical and Materials Engineering & Centre of Nanotechnology, IIT Roorkee, Roorkee 247667 (India); Jayaganthan, R., E-mail: rjayafmt@iitr.ernet.in [Department of Metallurgical and Materials Engineering & Centre of Nanotechnology, IIT Roorkee, Roorkee 247667 (India); Department of Engineering Design, Indian Institute of Technology Madras, Chennai 600036 (India); Jha, S. [Nuclear Fuel Complex Limited, Hyderabad 501301 (India); Srivastava, D. [Materials Science Division, Bhabha Atomic Research Centre, Mumbai 40085 (India)

    2016-04-15

    In the present work, the mechanical behavior of Zircaloy-4 subjected to various deformation strains by multiaxial forging (MAF) at cryogenic temperature (CT) was investigated. The alloy was strained up to different number of cycles, viz., 6 cycles, 9 cycles, and 12 cycles at cumulative strains of 2.96, 4.44, and 5.91, respectively. The mechanical properties of the alloy were investigated by performing the universal tensile test and the Vickers hardness test. Both the test showed improvement in the ultimate tensile strength and hardness value by 51% and 26%, respectively, at the highest cumulative strain of 5.91. The electron backscattered diffraction (EBSD) measurement and transmission electron microscopy (TEM) were used for analyzing the deformed microstructure. The microstructures of the alloy underwent deformation at various cumulative strains/cycles showed grain refinement with the evolution of shear and twin bands that were highest for the alloy deformed at the highest number of cycles. The effective grain refinement was due to twins formation and their intersection, which led to the improvement in mechanical properties of the MAFed alloy, as observed in the present work. - Highlights: • Zircaloy-4 was subjected to MAF at cryogenic temperature. • Microstructural evolution was studied through EBSD and TEM. • Deformed microstructure was marked with various types of twinning and shear banding. • Twins formations are responsible for effective grain refinement and enhanced mechanical properties.

  7. Microstructural, mechanical, corrosion and cytotoxicity characterization of the hot forged FeMn30(wt.%) alloy

    Czech Academy of Sciences Publication Activity Database

    Čapek, Jaroslav; Kubásek, J.; Vojtěch, D.; Jablonská, E.; Lipov, J.; Ruml, T.

    2016-01-01

    Roč. 58, Jan (2016), s. 900-908 ISSN 0928-4931 R&D Projects: GA ČR GBP108/12/G043 Institutional support: RVO:68378271 Keywords : FeMn alloys * biodegradability * cytotoxicity * microstructure * mechanical properties Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 4.164, year: 2016

  8. Microstructural characterization of mechanically alloyed Al–Cu–Mn alloy with zirconium

    Energy Technology Data Exchange (ETDEWEB)

    Prosviryakov, A.S., E-mail: pro.alex@mail.ru; Shcherbachev, K.D.; Tabachkova, N.Yu.

    2015-01-19

    An evolution of Al–Cu–Mn alloy microstructure during its mechanical alloying with zirconium 20 wt% and after subsequent annealing was studied by X-ray diffraction, light microscopy and transmission electron microscopy. The effect of milling time on powder microhardness, Al lattice parameter, lattice microstrain and crystallite size was determined.

  9. Mechanical Properties and Microstructural Characterization of Aged Nickel-based Alloy 625 Weld Metal

    Science.gov (United States)

    Silva, Cleiton Carvalho; de Albuquerque, Victor Hugo C.; Miná, Emerson Mendonça; Moura, Elineudo P.; Tavares, João Manuel R. S.

    2018-03-01

    The aim of this work was to evaluate the different phases formed during solidification and after thermal aging of the as-welded 625 nickel-based alloy, as well as the influence of microstructural changes on the mechanical properties. The experiments addressed aging temperatures of 650 and 950 °C for 10, 100, and 200 hours. The samples were analyzed by electron microscopy, microanalysis, and X-ray diffraction in order to identify the secondary phases. Mechanical tests such as hardness, microhardness, and Charpy-V impact test were performed. Nondestructive ultrasonic inspection was also conducted to correlate the acquired signals with mechanical and microstructural properties. The results show that the alloy under study experienced microstructural changes when aged at 650 °C. The aging was responsible by the dissolution of the Laves phase formed during the solidification and the appearance of γ″ phase within interdendritic region and fine carbides along the solidification grain boundaries. However, when it was aged at 950 °C, the Laves phase was continuously dissolved and the excess Nb caused the precipitation of the δ-phase (Ni3Nb), which was intensified at 10 hours of aging, with subsequent dissolution for longer periods such as 200 hours. Even when subjected to significant microstructural changes, the mechanical properties, especially toughness, were not sensitive to the dissolution and/or precipitation of the secondary phases.

  10. Microstructural and mechanical characterization of the ferritic martensitic steel eurofer'97 after simulated service conditions

    International Nuclear Information System (INIS)

    Fernandez, P.; Lancha, A. M.; Lapena, J.

    2002-01-01

    This report details the metallurgical characterization of the Eurofer'97 steel thermally aged in the range of temperatures from 400 degree centigrade to 600 degree centigrade up to 10000 H, microstructural studies and mechanical testing (hardness, tensile, Charpy and low cycle fatigue test) have been carried out

  11. Mechanical, electrical and microstructural properties of cement-based materials in conditions of stray current flow

    NARCIS (Netherlands)

    Susanto, A.; Koleva, D.A.; Copuroglu, O.; Van Beek, C.; Van Breugel, K.

    2013-01-01

    This investigation presents a comparative study on mechanical properties, electrical resistivity and microstructure of mortar under DC current, compared to mortar in rest (no current) conditions. Monitoring was performed from 24h after casting until 84 days of cement hydration. A current density

  12. Microstructure distribution and mechanical properties prediction of boron alloy during hot forming using FE simulation

    International Nuclear Information System (INIS)

    Cui Junjia; Lei Chengxi; Xing Zhongwen; Li Chunfeng

    2012-01-01

    Highlights: ► We model microstructural evolution during hot forming using a metallo-thermo-mechanical model. ► The effect of water-cooled on temperature distribution of blank and tools was investigated. ► The effect of process parameters on microstructure and mechanical properties were investigated. ► FE results were compared to experimental results and the errors of mechanical properties were in a reasonable scope. - Abstract: As a theoretical tool predicting microstructural evolution of boron alloy, the finite element (FE) method has received considerable attention in recent years. In this work, we focus on the boron alloy under non-isothermal hot forming conditions and establish a fully coupled metallo-thermo-mechanical model taking account of cooling and oxide. Based on the proposed model, we investigate the phase transformation and predict the hardness during the hot forming process via FE simulation. In addition, according to the hardness, the tensile strength during non-isothermal forming is predicted. Supporting the feasibility of the proposed model is the experiments where BR1500HS alloy is hot-worked at various conditions that derive a promising agreement of microstructures, hardness, and tensile strength to the simulation data.

  13. Effects of organic additives on microstructure and mechanical ...

    Indian Academy of Sciences (India)

    Administrator

    State Key Laboratory for Mechanical Behaviour of Materials, Xi'an Jiaotong University, Xi'an 710049, P.R. China ... porosity are of interest for engineering applications, as gas filters ... Flow diagram for fabricating porous silicon nitride samples.

  14. Wave dynamics and composite mechanics for microstructured materials and metamaterials

    CERN Document Server

    2017-01-01

    This volume deals with topical problems concerning technology and design in construction of modern metamaterials. The authors construct the models of mechanical, electromechanical and acoustical behavior of the metamaterials, which are founded upon mechanisms existing on micro-level in interaction of elementary structures of the material. The empiric observations on the phenomenological level are used to test the created models. The book provides solutions, based on fundamental methods and models using the theory of wave propagation, nonlinear theories and composite mechanics for media with micro- and nanostructure. They include the models containing arrays of cracks, defects, with presence of micro- and nanosize piezoelectric elements and coupled physical-mechanical fields of different nature. The investigations show that the analytical, numerical and experimental methods permit evaluation of the qualitative and quantitative properties of the materials of this sort, with diagnosis of their effective characte...

  15. Effect of cooling rate on the microstructure and mechanical ...

    Indian Academy of Sciences (India)

    2Research & Development Centre for Iron and Steel, Steel Authority of India ... Boron; ultra-high strength steel; thermo-mechanical simulation; CCT diagram; banded structure. 1. ... reduced flow stress is encountered, the spring back phenom-.

  16. TiTaCN-Co cermets prepared by mechanochemical technique: microstructure and mechanical properties

    OpenAIRE

    Fides, Martin; Hvizdoš, P.; Balko, Ján; Chicardi, E.; Gotor, F.J.

    2016-01-01

    Microstructure and mechanical characterization of (Ti,Ta)(C,N)-Co based solid solution cermets prepared by two mechanochemical synthesis processes (one- and two-step milling) and a pressureless sintering in protective helium atmosphere. Materials with composition of TixTa1- xC0.5N0.5-20%Co with two different Ti/Ta ratios (x = 0.9 and x = 0.95) were developed to prepare four groups of experimental materials. Microstructures were observed using confocal microscopy and grain size was ev...

  17. Microstructural and Mechanical Characterization of Shear Formed Aluminum Alloys for Airframe and Space Applications

    Science.gov (United States)

    Troeger, L. P.; Domack, M. S.; Wagner, J. A.

    1998-01-01

    Advanced manufacturing processes such as near-net-shape forming can reduce production costs and increase the reliability of launch vehicle and airframe structural components through the reduction of material scrap and part count and the minimization of joints. The current research is an investigation of the processing-microstructure-property relationship for shear formed cylinders of the Al-Cu-Li-Mg-Ag alloy 2195 for space applications and the Al-Cu-Mg-Ag alloy C415 for airframe applications. Cylinders which have undergone various amounts of shear-forming strain have been studied to assess the microstructure and mechanical properties developed during and after shear forming.

  18. Investigation of a hot-pressed Nb–Ti–Al alloy: Mechanical alloying, microstructure and mechanical property

    Energy Technology Data Exchange (ETDEWEB)

    Shi, Zhiwu; Wei, Hua; Zhang, Hongyu; Jin, Tao; Sun, Xiaofeng; Zheng, Qi, E-mail: qzheng@imr.ac.cn

    2016-01-10

    The Nb–23Ti–15Al (at%) alloy was prepared by mechanical alloying (MA) and hot-pressing (HPing). The microstructure evolution of powder particles during MA and its influence on the microstructure and mechanical properties of the hot-pressed (HPed) alloy have been investigated. The powder and HPed alloy were characterized via X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results indicate that particle size increases in the first stage and then decreases in the second stage during MA; as milling speed increases, mechanically alloyed (MAed) powder with convoluted elemental lamellae, homogeneous Nb solid-solution and an amorphous phase could be obtained respectively in 24 h. Higher homogeneity in microstructure and composition of the MAed powder particles promotes the precipitation of the δ phase and refines the β and Ti(O,C) phases in the HPed alloy. Moreover, due to the phase equilibrium changes caused by Fe and Cr in the amorphous powder, σ phase appears in the alloy as a stable phase instead of the δ phase. Properly MAed powder contributes to higher hardness of the HPed alloy, for reasons of microstructure refinement and sufficient precipitating of strengthening phases.

  19. Investigation of a hot-pressed Nb–Ti–Al alloy: Mechanical alloying, microstructure and mechanical property

    International Nuclear Information System (INIS)

    Shi, Zhiwu; Wei, Hua; Zhang, Hongyu; Jin, Tao; Sun, Xiaofeng; Zheng, Qi

    2016-01-01

    The Nb–23Ti–15Al (at%) alloy was prepared by mechanical alloying (MA) and hot-pressing (HPing). The microstructure evolution of powder particles during MA and its influence on the microstructure and mechanical properties of the hot-pressed (HPed) alloy have been investigated. The powder and HPed alloy were characterized via X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results indicate that particle size increases in the first stage and then decreases in the second stage during MA; as milling speed increases, mechanically alloyed (MAed) powder with convoluted elemental lamellae, homogeneous Nb solid-solution and an amorphous phase could be obtained respectively in 24 h. Higher homogeneity in microstructure and composition of the MAed powder particles promotes the precipitation of the δ phase and refines the β and Ti(O,C) phases in the HPed alloy. Moreover, due to the phase equilibrium changes caused by Fe and Cr in the amorphous powder, σ phase appears in the alloy as a stable phase instead of the δ phase. Properly MAed powder contributes to higher hardness of the HPed alloy, for reasons of microstructure refinement and sufficient precipitating of strengthening phases.

  20. Microstructure and Mechanical Properties of an Al-Li-Mg-Sc-Zr Alloy Subjected to ECAP

    Directory of Open Access Journals (Sweden)

    Anna Mogucheva

    2016-10-01

    Full Text Available The effect of post-deformation solution treatment followed by water quenching and artificial aging on microstructure and mechanical properties of an Al-Li-Mg-Sc-Zr alloy subjected to equal-channel angular pressing (ECAP was examined. It was shown that the deformed microstructure produced by ECAP remains essentially unchanged under solution treatment. However, extensive grain refinement owing to ECAP processing significantly affects the precipitation sequence during aging. In the aluminum-lithium alloy with ultrafine-grained (UFG microstructure, the coarse particles of the S1-phase (Al2LiMg precipitate on high-angle boundaries; no formation of nanoscale coherent dispersoids of the δ′-phase (Al3Li occurs within grain interiors. Increasing the number of high-angle boundaries leads to an increasing portion of the S1-phase. As a result, no significant increase in strength occurs despite extensive grain refinement by ECAP.

  1. Microstructural, mechanical characterisation and fractography of As-cast Ti-Al alloy

    International Nuclear Information System (INIS)

    Hamzah, E.; Ong, W.R.; Tamin, M.N.

    2007-01-01

    The effect of alloying element, namely chromium (Cr) on the microstructures, mechanical characterization and fracture surface of gamma titanium aluminide (Ti Al) has been studied. Micro-hardness and fatigue crack growth tests were performed on as-cast samples with composition of Ti-48at%Al and Ti-48%Al-2at%Cr. Prior to the micro-hardness tests; samples were metallurgically prepared for microstructural and structural analysis using optical microscope and scanning electron microscope. Field emission scanning electron microscope (FESEM) technique was employed to investigate the fracture surface of sample after fatigue crack growth test. Micro-hardness tests results showed increasing hardness value of Ti-48Al alloys when chromium is added. Both titanium aluminide alloys exhibited a nearly lamellae microstructure. However, finer laths of plates in lamellar structure have been observed in Ti-48at%Al-2at%Cr. FESEM micrograph of surface fracture indicates a mixed mode of failure for both alloys. (author)

  2. [Microstructure and mechanical property of a new IPS-Empress 2 dental glass-ceramic].

    Science.gov (United States)

    Luo, Xiao-ping; Watts, D C; Wilson, N H F; Silsons, N; Cheng, Ya-qin

    2005-03-01

    To investigate the microstructure and mechanical properties of a new IPS-Empress 2 dental glass-ceramic. AFM, SEM and XRD were used to analyze the microstructure and crystal phase of IPS-Empress 2 glass-ceramic. The flexural strength and fracture toughness were tested using 3-point bending method and indentation method respectively. IPS-Empress 2 glass-ceramic mainly consisted of lithium disilicate crystal, lithium phosphate and glass matrix, which formed a continuous interlocking structure. The crystal phases were not changed before and after hot-pressed treatment. AFM showed nucleating agent particles of different sizes distributed on the highly polished ceramic surface. The strength and fracture toughness were 300 MPa and 3.1 MPam(1/2). The high strength and fracture toughness of IPS-Empress 2 glass ceramic are attributed to the fine lithium disilicate crystalline, interlocking microstructure and crack deflection.

  3. Evolution of microstructure and mechanical properties of Al 6061 alloy tube in cyclic rotating bending process

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Zicheng, E-mail: zhangzicheng2004@126.com [School of Mechanical Engineering and Automation, Northeastern University, P.O. Box 319, No. 11 Lane 3, Wenhua Rd., Heping District, Shenyang 110819, Liaoning Province (China); Department of Mechanical Engineering, Tokyo Metropolitan University, 1-1 Minami-Osawa, Hachioji-shi, Tokyo (Japan); Shao, Shuai [School of Mechanical Engineering and Automation, Northeastern University, P.O. Box 319, No. 11 Lane 3, Wenhua Rd., Heping District, Shenyang 110819, Liaoning Province (China); Manabe, Ken-ichi [Department of Mechanical Engineering, Tokyo Metropolitan University, 1-1 Minami-Osawa, Hachioji-shi, Tokyo (Japan); Kong, Xiangwei [School of Mechanical Engineering and Automation, Northeastern University, P.O. Box 319, No. 11 Lane 3, Wenhua Rd., Heping District, Shenyang 110819, Liaoning Province (China); Li, Yanmei [State Key Laboratory of Rolling and Automation, Northeastern University, Shenyang 110004, Liaoning (China)

    2016-10-31

    To refine the microstructure and improve the mechanical properties of metal tubes, a new concept of severe plastic deformation process of cyclic rotating bending (CRB) was newly introduced. The current study focused on the investigation of evolution of microstructure and mechanical properties of Al 6061 tube in the CRB process with different deformation conditions. For this purpose, the CRB processes were performed with different deformation temperatures, bending angles and deformation times. The tensile test and Vickers hardness test were employed to evaluate the tensile properties and micro-hardness of the tube, respectively. While the Optical Microscope and Scanning Electronic Microscope equipped with Electron Back-Scattered Diffraction were utilized for the microstructure characterizations. The results shows that the deformation temperature, bending angle and deformation time have the strong influences on the mechanical properties and microstructure of the tubes processed by the CRB process. As a result, the tube with an average grain size of about 55 µm, as well as ultimate tensile strength of 244 MPa and total elongation of 10.05% was successfully obtained with the optimized deformation condition of the CRB process with a temperature of 100 °C, bending angle of 174°, the rotation speed of 20 r/min, and deformation time of 5 min, respectively.

  4. Investigation of microstructural and mechanical properties of cell walls of closed-cell aluminium alloy foams

    Energy Technology Data Exchange (ETDEWEB)

    Islam, M.A.; Kader, M.A.; Hazell, P.J.; Brown, A.D. [School of Engineering and Information Technology, UNSW Canberra, ACT 2610 (Australia); Saadatfar, M. [Department of Applied Mathematics, Australian National University, Canberra ACT 0200 (Australia); Quadir, M.Z [Electron Microscope Unit, Mark Wainwright Analytical Centre (MWAC), The University of New South Wales, Sydney, NSW 2052 (Australia); Microscopy and Microanalysis Facility (MMF), John de Laeter Centre (JdLC), Curtin University, WA 6102 (Australia); Escobedo, J.P., E-mail: J.Escobedo-Diaz@adfa.edu.au [School of Engineering and Information Technology, UNSW Canberra, ACT 2610 (Australia)

    2016-06-01

    This study investigates the influence of microstructure on the strength properties of individual cell walls of closed-cell stabilized aluminium foams (SAFs). Optical microscopy (OM), micro-computed X-ray tomography (µ-CT), electron backscattering diffraction (EBSD), and energy dispersive X-ray spectroscopy (EDS) analyses were conducted to examine the microstructural properties of SAF cell walls. Novel micro-tensile tests were performed to investigate the strength properties of individual cell walls. Microstructural analysis of the SAF cell walls revealed that the material consists of eutectic Al-Si and dendritic a-Al with an inhomogeneous distribution of intermetallic particles and micro-pores (void defects). These microstructural features affected the micro-mechanism fracture behaviour and tensile strength of the specimens. Laser-based extensometer and digital image correlation (DIC) analyses were employed to observe the strain fields of individual tensile specimens. The tensile failure mode of these materials has been evaluated using microstructural analysis of post-mortem specimens, revealing a brittle cleavage fracture of the cell wall materials. The micro-porosities and intermetallic particles reduced the strength under tensile loading, limiting the elongation to fracture on average to ~3.2% and an average ultimate tensile strength to ~192 MPa. Finally, interactions between crack propagation and obstructing intermetallic compounds during the tensile deformation have been elucidated.

  5. Poly(propylene carbonate): Insight into the Microstructure and Enantioselective Ring-Opening Mechanism

    KAUST Repository

    Salmeia, Khalifah A.

    2012-11-13

    Different poly(propylene carbonate) (PPC) microstructures have been synthesized from the alternating copolymerization of CO 2 with both racemic propylene oxide (PO) and various mixtures of PO enantiomers using chiral salen catalysts. The microstructures of the obtained copolymers as a function of polymerization time have been analyzed by a combination of chiral GC and high-resolution NMR spectroscopy. The 13C NMR spectra of selected poly(propylene carbonate) samples were recorded using a 900 MHz ( 1H) spectrometer, showing a previously unreported fine splitting of the carbonate resonances. This allowed a detailed assignment of signals for various copolymer microstructures taking into account the specifics in their stereo- and regioirregularities. For example, the enantioselectivity preference of the (R,R-salen)Co catalyst for (S)-PO at the beginning of the copolymerization leads predominantly to (S)-PO insertion, with any (R)-PO misinsertion being followed by incorporation of (S)-PO, so that the microstructure features isolated stereoerrors. K rel calculations for the copolymerization showed around 5-fold enantioselectivity for (S)-PO over (R)-PO at short reaction time. Analysis of the copolymer microstructures obtained under various reaction conditions appears to be an additional approach to differentiate the occurrence of bimetallic and bifunctional copolymerization mechanisms that are widely discussed in the literature. © 2012 American Chemical Society.

  6. Poly(propylene carbonate): Insight into the Microstructure and Enantioselective Ring-Opening Mechanism

    KAUST Repository

    Salmeia, Khalifah A.; Vagin, Sergei; Anderson, Carly E.; Rieger, Bernhard

    2012-01-01

    Different poly(propylene carbonate) (PPC) microstructures have been synthesized from the alternating copolymerization of CO 2 with both racemic propylene oxide (PO) and various mixtures of PO enantiomers using chiral salen catalysts. The microstructures of the obtained copolymers as a function of polymerization time have been analyzed by a combination of chiral GC and high-resolution NMR spectroscopy. The 13C NMR spectra of selected poly(propylene carbonate) samples were recorded using a 900 MHz ( 1H) spectrometer, showing a previously unreported fine splitting of the carbonate resonances. This allowed a detailed assignment of signals for various copolymer microstructures taking into account the specifics in their stereo- and regioirregularities. For example, the enantioselectivity preference of the (R,R-salen)Co catalyst for (S)-PO at the beginning of the copolymerization leads predominantly to (S)-PO insertion, with any (R)-PO misinsertion being followed by incorporation of (S)-PO, so that the microstructure features isolated stereoerrors. K rel calculations for the copolymerization showed around 5-fold enantioselectivity for (S)-PO over (R)-PO at short reaction time. Analysis of the copolymer microstructures obtained under various reaction conditions appears to be an additional approach to differentiate the occurrence of bimetallic and bifunctional copolymerization mechanisms that are widely discussed in the literature. © 2012 American Chemical Society.

  7. Effect of metallic dopants on the microstructure and mechanical properties of TiB2

    Czech Academy of Sciences Publication Activity Database

    Chlup, Zdeněk; Bača, L.; Halasová, Martina; Neubauer, E.; Hadraba, Hynek; Stelzer, N.; Roupcová, Pavla

    2015-01-01

    Roč. 35, č. 10 (2015), s. 2745-2754 ISSN 0955-2219 R&D Projects: GA ČR(CZ) GAP108/11/1644; GA MŠk(CZ) ED1.1.00/02.0068 Grant - others:The Austrian Research Promotion Agency (FFG)(AT) 834287 Institutional support: RVO:68081723 Keywords : Titanium diboride * Metallic dopants * Microstructure * Mechanical properties * Fracture behaviour1 Subject RIV: JL - Materials Fatigue, Friction Mechanics Impact factor: 2.933, year: 2015

  8. Microstructure and mechanical properties of Mg–HAP composites

    Indian Academy of Sciences (India)

    Administrator

    tion of load bearing capacity and suitable mechanical and metallurgical properties. ... lity as compared to β-TCP in our body fluid (Kwon et al. 2003). The HAP ... steel crucible under the protection of gas mixture contain- ing SF6 and CO2.

  9. Mechanisms of antibiotic resistance to enrofloxacin in uropathogenic Escherichia coli in dog.

    Science.gov (United States)

    Piras, Cristian; Soggiu, Alessio; Greco, Viviana; Martino, Piera Anna; Del Chierico, Federica; Putignani, Lorenza; Urbani, Andrea; Nally, Jarlath E; Bonizzi, Luigi; Roncada, Paola

    2015-09-08

    Escherichia coli (E. coli) urinary tract infections (UTIs) are becoming a serious problem both for pets and humans (zoonosis) due to the close contact and to the increasing resistance to antibiotics. This study has been performed in order to unravel the mechanism of induced enrofloxacin resistance in canine E. coli isolates that represent a good tool to study this pathology. The isolated E. coli has been induced with enrofloxacin and studied through 2D DIGE and shotgun MS. Discovered differentially expressed proteins are principally involved in antibiotic resistance and linked to oxidative stress response, to DNA protection and to membrane permeability. Moreover, since enrofloxacin is an inhibitor of DNA gyrase, the overexpression of DNA starvation/stationary phase protection protein (Dsp) could be a central point to discover the mechanism of this clone to counteract the effects of enrofloxacin. In parallel, the dramatic decrease of the synthesis of the outer membrane protein W, which represents one of the main gates for enrofloxacin entrance, could explain additional mechanism of E. coli defense against this antibiotic. All 2D DIGE and MS data have been deposited into the ProteomeXchange Consortium with identifier PXD002000 and DOI http://dx.doi.org/10.6019/PXD002000. This article is part of a Special Issue entitled: HUPO 2014. Copyright © 2015 Elsevier B.V. All rights reserved.

  10. Microstructure and mechanical properties of carbon fibre-reinforced ...

    Indian Academy of Sciences (India)

    2018-05-17

    May 17, 2018 ... was focussed on the characteristics of sol and the mechanical properties and high-temperature resistance of ... The reinforcement was 3D carbon fibre (T300 3k, ex-PAN ... where f (a/H) = 2.9(a/H)1/2−4.6(a/H)3/2+21.8(a/H)5/2.

  11. Microstructure and mechanical properties of carbon fiber reinforced ...

    Indian Academy of Sciences (India)

    68

    Alumina; composites; carbon fiber reinforcement; sol; mechanical properties. 1. Introduction ... The reinforcement was 3D carbon fiber (T300 3k, ex-PAN carbon fiber ... where f(a/H) = 2.9(a/H)1/2 – 4.6(a/H)3/2 + 21.8(a/H)5/2. – 37.6(a/H)7/2 + ...

  12. Study of Al-Si Alloy Oxygen Saturation on Its Microstructure and Mechanical Properties

    Directory of Open Access Journals (Sweden)

    Arkady Finkelstein

    2017-07-01

    Full Text Available One of the main goals of modern materials research is obtaining different microstructures and studying their influence on the mechanical properties of metals; aluminum alloys are particularly of interest due to their advanced performance. Traditionally, their required properties are obtained by alloying process, modification, or physical influence during solidification. The present work describes a saturation of the overheated AlSi7Fe1 casting alloy by oxides using oxygen blowing approach in overheated alloy. Changes in metals’ microstructural and mechanical properties are also described in the work. An Al10SiFe intermetallic complex compound was obtained as a preferable component to Al2O3 precipitation on it, and its morphology was investigated by scanning electron microscopy. The mechanical properties of the alloy after the oxygen blowing treatment are discussed in this work.

  13. Study of Al-Si Alloy Oxygen Saturation on Its Microstructure and Mechanical Properties.

    Science.gov (United States)

    Finkelstein, Arkady; Schaefer, Arseny; Chikova, Оlga; Borodianskiy, Konstantin

    2017-07-11

    One of the main goals of modern materials research is obtaining different microstructures and studying their influence on the mechanical properties of metals; aluminum alloys are particularly of interest due to their advanced performance. Traditionally, their required properties are obtained by alloying process, modification, or physical influence during solidification. The present work describes a saturation of the overheated AlSi₇Fe₁ casting alloy by oxides using oxygen blowing approach in overheated alloy. Changes in metals' microstructural and mechanical properties are also described in the work. An Al 10 SiFe intermetallic complex compound was obtained as a preferable component to Al₂O₃ precipitation on it, and its morphology was investigated by scanning electron microscopy. The mechanical properties of the alloy after the oxygen blowing treatment are discussed in this work.

  14. Microstructure and mechanical properties of Mg-6Al magnesium alloy with yttrium and neodymium

    Directory of Open Access Journals (Sweden)

    Chen Jun

    2009-05-01

    Full Text Available The effects of rare earth (RE elements Y and Nd on the microstructure and mechanical properties of Mg-6Al magnesium alloy were investigated. The results show that a proper level of RE elements can obviously refi ne the microstructure of Mg-6Al magnesium alloys, reduce the quantity of β-Mg17Al12 phase and form Al2Y and Al2Nd phases. The combined addition of Y and Nd dramatically enhances the tensile strength of the alloys in the temperature range of 20-175℃. When the content of RE elements is up to 1.8%, the values of tensile strength at room temperature and at 150℃ simultaneously reach their maximum of 253 MPa and 196 MPa, respectively. The main mechanisms of enhancement in the mechanical properties of Mg-6Al alloy with Y and Nd are the grain refi ning strengthening and the dispersion strengthening.

  15. Mechanisms of action of systemic antibiotics used in periodontal treatment and mechanisms of bacterial resistance to these drugs

    Directory of Open Access Journals (Sweden)

    Geisla Mary Silva Soares

    2012-06-01

    Full Text Available Antibiotics are important adjuncts in the treatment of infectious diseases, including periodontitis. The most severe criticisms to the indiscriminate use of these drugs are their side effects and, especially, the development of bacterial resistance. The knowledge of the biological mechanisms involved with the antibiotic usage would help the medical and dental communities to overcome these two problems. Therefore, the aim of this manuscript was to review the mechanisms of action of the antibiotics most commonly used in the periodontal treatment (i.e. penicillin, tetracycline, macrolide and metronidazole and the main mechanisms of bacterial resistance to these drugs. Antimicrobial resistance can be classified into three groups: intrinsic, mutational and acquired. Penicillin, tetracycline and erythromycin are broad-spectrum drugs, effective against gram-positive and gram-negative microorganisms. Bacterial resistance to penicillin may occur due to diminished permeability of the bacterial cell to the antibiotic; alteration of the penicillin-binding proteins, or production of β-lactamases. However, a very small proportion of the subgingival microbiota is resistant to penicillins. Bacteria become resistant to tetracyclines or macrolides by limiting their access to the cell, by altering the ribosome in order to prevent effective binding of the drug, or by producing tetracycline/macrolide-inactivating enzymes. Periodontal pathogens may become resistant to these drugs. Finally, metronidazole can be considered a prodrug in the sense that it requires metabolic activation by strict anaerobe microorganisms. Acquired resistance to this drug has rarely been reported. Due to these low rates of resistance and to its high activity against the gram-negative anaerobic bacterial species, metronidazole is a promising drug for treating periodontal infections.

  16. SOLUTION TREATMENT EFFECT ON MICROSTRUCTURE AND MECHANICAL PROPERTIES OF AUTOMOTIVE CAST ALLOY

    Directory of Open Access Journals (Sweden)

    Eva Tillová

    2012-02-01

    Full Text Available The contribution describes influence of the heat treatment (solution treatment at temperature 545°C and 565°C with different holding time 2, 4, 8, 16 and 32 hours; than water quenching at 40°C and natural aging at room temperature during 24 hours on mechanical properties (tensile strength and Brinell hardness and microstructure of the secondary AlSi12Cu1Fe automotive cast alloy. Mechanical properties were measured in line with EN ISO. A combination of different analytical techniques (light microscopy, scanning electron microscopy (SEM were therefore been used for study of microstructure. Solution treatment led to changes in microstructure includes the spheroidization and coarsening of eutectic silicon. The dissolution of precipitates and the precipitation of finer hardening phase further increase the hardness and tensile strength of the alloy. Optimal solution treatment (545°C/4 hours most improves mechanical properties and there mechanical properties are comparable with mechanical properties of primary AlSi12Cu1Fe alloy. Solution treatment at 565 °C caused testing samples distortion, local melting process and is not applicable for this secondary alloy with 12.5 % Si.

  17. Microstructure, mechanical properties and microtexture of friction stir welded S690QL high yield steel

    Energy Technology Data Exchange (ETDEWEB)

    Paillard, Pascal [Institut des Matériaux Jean Rouxel, UMR 6205, Polytech Nantes, Site de la Chantrerie, BP 50609, 44306 Nantes cedex 3 (France); Bertrand, Emmanuel, E-mail: emmanuel.bertrand@univ-nantes.fr [Institut des Matériaux Jean Rouxel, UMR 6205, Polytech Nantes, Site de la Chantrerie, BP 50609, 44306 Nantes cedex 3 (France); Allart, Marion; Benoit, Alexandre [Institut de Recherche Technologique Jules Verne, Chemin du Chaffault, 44340 Bouguenais (France); Ruckert, Guillaume [DCNS Research, Technocampus Ocean, 5 rue de l' Halbrane, 44340 Bouguenais (France)

    2016-12-15

    Two try-out campaigns of friction stir welding (FSW) were performed with different friction parameters to join S690QL high yield strength steel. The welds were investigated at macroscopic and microscopic scales using optical and electronic microscopy and microhardness mapping. Welds of the second campaign exhibit microstructures and mechanical properties in accordance with requirements for service use. Microtexture measurements were carried out in different zones of welds by electron backscattered diffraction (EBSD). It is shown that that texture of the bottom of the weld is similar to that of the base metal, suggesting a diffusion bonding mechanism. Finally, the mechanical properties (tensile strength, resilience, bending) were established on the most promising welds. It is shown that it is possible to weld this high yield strength steel using FSW process with satisfactory geometric, microstructural and mechanical properties. - Highlights: •1000 mm ∗ 400 mm ∗ 8 mm S690QL steel plates are joined by friction stir welding (FSW). •Maximum hardness is reduced by optimization of process parameters. •Various microstructures are formed but no martensite after process optimization. •Texture is modified in mechanically affected zones of the weld. •Texture in the bottom of the weld is preserved, suggesting diffusion bonding.

  18. Influence of Sc on microstructure and mechanical properties of Al-Si-Mg-Cu-Zr alloy

    Science.gov (United States)

    Li, Yukun; Du, Xiaodong; Zhang, Ya; Zhang, Zhen; Fu, Junwei; Zhou, Shi'ang; Wu, Yucheng

    2018-02-01

    In the present study, the effects of Mg, Cu, Sc and Zr combined additions on the microstructure and mechanical properties of hypoeutectic Al-Si cast alloy were systematically investigated. Characterization techniques such as optical microscopy (OM), scanning electron microscope (SEM), energy dispersive spectrometer (EDS), electron back-scatter diffraction (EBSD), atomic force microscopy (AFM), transmission electron microscope (TEM), Brinell hardness tester and universal testing machine were employed to analyze the microstructure and mechanical properties. The results showed that Sc served as modifier on the microstructure of Al-3Si-0.45Mg-0.45Cu-0.2Zr alloys, including modification of eutectic Si and grains. Extraordinarily, grain refinement was found to be related to the primary particles, which exhibited a close orientation to matrix. After T6 heat treatment, the grain structures were composed of nano-scaled secondary Al3(Sc, Zr) precipitates and spherical eutectic Si. Combined with T6 heat treatment, the highest hardness, yield strength, ultimate tensile strength and elongation were achieved in 0.56 wt.% Sc-modified alloy. Interestingly, the strength and ductility had a similar tendency. This paper demonstrated that combined additions of Mg, Cu, Sc and Zr could significantly improve the microstructure and performance of the hypoeutectic Al-Si cast alloy.

  19. Microstructure and mechanical properties of the TIG welded joints of fusion CLAM steel

    Energy Technology Data Exchange (ETDEWEB)

    Jiang Zhizhong, E-mail: zhizhongjiang2006@yahoo.com.c [School of Materials Science and Engineering, University of Science and Technology Beijing, Xueyuan Road, Beijing 100083 (China); Ren Litian; Huang Jihua; Ju Xin; Wu Huibin [School of Materials Science and Engineering, University of Science and Technology Beijing, Xueyuan Road, Beijing 100083 (China); Huang Qunying; Wu Yican [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei, Anhui 230031 (China)

    2010-12-15

    The CLAM steel plates were butt-welded through manual tungsten inert gas welding (TIG) process, and the following post-welding heat treatment (PWHT) at 740 {sup o}C for 1 h. The microstructure and mechanical properties of the welded joints were measured. The results show that both hardening and softening occur in the weld joints before PWHT, but the hardening is not removed completely in the weld metal and the fusion zone after PWHT. In as-welded condition, the microstructure of the weld metal is coarse lath martensite, and softened zone in heat-affected zone (HAZ) consists of a mixture of tempered martensite and ferrite. After PWHT, a lot of carbides precipitate at all zones in weld joints. The microstructure of softened zone transforms to tempered sorbite. Tensile strength of the weld metal is higher than that of HAZ and base metal regardless of PWHT. However, the weld metal has poor toughness without PWHT. The impact energy of the weld metal after PWHT reaches almost the same level as the base metal. So it is concluded that microstructure and mechanical properties of the CLAM steel welded joints can be improved by a reasonable PWHT.

  20. Investigation of the relationships between mechanical properties and microstructure in a Fe-9%Cr ODS steel

    Directory of Open Access Journals (Sweden)

    Hary Benjamin

    2016-01-01

    Full Text Available Ferritic-martensitic Oxide Dispersion Strengthened (ODS steels are potential materials for fuel pin cladding in Sodium Fast Reactor (SFR and their optimisation is essential for future industrial applications. In this paper, a feasibility study concerning the generation of tensile specimens using a quenching dilatometer is presented. The ODS steel investigated contains 9%Cr and exhibits a phase transformation between ferrite and austenite around 870 °C. The purpose was to generate different microstructures and to evaluate their tensile properties. Specimens were machined from a cladding tube and underwent controlled heat treatments inside the dilatometer. The microstructures were observed using Electron Backscatter Diffraction (EBSD and tensile tests were performed at room temperature and at 650 °C. Results show that a tempered martensitic structure is the optimum state for tensile loading at room temperature. At 650 °C, the strengthening mechanisms that are involved differ and the microstructures exhibit more similar yield strengths. It also appeared that decarburisation during heat treatment in the dilatometer induces a decrease in the mechanical properties and heterogeneities in the dual-phase microstructure. This has been addressed by proposing a treatment with a much shorter time in the austenitic domain. Thereafter, the relaxation of macroscopic residual stresses inside the tube during the heat treatment was evaluated. They appear to decrease linearly with increasing temperature and the phase transformation has a limited effect on the relaxation.

  1. Influence of intercritical austempering on the microstructure and mechanical properties of austempered ductile cast iron (ADI)

    International Nuclear Information System (INIS)

    Panneerselvam, Saranya; Putatunda, Susil K.; Gundlach, Richard; Boileau, James

    2017-01-01

    The focus of this investigation was to examine the influence of intercritical austempering process on the microstructure and mechanical properties of low-alloyed austempered ductile cast iron (ADI). The investigation also examined the influence of intercritical austempering process on the plane strain fracture toughness of the material. The effect of both austenitization and austempering temperature on the microstructure and mechanical properties was examined. The microstructural analysis was carried out using optical microscopy, scanning electron microscopy and X-ray diffraction. The test results indicate that by intercritical austempering it is possible to produce proeutectoid ferrite in the matrix microstructure. Lower austenitizing temperature produces more proeutectoid ferrite in the matrix. Furthermore, the yield, tensile strength and the fracture toughness of the ADI decreases with decrease in austenitizing temperature. A considerable increase in ductility was observed in the samples with higher proeutectoid ferrite content. The fracture surfaces of the ADI samples revealed that dimple ductile fracture produced higher fracture toughness of 60±5 MPa√m in this intercritically austempered ADI.

  2. Microstructures and mechanical properties of age-formed 7050 aluminum alloy

    International Nuclear Information System (INIS)

    Chen, J.F.; Zhen, L.; Jiang, J.T.; Yang, L.; Shao, W.Z.; Zhang, B.Y.

    2012-01-01

    Highlights: ► Age-forming leads to the grain elongation in 7050 alloy. ► Age-forming varies the texture components in 7050 alloy. ► Age-forming promotes precipitates growth and PFZ enlargement in 7050 alloy. ► Age-forming induces to descend apparently elongation in 7050 alloy. ► The effect of age-forming on microstructure and properties is discussed in-depth. - Abstract: The effects of age-forming on microstructures and mechanical properties of 7050 Al alloy were investigated in this work. The alloy was subjected to age-forming as well as stress-free ageing at 160 °C for 6, 12, 18 and 24 h, and its microstructures were characterized by electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM). It was shown that creep might lead to grain elongation during age-forming, and the applied stress induces the coarsening of precipitates in 7050 Al alloy. The texture in the alloy was also influenced by age-forming. Consequently, the differences in microstructures result in differences in mechanical properties of age-forming versus traditional stress-free ageing. The ultimate tensile strength of age-formed samples were slightly lower than that of stress-free aged samples, while the yield strength of age-formed samples were apparently lower than that of stress-free aged samples. Specifically, the elongation of samples age-formed displays apparently decrease.

  3. Influence of intercritical austempering on the microstructure and mechanical properties of austempered ductile cast iron (ADI)

    Energy Technology Data Exchange (ETDEWEB)

    Panneerselvam, Saranya [Wayne State University, Detroit, MI (United States); Putatunda, Susil K., E-mail: sputa@eng.wayne.edu [Wayne State University, Detroit, MI (United States); Gundlach, Richard [Element Materials Technology, MI (United States); Boileau, James [Ford Motor Company, Dearborn, MI (United States)

    2017-05-10

    The focus of this investigation was to examine the influence of intercritical austempering process on the microstructure and mechanical properties of low-alloyed austempered ductile cast iron (ADI). The investigation also examined the influence of intercritical austempering process on the plane strain fracture toughness of the material. The effect of both austenitization and austempering temperature on the microstructure and mechanical properties was examined. The microstructural analysis was carried out using optical microscopy, scanning electron microscopy and X-ray diffraction. The test results indicate that by intercritical austempering it is possible to produce proeutectoid ferrite in the matrix microstructure. Lower austenitizing temperature produces more proeutectoid ferrite in the matrix. Furthermore, the yield, tensile strength and the fracture toughness of the ADI decreases with decrease in austenitizing temperature. A considerable increase in ductility was observed in the samples with higher proeutectoid ferrite content. The fracture surfaces of the ADI samples revealed that dimple ductile fracture produced higher fracture toughness of 60±5 MPa√m in this intercritically austempered ADI.

  4. A Mechanism of Unidirectional Transformation, Leading to Antibiotic Resistance, Occurs within Nasopharyngeal Pneumococcal Biofilm Consortia.

    Science.gov (United States)

    Lattar, Santiago M; Wu, Xueqing; Brophy, Jennifer; Sakai, Fuminori; Klugman, Keith P; Vidal, Jorge E

    2018-05-15

    Streptococcus pneumoniae acquires genes for resistance to antibiotics such as streptomycin (Str) or trimethoprim (Tmp) by recombination via transformation of DNA released by other pneumococci and closely related species. Using naturally transformable pneumococci, including strain D39 serotype 2 (S2) and TIGR4 (S4), we studied whether pneumococcal nasopharyngeal transformation was symmetrical, asymmetrical, or unidirectional. Incubation of S2 Tet and S4 Str in a bioreactor simulating the human nasopharynx led to the generation of Spn Tet/Str recombinants. Double-resistant pneumococci emerged soon after 4 h postinoculation at a recombination frequency (rF) of 2.5 × 10 -4 while peaking after 8 h at a rF of 1.1 × 10 -3 Acquisition of antibiotic resistance genes by transformation was confirmed by treatment with DNase I. A high-throughput serotyping method demonstrated that all double-resistant pneumococci belonged to one serotype lineage (S2 Tet/Str ) and therefore that unidirectional transformation had occurred. Neither heterolysis nor availability of DNA for transformation was a factor for unidirectional transformation given that the density of each strain and extracellular DNA (eDNA) released from both strains were similar. Unidirectional transformation occurred regardless of the antibiotic-resistant gene carried by donors or acquired by recipients and regardless of whether competence-stimulating peptide-receptor cross talk was allowed. Moreover, unidirectional transformation occurred when two donor strains (e.g., S4 Str and S19F Tmp ) were incubated together, leading to S19F Str/Tmp but at a rF 3 orders of magnitude lower (4.9 × 10 -6 ). We finally demonstrated that the mechanism leading to unidirectional transformation was due to inhibition of transformation of the donor by the recipient. IMPORTANCE Pneumococcal transformation in the human nasopharynx may lead to the acquisition of antibiotic resistance genes or genes encoding new capsular variants

  5. Microstructure and Mechanical Properties of Aligned Natural Fibre Composites

    DEFF Research Database (Denmark)

    Rask, Morten

    properties (stiffness-to-density ratio). The perspective of using natural fibres is to have a sustainable, biodegradable, CO2-neutral alternative to glass fibres. However, so far, it has not been possible to take full advantage of the natural fibre properties when using them for composite applications....... Several challenges have to be addressed and solved, many of which pertain to the fact that the fibres are sourced from a natural resource: 1) Inconsistent properties, depending on plant species, growth and harvest conditions, and fibre extraction techniques. 2) Strength values of composites are lower than...... microscopy during tensile tests of small composite specimens. With this technique, 3D images can be obtained with spatial resolution mechanisms have been identified: (i) Interface...

  6. The influence of thermo-mechanical processing on the microstructure of steel 20MoCrS4

    Energy Technology Data Exchange (ETDEWEB)

    Jandova, D.; Meyer, L.W.; Masek, B.; Novy, Z.; Kesner, D.; Motycka, P

    2003-05-25

    The influence of thermo-mechanical processing (TMP) on the microstructure and mechanical properties of 0.22%C-0.87%Mn-0.73Cr-0.40Mo steel was investigated. The transformation CCT diagram and CCCT diagram were determined by dilatometric measurements. Hot deformation before austenite decomposition slightly accelerates ferritic transformation, retards bainitic reactions and decreases the bainite start temperature. Special methods of TMP were performed consisting of hot and/or warm compression deformations and dwell at an elevated temperature. The microstructure was studied using metallography and transmission electron microscopy. The compression deformation results in a remarkable refinement of the microstructure and an improvement of mechanical properties. Warm deformation followed by dwell at 470 deg. C was found to be suitable for an increase of tensile strength and notch toughness; the corresponding microstructure is a fine lath-like bainitic microstructure with a relatively homogeneous distribution of carbide particles.

  7. Microstructure and mechanical behavior of direct metal laser sintered Inconel alloy 718

    Energy Technology Data Exchange (ETDEWEB)

    Smith, Derek H. [Department of Mechanical Engineering, University of New Hampshire, Durham, NH 03824 (United States); Bicknell, Jonathan; Jorgensen, Luke [Turbocam Energy Solutions, Turbocam International, Dover, NH 03820 (United States); Patterson, Brian M.; Cordes, Nikolaus L. [Materials Science Division, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Tsukrov, Igor [Department of Mechanical Engineering, University of New Hampshire, Durham, NH 03824 (United States); Knezevic, Marko, E-mail: marko.knezevic@unh.edu [Department of Mechanical Engineering, University of New Hampshire, Durham, NH 03824 (United States)

    2016-03-15

    In this paper, we investigate microstructure and quasi-static mechanical behavior of the direct metal laser sintered Inconel 718 superalloy as a function of build direction (BD). The printed material was further processed by annealing and double-aging, hot isostatic pressing (HIP), and machining. We characterize porosity fraction and distribution using micro X-ray computed tomography (μXCT), grain structure and crystallographic texture using electron backscattered diffraction (EBSD), and mechanical response in quasi-static tension and compression using standard mechanical testing at room temperature. Analysis of the μXCT imaging shows that majority of porosity develops in the outer layer of the printed material. However, porosity inside the material is also present. The EBSD measurements reveal formation of columnar grains, which favor < 001 > fiber texture components along the BD. These measurements also show evidence of coarse-grained microstructure present in the samples treated by HIP. Finally, analysis of grain boundaries reveal that HIP results in a large number of annealing twins compared to that in samples that underwent annealing and double-aging. The yield strength varies with the testing direction by approximately 7%, which is governed by a combination of grain morphology and crystallographic texture. In particular, we determine tension–compression asymmetry in the yield stress as well as anisotropy of the material flow during compression. We find that HIP lowers yield stress but improves ductility relative to the annealed and aged material. These results are discussed and critically compared with the data reported for wrought material in the same condition. - Highlights: • Microstructure and mechanical properties of DMLS Inconel 718 are studied in function of build direction. • Inhomogeneity of microstructure in the material in several conditions is quantified by μXCT and EBSD. • Anisotropy and asymmetry in the mechanical response are

  8. Microstructure and mechanical behavior of direct metal laser sintered Inconel alloy 718

    International Nuclear Information System (INIS)

    Smith, Derek H.; Bicknell, Jonathan; Jorgensen, Luke; Patterson, Brian M.; Cordes, Nikolaus L.; Tsukrov, Igor; Knezevic, Marko

    2016-01-01

    In this paper, we investigate microstructure and quasi-static mechanical behavior of the direct metal laser sintered Inconel 718 superalloy as a function of build direction (BD). The printed material was further processed by annealing and double-aging, hot isostatic pressing (HIP), and machining. We characterize porosity fraction and distribution using micro X-ray computed tomography (μXCT), grain structure and crystallographic texture using electron backscattered diffraction (EBSD), and mechanical response in quasi-static tension and compression using standard mechanical testing at room temperature. Analysis of the μXCT imaging shows that majority of porosity develops in the outer layer of the printed material. However, porosity inside the material is also present. The EBSD measurements reveal formation of columnar grains, which favor fiber texture components along the BD. These measurements also show evidence of coarse-grained microstructure present in the samples treated by HIP. Finally, analysis of grain boundaries reveal that HIP results in a large number of annealing twins compared to that in samples that underwent annealing and double-aging. The yield strength varies with the testing direction by approximately 7%, which is governed by a combination of grain morphology and crystallographic texture. In particular, we determine tension–compression asymmetry in the yield stress as well as anisotropy of the material flow during compression. We find that HIP lowers yield stress but improves ductility relative to the annealed and aged material. These results are discussed and critically compared with the data reported for wrought material in the same condition. - Highlights: • Microstructure and mechanical properties of DMLS Inconel 718 are studied in function of build direction. • Inhomogeneity of microstructure in the material in several conditions is quantified by μXCT and EBSD. • Anisotropy and asymmetry in the mechanical response are determined by

  9. Influence of mechanical and thermal treatments on microstructure and mechanical properties of titanium stabilized austenitic stainless steels

    International Nuclear Information System (INIS)

    Sidhom, H.

    1983-12-01

    Thermal and mechanical treatments for microstructure optimization in titanium stabilized austenitic stainless steels used in nuclear industry are examined. The steels studied Z10CNDT15-15B and Z6CNDT17-13 are of the type 15-15 Ti and 316 Ti. These treatments allow the elimination of casting heterogeneity produced by dendritic solidification, improve mechanical properties particularly creep and the best compromise between grain size solid solution of metal additions is obtained. Secondary precipitation of (TiMo)C on dislocations is improved by a previous strain hardening. The precipitation reinforce the good effect of strain hardening by stabilization of the microstructure producing a better resistance to recrystallization [fr

  10. Experimental investigation of thixoforging process on microstructure and mechanical properties of the centrifugal pump flange

    Energy Technology Data Exchange (ETDEWEB)

    Kazemi, A.; Nourouzi, S.; Gorji, A. [Babol University of Technology, Babol (Iran, Islamic Republic of); Kolahdooz, A. [Islamic Azad University, Isfahan (Iran, Islamic Republic of)

    2015-07-15

    In this paper, a thixoforging method is studied as one of the semi-solid forming processes. At the first step, the influence of semi-solid temperature, holding time, and ram speed of the hydraulic press are investigated on microstructure and mechanical properties of thixoforged A356 aluminum alloy parts. For this purpose, the slope plate casted billets are heated up to semi-solid temperature of 580, 590, and 600 .deg. C and holding time of 5, 10, and 15 minutes and then are deformed using the press with ram speeds of 1, 3 and 5 mm/s. Results show that the best mechanical properties are related to the thixoforged specimen with the finest microstructure which is thixoforged at semi-solid temperature of 600 .deg. C, holding time of 5 minutes and ram speed of 5 mm/s. Afterwards, the T6 heat treatment is performed to improve mechanical properties of parts produced by thixoforging process. At the final step of experiments in order to investigate the effect of using slope plate prior to reheating on microstructure and mechanical properties, semi-solid forging is done by using the gravity casted billet.

  11. Microstructural evolution of 316L stainless steels with yttrium addition after mechanical milling and heat treatment

    Energy Technology Data Exchange (ETDEWEB)

    Kotan, Hasan, E-mail: hasankotan@gmail.com

    2015-10-28

    Nanocrystalline 316L stainless steels with yttrium addition were prepared by mechanical milling at cryogenic temperature and subjected to annealing treatments at various temperatures up to 1200 °C. The dependence of hardness on the microstructure was utilized to study the mechanical changes in the steels occurring during annealing. The microstructural evolution of the as-milled and annealed steels was characterized by means of X-ray diffraction (XRD), focused ion beam microscopy (FIB) and transmission electron microscopy (TEM) techniques. The results have revealed that austenite in as-received powder partially transformed to martensite phase during mechanical milling whereas the annealing induced reverse transformation of martensite-to-austenite. Furthermore, while the austenite-to-martensite phase ratio increased with increasing annealing temperature, the equilibrium structure was not achieved after three hours heat treatments up to 1200 °C resulting in a dual-phased steels with around 10% martensite. The grain size of 316L steel was 19 nm after mechanical milling and remained around 116 nm at 1100 °C with yttrium addition as opposed to micron size grains of plain 316L steel at the same annealing temperature. Such microstructural features facilitate the use of these materials at elevated temperatures, as well as the development of scalable processing routes into a dense nanocrystalline compact.

  12. Microstructure and mechanical properties of unirradiated low activation ferritic steel

    International Nuclear Information System (INIS)

    Hsu, C.Y.; Lechtenberg, T.A.

    1986-01-01

    Transmission electron micrographs of normalized and tempered 9Cr-2.5W-0.3V-0.15C low activation ferritic steel showed tempered lath-type martensite with precipitation of rod and plate-like carbides at lath and grain boundaries. X-ray diffraction analysis of the extracted replicas revealed nearly 100% M 23 C 6 carbides (a=1.064 nm), with no indication of Fe 2 W-type Laves phase even after thermal aging at 600 0 C/1000 h. Thermal aging increased the number density of rod-like M 23 C 6 along prior austenite grain boundaries and martensite lath boundaries. The elevated-temperature tensile strengths of this steel are about 10% higher than the average strengths of commercial heats of 9Cr-1Mo and modified 9Cr-1Mo steels up to 650 0 C, with equivalent uniform elongation and ∝50% decrease in total elongation. The DBTT was determined to be -25 0 C which is similar to other 9Cr-1Mo steels. Fractographic examination of tensile tested specimens shows a mixed mode of equiaxed and elongated dimples at test temperatures above 400 0 C. Modification of the Ga3X alloy composition for opimization of materials properties is discussed. However, the proposed low activation ferritic steel shows the promise of improved mechanical properties over 9Cr-1Mo steels. (orig.)

  13. Microstructural stress relaxation mechanics in functionally different tendons.

    Science.gov (United States)

    Screen, H R C; Toorani, S; Shelton, J C

    2013-01-01

    Tendons experience widely varying loading conditions in vivo. They may be categorised by their function as either positional tendons, which are used for intricate movements and experience lower stress, or as energy storage tendons which act as highly stressed springs during locomotion. Structural and compositional differences between tendons are thought to enable an optimisation of their properties to suit their functional environment. However, little is known about structure-function relationships in tendon. This study adopts porcine flexor and extensor tendon fascicles as examples of high stress and low stress tendons, comparing their mechanical behaviour at the micro-level in order to understand their stress relaxation response. Stress-relaxation was shown to occur predominantly through sliding between collagen fibres. However, in the more highly stressed flexor tendon fascicles, more fibre reorganisation was evident when the tissue was exposed to low strains. By contrast, the low load extensor tendon fascicles appears to have less capacity for fibre reorganisation or shearing than the energy storage tendon, relying more heavily on fibril level relaxation. The extensor fascicles were also unable to sustain loads without rapid and complete stress relaxation. These findings highlight the need to optimise tendon repair solutions for specific tendons, and match tendon properties when using grafts in tendon repairs. Copyright © 2012 IPEM. Published by Elsevier Ltd. All rights reserved.

  14. Flaking behavior and microstructure evolution of nickel and copper powder during mechanical milling in liquid environment

    International Nuclear Information System (INIS)

    Xiao Xiao; Zeng Zigao; Zhao Zhongwei; Xiao Songwen

    2008-01-01

    To prepare metal flakes with a high flaking level and investigate the microstructure of metal flakes, nickel and copper powder were mechanically milled in liquid environment and the microstructure of powders was investigated by X-ray diffraction. The milling process can be divided into flaking and broken stages. At the flaking stage, milled metal powders exhibited high flaking level and flaky microshape, and became preferred orientation. While at the broken stage, the milled powders presented a low flaking level and irregular microshape, and was not preferred orientation any longer. The grain size, microstrain and dislocation density along direction varied with milling time differently from that along direction. The flaking level of the milled powders was related to the preferred orientation, and more closely to the deformation mechanism. We can strengthen the formation of preferred orientation to obtain metal powders with a high flaking level

  15. Flaking behavior and microstructure evolution of nickel and copper powder during mechanical milling in liquid environment

    Energy Technology Data Exchange (ETDEWEB)

    Xiao Xiao [College of Metallurgical Science and Engineering, Central South University, Changsha 410083, Hunan (China); Changsha Research Institute of Mining and Metallurgy, Changsha 410012, Hunan (China); Zeng Zigao [Changsha Research Institute of Mining and Metallurgy, Changsha 410012, Hunan (China); Zhao Zhongwei [College of Metallurgical Science and Engineering, Central South University, Changsha 410083, Hunan (China); Xiao Songwen [Changsha Research Institute of Mining and Metallurgy, Changsha 410012, Hunan (China)], E-mail: swinxiao@yahoo.com.cn

    2008-02-25

    To prepare metal flakes with a high flaking level and investigate the microstructure of metal flakes, nickel and copper powder were mechanically milled in liquid environment and the microstructure of powders was investigated by X-ray diffraction. The milling process can be divided into flaking and broken stages. At the flaking stage, milled metal powders exhibited high flaking level and flaky microshape, and <2 0 0> became preferred orientation. While at the broken stage, the milled powders presented a low flaking level and irregular microshape, and <2 0 0> was not preferred orientation any longer. The grain size, microstrain and dislocation density along <2 0 0> direction varied with milling time differently from that along <1 1 1> direction. The flaking level of the milled powders was related to the <2 0 0> preferred orientation, and more closely to the deformation mechanism. We can strengthen the formation of <2 0 0> preferred orientation to obtain metal powders with a high flaking level.

  16. Microstructure and mechanical properties of laser-welded joints of TWIP and TRIP steels

    International Nuclear Information System (INIS)

    Mujica, L.; Weber, S.; Pinto, H.; Thomy, C.; Vollertsen, F.

    2010-01-01

    With the aim of investigating a laser-welded dissimilar joint of TWIP and TRIP steel sheets, the microstructure was characterized by means of OM, SEM, and EBSD to differentiate the fusion zone, heat-affected zone, and the base material. OIM was used to differentiate between ferritic, bainitic, and martensitic structures. Compositions were measured by means of optical emission spectrometry and EDX to evaluate the effect of manganese segregation. Microhardness measurements and tensile tests were performed to evaluate the mechanical properties of the joint. Residual stresses and XRD phase quantification were used to characterize the weld. Grain coarsening and martensitic areas were found in the fusion zone, and they had significant effects on the mechanical properties of the weld. The heat-affected zone of the TRIP steel and the corresponding base material showed considerable differences in the microstructure and properties.

  17. Effect of heat treatments on precipitate microstructure and mechanical properties of CuCrZr alloy

    DEFF Research Database (Denmark)

    Singh, B.N; Edwards, D.J.; Tähtinen, S.

    2004-01-01

    A number of specimens of CuCrZr alloy was prime aged and then overaged at 600oC for 1, 2 and 4 hours and for 4 hours at 700 and 850oC. After different heat treatments, both the precipitate microstructure and mechanical properties were characterized.Mechanical properties were determined at 50...... and 300oC. Some selected specimens in the prime aged as well as overaged conditions were irradiated in the BR-2 reactor at Mol at 60 and 300oC to a displacement dose level of ~0.3 dpa. Irradiated specimens weremechanically tested at 60 and 300oC. The post-deformation microstructure of the irradiated...

  18. Microstructural Evolution and Mechanical Behavior of High Temperature Solders: Effects of High Temperature Aging

    Science.gov (United States)

    Hasnine, M.; Tolla, B.; Vahora, N.

    2018-04-01

    This paper explores the effects of aging on the mechanical behavior, microstructure evolution and IMC formation on different surface finishes of two high temperature solders, Sn-5 wt.% Ag and Sn-5 wt.% Sb. High temperature aging showed significant degradation of Sn-5 wt.% Ag solder hardness (34%) while aging has little effect on Sn-5 wt.% Sb solder. Sn-5 wt.% Ag experienced rapid grain growth as well as the coarsening of particles during aging. Sn-5 wt.% Sb showed a stable microstructure due to solid solution strengthening and the stable nature of SnSb precipitates. The increase of intermetallic compound (IMC) thickness during aging follows a parabolic relationship with time. Regression analysis (time exponent, n) indicated that IMC growth kinetics is controlled by a diffusion mechanism. The results have important implications in the selection of high temperature solders used in high temperature applications.

  19. Correlation between microstructure and mechanical properties of stable mixtures formed by austenite and martensite

    International Nuclear Information System (INIS)

    Eckstein, C.B.

    1982-03-01

    The influence of martensite in mechanical properties of stable mixtures formed by austenite and martensite was studied by varying the amount of martensite in the mixtures. Microstructural parameters were determined by Optical Quantitative Metallography and used to establish the correlation between the mechanical response of the mixtures in tension and their microstructures. The 'in situ' deformation of each phase in mixtures was determined experimentally in terms of the rule of mixtures. It is shown that the partitioning of the deformation depends on the amount of martensite in the mixture and that it tends to a condition of isostrain at higher martensite volume fractions. Optical observation of fractured specimens showed that the beginning of the fracture process may related to regions of the austenite grain boundaries where they meet martensite plates. (Author) [pt

  20. Microstructure characterization of nanocrystalline TiC synthesized by mechanical alloying

    International Nuclear Information System (INIS)

    Ghosh, B.; Pradhan, S.K.

    2010-01-01

    Nanocrystalline TiC is produced by mechanical milling the stoichiometric mixture of α-Ti and graphite powders at room temperature under argon atmosphere within 35 min of milling through a self-propagating combustion reaction. Microstructure characterization of the unmilled and ball-milled samples was done by both X-ray diffraction and electron microscopy. It reveals the fact that initially graphite layers were oriented along and in the course of milling, thin graphite layers were distributed evenly among the grain boundaries of α-Ti particles. Both α-Ti and TiC lattices contain stacking faults of different kinds. The grain size distribution obtained from the Rietveld's method and electron microscopy studies ensure that nanocrystalline TiC particles with almost uniform size (∼13 nm) can be prepared by mechanical alloying technique. The result obtained from X-ray analysis corroborates well with the microstructure characterization of nanocrystalline TiC by electron microscopy.

  1. Microstructure and mechanical properties of ARB processed Mg-3%Gd alloy

    DEFF Research Database (Denmark)

    Wu, J.Q.; Huang, S.; Wang, Y.H.

    2015-01-01

    by accumulative roll-bonding (ARB) at 400℃ to 4 cycles followed by annealing at various temperatures. The microstructures after annealing were characterized by the electron backscatter diffraction technique and the mechanical properties were measured by a tensile test. It was found that the alloy has a good...... combination of strength and ductility after 2 cycle ARB processing followed by annealing at 290℃ for 1h. The strength is 2.3 times higher than that of the fully annealed coarse grained alloy, and the elongation is comparable with that of fully annealed coarse grained counterpart. The good mechanical...... properties were related to the fine-sized heterogeneous microstructures and weakened texture....

  2. Microstructure, mechanical behavior and biocompatibility of powder metallurgy Nb-Ti-Ta alloys as biomedical material.

    Science.gov (United States)

    Liu, Jue; Chang, Lin; Liu, Hairong; Li, Yongsheng; Yang, Hailin; Ruan, Jianming

    2017-02-01

    Microstructures, mechanical properties, apatite-forming ability and in vitro experiments were studied for Nb-25Ti-xTa (x=10, 15, 20, 25, 35at.%) alloys fabricated by powder metallurgy. It is confirmed that the alloys could achieve a relative density over 80%. Meanwhile, the increase in Ta content enhances the tensile strength, elastic modulus and hardness of the as-sintered alloys. When increasing the sintering temperatures, the microstructure became more homogeneous for β phase, resulting in a decrease in the modulus and strength. Moreover, the alloys showed a good biocompatibility due to the absence of cytotoxic elements, and were suitable for apatite formation and cell adhesion. In conclusion, Nb-25Ti-xTa alloys are potentially useful in biomedical applications with their mechanical and biological properties being evaluated in this work. Copyright © 2016 Elsevier B.V. All rights reserved.

  3. Understanding of mechanical properties of graphite on the basis of mesoscopic microstructure (review)

    International Nuclear Information System (INIS)

    Ishihara, M.; Shibata, T.; Takahashi, T.; Baba, S.; Hoshiya, T.

    2002-01-01

    With the aim of nuclear application of ceramics in the high-temperature engineering field, the authors have investigated the mesoscopic microstructure related to the mechanical and thermal properties of ceramics. In this paper, recent activities concerning mechanical properties, strength and Young's modulus are presented. In the strength research field, the brittle fracture model considering pore/grain mesoscopic microstructure was expanded so as to render possible an estimation of the strength under stress gradient conditions. Furthermore, the model was expanded to treat the pore/crack interaction effect. The performance of the developed model was investigated from a comparison with experimental data and the Weibull strength theory. In the field of Young's modulus research, ultrasonic wave propagation was investigated using the pore/wave interaction model. Three kinds of interaction modes are treated in the model. The model was applied to the graphite, and its applicability was investigated through comparison with experimental data. (authors)

  4. Microstructural and mechanical characterization of the parabolic spring steel 51CrV4

    Energy Technology Data Exchange (ETDEWEB)

    Koemec, Aydin [TT Celikyay Co., Duezce (Turkey); Dikci, Kazim [TT Celikyay Co., Duezce (Turkey). Quality Dept.; Atapek, S. Hakan; Polat, Seyda; Aktas Celik, Guelsah [Kocaeli Univ. (Turkey). Dept. of Metallurgical and Materials Engineering

    2017-07-01

    Findings about the microstructural features of, spring steels are necessary for the producers to enhance their mechanical properties. There are several reports revealing the basic relation between microstructure and fatigue performance. However, the results are commonly obtained from universal test procedures and have limited use due to the lack of real service conditions. In this study, the microstructural features of 51CrV4 alloy, used as spring steel component, were investigated by metallographic examinations starting from raw material to the final product. Its fatigue behavior was investigated using a self-designed test machine and a test procedure approved by the automotive industry to simulate the service conditions. Fractographic examination of fatigue failed surface was carried out to specify the effect of microstructural features on the fracture. It was concluded that (i) both oxide and decarburization layers were minimized by shot peening and (ii) although tested samples had superior fatigue resistance and failed above 10{sup 5} cycles limit, oxide layer played a major role for crack initiation.

  5. Effect of cooling rate on the microstructure and mechanical properties of Nb-microalloyed steels

    International Nuclear Information System (INIS)

    Shanmugam, S.; Ramisetti, N.K.; Misra, R.D.K.; Mannering, T.; Panda, D.; Jansto, S.

    2007-01-01

    We describe here the effect of cooling rate on the microstructure and mechanical properties of Nb-microalloyed steels that were processed as structural beams at three different cooling rates. Nb-microalloyed steels exhibited increase in yield strength with increase in cooling rate during processing. However, the increase in the yield strength was not accompanied by loss in toughness. The microstructure at conventional cooling rate, primarily consisted of polygonal ferrite-pearlite microconstituents, while at intermediate cooling rate besides polygonal ferrite and pearlite contained significant fraction of degenerated pearlite and lath-type ferrite. At higher cooling rate, predominantly, lath-type (acicular) or bainitic ferrite was obtained. The precipitation characteristics were similar at the three cooling rates investigated with precipitation occurring at grain boundaries, on dislocations, and in the ferrite matrix. The fine scale (∼8-12 nm) precipitates in the ferrite matrix were MC type of niobium carbides. The microstructural studies suggest that the increase in toughness of Nb-microalloyed steels with increase in cooling rate is related to the change in the microstructure from predominantly ferrite-pearlite to predominantly bainitic ferrite

  6. Effect of cooling rate on the microstructure and mechanical properties of Nb-microalloyed steels

    Energy Technology Data Exchange (ETDEWEB)

    Shanmugam, S. [Center for Structural and Functional Materials, University of Louisiana at Lafayette, Lafayette, LA 70504-4130 (United States); Ramisetti, N.K. [Department of Chemical Engineering, University of Louisiana at Lafayette, Lafayette, LA 70504-4130 (United States); Misra, R.D.K. [Center for Structural and Functional Materials, University of Louisiana at Lafayette, Lafayette, LA 70504-4130 (United States); Department of Chemical Engineering, University of Louisiana at Lafayette, Lafayette, LA 70504-4130 (United States)], E-mail: dmisra@louisiana.edu; Mannering, T. [Nucor-Yamato Steel, P.O. Box 1228, 5929 East State Highway 18, Blytheville, AR 72316 (United States); Panda, D. [Nucor-Yamato Steel, P.O. Box 1228, 5929 East State Highway 18, Blytheville, AR 72316 (United States); Jansto, S. [Reference Metals, 1000 Old Pond Road, Bridgeville, PA 15017 (United States)

    2007-07-15

    We describe here the effect of cooling rate on the microstructure and mechanical properties of Nb-microalloyed steels that were processed as structural beams at three different cooling rates. Nb-microalloyed steels exhibited increase in yield strength with increase in cooling rate during processing. However, the increase in the yield strength was not accompanied by loss in toughness. The microstructure at conventional cooling rate, primarily consisted of polygonal ferrite-pearlite microconstituents, while at intermediate cooling rate besides polygonal ferrite and pearlite contained significant fraction of degenerated pearlite and lath-type ferrite. At higher cooling rate, predominantly, lath-type (acicular) or bainitic ferrite was obtained. The precipitation characteristics were similar at the three cooling rates investigated with precipitation occurring at grain boundaries, on dislocations, and in the ferrite matrix. The fine scale ({approx}8-12 nm) precipitates in the ferrite matrix were MC type of niobium carbides. The microstructural studies suggest that the increase in toughness of Nb-microalloyed steels with increase in cooling rate is related to the change in the microstructure from predominantly ferrite-pearlite to predominantly bainitic ferrite.

  7. Microstructural evolution and mechanical properties of Ti3SiC2-TiC composites

    International Nuclear Information System (INIS)

    Tian, WuBian; Sun, ZhengMing; Hashimoto, Hitoshi; Du, YuLei

    2010-01-01

    Ti 3 SiC 2 -TiC composites were fabricated by pulse discharge sintering technique using three different sets of powder mixtures, i.e. Ti/Si/TiC (TC30), Ti/Si/C/TiC (SI30) and Ti/Si/C (TSC30). Based on X-ray diffraction (XRD) analysis and microstructural observations, starting powder reactants were found to have little effect on phase content but strong influence on the microstructure in terms of phase distribution. The phase distribution mainly relies on the heat released from reaction and the liquid phase content formed during sintering. The mechanical properties of the fabricated dense samples demonstrate that more homogeneous phase distribution, available by choosing the starting reactants of SI30, results in higher flexural strength, whereas the Vickers hardness is almost independent of the microstructure. The enhanced flexural strength in sample SI30 sintered at 1400 o C is mainly attributed to the homogeneous TiC distribution in the microstructure.

  8. SLM processing-microstructure-mechanical property correlation in an aluminum alloy produced by additive manufacturing

    Science.gov (United States)

    Alejos, Martin Fernando

    Additive manufacturing has become a highly researched topic in recent years all over the world. The current research evaluates the merits of additive manufacturing based on the mechanical, microstructural, and fracture properties of additive manufactured AlSi10Mg test specimens. The additive manufactured build plates consisted of tensile and fatigue test specimens. They were printed in the 0°, 30°, 60°, and 90° orientations relative to the build platform. Tensile and dynamic fatigue tests were conducted followed by microstructural characterization and fracture analysis. A wrought 6061 T6 aluminum alloy was also tested for comparison. Tensile tests revealed similar ultimate tensile strengths for all aluminum tensile specimens (350-380 MPa). Fatigue strength was greatest for wrought 6061 T6 aluminum (175 MPa). The fatigue behavior was a strong function of build orientation for the additive manufactured specimens. The 0°, 30°, and 60° orientations had fatigue strengths close to 104 MPa while the 90° orientation had a fatigue strength of 125 MPa. All test specimens failed primarily in a ductile manner. The effect of laser power, hatch spacing, and scan speed were also studied using microstructural analysis. Increasing laser power decreased grain size and void size. Increasing scan speed led to the formation of columnar grains. Increasing hatch spacing decreased grain size and the amount of voids present in the microstructure.

  9. Microstructure and mechanical properties of electron beam welded dissimilar steel to Fe–Al alloy joints

    Energy Technology Data Exchange (ETDEWEB)

    Dinda, Soumitra Kumar; Basiruddin Sk, Md.; Roy, Gour Gopal [Department of Metallurgical and Materials Engineering, Indian Institute of Technology, Kharagpur (India); Srirangam, Prakash, E-mail: p.srirangam@warwick.ac.uk [Warwick Manufacturing Group (WMG), University of Warwick, Coventry CV4 7AL (United Kingdom)

    2016-11-20

    Electron beam welding (EBW) technique was used to perform dissimilar joining of plain carbon steel to Fe–7%Al alloy under three different weld conditions such as with beam oscillation, without beam oscillation and at higher welding speed. The effect of weld parameters on the microstructure and mechanical properties of dissimilar joints was studied using optical microscopy, SEM, EBSD, hardness, tensile and erichsen cup tests. Microstructure results show that the application of beam oscillation resulted in uniform and homogeneous microstructure compared to without beam oscillations and higher welding speed. Further, it was observed that weld microstructure changes from equiaxed to columnar grains depending on the weld speed. High weld speed results in columnar grain structure in the weld joint. Erichsen cup test results show that the application of beam oscillation results in excellent formability as compared to high weld speed. Tensile test results show no significant difference in strength properties in all three weld conditions, but the ductility was found to be highest for joints obtained with the application of weld beam oscillation as compared to without beam oscillation and high weld speed. This study shows that the application of beam oscillations plays an important role in improving the weld quality and performance of EBW dissimilar steel to Fe–Al joints.

  10. Microstructure and mechanical properties of an extruded Mg-8Bi-1Al-1Zn (wt%) alloy

    Energy Technology Data Exchange (ETDEWEB)

    Meng, Shuaiju [School of Materials Science and Engineering, Hebei University of Technology, Tianjin 300130 (China); Yu, Hui, E-mail: yuhuidavid@gmail.com [School of Materials Science and Engineering, Hebei University of Technology, Tianjin 300130 (China); Materials Commercialization Center, Korea Institute of Materials Science, Changwon 51508 (Korea, Republic of); Zhang, Huixing [Mechanical and Material School, Tianjin Sino-German University of Applied Sciences, Tianjin 300350 (China); Cui, Hongwei [School of Materials Science and Engineering, Shangdong University of Technology, Zibo 255049 (China); Park, Sung Hyuk [School of Materials Science and Engineering, Kyungpook National University, Daegu 702701 (Korea, Republic of); Zhao, Weiming [School of Materials Science and Engineering, Hebei University of Technology, Tianjin 300130 (China); You, Bong Sun [Materials Commercialization Center, Korea Institute of Materials Science, Changwon 51508 (Korea, Republic of)

    2017-04-06

    In this study, the microstructural evolution and mechanical properties of a newly developed rare earth free Mg-8Bi-1Al-1Zn (BAZ811, in wt%) alloy were investigated and compared with those of a commercial AZ31 alloy. The as-extruded BAZ811 alloy with much finer grain size shows more homogeneous dynamical recrystallized (DRXed) microstructure and weaker basal texture than those of AZ31 alloy. In addition, compared with bimodal structure AZ31 alloy containing only relatively coarse and sparse Al{sub 8}Mn{sub 5} phases, the coexistence of strip-like fragmented Mg{sub 3}Bi{sub 2} precipitate and nano-size Mg{sub 3}Bi{sub 2} particles in the microstructure was observed in BAZ811 alloy. Moreover, the BAZ811 alloy exhibits a tensile yield stress of 291 MPa, an ultimate tensile strength of 331 MPa, an elongation to failure of 14.6% as well as a reduction in yield asymmetry, which is mainly attributed to the combined effects of grain refinement and micro-scale broken Mg{sub 3}Bi{sub 2} particles together with nano-scale spherical Mg{sub 3}Bi{sub 2} precipitates. The strain hardening behavior of both BAZ811 and AZ31 alloys were also discussed in terms of microstructure variation.

  11. Microstructure and physical properties of mechanically alloyed Fe-Mo powder

    Czech Academy of Sciences Publication Activity Database

    Jirásková, Yvonna; Zábranský, Karel; Turek, Ilja; Buršík, Jiří; Jančík, D.

    2009-01-01

    Roč. 477, - (2009), s. 55-61 ISSN 0925-8388 R&D Projects: GA ČR GA202/05/2111; GA ČR GD106/05/H008 Institutional research plan: CEZ:AV0Z20410507 Keywords : Nanostructured materials * Mechanical alloying * Microstructure * Magnetic measurements * Mössbauer spectroscopy Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.135, year: 2009

  12. Modal loss mechanism of micro-structured VCSELs studied using full vector FDTD method.

    Science.gov (United States)

    Jo, Du-Ho; Vu, Ngoc Hai; Kim, Jin-Tae; Hwang, In-Kag

    2011-09-12

    Modal properties of vertical cavity surface-emitting lasers (VCSELs) with holey structures are studied using a finite difference time domain (FDTD) method. We investigate loss behavior with respect to the variation of structural parameters, and explain the loss mechanism of VCSELs. We also propose an effective method to estimate the modal loss based on mode profiles obtained using FDTD simulation. Our results could provide an important guideline for optimization of the microstructures of high-power single-mode VCSELs.

  13. Effect of ECAP on microstructure and mechanical properties of cast AZ91 magnesium alloy

    International Nuclear Information System (INIS)

    Chung, C W; Gao, W; Ding, R G; Chiu, Y L

    2010-01-01

    An as-cast AZ91 magnesium alloy was processed by Equal Channel Angular Pressing (ECAP) at 320 0 C. The microstructure and mechanical properties were studied. It has been found that ECAP refines both the grains and precipitates, thus modifies the strength and ductility of the processed alloy. After the first pass of ECAP, the yield stress improves significantly from 71 MPa to 140 MPa.

  14. Microstructure, mechanical and functional properties of NiTi-based shape memory ribbons

    International Nuclear Information System (INIS)

    Mehrabi, K.; Bruncko, M.; Kneissl, A.C.

    2012-01-01

    Highlights: ► Melt-spun samples exhibited martensite structure and shape memory effects immediately after processing at room temperature. ► Using a new etchant and interference contrast, it is possible to reveal the fine microstructures and grain boundaries. ► The martensite structure in NiTi is very fine, and nano-sized twin boundaries could be revealed using TEM only. ► Two-way effects have been successfully introduced by different thermomechanical training methods in NiTi, NiTiCu and NiTiW alloys, which can be used for several applications, e.g. microsensors and microactuators. - Abstract: The present work has been aimed to study the microstructures, functional properties and the influence of different thermomechanical training methods on the two-way shape memory effect in NiTi-based melt-spun ribbons. In order to get small-dimensioned shape memory alloys (SMAs) with good functional and mechanical properties, a rapid solidification technique was employed. Their fracture and elasticity characteristics have been determined, as well as shape memory properties by thermomechanical cycling. The ribbons were trained under tensile and bending deformation by thermal cycling through the phase transformation temperature range. The results displayed that all different training methods were effective in developing a two-way shape memory effect (TWSME). The influence of copper (5–25 at.% Cu) and tungsten (2 at.% W) on the microstructure, and the functional and mechanical behavior of NiTi thin ribbons was also investigated. All samples show a shape memory effect immediately after processing without further heat treatment. The melt-spun ribbons were trained under constant strain (bending and tensile deformation) by thermal cycling through the phase transformation temperature range. The addition of copper was effective to narrow the transformation hysteresis. The W addition has improved the TWSME stability of the NiTi alloys and mechanical properties. Results about

  15. Microstructures and Mechanical Properties of Inconel 718 Alloy at Ultralow Temperatures

    Science.gov (United States)

    Yao, C. G.; Lv, H. J.; Yi, D. Q.; Meng, S.; Xiao, L. R.; Wang, B.

    2018-05-01

    The microstructures and mechanical properties of powder metallurgy Inconel 718 alloy were investigated in the temperatures range between 25 and - 253 °C. Tensile strength increased with the decrease in temperature, while the ductility first increased and then decreased. There was no significant change in impact toughness. When the temperature was - 253 °C, a zigzag stress-strain curve was observed for the alloy, owing to the interaction of dislocation glide and twinning, which effectively maintained the relatively good ductility.

  16. Studies on microstructure, mechanical and corrosion properties of high nitrogen stainless steel shielded metal arc welds

    Science.gov (United States)

    Mohammed, Raffi; Madhusudhan Reddy, G.; Srinivasa Rao, K.

    2018-03-01

    The present work is aimed at studying the microstructure, mechanical and corrosion properties of high nitrogen stainless steel shielded metal arc (SMA) welds made with Cromang-N electrode. Basis for selecting this electrode is to increase the solubility of nitrogen in weld metal due to high chromium and manganese content. Microstructures of the welds were characterized using optical microscopy (OM), field emission scanning electron microscopy (FESEM) and electron back scattered diffraction (EBSD) mainly to determine the morphology, phase analysis, grain size and orientation image mapping. Hardness, tensile and ductility bend tests were carried out to determine mechanical properties. Potentio-dynamic polarization testing was carried out to study the pitting corrosion resistance using a GillAC basic electrochemical system. Constant load type testing was carried out to study stress corrosion cracking (SCC) behaviour of welds. The investigation results shown that the selected Cr–Mn–N type electrode resulted in favourable microstructure and completely solidified as single phase coarse austenite. Mechanical properties of SMA welds are found to be inferior when compared to that of base metal and is due to coarse and dendritic structure.

  17. Correlation between microstructural features and mechanical properties of irradiated LONGLIFE RPV steels

    International Nuclear Information System (INIS)

    Serrano, M.; Hermandez-Mayoral, E.; Bergner, F.; Viehrig, H.W.; Altstadt, E.; Radiguet, B.; Lim, J.H.; Grovenor, C.R.M.; Meslin, E.; Van Renterghem, W.; Chaouadi, R.; Ortner, S.; Hein, H.; Gillemot, F.; Todeschini, P.; Planman, T.; Wilford, K.; Kocik, J.; Brumovsky, M.; Ruoden, J.

    2015-01-01

    The possibility of extending the operational life of reactor pressure vessels (RPV) up to 80 years presents the problem of the availability of materials irradiated at high neutron fluence and low neutron flux. The ability of the existing trend curves to predict high fluence embrittlement is a question of debate, and a critical analysis of these curves should be based on a consistent microstructural examination of irradiated materials. Within the LONGLIFE 7FWP, neutron irradiated RPV materials, relevant for long term operation, some of them coming from surveillance programs, have been characterized by means of a combination of microstructural techniques (APT, SANS, TEM) and mechanical tests (hardness, tensile, impact and fracture toughness). In this paper the analysis of the links between microstructural features (solute nano-clusters, dislocation loops and voids) and hardening and embrittlement measurements by mechanical testing, is presented. Current hardening models, based on the contribution of precipitates, or nano-clusters, seem to underestimate irradiation hardening for very high fluences, mainly when matrix damage (dislocation loops) is observed. Regarding chemical composition effects, the predominant role of Ni and the synergism between Ni-Mn and Si are also identified. Low-Cu alloys show a threshold value of radiation induced features to produce an effect on mechanical properties which calls for further in-depth analyses. (authors)

  18. Microstructural and Mechanical Study of Press Hardening of Thick Boron Steel Sheet

    Science.gov (United States)

    Pujante, J.; Garcia-Llamas, E.; Golling, S.; Casellas, D.

    2017-09-01

    Press hardening has become a staple in the production of automotive safety components, due to the combination of high mechanical properties and form complexity it offers. However, the use of press hardened components has not spread to the truck industry despite the advantages it confers, namely affordable weight reduction without the use of exotic materials, would be extremely attractive for this sector. The main reason for this is that application of press hardened components in trucks implies adapting the process to the manufacture of thick sheet metal. This introduces an additional layer of complexity, mainly due to the thermal gradients inside the material resulting in though-thickness differences in austenitization and cooling, potentially resulting in complex microstructure and gradient of mechanical properties. This work presents a preliminary study on the press hardening of thick boron steel sheet. First of all, the evolution of the sheet metal during austenitization is studied by means of dilatometry tests and by analysing the effect of furnace dwell time on grain size. Afterwards, material cooled using different cooling strategies, and therefore different effective cooling rates, is studied in terms of microstructure and mechanical properties. Initial results from finite element simulation are compared to experimental results, focusing on the phase composition in through thickness direction. Results show that industrial-equivalent cooling conditions do not lead to gradient microstructures, even in extreme scenarios involving asymmetrical cooling.

  19. Effects of deep cryogenic treatment on the microstructure and mechanical properties of commercial pure zirconium

    Energy Technology Data Exchange (ETDEWEB)

    Yuan, Chao; Wang, Yunpeng; Sang, Deli; Li, Yijun; Jing, Lei; Fu, Ruidong, E-mail: rdfu@ysu.edu.cn; Zhang, Xiangyi

    2015-01-15

    Highlights: • The microstructure and mechanical properties of DCT-treated Zr were investigated. • DCT induced a change in grain orientation and improved internal stress. • Changes in grain orientation and internal stress increased dislocation density. • Hardness in basal planes was significantly larger than that in prism planes. • Strength levels were high and good ductility could still be achieved after DCT. - Abstract: The effects of deep cryogenic treatment (DCT) on the microstructure and mechanical properties of commercial pure zirconium were investigated. Experimental results indicated that DCT induced a change in grain orientation and improved internal stress, which in turn increased dislocation density that led to improved hardness. Hardness in basal planes was found to be significantly larger than that in prism planes. Moreover, strength was enhanced in DCT-treated zirconium and the ductility was comparable to that of as-annealed zirconium. This phenomenon was due to the increase in dislocation density and the good ductility resulting from the motion of pre-existing dislocations and specific dislocation configurations. DCT led to the transformation of tensile fracture mode from mixed-rupture characteristics of quasi-cleavage and dimples to quasi-cleavage, thereby increasing compatible deformation capabilities. The possible mechanisms underlying microstructural modification, tensile strength, and hardness improvement were discussed.

  20. Powder injection molding of Stellite 6 powder: Sintering, microstructural and mechanical properties

    International Nuclear Information System (INIS)

    Gülsoy, H. Özkan; Özgün, Özgür; Bilketay, Sezer

    2016-01-01

    The purpose of this study was to produce Co-based Stellite 6 superalloy components by using the method of Powder Injection Molding (PIM) and to characterize the microstructural and mechanical properties of the produced components. The experimental studies were started through the formation of feedstock by mixing Stellite 6 powder with a multicomponent binder system. Prepared feedstock was formed by utilizing powder injection molding technique. Then the molded samples were subjected to the solvent and thermal debinding processes. Different sintering cycles were applied to the raw components for the purpose of determining the optimum sintering conditions. The densities of the sintered components were determined in accordance with the Archimedes' principle. The microstructural characterization was performed through scanning electron microscope (SEM) analysis, energy dispersive spectrometry (EDS) analyses, and X-ray diffraction (XRD) analysis. Hardness measurement and tensile test were conducted in order to determine the mechanical properties. The results illustrated that the injection molded Stellite 6 components were composed of fine and equiaxed grains, plenty of carbide precipitates exhibiting homogenous distribution throughout the microstructure formed at the grain boundaries and thus the mechanical properties were considerably high.

  1. Effects of Bi Addition on the Microstructure and Mechanical Properties of Nanocrystalline Ag Coatings

    Directory of Open Access Journals (Sweden)

    Yuxin Wang

    2017-08-01

    Full Text Available In this study we investigated the effects of Bi addition on the microstructure and mechanical properties of an electrodeposited nanocrystalline Ag coating. Microstructural features were investigated with transmission electron microscopy (TEM. The results indicate that the addition of Bi introduced nanometer-scale Ag-Bi solid solution particles and more internal defects to the initial Ag microstructures. The anisotropic elastic-plastic properties of the Ag nanocrystalline coating with and without Bi addition were examined with nanoindentation experiments in conjunction with the recently-developed inverse method. The results indicate that the as-deposited nanocrystalline Ag coating contained high mechanical anisotropy. With the addition of 1 atomic percent (at% Bi, the anisotropy within Ag-Bi coating was very small, and yield strength of the nanocrystalline Ag-Bi alloy in both longitudinal and transverse directions were improved by over 100% compared to that of Ag. On the other hand, the strain-hardening exponent of Ag-Bi was reduced to 0.055 from the original 0.16 of the Ag coating. Furthermore, the addition of Bi only slightly increased the electrical resistivity of the Ag-Bi coating in comparison to Ag. Results of our study indicate that Bi addition is a promising method for improving the mechanical and physical performances of Ag coating for electrical contacts.

  2. Effects of deep cryogenic treatment on the microstructure and mechanical properties of commercial pure zirconium

    International Nuclear Information System (INIS)

    Yuan, Chao; Wang, Yunpeng; Sang, Deli; Li, Yijun; Jing, Lei; Fu, Ruidong; Zhang, Xiangyi

    2015-01-01

    Highlights: • The microstructure and mechanical properties of DCT-treated Zr were investigated. • DCT induced a change in grain orientation and improved internal stress. • Changes in grain orientation and internal stress increased dislocation density. • Hardness in basal planes was significantly larger than that in prism planes. • Strength levels were high and good ductility could still be achieved after DCT. - Abstract: The effects of deep cryogenic treatment (DCT) on the microstructure and mechanical properties of commercial pure zirconium were investigated. Experimental results indicated that DCT induced a change in grain orientation and improved internal stress, which in turn increased dislocation density that led to improved hardness. Hardness in basal planes was found to be significantly larger than that in prism planes. Moreover, strength was enhanced in DCT-treated zirconium and the ductility was comparable to that of as-annealed zirconium. This phenomenon was due to the increase in dislocation density and the good ductility resulting from the motion of pre-existing dislocations and specific dislocation configurations. DCT led to the transformation of tensile fracture mode from mixed-rupture characteristics of quasi-cleavage and dimples to quasi-cleavage, thereby increasing compatible deformation capabilities. The possible mechanisms underlying microstructural modification, tensile strength, and hardness improvement were discussed

  3. The temperature-dependent microstructure of PEDOT/PSS films: insights from morphological, mechanical and electrical analyses

    KAUST Repository

    Zhou, Jian

    2014-09-24

    Poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT/PSS) is a widely used conductive polymer in the field of flexible electronics. The ways its microstructure changes over a broad range of temperatures remain unclear. This paper describes microstructure changes at different temperatures and correlates the microstructure with its physical properties (mechanical and electrical). We used High-Angle Annular Dark-Field Scanning Electron Microscopy (HAADF-STEM) combined with electron energy loss spectroscopy (EELS) to determine the morphology and elemental atomic ratio of the film at different temperatures. These results together with the Atomic Force Microscopy (AFM) analysis provide the foundation for a model of how the temperature affects the microstructure of PEDOT/PSS. Moreover, dynamic mechanical analysis (DMA) and electrical characterization were performed to analyze the microstructure and physical property correlations.

  4. Microstructure and mechanical properties of a novel rapidly solidified, high-temperature Al-alloy

    Energy Technology Data Exchange (ETDEWEB)

    Overman, N.R., E-mail: Nicole.Overman@pnnl.gov [Pacific Northwest National Laboratory, P.O. Box 999, Richland, WA 99352 (United States); Mathaudhu, S.N. [Pacific Northwest National Laboratory, P.O. Box 999, Richland, WA 99352 (United States); University of California, Riverside, 3401 Watkins Dr., Riverside, CA 92521 (United States); Choi, J.P.; Roosendaal, T.J.; Pitman, S. [Pacific Northwest National Laboratory, P.O. Box 999, Richland, WA 99352 (United States)

    2016-02-15

    Rapid solidification (RS) processing, as a production method, offers a variety of unique properties based on far-from-equilibrium microstructures obtained through rapid cooling rates. In this study, we seek to investigate the microstructures and properties of a novel Al-alloy specifically designed for high temperature mechanical stability. Synthesis of, AlFe{sub 11.4}Si{sub 1.8}V{sub 1.6}Mn{sub 0.9} (wt.%), was performed by two approaches: rotating cup atomization (“shot”) and melt spinning (“flake”). These methods were chosen because of their ability to produce alloys with tailored microstructures due to their inherent differences in cooling rate. The as-solidified precursor materials were microstructurally characterized with electron microscopy. The results show that the higher cooling rate flake material exhibited the formation of nanocrystalline regions as well additional phase morphologies not seen in the shot material. Secondary dendritic branching in the flake material was on the order of 0.1–0.25 μm whereas branching in the shot material was 0.5–1.0 μm. Consolidated and extruded material from both precursor materials was mechanically evaluated at both ambient and high (300 °C) temperature. The consolidated RS flake material is shown to exhibit higher strengths than the shot material. The ultimate tensile strength of the melt spun flake was reported as 544.2 MPa at room temperature and 298.0 MPa at 300 °C. These results forecast the ability to design alloys and processing approaches with unique non-equilibrium microstructures with robust mechanical properties at elevated temperatures. - Highlights: • A novel alloy, AlFe{sub 11.4}Si{sub 1.8}V{sub 1.6}Mn{sub 0.9} was fabricated by rapid solidification. • Room temperature yield strength exceeded 500 MPa. • Elevated temperature (300 °C) yield strength exceeded 275 MPa. • Forging, after extrusion of the alloy resulted in microstructural coarsening. • Decreased strength and ductility was

  5. Mechanical properties and microstructure analysis of fly ash geopolymeric recycled concrete

    International Nuclear Information System (INIS)

    Shi, X.S.; Collins, F.G.; Zhao, X.L.; Wang, Q.Y.

    2012-01-01

    Highlights: ► Sodium silicate solution and sodium hydroxide solution were used to activate fly ash, which substitute cement totally in the concrete. ► Utilizing two kinds of waste materials (fly ash and recycled aggregates) at the same time. ► The mechanical properties and microstructures were studied and compared with different recycled aggregates replacement ratios. ► Such concrete has greater compressive strength and better microstructure than ordinary concrete and also geopolymer concrete. - Abstract: Six mixtures with different recycled aggregate (RA) replacement ratios of 0%, 50% and 100% were designed to manufacture recycled aggregate concrete (RAC) and alkali-activated fly ash geopolymeric recycled concrete (GRC). The physical and mechanical properties were investigated indicating different performances from each other. Optical microscopy under transmitted light and scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDX) were carried out in this study in order to identify the mechanism underlying the effects of the geopolymer and RA on concrete properties. The features of aggregates, paste and interfacial transition zone (ITZ) were compared and discussed. Experimental results indicate that using alkali-activated fly ash geopolymer as replacement of ordinary Portland cement (OPC) effectively improved the compressive strength. With increasing of RA contents in both RAC and GRC, the compressive strength decreased gradually. The microstructure analysis shows that, on one hand, the presence of RA weakens the strength of the aggregates and the structure of ITZs; on the other hand, due to the alkali-activated fly ash in geopolymer concrete, the contents of Portlandite (Ca(OH) 2 ) and voids were reduced, as well as improved the matrix homogeneity. The microstructure of GRC was changed by different reaction products, such as aluminosilicate gel.

  6. Unconventional barometry and rheometry: new quantification approaches for mechanically-controlled microstructures

    Science.gov (United States)

    Tajcmanova, L.; Moulas, E.; Vrijmoed, J.; Podladchikov, Y.

    2016-12-01

    Estimation of pressure-temperature (P-T) from petrographic observations in metamorphic rocks has become a common practice in petrology studies during the last 50 years. This data often serves as a key input in geodynamic reconstructions and thus directly influences our understanding of lithospheric processes. Such an approach might have led the metamorphic geology field to a certain level of quiescence. In the classical view of metamorphic quantification approaches, fast viscous relaxation (and therefore constant pressure across the rock microstructure) is assumed, with chemical diffusion being the limiting factor in equilibration. Recently, we have focused on the other possible scenario - fast chemical diffusion and slow viscous relaxation - and brings an alternative interpretation of chemical zoning found in high-grade rocks. The aim has been to provide insight into the role of mechanically maintained pressure variations on multi-component chemical zoning in minerals. Furthermore, we used the pressure information from the mechanically-controlled microstructure for rheological constrains. We show an unconventional way of relating the direct microstructural observations in rocks to the nonlinearity of rheology at time scales unattainable by laboratory measurements. Our analysis documents that mechanically controlled microstructures that have been preserved over geological times can be used to deduce flow-law parameters and in turn estimate stress levels of minerals in their natural environment. The development of the new quantification approaches has opened new horizons in understanding the phase transformations in the Earth's lithosphere. Furthermore, the new data generated can serve as a food for thought for the next generation of fully coupled numerical codes that involve reacting materials while respecting conservation of mass, momentum and energy.

  7. A new characterization approach for studying relationships between microstructure and creep damage mechanisms of uranium dioxide

    Energy Technology Data Exchange (ETDEWEB)

    Iltis, X., E-mail: xaviere.iltis@cea.fr [CEA, DEN, DEC, Cadarache, 13108 Saint-Paul-Lez-Durance (France); Ben Saada, M. [CEA, DEN, DEC, Cadarache, 13108 Saint-Paul-Lez-Durance (France); Laboratoire d' Etudes des Microstructures et de Mécanique des Matériaux (LEM3), CNRS UMR 7239, Université de Lorraine, Ile du Saulcy, 57045 Metz Cedex 1 (France); Mansour, H.; Gey, N.; Hazotte, A.; Maloufi, N. [Laboratoire d' Etudes des Microstructures et de Mécanique des Matériaux (LEM3), CNRS UMR 7239, Université de Lorraine, Ile du Saulcy, 57045 Metz Cedex 1 (France)

    2016-06-15

    Four batches of UO{sub 2} pellets were studied comparatively, before and after creep tests, to evaluate a characterization methodology aimed to determine the links between microstructure and damage mechanisms induced by compressive creep of uranium dioxide at 1500 °C. They were observed by means of scanning electron microscopy (SEM) coupled with image analysis, to quantify their fabrication porosity and the occurrence of inter-granular cavities after creep, and electron back scattered diffraction (EBSD), especially to characterize sub-structures development associated with plastic deformation. Electron channeling contrast imaging (ECCI) was also applied to evidence dislocations, at an exploratory stage, on one of the deformed pellets. This approach helped to identify and quantify microstructural differences between batches. Their as-fabricated microstructures differed in terms of grain size and fabrication porosity distribution. The pellets which had the lowest strain rates were those with the largest number of intra-granular pores, regardless of their grain size. They also exhibited less numerous sub-boundaries within the grains. These first results clearly illustrate the benefit of systematic examinations of crept UO{sub 2} pellets at a mesoscopic scale, by SEM and EBSD, to study their deformation process. In addition, ECCI appears as a powerful tool to evidence local dislocations arrangements, in bulk samples. Even if the sampling was limited, the results of this study also tend to indicate that the intra-granular pores population, resulting from the manufacturing of the samples by powder metallurgy, could have a significant influence on the UO{sub 2} viscoplastic deformation mechanisms. - Highlights: • Four different UO{sub 2} pellets batches are microstructurally compared, before and after compression creep tests. • Development of sub-boundaries within the original grains, in crept samples, is quantified by EBSD. • Links are observed between the intra

  8. Microstructure and mechanical properties of resistance upset butt welded 304 austenitic stainless steel joints

    International Nuclear Information System (INIS)

    Sharifitabar, M.; Halvaee, A.; Khorshahian, S.

    2011-01-01

    Graphical abstract: Three different microstructural zones formed at different distances from the joint interface in resistance upset butt welding of 304 austenitic stainless steel. Highlights: → Evaluation of microstructure in resistance upset welding of 304 stainless steel. → Evaluation of welding parameters effects on mechanical properties of the joint. → Introducing the optimum welding condition for joining stainless steel bars. -- Abstract: Resistance upset welding (UW) is a widely used process for joining metal parts. In this process, current, time and upset pressure are three parameters that affect the quality of welded products. In the present research, resistance upset butt welding of 304 austenitic stainless steel and effect of welding power and upset pressure on microstructure, tensile strength and fatigue life of the joint were investigated. Microstructure of welds were studied using scanning electron microscopy (SEM). X-ray diffraction (XRD) analysis was used to distinguish the phase(s) that formed at the joint interface and in heat affected zone (HAZ). Energy dispersive spectroscopy (EDS) linked to the SEM was used to determine chemical composition of phases formed at the joint interface. Fatigue tests were performed using a pull-push fatigue test machine and the fatigue properties were analyzed drawing stress-number of cycles to failure (S-N) curves. Also tensile strength tests were performed. Finally tensile and fatigue fracture surfaces were studied by SEM. Results showed that there were three different microstructural zones at different distances from the joint interface and delta ferrite phase has formed in these regions. There was no precipitation of chromium carbide at the joint interface and in the HAZ. Tensile and fatigue strengths of the joint decreased with welding power. Increasing of upset pressure has also considerable influence on tensile strength of the joint. Fractography of fractured samples showed that formation of hot spots at

  9. Microstructural development and mechanical properties of iron based cermets processed by pressureless and spark plasma sintering

    International Nuclear Information System (INIS)

    Alvaredo, P.; Gordo, E.; Van der Biest, O.; Vanmeensel, K.

    2012-01-01

    Highlights: ► Processing of Fe-based cermets by pressureless sintering and spark plasma sintering. ► Influence of carbon content on the sintering mechanism and hardness. ► The cermet phase diagram was calculated and permits to explain the microstructure. ► SPS provides ferritic matrix and different carbide distribution than CPS samples. ► Pressureless sintered samples contain retained austenite at room temperature. - Abstract: Iron-based cermets are an interesting class of metal-ceramic composites in which properties and the factors influencing them are to be explored. In this work the metal matrix contains Cr, W, Mo and V as alloying elements, and the hard phase is constituted by 50 vol% of titanium carbonitride (TiCN) particles. The work studies the influence of the C content and the processing method on the sinterability, microstructure and hardness of the developed cermet materials. For that purpose, cermet samples with different C content in the matrix (0 wt%, 0.25 wt%, 0.5 wt%, 1.0 wt%) were prepared by conventional pressureless sintering (CPS) and, in order to achieve finer microstructures and to reduce the sintering time, by spark plasma sintering (SPS). The density and hardness (HV30) of the processed materials was evaluated, while their phase composition and microstructure was characterised by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The equilibrium phase diagram of the composite material was calculated by ThermoCalc software in order to elucidate the influence of the carbon content on the obtained phases and developed microstructures.

  10. Bacterial biofilm mechanical properties persist upon antibiotic treatment and survive cell death

    International Nuclear Information System (INIS)

    Zrelli, K; Galy, O; Henry, N; Latour-Lambert, P; Ghigo, J M; Beloin, C; Kirwan, L

    2013-01-01

    Bacteria living on surfaces form heterogeneous three-dimensional consortia known as biofilms, where they exhibit many specific properties one of which is an increased tolerance to antibiotics. Biofilms are maintained by a polymeric network and display physical properties similar to that of complex fluids. In this work, we address the question of the impact of antibiotic treatment on the physical properties of biofilms based on recently developed tools enabling the in situ mapping of biofilm local mechanical properties at the micron scale. This approach takes into account the material heterogeneity and reveals the spatial distribution of all the small changes that may occur in the structure. With an Escherichia coli biofilm, we demonstrate using in situ fluorescent labeling that the two antibiotics ofloxacin and ticarcillin—targeting DNA replication and membrane assembly, respectively—induced no detectable alteration of the biofilm mechanical properties while they killed the vast majority of the cells. In parallel, we show that a proteolytic enzyme that cleaves extracellular proteins into short peptides, but does not alter bacterial viability in the biofilm, clearly affects the mechanical properties of the biofilm structure, inducing a significant increase of the material compliance. We conclude that conventional biofilm control strategy relying on the use of biocides targeting cells is missing a key target since biofilm structural integrity is preserved. This is expected to efficiently promote biofilm resilience, especially in the presence of persister cells. In contrast, the targeting of polymer network cross-links—among which extracellular proteins emerge as major players—offers a promising route for the development of rational multi-target strategies to fight against biofilms. (paper)

  11. Structural studies of the mechanism for biosensing antibiotics in a fluorescein-labeled β-lactamase

    Directory of Open Access Journals (Sweden)

    Wong Kwok-Yin

    2011-03-01

    Full Text Available Abstract Background β-lactamase conjugated with environment-sensitive fluorescein molecule to residue 166 on the Ω-loop near its catalytic site is a highly effective biosensor for β-lactam antibiotics. Yet the molecular mechanism of such fluorescence-based biosensing is not well understood. Results Here we report the crystal structure of a Class A β-lactamase PenP from Bacillus licheniformis 749/C with fluorescein conjugated at residue 166 after E166C mutation, both in apo form (PenP-E166Cf and in covalent complex form with cefotaxime (PenP-E166Cf-cefotaxime, to illustrate its biosensing mechanism. In the apo structure the fluorescein molecule partially occupies the antibiotic binding site and is highly dynamic. In the PenP-E166Cf-cefatoxime complex structure the binding and subsequent acylation of cefotaxime to PenP displaces fluorescein from its original location to avoid steric clash. Such displacement causes the well-folded Ω-loop to become fully flexible and the conjugated fluorescein molecule to relocate to a more solvent exposed environment, hence enhancing its fluorescence emission. Furthermore, the fully flexible Ω-loop enables the narrow-spectrum PenP enzyme to bind cefotaxime in a mode that resembles the extended-spectrum β-lactamase. Conclusions Our structural studies indicate the biosensing mechanism of a fluorescein-labelled β-lactamase. Such findings confirm our previous proposal based on molecular modelling and provide useful information for the rational design of β-lactamase-based biosensor to detect the wide spectrum of β-lactam antibiotics. The observation of increased Ω-loop flexibility upon conjugation of fluorophore may have the potential to serve as a screening tool for novel β-lactamase inhibitors that target the Ω-loop and not the active site.

  12. Bacterial biofilm mechanical properties persist upon antibiotic treatment and survive cell death

    Science.gov (United States)

    Zrelli, K.; Galy, O.; Latour-Lambert, P.; Kirwan, L.; Ghigo, J. M.; Beloin, C.; Henry, N.

    2013-12-01

    Bacteria living on surfaces form heterogeneous three-dimensional consortia known as biofilms, where they exhibit many specific properties one of which is an increased tolerance to antibiotics. Biofilms are maintained by a polymeric network and display physical properties similar to that of complex fluids. In this work, we address the question of the impact of antibiotic treatment on the physical properties of biofilms based on recently developed tools enabling the in situ mapping of biofilm local mechanical properties at the micron scale. This approach takes into account the material heterogeneity and reveals the spatial distribution of all the small changes that may occur in the structure. With an Escherichia coli biofilm, we demonstrate using in situ fluorescent labeling that the two antibiotics ofloxacin and ticarcillin—targeting DNA replication and membrane assembly, respectively—induced no detectable alteration of the biofilm mechanical properties while they killed the vast majority of the cells. In parallel, we show that a proteolytic enzyme that cleaves extracellular proteins into short peptides, but does not alter bacterial viability in the biofilm, clearly affects the mechanical properties of the biofilm structure, inducing a significant increase of the material compliance. We conclude that conventional biofilm control strategy relying on the use of biocides targeting cells is missing a key target since biofilm structural integrity is preserved. This is expected to efficiently promote biofilm resilience, especially in the presence of persister cells. In contrast, the targeting of polymer network cross-links—among which extracellular proteins emerge as major players—offers a promising route for the development of rational multi-target strategies to fight against biofilms.

  13. Retraction: Graphene-SnO2 nanocomposites decorated with quantum tunneling junctions: preparation strategies, microstructures and formation mechanism.

    Science.gov (United States)

    Simpson, Anna

    2017-09-20

    Retraction of 'Graphene-SnO 2 nanocomposites decorated with quantum tunneling junctions: preparation strategies, microstructures and formation mechanism' by Qingxiu Wang et al., Phys. Chem. Chem. Phys., 2014, 16, 19351-19357.

  14. Effect of heat treatments on precipitate microstructure and mechanical properties of CuCrZr alloy

    OpenAIRE

    Singh, B.N; Edwards, D.J.; Tähtinen, S.

    2004-01-01

    A number of specimens of CuCrZr alloy was prime aged and then overaged at 600oC for 1, 2 and 4 hours and for 4 hours at 700 and 850oC. After different heat treatments, both the precipitate microstructure and mechanical properties were characterized.Mechanical properties were determined at 50 and 300oC. Some selected specimens in the prime aged as well as overaged conditions were irradiated in the BR-2 reactor at Mol at 60 and 300oC to a displacement dose level of ~0.3 dpa. Irradiated specimen...

  15. Microstructure and mechanical properties of composite resins subjected to accelerated artificial aging.

    Science.gov (United States)

    dos Reis, Andréa Cândido; de Castro, Denise Tornavoi; Schiavon, Marco Antônio; da Silva, Leandro Jardel; Agnelli, José Augusto Marcondes

    2013-01-01

    The aim of this study was to investigate the influence of accelerated artificial aging (AAA) on the microstructure and mechanical properties of the Filtek Z250, Filtek Supreme, 4 Seasons, Herculite, P60, Tetric Ceram, Charisma and Filtek Z100. composite resins. The composites were characterized by Fourier-transform Infrared spectroscopy (FTIR) and thermal analyses (Differential Scanning Calorimetry - DSC and Thermogravimetry - TG). The microstructure of the materials was examined by scanning electron microscopy. Surface hardness and compressive strength data of the resins were recorded and the mean values were analyzed statistically by ANOVA and Tukey's test (α=0.05). The results showed significant differences among the commercial brands for surface hardness (F=86.74, p<0.0001) and compressive strength (F=40.31, p<0.0001), but AAA did not affect the properties (surface hardness: F=0.39, p=0.53; compressive strength: F=2.82, p=0.09) of any of the composite resins. FTIR, DSC and TG analyses showed that resin polymerization was complete, and there were no differences between the spectra and thermal curve profiles of the materials obtained before and after AAA. TG confirmed the absence of volatile compounds and evidenced good thermal stability up to 200 °C, and similar amounts of residues were found in all resins evaluated before and after AAA. The AAA treatment did not significantly affect resin surface. Therefore, regardless of the resin brand, AAA did not influence the microstructure or the mechanical properties.

  16. Effect of P on Microstructure and Mechanical Properties of Sn-Bi Solder

    Directory of Open Access Journals (Sweden)

    WANG Xiao-jing

    2016-07-01

    Full Text Available Micro alloy metals P or P/Cu/Zn were added into Sn-Bi alloy to investigate the doping effects on microstructure, mechanical property, deformation fracture from the function of P in pure tin. The results show that doping 1%( mass fraction, same as below P to pure tin can improve the strength and stiffness, decrease the plasticity. Only 0.1%P additive degenerates the mechanical property of Sn-Bi alloy, this is related to the existing form of element P in the base metal and the microstructure of the base metal. In Sn base alloy, P is distributed in phase or grain boundaries in the form of Sn-P intermetallic compounds (IMC, restricting the diffusion and shifting of deformation. Therefore, Sn-1P alloy, IMC distributed in beta-tin base plays a role of strengthening in pure tin doped situation, in Sn-Bi alloy instead, enhancing the deformation mismatch under loading becoming the weak spots where cracks may initiate and propagate, and leading to brittle fracture . Finally, addition of P/Zn/Cu simultaneously to Sn-Bi alloy, the doping can optimize the microstructure, improve the strength and enhance the ultimate tensile strength (UTS of Sn-Bi alloys.

  17. Microstructure and Mechanical Properties of CrMoV Steel after Long-Term Service

    Directory of Open Access Journals (Sweden)

    Golański G.

    2016-03-01

    Full Text Available The paper presents the results of research on the microstructure and mechanical properties of 12HMF steel after longterm service. The investigated material was taken from a pipeline with circumferential welded joint after 419 988 hours of service at the temperature of 490°C, steam pressure 8 MPa. Performed research has shown that the 12HMF steel after service was characterized by a typical microstructure for this grade of steel, that is a ferritic-bainitic microstructure without any visible advanced processes of its degradation. The investigation of mechanical properties has shown that the examined steel after service was characterized by a very low impact energy KV, and yield strength lower than the required minimum. Whilst tensile strength and yield strength determined at elevated temperature was higher and similar to the standard requirements, respectively. It has been proved that the main cause of an increase in brittleness and a decrease in yield strength of the examined steel should be seen in the segregation of phosphorus to grain boundaries and the formation of precipitate free zones near the boundaries.

  18. Microstructure and mechanical properties of internal crack healing in a low carbon steel

    Energy Technology Data Exchange (ETDEWEB)

    Xin, Ruishan [Department of Mechanical Engineering, Tsinghua University, Beijing 100084 (China); Key Laboratory for Advanced Materials Processing Technology of Ministry of Education, Tsinghua University, Beijing 100084 (China); Ma, Qingxian, E-mail: maqxdme@mail.tsinghua.edu.cn [Department of Mechanical Engineering, Tsinghua University, Beijing 100084 (China); Key Laboratory for Advanced Materials Processing Technology of Ministry of Education, Tsinghua University, Beijing 100084 (China); Li, Weiqi [Department of Mechanical Engineering, Tsinghua University, Beijing 100084 (China); Key Laboratory for Advanced Materials Processing Technology of Ministry of Education, Tsinghua University, Beijing 100084 (China)

    2016-04-26

    The behavior of internal crack healing in a low carbon steel at elevated temperatures was investigated. The internal cracks were introduced into low carbon steel samples via the drilling and compression method. The microstructure of crack healing zone was observed using optical microscopy and scanning electron microscopy. The mechanical properties of crack healing zone at room temperature were tested. The results show that there are two mechanisms of crack healing in the low carbon steel. Crack healing is caused by atomic diffusion at lower temperatures, and mainly depends on recrystallization and grain growth at higher temperatures. The microstructural evolution of crack healing zone can be divided into four stages, and the fracture morphology of crack healing zone can be classified into five stages. At the initial healing stage, the fracture exhibits brittle or low ductile dimple fracture. The ultimate fracture mode is dimple and quasi-cleavage mixed fracture. Fine grain microstructures improve the ultimate tensile strength of crack healing zone, which is even higher than that of the matrix. The strength recovery rate is higher than that of the plasticity.

  19. Microstructural and mechanical properties analysis of extruded Sn–0.7Cu solder alloy

    Directory of Open Access Journals (Sweden)

    Abdoul-Aziz Bogno

    2015-01-01

    Full Text Available The properties and performance of lead-free solder alloys such as fluidity and wettability are defined by the alloy composition and solidification microstructure. Rapid solidification of metallic alloys is known to result in refined microstructures with reduced microsegregation and improved mechanical properties of the final products as compared to normal castings. The rapidly solidified Sn-based solders by melt spinning were shown to be suitable for soldering with low temperature and short soldering duration. In the present study, rapidly solidified Sn–0.7 wt.%Cu droplets generated by impulse atomization (IA were achieved as well as directional solidification under transient conditions at lower cooling rate. This paper reports on a comparative study of the rapidly solidified and the directionally solidified samples. Different but complementary characterization techniques were used to fully analyze the solidification microstructures of the samples obtained under the two cooling regimes. These include X-ray diffractometry (XRD and scanning electron microscopy (SEM. In order to compare the tensile strength and elongation to fracture of the directionally solidified ingot and strip castings with the atomized droplet, compaction and extrusion of the latter were carried out. It was shown that more balanced and superior tensile mechanical properties are available for the hot extruded samples from compacted as-atomized Sn–0.7 wt.%Cu droplets. Further, elongation-to-fracture was 2–3× higher than that obtained for the directionally solidified samples.

  20. Microstructure and mechanical properties of friction stir welded 9Cr ODS steel

    International Nuclear Information System (INIS)

    Min, Hyoung Kee; Kang, Suk Hoon; Noh, Sanghoon; Lee, Jung Gu; Jang, Jinsung; Kim, Tae Kyu

    2013-01-01

    It is well known that the welding of ODS steel with a conventional melting.solidification process is not adequate to reserve nano-oxide particles in the matrix homogeneously. To reserve nano-oxide particles in the matrix homogeneously, friction stir welding (FSW) is the most promising technique to join ODS alloys. In this study, the effects of FSW on the microstructure and mechanical properties of a ODS steel were studied to apply the FSW process to 9Cr ODS steels. Microstructures were observed by means of optical microscopy, electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM). A tensile test and hardness test were carried out to the investigate mechanical properties. FSW could successfully produce defect-free welds on ODS plates. FSW produced a fine grain structure consisting of ferrite and martensite. Tensile strengths and elongations of the SZs were excellent at 298 K, compared to those of the BM. This study suggests that FSW might be an appropriate welding method of ODS steels. Oxide dispersion strengthened (ODS) ferritic-martensitic (FM) steel containing 9 wt%Cr is a promising candidate material for high temperature components operating in aggressive environments such as nuclear fusion and fission systems because of the excellent elevated temperature strength, corrosion and radiation resistance. These characteristics come from microstructures consisting of fine grains and nano-oxide particles dispersed in high number density. However, for more applications of ODS steel in nuclear systems, its weldability is the one of the barrier to be solved

  1. The Mechanical Properties and Microstructure Characters of Hybrid Composite Geopolymers-Pineapple Fiber Leaves (PFL)

    Science.gov (United States)

    Amalia, N.; Hidayatullah, S.; Nurfadilla; Subaer

    2017-03-01

    The objective of this research is to study the influence of organic fibers on the mechanical properties and microstructure characters of hybrid composite geopolymers-pineapple fibers (PFL). Geopolymers were synthesized by using alkali activated of class C-fly ash added manually with short pineapple fiber leaves (PFL) and then cured at 60°C for 1 hour. The resulting composites were stored in open air for 28 days prior to mechanical and microstructure characterizations. The samples were subjected to compressive and flexural strength measurements, heat resistance as well as acid attack (1M H2SO4 solution). The microstructure of the composites were examined by using Scanning Electron Microscopy-Energy Dispersive Spectroscopy (SEM-EDS). The measurement showed that the addition of pineapple fibers was able to improve the compressive and flexural strength of geopolymers. The resulting hybrid composites were able to resist fire to a maximum temperature of 1500°C. SEM examination showed the presence of good bond between geopolymer matrix and pineapple fibers. It was also found that there were no chemical constituents of geopolymers leached out during acid liquid treatment. It is concluded that hybrid composite geopolymers-pineapple fibers are potential composites for wide range applications.

  2. Influence of Cu Content on the Microstructure and Mechanical Properties of Cr-Cu-N Coatings

    Directory of Open Access Journals (Sweden)

    Ji Cheng Ding

    2018-01-01

    Full Text Available The Cr-Cu-N coatings with various Cu contents (0–25.18 (±0.17 at.% were deposited on Si wafer and stainless steel (SUS 304 substrates in reactive Ar+N2 gas mixture by a hybrid coating system combining pulsed DC and RF magnetron sputtering techniques. The influence of Cu content on the coating composition, microstructure, and mechanical properties was investigated. The microstructure of the coatings was significantly altered by the introduction of Cu. The deposited coatings exhibit solid solution structure with different compositions in all of the samples. Addition of Cu is intensively favored for preferred orientation growth along (200 direction by restricting in (111 direction. With increasing Cu content, the surface and cross-sectional morphology of coatings were changed from triangle cone-shaped, columnar feature to broccoli-like and compact glassy microstructure, respectively. The mechanical properties including the residual stress, nanohardness, and toughness of the coatings were explored on the basis of Cu content. The highest hardness was obtained at the Cu content of 1.49 (±0.10 at.%.

  3. Mechanical and microstructural aspects of severe plastic deformation of austenitic steel

    Science.gov (United States)

    Rodak, K.; Pawlicki, J.; Tkocz, M.

    2012-05-01

    The paper presents the effects of severe plastic deformation by multiple compression in the orthogonal directions on the microstructure and the mechanical properties of austenitic steel. Several deformation variants were conducted with different number of passes. FEM simulations were performed in order to evaluate the actual values of the effective strain in the examined, central parts of the compressed samples. The deformed microstructure was investigated by means of the scanning transmission electron microscopy (STEM) and the scanning electron microscopy (SEM) supported by the electron back scattered diffraction (EBSD). X-ray phase analysis was performed to evaluate the martensite volume fraction. The mechanical properties were determined by means of the digital image correlation method and hardness testing. It is shown that the applied forming technique leads to strong grain refinement in the austenitic steel. Moreover, deformation induces the martensitic γ- α' transformation. The microstructural changes cause an improvement in the strength properties. The material exhibits the ultimate tensile strength of 1560 MPa and the yield stress of 1500 MPa after reaching the effective strain of 10.

  4. Mechanical and microstructural aspects of severe plastic deformation of austenitic steel

    International Nuclear Information System (INIS)

    Rodak, K; Pawlicki, J; Tkocz, M

    2012-01-01

    The paper presents the effects of severe plastic deformation by multiple compression in the orthogonal directions on the microstructure and the mechanical properties of austenitic steel. Several deformation variants were conducted with different number of passes. FEM simulations were performed in order to evaluate the actual values of the effective strain in the examined, central parts of the compressed samples. The deformed microstructure was investigated by means of the scanning transmission electron microscopy (STEM) and the scanning electron microscopy (SEM) supported by the electron back scattered diffraction (EBSD). X-ray phase analysis was performed to evaluate the martensite volume fraction. The mechanical properties were determined by means of the digital image correlation method and hardness testing. It is shown that the applied forming technique leads to strong grain refinement in the austenitic steel. Moreover, deformation induces the martensitic γ– α' transformation. The microstructural changes cause an improvement in the strength properties. The material exhibits the ultimate tensile strength of 1560 MPa and the yield stress of 1500 MPa after reaching the effective strain of 10.

  5. Microstructure, consolidation and mechanical behaviour of Mg/n-TiC composite

    Directory of Open Access Journals (Sweden)

    N. Vijay Ponraj

    2016-09-01

    Full Text Available In this work, the microstructure, consolidation and mechanical properties of pure magnesium, magnesium based composite containing with different fractions (5, 10, 15 wt% of Titanium carbide nanoparticles (n-TiC were fabricated via powder metallurgy technique. The fabricated composites exhibited homogeneous distribution of TiC with little porosity. Microstructure of the composite and powders was studied using X-ray diffraction, Scanning electron microscope, and Transmission electron microscope. Microstructural characterization of the materials exposed that the accumulation of nanosized titanium carbide reinforcement enhanced the homogenization during mechanical blending. The relative density, compressibility, green compressive strength, sinterability and hardness of the nanocomposites were also examined. The effect of reinforcement on the densification was studied and reported in terms of the relative density and consolidation behaviour of the Magnesium matrix with n-TiC was studied and best compacted fit obtained through the Heckel, Panelli Ambrosio Filho and Ge equations. The compressive strength of the composite significantly increases from 230 MPa to 389 MPa with content of n-TiC and sintering temperature. Experiments have been performed under different conditions of temperature, n-TiC Content, and compacting pressure.

  6. Effect of long time service exposure on microstructure and mechanical properties of gas turbine vanes made of IN939 alloy

    International Nuclear Information System (INIS)

    Jahangiri, M.R.; Abedini, M.

    2014-01-01

    Highlights: • Microstructure of service-exposed turbine vanes made of IN939 was investigated. • Mechanical properties of service-exposed alloy were also investigated. • Formation of M 23 C 6 films on GBs and degeneration of MCs are microstructural changes. • Despite its thermodynamic favorability, σ phase is not observed in microstructure. • Microstructural changes lead to a loss in tensile ductility and creep life. - Abstract: In the present study, the effects of long-term service exposure have been investigated on microstructure and mechanical properties of gas turbine vanes made of IN939 superalloy. The major microstructural changes for the investigated service-exposed vanes include the formation of continuous grain boundary carbides and the transformation (degeneration) of MC carbides located at the grain boundaries. The brittle σ phase, which is predicted to be stable on the basis of thermodynamic calculations, is not observed in the microstructure of service-exposed vanes. The microstructural changes during service lead to a loss in room temperature ductility as well as in creep properties of the alloy

  7. Effect of Controlled Rolling and Cooling On Microstructure and Mechanical Properties of 30crmnti Wire Rod

    Science.gov (United States)

    Ruan, Shipeng; Dong, Qing; Zhang, Lei; Wang, Lijun

    2017-09-01

    The effect of controlled rolling and cooling on microstructure and mechanical properties of alloy structure steel 30CrMnTi wire rod with diameter 6.5mm was studied. The results show that the lower finish rolling temperature resulted in a decrease in tensile strength but an increase in elongation and reduction of area. When the finish rolling temperature decreases from 950°C to 850°C, the tensile strength value decreases from 750MPa to 660MPa, and the elongation increases from 21% to 30%, the reduction of area increases from 64% to 71%. The grain size also refines from 20μm to 9.9μm when the finish rolling temperature decreases from 950°C to 850°C. The decrease of tensile strength is due to the change of microstructure which evolved from more bainite to ferrite and pearlite.

  8. Microstructure and Mechanical Properties of Austempered Medium-Carbon Spring Steel

    Science.gov (United States)

    Kim, Seong Hoon; Kim, Kwan-Ho; Bae, Chul-Min; Lee, Jae Sang; Suh, Dong-Woo

    2018-03-01

    Changes in microstructure and mechanical properties of medium-carbon spring steel during austempering were investigated. After austempering for 1 h at 290 °C or 330 °C, the bainite transformation stabilized austenite, and microstructure consisting of bainitic ferrite and austenite could be obtained after final cooling; the retained austenite fraction was smaller in the alloy austempered at 290 °C because carbon redistribution between bainitic ferrite and austenite slowed as the temperature decreased, and thereby gave persistent driving force for the bainite transformation. The products of tensile strength and reduction of area in the austempered alloy were much larger in the austempered steel than in quenched and tempered alloy, mainly because of significant increase in reduction of area in austempered alloy.

  9. Microstructure and anisotropic mechanical behavior of friction stir welded AA2024 alloy sheets

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Zhihan [State Key Laboratory of Solidification Processing, Shaanxi Key Laboratory of Friction Welding Technologies, Northwestern Polytechnical University, Xi' an 710072, Shaanxi (China); Li, Wenya, E-mail: liwy@nwpu.edu.cn [State Key Laboratory of Solidification Processing, Shaanxi Key Laboratory of Friction Welding Technologies, Northwestern Polytechnical University, Xi' an 710072, Shaanxi (China); Li, Jinglong [State Key Laboratory of Solidification Processing, Shaanxi Key Laboratory of Friction Welding Technologies, Northwestern Polytechnical University, Xi' an 710072, Shaanxi (China); Chao, Y.J. [Department of Mechanical Engineering, University of South Carolina, Columbia, SC 29208 (United States); Vairis, A. [Mechanical Engineering Department, TEI of Crete, Heraklion, Crete 71004 (Greece)

    2015-09-15

    The anisotropic mechanical properties of friction stir welded (FSW) AA2024-T3 alloy joints were investigated based on the uniaxial tensile tests. The joint microstructure was examined by using electron back-scattered diffraction and transmission electron microscope. Results show that the evident anisotropic failure and yielding are present in the FSW joints. With the increase of loading angle from 0° to 90° the ultimate tensile strength and elongation of the specimens consistently decrease, or at first decrease and then increase, depending on the FSW process parameters. The specimen cut from the weld direction, i.e. a loading angle of 0°, exhibits the highest strength and elongation. - Highlights: • Microstructure and anisotropy of friction stir welded joints were studied. • The evident anisotropic failure and yielding are present in joints. • The lowest yield stress and UTS are at 45° and 60° loadings, respectively. • Rotation speed heavily impact on the anisotropy of joints.

  10. Microstructure and mechanical behaviour of an elevated temperature Mg-rare earth based alloy

    Energy Technology Data Exchange (ETDEWEB)

    Bettles, C.J. [ARC Centre of Excellence for Design in Light Metals, Department of Materials Engineering, Monash University, Clayton 3800, Vic. (Australia); CAST CRC, CSIRO Materials Science and Engineering, Private Bag 33, Clayton South MDC, Clayton 3169, Vic. (Australia)], E-mail: colleen.bettles@eng.monash.edu.au; Gibson, M.A. [CAST CRC, CSIRO Materials Science and Engineering, Private Bag 33, Clayton South MDC, Clayton 3169, Vic. (Australia); Zhu, S.M. [CAST CRC, Department of Materials Engineering, Monash University, Clayton 3800, Vic. (Australia)

    2009-04-15

    AM-SC1 is a heat treatable magnesium alloy that has been specifically developed to achieve the elevated temperature strength and creep properties necessary for engine block applications. This paper describes the interrelationship between the microstructure and the mechanical properties of AM-SC1. The compressive and tensile strengths are relatively insensitive to temperature up to and including 450 K and the tensile yield behaviour deviates from a standard Hall-Petch relationship at grain sizes below 200 {mu}m. The microstructural features contributing to the creep resistance are both inter- and intra-granular in nature and are on length scales from nanometers to micrometers. The creep behaviour at 423 K and 450 K is diffusion controlled, with any contribution from the grain boundaries being negligible.

  11. Tensile Deformation Temperature Impact on Microstructure and Mechanical Properties of AISI 316LN Austenitic Stainless Steel

    Science.gov (United States)

    Xiong, Yi; He, Tiantian; Lu, Yan; Ren, Fengzhang; Volinsky, Alex A.; Cao, Wei

    2018-03-01

    Uniaxial tensile tests were conducted on AISI 316LN austenitic stainless steel from - 40 to 300 °C at a rate of 0.5 mm/min. Microstructure and mechanical properties of the deformed steel were investigated by optical, scanning and transmission electron microscopies, x-ray diffraction, and microhardness testing. The yield strength, ultimate tensile strength, elongation, and microhardness increase with the decrease in the test temperature. The tensile fracture morphology has the dimple rupture feature after low-temperature deformations and turns to a mixture of transgranular fracture and dimple fracture after high-temperature ones. The dominating deformation microstructure evolves from dislocation tangle/slip bands to large deformation twins/slip bands with temperature decrease. The deformation-induced martensite transformation can only be realized at low temperature, and its quantity increases with the decrease in the temperature.

  12. Microstructure and anisotropic mechanical behavior of friction stir welded AA2024 alloy sheets

    International Nuclear Information System (INIS)

    Zhang, Zhihan; Li, Wenya; Li, Jinglong; Chao, Y.J.; Vairis, A.

    2015-01-01

    The anisotropic mechanical properties of friction stir welded (FSW) AA2024-T3 alloy joints were investigated based on the uniaxial tensile tests. The joint microstructure was examined by using electron back-scattered diffraction and transmission electron microscope. Results show that the evident anisotropic failure and yielding are present in the FSW joints. With the increase of loading angle from 0° to 90° the ultimate tensile strength and elongation of the specimens consistently decrease, or at first decrease and then increase, depending on the FSW process parameters. The specimen cut from the weld direction, i.e. a loading angle of 0°, exhibits the highest strength and elongation. - Highlights: • Microstructure and anisotropy of friction stir welded joints were studied. • The evident anisotropic failure and yielding are present in joints. • The lowest yield stress and UTS are at 45° and 60° loadings, respectively. • Rotation speed heavily impact on the anisotropy of joints

  13. Evolution of microstructure and mechanical properties during annealing of cold-rolled AA8011 alloy

    Energy Technology Data Exchange (ETDEWEB)

    Roy, Rajat Kumar [Department of Metallurgical and Materials Engineering, Indian Institute of Technology, Kharagpur 721302 (India)], E-mail: r.roy@rediffmail.com; Kar, Sujoy [Department of Metallurgical and Materials Engineering, Indian Institute of Technology, Kharagpur 721302 (India); Department of Materials Science and Engineering, The Ohio State University, OH 43210 (United States); Das, Siddhartha [Department of Metallurgical and Materials Engineering, Indian Institute of Technology, Kharagpur 721302 (India)], E-mail: sdas@metal.iitkgp.ernet.in

    2009-01-22

    The evolution of recrystallized microstructure of cold-rolled aluminium alloy AA8011 is investigated with the help of optical metallography, orientation imaging microscopy (OIM), transmission electron microscopy (TEM), differential scanning calorimetry (DSC), electrical resistivity and microhardness measurements at different annealing conditions. Tensile testing of the isochronally annealed specimens is performed to examine the effect of annealing temperature and microstructure on mechanical properties. Precipitates affect the grain growth behaviour and texture evolution. Normal grain growth takes place prior to abnormal grain growth. A wide range of grain size distribution and a combination of cube, rolling and random texture is observed at complete recrystallized condition. Our results provide not only new insight into aluminium packaging materials (i.e., foils, cans, and air conditioning ducts) but also a platform to better understand the recrystallization of a wide range of related alloys.

  14. Dynamic mechanical properties of hydroxyapatite/polyethylene oxide nanocomposites: characterizing isotropic and post-processing microstructures

    Science.gov (United States)

    Shofner, Meisha; Lee, Ji Hoon

    2012-02-01

    Compatible component interfaces in polymer nanocomposites can be used to facilitate a dispersed morphology and improved physical properties as has been shown extensively in experimental results concerning amorphous matrix nanocomposites. In this research, a block copolymer compatibilized interface is employed in a semi-crystalline matrix to prevent large scale nanoparticle clustering and enable microstructure construction with post-processing drawing. The specific materials used are hydroxyapatite nanoparticles coated with a polyethylene oxide-b-polymethacrylic acid block copolymer and a polyethylene oxide matrix. Two particle shapes are used: spherical and needle-shaped. Characterization of the dynamic mechanical properties indicated that the two nanoparticle systems provided similar levels of reinforcement to the matrix. For the needle-shaped nanoparticles, the post-processing step increased matrix crystallinity and changed the thermomechanical reinforcement trends. These results will be used to further refine the post-processing parameters to achieve a nanocomposite microstructure with triangulated arrays of nanoparticles.

  15. Numerical simulation of temperature field, microstructure evolution and mechanical properties of HSS during hot stamping

    International Nuclear Information System (INIS)

    Shi, Dongyong; Liu, Wenquan; Ying, Liang; Hu, Ping; Shen, Guozhe

    2013-01-01

    The hot stamping of boron steels is widely used to produce ultra high strength automobile components without any spring back. The ultra high strength of final products is attributed to the fully martensitic microstructure that is obtained through the simultaneous forming and quenching of the hot blanks after austenization. In the present study, a mathematical model incorporating both heat transfer and the transformation of austenite is presented. A FORTRAN program based on finite element technique has been developed which permits the temperature distribution and microstructure evolution of high strength steel during hot stamping process. Two empirical diffusion-dependent transformation models under isothermal conditions were employed respectively, and the prediction capability on mechanical properties of the models were compared with the hot stamping experiment of an automobile B-pillar part

  16. Microstructure and mechanical properties of friction stir welded SAF 2507 super duplex stainless steel

    International Nuclear Information System (INIS)

    Sato, Y.S.; Nelson, T.W.; Sterling, C.J.; Steel, R.J.; Pettersson, C.-O.

    2005-01-01

    The microstructure and mechanical properties of friction stir (FS) welded SAF 2507 super duplex stainless steel were examined. High-quality, full-penetration welds were successfully produced in the super duplex stainless steel by friction stir welding (FSW) using polycrystalline cubic boron nitride (PCBN) tool. The base material had a microstructure consisting of the ferrite matrix with austenite islands, but FSW refined grains of the ferrite and austenite phases in the stir zone through dynamic recrystallisation. Ferrite content was held between 50 and 60% throughout the weld. The smaller grain sizes of the ferrite and austenite phases caused increase in hardness and strength within the stir zone. Welded transverse tensile specimen failed near the border between the stir zone and TMAZ at the retreating side as the weld had roughly the same strengths as the base material

  17. Effects of heat treatment on the microstructure and mechanical properties of AA2618 DC cast alloy

    International Nuclear Information System (INIS)

    Elgallad, E.M.; Shen, P.; Zhang, Z.; Chen, X.-G.

    2014-01-01

    Highlights: • The microstructure and mechanical properties of AA2618 DC cast alloy were studied. • The Al 2 CuMg, Al 2 Cu, Al 7 Cu 4 Ni, Al 7 Cu 2 (Fe,Ni) and Al 9 FeNi phases were identified. • Solution treatment at 530 °C for 5 h is the optimum solution treatment. • Different combinations of strength and ductility can be achieved. • The strengthening of AA2618 DC cast alloy was caused by GPB zones and S′ phase. - Abstract: Direct chill (DC) cast ingot plates of AA2618 alloy have been increasingly used for large-mold applications in the plastics and automotive industries. The effects of different heat treatments on the microstructure and mechanical properties of AA2618 DC cast alloy were investigated using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and hardness and tensile testing. The as-cast microstructure contained a considerable amount of coarse intermetallic phases, including Al 2 CuMg, Al 2 Cu, Al 7 Cu 4 Ni, Al 7 Cu 2 (Fe,Ni) and Al 9 FeNi, resulting in poor mechanical properties. Solution treatment at 530 °C for 5 h dissolved the first three phases into the solid solution and consequently improved the mechanical properties of the alloy. By utilizing the appropriate aging temperature and time, different combinations of strength and ductility could be obtained to fulfill the design requirements of large-mold applications. The strengthening of AA2618 DC cast alloy under the aging conditions studied was caused by GPB zones and S′ precipitates. The evolution of both precipitates in terms of their size and density was observed to have a significant effect on the mechanical properties of the alloy

  18. Microstructural and electrical changes in nickel manganite powder induced by mechanical activation

    International Nuclear Information System (INIS)

    Savic, S.M.; Mancic, L.; Vojisavljevic, K.; Stojanovic, G.; Brankovic, Z.; Aleksic, O.S.; Brankovic, G.

    2011-01-01

    Highlights: → The influence of mechanical activation on microstructure evolution in the nickel manganite powder was investigated as well as electrical properties of the sintered samples. → Structural refinement obtained by Topas-Academic software based on Rietveld analysis showed that the milling process remarkably changed the powder morphology and microstructure. → SEM studies of sintered samples also revealed the strong influence of milling time on ceramics density (increases with milling time). → The electrical properties of ceramic samples are clearly conditioned by terms of synthesis, in our case the time of mechanical activation. → The highest density and higher values of dielectric constant were achieved at the sample activated for 45 min. -- Abstract: Nickel manganite powder synthesized by calcination of a stoichiometric mixture of manganese and nickel oxide was additionally mechanically activated in a high energy planetary ball mill for 5-60 min in order to obtain a pure NiMn 2 O 4 phase. The as-prepared powders were uniaxially pressed into disc shape pellets and then sintered for 60 min at 1200 o C. Changes in the particle morphology induced by mechanical activation were monitored using scanning electron microscopy, while changes in powder structural characteristics were followed using X-ray powder diffraction. The ac impedance spectroscopy was performed on sintered nickel manganite samples at 25 o C, 50 o C and 80 o C. It was shown that mechanical activation intensifies transport processes causing a decrease in the average crystallites size, while longer activation times can lead to the formation of aggregates, defects and increase of lattice microstrains. The observed changes in microstructures were correlated with measured electrical properties in order to define optimal processing conditions.

  19. Microstructure, mechanical properties, bio-corrosion properties and antibacterial properties of Ti-Ag sintered alloys.

    Science.gov (United States)

    Chen, Mian; Zhang, Erlin; Zhang, Lan

    2016-05-01

    In this research, Ag element was selected as an antibacterial agent to develop an antibacterial Ti-Ag alloy by a powder metallurgy. The microstructure, phase constitution, mechanical properties, corrosion resistance and antibacterial properties of the Ti-Ag sintered alloys have been systematically studied by X-ray diffraction (XRD), scanning electron microscope (SEM), compressive test, electrochemical measurements and antibacterial test. The effects of the Ag powder size and the Ag content on the antibacterial property and mechanical property as well as the anticorrosion property have been investigated. The microstructure results have shown that Ti-Ag phase, residual pure Ag and Ti were the mainly phases in Ti-Ag(S75) sintered alloy while Ti2Ag was synthesized in Ti-Ag(S10) sintered alloy. The mechanical test indicated that Ti-Ag sintered alloy showed a much higher hardness and the compressive yield strength than cp-Ti but the mechanical properties were slightly reduced with the increase of Ag content. Electrochemical results showed that Ag powder size had a significant effect on the corrosion resistance of Ti-Ag sintered alloy. Ag content increased the corrosion resistance in a dose dependent way under a homogeneous microstructure. Antibacterial tests have demonstrated that antibacterial Ti-Ag alloy was successfully prepared. It was also shown that the Ag powder particle size and the Ag content influenced the antibacterial activity seriously. The reduction in the Ag powder size was benefit to the improvement in the antibacterial property and the Ag content has to be at least 3wt.% in order to obtain a strong and stable antibacterial activity against Staphylococcus aureus bacteria. The bacterial mechanism was thought to be related to the Ti2Ag and its distribution. Copyright © 2016 Elsevier B.V. All rights reserved.

  20. Welding of nickel free high nitrogen stainless steel: Microstructure and mechanical properties

    Directory of Open Access Journals (Sweden)

    Raffi Mohammed

    2017-04-01

    Full Text Available High nitrogen stainless steel (HNS is a nickel free austenitic stainless steel that is used as a structural component in defence applications for manufacturing battle tanks as a replacement of the existing armour grade steel owing to its low cost, excellent mechanical properties and better corrosion resistance. Conventional fusion welding causes problems like nitrogen desorption, solidification cracking in weld zone, liquation cracking in heat affected zone, nitrogen induced porosity and poor mechanical properties. The above problems can be overcome by proper selection and procedure of joining process. In the present work, an attempt has been made to correlate the microstructural changes with mechanical properties of fusion and solid state welds of high nitrogen steel. Shielded metal arc welding (SMAW, gas tungsten arc welding (GTAW, electron beam welding (EBW and friction stir welding (FSW processes were used in the present work. Optical microscopy, scanning electron microscopy and electron backscatter diffraction were used to characterize microstructural changes. Hardness, tensile and bend tests were performed to evaluate the mechanical properties of welds. The results of the present investigation established that fully austenitic dendritic structure was found in welds of SMAW. Reverted austenite pools in the martensite matrix in weld zone and unmixed zones near the fusion boundary were observed in GTA welds. Discontinuous ferrite network in austenite matrix was observed in electron beam welds. Fine recrystallized austenite grain structure was observed in the nugget zone of friction stir welds. Improved mechanical properties are obtained in friction stir welds when compared to fusion welds. This is attributed to the refined microstructure consisting of equiaxed and homogenous austenite grains.

  1. Microstructural and electrical changes in nickel manganite powder induced by mechanical activation

    Energy Technology Data Exchange (ETDEWEB)

    Savic, S.M., E-mail: slavicas@cms.bg.ac.rs [Institute for Multidisciplinary Research-University of Belgrade, Kneza Viseslava 1a, 11030 Belgrade (Serbia); Mancic, L. [Institute of Technical Sciences SASA, Knez Mihailova 35/IV, 11000 Belgrade (Serbia); Vojisavljevic, K. [Institute for Multidisciplinary Research-University of Belgrade, Kneza Viseslava 1a, 11030 Belgrade (Serbia); Stojanovic, G. [Faculty of Technical Sciences University of Novi Sad, Trg Dositeja Obradovica 6, 21000 Novi Sad (Serbia); Brankovic, Z.; Aleksic, O.S.; Brankovic, G. [Institute for Multidisciplinary Research-University of Belgrade, Kneza Viseslava 1a, 11030 Belgrade (Serbia)

    2011-07-15

    Highlights: {yields} The influence of mechanical activation on microstructure evolution in the nickel manganite powder was investigated as well as electrical properties of the sintered samples. {yields} Structural refinement obtained by Topas-Academic software based on Rietveld analysis showed that the milling process remarkably changed the powder morphology and microstructure. {yields} SEM studies of sintered samples also revealed the strong influence of milling time on ceramics density (increases with milling time). {yields} The electrical properties of ceramic samples are clearly conditioned by terms of synthesis, in our case the time of mechanical activation. {yields} The highest density and higher values of dielectric constant were achieved at the sample activated for 45 min. -- Abstract: Nickel manganite powder synthesized by calcination of a stoichiometric mixture of manganese and nickel oxide was additionally mechanically activated in a high energy planetary ball mill for 5-60 min in order to obtain a pure NiMn{sub 2}O{sub 4} phase. The as-prepared powders were uniaxially pressed into disc shape pellets and then sintered for 60 min at 1200 {sup o}C. Changes in the particle morphology induced by mechanical activation were monitored using scanning electron microscopy, while changes in powder structural characteristics were followed using X-ray powder diffraction. The ac impedance spectroscopy was performed on sintered nickel manganite samples at 25 {sup o}C, 50 {sup o}C and 80 {sup o}C. It was shown that mechanical activation intensifies transport processes causing a decrease in the average crystallites size, while longer activation times can lead to the formation of aggregates, defects and increase of lattice microstrains. The observed changes in microstructures were correlated with measured electrical properties in order to define optimal processing conditions.

  2. Multi-scale hierarchy of Chelydra serpentina: microstructure and mechanical properties of turtle shell.

    Science.gov (United States)

    Balani, Kantesh; Patel, Riken R; Keshri, Anup K; Lahiri, Debrupa; Agarwal, Arvind

    2011-10-01

    Carapace, the protective shell of a freshwater snapping turtle, Chelydra serpentina, shields them from ferocious attacks of their predators while maintaining light-weight and agility for a swim. The microstructure and mechanical properties of the turtle shell are very appealing to materials scientists and engineers for bio-mimicking, to obtain a multi-functional surface. In this study, we have elucidated the complex microstructure of a dry Chelydra serpentina's shell which is very similar to a multi-layered composite structure. The microstructure of a turtle shell's carapace elicits a sandwich structure of waxy top surface with a harder sub-surface layer serving as a shielding structure, followed by a lamellar carbonaceous layer serving as shock absorber, and the inner porous matrix serves as a load-bearing scaffold while acting as reservoir of retaining water and nutrients. The mechanical properties (elastic modulus and hardness) of various layers obtained via nanoindentation corroborate well with the functionality of each layer. Elastic modulus ranged between 0.47 and 22.15 GPa whereas hardness varied between 53.7 and 522.2 MPa depending on the microstructure of the carapace layer. Consequently, the modulus of each layer was represented into object oriented finite element (OOF2) modeling towards extracting the overall effective modulus of elasticity (~4.75 GPa) of a turtle's carapace. Stress distribution of complex layered structure was elicited with an applied strain of 1% in order to understand the load sharing of various composite layers in the turtle's carapace. Copyright © 2011 Elsevier Ltd. All rights reserved.

  3. On the processing, microstructure, mechanical and wear properties of cermet/stainless steel layer composites

    International Nuclear Information System (INIS)

    Farid, Akhtar; Guo Shiju

    2007-01-01

    This study deals with layer composites of carbide reinforcements and stainless steel prepared successfully by powder technology. The layer material consisted of two layers. The top layer consisted of reinforcements (TiC and NbC) and 465 stainless steel as the binder material for the carbides. The bottom layer was entirely of binder material (465 stainless steel). The microstructure of the composite was characterized by scanning electron microscopy. The microstructural study revealed that the top layer (TiC-NbC/465 stainless steel) showed the typical core-rim microstructure of conventional steel bonded cermets and the bottom layer showed the structure of sintered steel. An intermediate layer was found with a gradient microstructure, having a higher carbide content towards the cermet layer and lower carbide content towards the stainless steel layer. The bending strength of the layered material measured in the direction perpendicular to the layer alignment was remarkably high. The variation of strength as a function of the thickness of the bottom layer revealed that the character of the material changed from the cermet, to a layer composite and then towards metallic materials. The wear resistance of the top layer was studied against high speed steel. The wear mechanisms were discussed by means of microscopical observations on the worn surfaces. The wear was severe at higher wear loads and lower TiC content. Microploughing of the stainless steel matrix was found to be the dominant wear mechanism. Heavy microploughing and rapid removal of material from the wear surface was observed at high wear load. The fracture morphologies of the top, bottom and intermediate layers are reported

  4. Effect of SMAT on microstructural and mechanical properties of AA2024

    International Nuclear Information System (INIS)

    Tadge, Prashant; Sasikumar, C.

    2016-01-01

    In recent days surface mechanical attrition treatment (SMAT) had attracted the attention of researchers as it produces a nano-crystalline surface with improved mechanical properties. In the present study Al-4%Cu alloy used in automobile and aerospace application is subjected to surface mechanical attrition treatment using steel shots. The microstructural changes introduced on the surface of the Al alloy was investigated using Scanning Electron Microscopy (SEM). The secondary phases formed during the SMAT process is been investigated using EDX and XRD analysis. The effects of SMAT on the mechanical properties were analyzed using a tensile testing. The SMA treatment had resulted in severe plastic deformation of the surface, thereby yielded a nanocrystalline surface with a grain size of 30 to 50 nm. Further, it is also found that the SMAT produced ultra nanocrystalline particles of Cu_2Al dispersed uniformly into α-Al matrix. These microstructural changes had resulted in considerable change in the mechanical properties of these alloys. The tensile strength of these alloys had increased from ∼212 MPa to 303 MPa while the fracture toughness increased up to 28% in 10 minutes of SMAT.

  5. Analysis of the mechanical response of biomimetic materials with highly oriented microstructures through 3D printing, mechanical testing and modeling.

    Science.gov (United States)

    de Obaldia, Enrique Escobar; Jeong, Chanhue; Grunenfelder, Lessa Kay; Kisailus, David; Zavattieri, Pablo

    2015-08-01

    Many biomineralized organisms have evolved highly oriented nanostructures to perform specific functions. One key example is the abrasion-resistant rod-like microstructure found in the radular teeth of Chitons (Cryptochiton stelleri), a large mollusk. The teeth consist of a soft core and a hard shell that is abrasion resistant under extreme mechanical loads with which they are subjected during the scraping process. Such remarkable mechanical properties are achieved through a hierarchical arrangement of nanostructured magnetite rods surrounded with α-chitin. We present a combined biomimetic approach in which designs were analyzed with additive manufacturing, experiments, analytical and computational models to gain insights into the abrasion resistance and toughness of rod-like microstructures. Staggered configurations of hard hexagonal rods surrounded by thin weak interfacial material were printed, and mechanically characterized with a cube-corner indenter. Experimental results demonstrate a higher contact resistance and stiffness for the staggered alignments compared to randomly distributed fibrous materials. Moreover, we reveal an optimal rod aspect ratio that lead to an increase in the site-specific properties measured by indentation. Anisotropy has a significant effect (up to 50%) on the Young's modulus in directions parallel and perpendicular to the longitudinal axis of the rods, and 30% on hardness and fracture toughness. Optical microscopy suggests that energy is dissipated in the form of median cracks when the load is parallel to the rods and lateral cracks when the load is perpendicular to the rods. Computational models suggest that inelastic deformation of the rods at early stages of indentation can vary the resistance to penetration. As such, we found that the mechanical behavior of the system is influenced by interfacial shear strain which influences the lateral load transfer and therefore the spread of damage. This new methodology can help to elucidate

  6. Impact load-induced micro-structural damage and micro-structure associated mechanical response of concrete made with different surface roughness and porosity aggregates

    International Nuclear Information System (INIS)

    Erdem, Savaş; Dawson, Andrew Robert; Thom, Nicholas Howard

    2012-01-01

    The relationship between the nature of micro damage under impact loading and changes in mechanical behavior associated with different microstructures is studied for concretes made with two different coarse aggregates having significant differences mainly in roughness and porosity — sintered fly ash and uncrushed gravel. A range of techniques including X-ray diffraction, digital image analysis, mercury porosimetry, X-ray computed tomography, laser surface profilometry and scanning electron microscopy were used to characterize the aggregates and micro-structures. The concrete prepared with lightweight aggregates was stronger in compression than the gravel aggregate concrete due to enhanced hydration as a result of internal curing. In the lightweight concrete, it was deduced that an inhomogeneous micro-structure led to strain incompatibilities and consequent localized stress concentrations in the mix, leading to accelerated failure. The pore structure, compressibility, and surface texture of the aggregates are of paramount importance for the micro-cracking growth.

  7. Thermal Mechanical Processing Effects on Microstructure Evolution and Mechanical Properties of the Sintered Ti-22Al-25Nb Alloy.

    Science.gov (United States)

    Wang, Yuanxin; Lu, Zhen; Zhang, Kaifeng; Zhang, Dalin

    2016-03-11

    This work illustrates the effect of thermal mechanical processing parameters on the microstructure and mechanical properties of the Ti-22Al-25Nb alloy prepared by reactive sintering with element powders, consisting of O, B2 and Ti₃Al phases. Tensile and plane strain fracture toughness tests were carried out at room temperature to understand the mechanical behavior of the alloys and its correlation with the microstructural features characterized by scanning and transmission electron microscopy. The results show that the increased tensile strength (from 340 to 500 MPa) and elongation (from 3.6% to 4.2%) is due to the presence of lamellar O/B2 colony and needle-like O phase in B2 matrix in the as-processed Ti-22Al-25Nb alloys, as compared to the coarse lath O adjacent to B2 in the sintered alloys. Changes in morphologies of O phase improve the fracture toughness ( K IC ) of the sintered alloys from 7 to 15 MPa·m -1/2 . Additionally, the fracture mechanism shifts from cleavage fracture in the as-sintered alloys to quasi-cleavage fracture in the as-processed alloys.

  8. Effect of thermo-mechanical treatments on the microstructure and mechanical properties of an ODS ferritic steel

    International Nuclear Information System (INIS)

    Oksiuta, Z.; Mueller, P.; Spaetig, P.; Baluc, N.

    2011-01-01

    The Fe-14Cr-2W-0.3Ti-0.3Y 2 O 3 oxide dispersion strengthened (ODS) reduced activation ferritic (RAF) steel was fabricated by mechanical alloying of a pre-alloyed, gas atomised powder with yttria nano-particles, followed by hot isostatic pressing and thermo-mechanical treatments (TMTs). Two kinds of TMT were applied: (i) hot pressing, or (ii) hot rolling, both followed by annealing in vacuum at 850 deg. C. The use of a thermo-mechanical treatment was found to yield strong improvement in the microstructure and mechanical properties of the ODS RAF steel. In particular, hot pressing leads to microstructure refinement, equiaxed grains without texture, and an improvement in Charpy impact properties, especially in terms of the upper shelf energy (about 4.5 J). Hot rolling leads to elongated grains in the rolling direction, with a grain size ratio of 6:1, higher tensile strength and reasonable ductility up to 750 deg. C, and better Charpy impact properties, especially in terms of the ductile-to-brittle transition temperature (about 55 deg. C).

  9. Effect of thermo-mechanical treatments on the microstructure and mechanical properties of an ODS ferritic steel

    Energy Technology Data Exchange (ETDEWEB)

    Oksiuta, Z., E-mail: oksiuta@pb.edu.pl [Bialystok Technical University, Mechanical Department, Wiejska 45c, 15-351 Bialystok (Poland); Mueller, P.; Spaetig, P.; Baluc, N. [Ecole Polytechnique Federale de Lausanne (EPFL), Centre de Recherches en Physique des Plasmas, Association Euratom-Confederation Suisse, 5232 Villigen PSI (Switzerland)

    2011-05-15

    The Fe-14Cr-2W-0.3Ti-0.3Y{sub 2}O{sub 3} oxide dispersion strengthened (ODS) reduced activation ferritic (RAF) steel was fabricated by mechanical alloying of a pre-alloyed, gas atomised powder with yttria nano-particles, followed by hot isostatic pressing and thermo-mechanical treatments (TMTs). Two kinds of TMT were applied: (i) hot pressing, or (ii) hot rolling, both followed by annealing in vacuum at 850 deg. C. The use of a thermo-mechanical treatment was found to yield strong improvement in the microstructure and mechanical properties of the ODS RAF steel. In particular, hot pressing leads to microstructure refinement, equiaxed grains without texture, and an improvement in Charpy impact properties, especially in terms of the upper shelf energy (about 4.5 J). Hot rolling leads to elongated grains in the rolling direction, with a grain size ratio of 6:1, higher tensile strength and reasonable ductility up to 750 deg. C, and better Charpy impact properties, especially in terms of the ductile-to-brittle transition temperature (about 55 deg. C).

  10. New insights into virulence mechanisms of rice pathogen Acidovorax avenae subsp. avenae strain RS-1 following exposure to ?-lactam antibiotics

    OpenAIRE

    Li, Bin; Ge, Mengyu; Zhang, Yang; Wang, Li; Ibrahim, Muhammad; Wang, Yanli; Sun, Guochang; Chen, Gongyou

    2016-01-01

    Recent research has shown that pathogen virulence can be altered by exposure to antibiotics, even when the growth rate is unaffected. Investigating this phenomenon provides new insights into understanding the virulence mechanisms of bacterial pathogens. This study investigates the phenotypic and transcriptomic responses of the rice pathogenic bacterium Acidovorax avenae subsp. avenae (Aaa) strain RS-1 to ?-lactam antibiotics especially Ampicillin (Amp). Our results indicate that exposure to A...

  11. Microstructure and mechanical properties of hard zone in friction stir welded X80 pipeline steel relative to different heat input

    Energy Technology Data Exchange (ETDEWEB)

    Aydin, Hakan, E-mail: hakanay@uludag.edu.tr [Engineering and Architecture Faculty, Mechanical Engineering Department, Uludag University, 16059 Gorukle-Bursa (Turkey); Nelson, Tracy W. [Mechanical Engineering Department, Brigham Young University, 435 CTB, Provo, UT 84602 (United States)

    2013-12-01

    The study was conducted to investigate the microstructure and mechanical properties of the hard zone in friction stir welded X80 pipeline steel at different heat inputs. Microstructural analysis of the welds was carried out using optical microscopy, transmission electron microscopy, and microhardness. Heat input during friction stir welding process had a significant influence on the microstructure and mechanical properties in the hard zone along the advancing side of the weld nugget. Based on the results, the linear relationships between heat input and post-weld microstructures and mechanical properties in the hard zone of friction stir welded X80 steels were established. It can be concluded that with decrease in heat input the bainitic structure in the hard zone becomes finer and so hard zone strength increases.

  12. Microstructure and mechanical properties of hard zone in friction stir welded X80 pipeline steel relative to different heat input

    International Nuclear Information System (INIS)

    Aydin, Hakan; Nelson, Tracy W.

    2013-01-01

    The study was conducted to investigate the microstructure and mechanical properties of the hard zone in friction stir welded X80 pipeline steel at different heat inputs. Microstructural analysis of the welds was carried out using optical microscopy, transmission electron microscopy, and microhardness. Heat input during friction stir welding process had a significant influence on the microstructure and mechanical properties in the hard zone along the advancing side of the weld nugget. Based on the results, the linear relationships between heat input and post-weld microstructures and mechanical properties in the hard zone of friction stir welded X80 steels were established. It can be concluded that with decrease in heat input the bainitic structure in the hard zone becomes finer and so hard zone strength increases

  13. Microstructural Characterization and Mechanical Properties of Electron Beam Welded Joint of High Strength Steel Grade S690QL

    Directory of Open Access Journals (Sweden)

    Błacha S.

    2016-06-01

    Full Text Available In the paper the results of metallographic examination and mechanical properties of electron beam welded joint of quenched and tempered steel grade S690QL are presented. Metallographic examination revealed that the concentrated electron beam significantly affect the changes of microstructure in the steel. Parent material as a delivered condition (quenched and tempered had a bainitic-martensitic microstructure at hardness about 290 HV0.5. After welding, the microstructure of heat affected zone is composed mainly of martensite (in the vicinity of the fusion line of hardness 420 HV0.5. It should be noted, however, that the microstructure of steel in the heat affected zone varies with the distance from the fusion line. The observed microstructural changes were in accordance with the CCT-S transformation diagram for the examined steel.

  14. Mechanical and microstructural stability of P92 steel under uniaxial tension at high temperature

    International Nuclear Information System (INIS)

    Giroux, P.F.; Dalle, F.; Sauzay, M.; Malaplate, J.; Fournier, B.; Gourgues-Lorenzon, A.F.

    2010-01-01

    9-12%Cr creep-resistant ferritic-martensitic steels are candidates for structural components of Generation IV nuclear power plants. However, they are sensitive to softening during low-cycle fatigue, creep and creep-fatigue tests, due to the destabilisation of the tempered martensite microstructure, possibly inducing a decrease in further creep resistance. To better identify the softening mechanisms in P92 steel during uniaxial deformation, tensile tests were carried out at 823 K, showing an extended and stable softening stage on true stress-strain curves after some work-hardening. Three phenomena were studied in order to understand this behaviour: mechanical instability (necking), damage and grain size evolution. Examination of fractured and non-fractured tensile specimens (light optical and electron microscopy, macrohardness) suggested that the physical mechanisms responsible for softening are mainly (sub)grain size evolution and diffuse necking. Models were proposed to predict grain growth and beginning of the mechanical instability during homogeneous deformation.

  15. Microstructure features and mechanical properties of a UFG Al-Mg-Si alloy produced via SPD

    International Nuclear Information System (INIS)

    Bobruk, E; Kazykhanov, V; Valiev, R; Murashkin, M; Sabirov, I

    2014-01-01

    The effect of equal channel angular pressing in parallel channels (ECAP-PC) and subsequient artificial ageing on the microstructure and room temperature mechanical properties of the commercial aluminum alloys 6063 (Al-0.6Mg-0.5Si, wt.%) and 6010 (Al-0.8Mg-1.0Si-0.15Cu-0.25Mn, wt.%) was investigated. It was shown that mechanical strength of the ECAP-PC processed Al alloys is higher compared to that achieved in these alloys after conventional thermo-mechanical processing. Prior ECAP- PC solution treatment and post-ECAP-PC artificial aging can additionally increase the mechanical strength of both Al alloys. Under optimal artificial ageing conditions, the yield strength (YS) of 299 MPa and ultimate tensile strength (UTS) of 308 MPa was achieved in the 6063 alloy, whereas YS of 423 MPa and UTS of 436 MPa was achieved in the 6010 alloy

  16. Effects of Yb on the mechanical properties and microstructures of an Al-Mg alloy

    International Nuclear Information System (INIS)

    Song Min; Wu Zhenggang; He Yuehui

    2008-01-01

    This paper reported a first study of the effects of Yb on the microstructures and mechanical properties of an extruded Al-Mg alloy. It has been shown that the addition of 0.3 wt.% Yb decreases the mechanical properties of the alloy since Mg- and Yb-containing constituents decrease the concentration of Mg solute atoms in Al matrix, and thus the solution strengthening effect. However, the addition of 1 wt.% Yb substantially improves the mechanical behavior of the alloy because the concentration of Yb solute atoms in Al matrix is high enough to generate solution strengthening effect. The improvement in the mechanical properties is due to the large work-hardening and high dislocation density caused by the interaction between dislocations and Yb and Mg solute atoms. The Yb and Mg atoms inhibit the dynamic recovery and recrystallization of the alloy, thus provide a uniformly distributed dislocation structure with high density

  17. Studies on Fusion Welding of High Nitrogen Stainless Steel: Microstructure, Mechanical and corrosion Behaviour

    Science.gov (United States)

    Mohammed, Raffi; Srinivasa Rao, K.; Madhusudhan Reddy, G.

    2018-03-01

    An attempt has been made in the present investigation to weld high nitrogen steel of 5mm thick plates using various process i.e., shielded metal arc welding (SMAW), gas tungsten arc welding (GTAW) and autogenous electron beam welding (EBW) process. Present work is aimed at studying the microstructural changes and its effects on mechanical properties and corrosion resistance. Microstructure is characterized by optical, scanning electron microscopy and electron back scattered diffraction technique. Vickers hardness, tensile properties, impact toughness and face bend ductility testing of the welds was carried out. Pitting corrosion resistance of welds was determined using potentio-dynamic polarization testing in 3.5%NaCl solution. Results of the present investigation established that SMA welds made using Cr-Mn-N electrode were observed to have a austenite dendritic grain structure in the weld metal and is having poor mechanical properties but good corrosion resistance. GTA welds made using 18Ni (MDN 250) filler wire were observed to have a reverted austenite in martensite matrix of the weld metal and formation of unmixed zone at the fusion boundary which resulted in better mechanical properties and poor corrosion resistance. Fine grains and uniform distribution of delta ferrite in the austenite matrix and narrow width of weld zone are observed in autogeneous electron beam welds. A good combination of mechanical properties and corrosion resistance was achieved for electron beam welds of high nitrogen steel when compared to SMA and GTA welds.

  18. Mechanical and microstructural characteristics of an Al-Li-Cu-Zr alloy during superplastic deformation

    International Nuclear Information System (INIS)

    Ren, B.

    1991-01-01

    If the above alloys are heavily cold- or warm-worked prior to superplastic deformation, they are resistant to static recrystallization but dynamically recrystallize with a clear strain dependence, and are superplastic deformable at relative high strain rates in the approximate range of 10 -3 to 10 -1 s -1 . The microstructural source of superplasticity has been the subject of less-detailed study than the more classical fully recrystallized materials. In this study, an effort was made to provide a somewhat greater insight into the mechanical behavior during the dynamic recrystallization of an Al-Li-Cu-Zr alloy, and to relate the mechanical behavior to the microstructure and its evolution. As part of the study, internal stresses were measured by the strain dip test, and effective stresses and their development were determined over a range of temperatures and strain rates. mechanisms for the superplastic flow and the internal-stress development during the initial stage of deformation were suggested. A variable-strain-rate model was developed based on the understanding of the mechanical behavior of this material

  19. Effect of Sb-Modification on the Microstructure and Mechanical Properties of Secondary Alloy 319

    Directory of Open Access Journals (Sweden)

    Medlen D.

    2016-06-01

    Full Text Available 319 alloy has been selected for the study in the present work due to its wide use in many applications. 319 alloy is used in automotive and aerospace industry for the complicated castings which must comply high strength requirements. In practice, the most common elements with the modifying effect are strontium, sodium and antimony. The addition of these elements leads to a change in the shape of eutectic silicon, resulting in an increase of the mechanical characteristics and the microstructure. An experimental program has been undertaken to explore the effect of antimony on chosen mechanical properties and the microstructure of investigated alloy. An analysis of the results of these experimental works is made in order to determine an optimum Sb (Al-10% Sb addition to produce material exhibiting desirable properties. Experimental works have showed that the addition of the Al-10% Sb results in similar or even higher mechanical properties than the conventional 319 alloy. Based on the carried out experiments the best combination of mechanical properties has been achieved by the addition of 2 000 ppm Al-10% Sb.

  20. Evaluation of Biaxial Mechanical Properties of Aortic Media Based on the Lamellar Microstructure

    Directory of Open Access Journals (Sweden)

    Hadi Taghizadeh

    2015-01-01

    Full Text Available Evaluation of the mechanical properties of arterial wall components is necessary for establishing a precise mechanical model applicable in various physiological and pathological conditions, such as remodeling. In this contribution, a new approach for the evaluation of the mechanical properties of aortic media accounting for the lamellar structure is proposed. We assumed aortic media to be composed of two sets of concentric layers, namely sheets of elastin (Layer I and interstitial layers composed of mostly collagen bundles, fine elastic fibers and smooth muscle cells (Layer II. Biaxial mechanical tests were carried out on human thoracic aortic samples, and histological staining was performed to distinguish wall lamellae for determining the dimensions of the layers. A neo-Hookean strain energy function (SEF for Layer I and a four-parameter exponential SEF for Layer II were allocated. Nonlinear regression was used to find the material parameters of the proposed microstructural model based on experimental data. The non-linear behavior of media layers confirmed the higher contribution of elastic tissue in lower strains and the gradual engagement of collagen fibers. The resulting model determines the nonlinear anisotropic behavior of aortic media through the lamellar microstructure and can be assistive in the study of wall remodeling due to alterations in lamellar structure during pathological conditions and aging.

  1. Microstructural modification of pure Mg for improving mechanical and biocorrosion properties.

    Science.gov (United States)

    Ahmadkhaniha, D; Järvenpää, A; Jaskari, M; Sohi, M Heydarzadeh; Zarei-Hanzaki, A; Fedel, M; Deflorian, F; Karjalainen, L P

    2016-08-01

    In this study, the effect of microstructural modification on mechanical properties and biocorrosion resistance of pure Mg was investigated for tailoring a load-bearing orthopedic biodegradable implant material. This was performed utilizing the friction stir processing (FSP) in 1-3 passes to refine the grain size. Microstructure was examined in an optical microscope and scanning electron microscope with an electron backscatter diffraction unit. X-ray diffraction method was used to identify the texture. Mechanical properties were measured by microhardness and tensile testing. Electrochemical impedance spectroscopy was applied to evaluate corrosion behavior. The results indicate that even applying a single pass of FSP refined the grain size significantly. Increasing the number of FSP passes further refined the structure, increased the mechanical strength and intensified the dominating basal texture. The best combination of mechanical properties and corrosion resistance were achieved after three FSP passes. In this case, the yield strength was about six times higher than that of the as-cast Mg and the corrosion resistance was also improved compared to that in the as-cast condition. Copyright © 2016 Elsevier Ltd. All rights reserved.

  2. Microstructural characterizations and mechanical properties in underwater friction stir welding of aluminum and magnesium dissimilar alloys

    International Nuclear Information System (INIS)

    Zhao, Yong; Lu, Zhengping; Yan, Keng; Huang, Linzhao

    2015-01-01

    Highlights: • Aluminum and magnesium alloys were joined by underwater friction stir welding. • Underwater FSW was conducted to improve properties of joint with lower heat input. • Microstructures and mechanical properties of dissimilar joint were investigated. • Intermetallic compounds developed in the fracture interface were analyzed. • Fracture features of the tensile samples were analyzed. - Abstract: Formation of intermetallic compounds in the stir zone of dissimilar welds affects the mechanical properties of the joints significantly. In order to reduce heat input and control the amount and morphological characteristics of brittle intermetallic compounds underwater friction stir welding of 6013 Al alloy and AZ31 Mg alloy was carried out. Microstructures, mechanical properties, elements distribution, and the fracture surface of the joints were analyzed by optical microscopy, scanning electron microscopy and energy dispersive X-ray spectroscopy, etc. The result shows that sound dissimilar joint with good mechanical properties can be obtained by underwater friction stir welding. Al and Mg alloys were stirred together and undergone the process of recrystallization, forming complex intercalated flow patterns in the stir zone. Tensile strength of the dissimilar joint was up to 152.3 MPa. Maximum hardness (142HV) appeared in the middle of the centerline of the specimen. Intermetallic compounds layer consisting of Al 3 Mg 2 and Mg 17 Al 12 formed in the Al/Mg interface and resulted in the fracture of the joint

  3. Microstructure and mechanical properties of metal/oxide and metal/silicide interfaces

    International Nuclear Information System (INIS)

    Shaw, L.; Miracle, D.; Abbaschian, R.

    1995-01-01

    Fracture energies of Al 2 O 3 /Nb interfaces and MoSi 2 /Nb interfaces with and without Al 2 O 3 coating were measured using sandwich-type chevron-notched specimens. The relations between the mechanical properties, microstructures, types of bonds at the interface and processing routes were explored. The fracture energy of the Al 2 O 3 /Nb interface was determined to be 9 J/m 2 and changed to 16 J/m 2 when Nb was pre-oxidized before the formation of the Al 2 O 3 /Nb interface. The fracture energy of the MoSi 2 /Nb interface could not be determined directly because of the formation of the interfacial compounds. However, the fracture energy at the MoSi 2 /Nb interfacial region was found to depend on the interfacial bond strength, roughness of interfaces and microstructure of interfacial compounds. The interfacial fracture energies of Al 2 O 3 with silicides, MoSi 2 , Nb 5 Si 3 , or (Nb, Mo)Si 2 were estimated to be about 16 J/m 2 , while the interfacial fracture energies between two silicides or between Nb and a silicide were larger than 34 J/m 2 . The measured fracture energies between two silicides or between Nb and a silicide were larger than 34 J/m 2 . The measured fracture energies of the various interfaces are discussed in terms of the interfacial microstructures and types of bonds at the interfaces

  4. Progress of research on the mechanism of microstructure evolution during irradiation with collision cascades

    International Nuclear Information System (INIS)

    Kiritani, Michio

    1997-01-01

    Progress of the research on microstructural evolution during radiation damage accompanied with collision cascades, particularly by neutrons, is summarized from the researches reported in 1995 and 1996. The major part of irradiation was performed with JMTR (Japan Material Testing Reactor), and comparisons were made with the result of D-T fusion neutron irradiation with RTNS-II (Rotating Target Neutron Source, LLNL). The subjects concerned are: (1) Microstructure evolution during irradiation, (2) Processes controlling the accumulation of defects during cascade damage, (3) Subcascades from the viewpoint of point defect cluster formation, (4) Mechanism of suppression of microstructure evolution during temperature cycle neutron irradiation of nickel, (5) Identification of the nature of neutron-irradiation-induced point defect clusters in copper by means of electron irradiation, (6) Easy one-dimensional motion of small interstitial clusters, (7) Identification of the nature of small point defect clusters in neutron irradiated Fe-16Ni-15Cr, (8) Spatial distribution of nucleation of point defect clusters by high energy particle irradiation, (9) Crystallographic orientation dependence of dislocation structures in neutron irradiated metals, (10) Examination of defect accumulation mode with multi-section-removable-irradiation-rig in Japan Material Testing Reactor, (11) Estimation of freely migrating point defects during cascade damage by the growth of helical dislocations, (12) Identification of the nature of neutron-irradiation-induced small point defect clusters in Nickel by means of electron irradiation, (13) Thermal stability of point defect clusters in neutron irradiated Fe-16Ni-15Cr. (author)

  5. Computational simulation of weld microstructure and distortion by considering process mechanics

    Science.gov (United States)

    Mochizuki, M.; Mikami, Y.; Okano, S.; Itoh, S.

    2009-05-01

    Highly precise fabrication of welded materials is in great demand, and so microstructure and distortion controls are essential. Furthermore, consideration of process mechanics is important for intelligent fabrication. In this study, the microstructure and hardness distribution in multi-pass weld metal are evaluated by computational simulations under the conditions of multiple heat cycles and phase transformation. Because conventional CCT diagrams of weld metal are not available even for single-pass weld metal, new diagrams for multi-pass weld metals are created. The weld microstructure and hardness distribution are precisely predicted when using the created CCT diagram for multi-pass weld metal and calculating the weld thermal cycle. Weld distortion is also investigated by using numerical simulation with a thermal elastic-plastic analysis. In conventional evaluations of weld distortion, the average heat input has been used as the dominant parameter; however, it is difficult to consider the effect of molten pool configurations on weld distortion based only on the heat input. Thus, the effect of welding process conditions on weld distortion is studied by considering molten pool configurations, determined by temperature distribution and history.

  6. Microstructure and Mechanical Properties of 21-6-9 Stainless Steel Electron Beam Welds

    Science.gov (United States)

    Elmer, John W.; Ellsworth, G. Fred; Florando, Jeffrey N.; Golosker, Ilya V.; Mulay, Rupalee P.

    2017-04-01

    Welds can either be stronger or weaker than the base metals that they join depending on the microstructures that form in the fusion and heat-affected zones of the weld. In this paper, weld strengthening in the fusion zone of annealed 21-6-9 stainless steel is investigated using cross-weld tensile samples, hardness testing, and microstructural characterization. Due to the stronger nature of the weld, the cross-weld tensile tests failed in the base metal and were not able to generate true fusion zone mechanical properties. Nanoindentation with a spherical indenter was instead used to predict the tensile behavior for the weld metal. Extrapolation of the nanoindentation results to higher strains was performed using the Steinberg-Guinan and Johnson-Cook strength models, and the results can be used for weld strength modeling purposes. The results illustrate how microstructural refinement and residual ferrite formation in the weld fusion zone can be an effective strengthener for 21-6-9 stainless steel.

  7. The formation mechanism of eutectic microstructures in NiAl-Cr composites.

    Science.gov (United States)

    Tang, Bin; Cogswell, Daniel A; Xu, Guanglong; Milenkovic, Srdjan; Cui, Yuwen

    2016-07-20

    NiAl-based eutectic alloys, consisting of an ordered bcc matrix (B2) and disordered bcc fibers (A2), have been a subject of intensive efforts aimed at tailoring the properties of many of the currently used nickel-based superalloys. A thermodynamic phase field model was developed on a thermodynamic foundation and fully integrated with a thermo-kinetic database of the Ni-Al-Cr ternary system to elucidate the resulting peculiar eutectic microstructure. Invoking a variation of the liquid/solid interfacial thickness with temperature, we simulated the characteristic sunflower-like eutectic microstructures in the NiAl-Cr composites, consistent with experimental observations. The mechanism that governs the formation of the peculiar eutectic morphology was envisioned from the modeled evolutions associated with six sequential steps. Our calculations show that the conditional spinodal decomposition occurring in sequence could further trim and revise the microstructure of the eutectics by generating fine-domain structures, thereby providing an additional method to explore the novel NiAl-based eutectic composites with tunable properties at elevated temperatures.

  8. The influence of untreated sugarcane bagasse ash on the microstructural and mechanical properties of mortars

    International Nuclear Information System (INIS)

    Maldonado-García, M.A.; Hernández-Toledo, U.I.; Montes-García, P.; Valdez-Tamez, P.L.

    2018-01-01

    This study investigated the effects of the addition of untreated sugarcane bagasse ash (UtSCBA) on the microstructural and mechanical properties of mortars. The SCBA was sieved for only five minutes through a No. 200 ASTM mesh, and fully characterized by chemical composition analysis, laser ray diffraction, the physical absorption of gas, scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques. Mortar mixtures with 0, 10 and 20% UtSCBA as cement replacement and a constant 0.63 water/cementitious material ratio were prepared. Fresh properties of the mortars were obtained. The microstructural characteristics of the mortars at 1, 7, 28, 90 and 600 days were evaluated by SEM and XRD. The compressive strengths of the mortars at the same ages were then obtained. The results show that the addition of 10 and 20% UtSCBA caused a slight decrease in workability of the mortars but improved their microstructure, increasing the long-term compressive strength. [es

  9. The relationship between microstructure and mechanical properties of ferritic chromium steel weldments

    Energy Technology Data Exchange (ETDEWEB)

    Mayr, Peter; Cerjak, Horst [Graz Univ. of Technology (Austria); Toda, Yoshiaki; Hara, Toru; Abe, Fujio [National Institute for Materials Science (Japan)

    2008-07-01

    Welding as the major joining and repair technology for steels in thermal power plants has a significant influence on the steels microstructure and, therefore, on its properties. Heat-resistant martensitic 9-12% chromium steels show an affinity to the retention of delta ferrite in the heat-affected zone of their weldments. This is related to their high level of ferrite stabilizing alloying elements such as Cr, W or Mo. Retained delta ferrite in martensitic steel grades has a significant negative influence on creep strength, fatigue strength, toughness and oxidation resistance. In the long-term range of creep exposure, many weldments of martensitic heatresistant steels fail by Type IV cracking in the fine-grained region of the heat-affected zone. In this work, the formation of the heat-affected zone microstructures in martensitic chromium steels is studied by in-situ X-ray diffraction using synchrotron radiation, optical microscopy as well as most advanced electron microscopical methods. The observed microstructure is directly linked to the mechanical properties, i.e. ductility, toughness and creep strength. Characteristic failure modes are discussed in detail. (orig.)

  10. Synthesis, microstructural, optical and mechanical properties of yttria stabilized zirconia thin films

    International Nuclear Information System (INIS)

    Amézaga-Madrid, P.; Hurtado-Macías, A.; Antúnez-Flores, W.; Estrada-Ortiz, F.; Pizá-Ruiz, P.; Miki-Yoshida, M.

    2012-01-01

    Highlights: ► Thin films of YSZ obtained by AACVD have high quality. ► They are uniform, very transparent, and have high hardness. ► Optical characterization were performed in detail, optical constants and band gap energy were determined as a function of dopant content. - Abstract: Thin films of yttria-stabilized zirconia (YSZ) exhibit exceptional properties, such as high thermal, chemical and mechanical stability. Here, we report the synthesis of YSZ thin films by aerosol assisted chemical vapour deposition onto borosilicate glass and fused silica substrates. Optimum deposition temperature was 673 ± 5 K. In addition, different Y content was tried to analyse its influence in the microstructure and properties of the films. The films were uniform, transparent and non-light scattering. Surface morphology and cross sectional microstructure were studied by field emission scanning electron microscopy. The microstructure of the films was characterized by grazing incidence X-ray diffraction. Crystallite size and lattice parameter were obtained. Optical properties were analysed from reflectance and transmittance spectra; from these measurements, optical constants and band gap were obtained. Quantum confinement effect, due to the small grain size of the films, was evident in the high band gap energy obtained. Nanoindentation tests were realized at room temperature employing the continuous stiffness measurement method, to determine the hardness and elastic modulus as a function of Y content.

  11. Microstructure and Mechanical Properties of TIG Weld Joint of ZM5 Magnesium Alloy

    Directory of Open Access Journals (Sweden)

    QIN Ren-yao

    2016-06-01

    Full Text Available The ZM5 magnesium alloy plates were welded by TIG welding method. The microstructural characteristics and mechanical properties of ZM5 magnesium alloy joint were studied by optical microscopy, microhardness and tensile testers. The results show that the TIG weld joint of ZM5 magnesium alloy is composed of heat affected zone, partially melted zone and weld metal. The heat affected zone is consisted of primary α-Mg phase and eutectic phase that is composed of eutectic α-Mg and eutectic β-Mg17Al12 phase and mainly precipitated at grain boundaries. In the partially melted zone, the eutectic phase is not only increasingly precipitated at grain boundaries, but also dispersed in grains, and the growth of the β-Mg17Al12 phase is obviously observed. The microstructure in the weld is the typical dendritic morphology. The dendrites are considered as primary α-Mg phase, and the interdendritic regions are α+β eutectic phase. The difference in the microstructure of the heat affected zone, partially melted zone and weld results in their various microhardness values, and leads to the smaller tensile strength and ductility in the ZM5 alloy weld joint than parent metal.

  12. Effect of revert addition on microstructure and mechanical properties of M951 Ni-base superalloy

    International Nuclear Information System (INIS)

    Yang, Y.H.; Yu, J.J.; Sun, X.F.; Jin, T.; Guan, H.R.; Hu, Z.Q.

    2012-01-01

    Highlights: ► The microstructure is not influenced by the additions of recycled alloy. ► The stress rupture life significantly decreases with addition of recycled alloy. ► The stress rupture life is remarkably dependent on various revert additions. ► The stress rupture life has been significantly improved after filtration. ► The melt filtered through 20 ppi shows the lowest stress rupture life. - Abstract: The effect of recycled alloy proportion on the composition, microstructure and mechanical properties of M951 alloy has been investigated. With the addition of the recycled alloy proportion, the concentrations of boron and carbon obviously decrease. The microstructure is not influenced by the additions of recycled alloy. The stress rupture life significantly decreases with the addition of recycled alloy proportion. Because of the removal of oxide inclusions by filtration, the stress rupture life has been significantly improved, and it also shows a clear dependence upon passage size of the filter. The melt filtered through passage size of 20 ppi shows the lowest stress rupture life.

  13. Effect of tempering on the microstructure and mechanical properties of a medium carbon bainitic steel

    Energy Technology Data Exchange (ETDEWEB)

    Kang, J. [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China); Zhang, F.C., E-mail: zfc@ysu.edu.cn [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China); National Engineering Research Center for Equipment and Technology of Cold Strip Rolling, Yanshan University, Qinhuangdao 066004 (China); Yang, X.W. [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China); Lv, B. [College of Environmental and Chemical Engineering, Yanshan University, Qinhuangdao 066004 (China); Wu, K.M. [International Research Institute for Steel Technology, Wuhan University of Science and Technology, Wuhan 430081 (China); Materials Science and Metallurgy, University of Cambridge, Cambridge CB2 3QZ (United Kingdom)

    2017-02-16

    The effect of tempering on the microstructure and mechanical properties of a medium carbon bainitic steel has been investigated through optical microscopy, electron back-scattered diffraction, transmission electron microscopy and X-ray diffraction analyses. A nano-level microstructure containing plate-like bainitic ferrite and film-like retained austenite is obtained by isothermal transformation at Ms+10 °C followed by tempering within 240–450 °C. Results show that the sample tempered at 340 °C occupies the optimal balance of strength and toughness by maintaining a certain level of plasticity; samples tempered at 320 °C and 360 °C with low and high yield ratio come second. The microstructure of the steel is not sensitive to tempering temperatures before 360 °C. When the temperature is increased to 450 °C, the significantly coarsened bainitic ferrite plate and the occurrence of a small quantity of carbide precipitation account for its low toughness. The amount of retained austenite increases with the tempering temperature before 400 °C, followed by decreasing with further increase in the temperature. This behavior is related to the competition between retained austenite further transforming into bainite and decomposing into carbide during tempering.

  14. Precise Analysis of Microstructural Effects on Mechanical Properties of Cast ADC12 Aluminum Alloy

    Science.gov (United States)

    Okayasu, Mitsuhiro; Takeuchi, Shuhei; Yamamoto, Masaki; Ohfuji, Hiroaki; Ochi, Toshihiro

    2015-04-01

    The effects of microstructural characteristics (secondary dendrite arm spacing, SDAS) and Si- and Fe-based eutectic structures on the mechanical properties and failure behavior of an Al-Si-Cu alloy are investigated. Cast Al alloy samples are produced using a special continuous-casting technique with which it is easy to control both the sizes of microstructures and the direction of crystal orientation. Dendrite cells appear to grow in the casting direction. There are linear correlations between SDAS and tensile properties (ultimate tensile strength σ UTS, 0.2 pct proof strength σ 0.2, and fracture strain ɛ f). These linear correlations, however, break down, especially for σ UTS vs SDAS and ɛ f vs SDAS, as the eutectic structures become more than 3 μm in diameter, when the strength and ductility ( σ UTS and ɛ f) decrease significantly. For eutectic structures larger than 3 μm, failure is dominated by the brittle eutectic phases, for which SDAS is no longer strongly correlated with σ UTS and ɛ f. In contrast, a linear correlation is obtained between σ 0.2 and SDAS, even for eutectic structures larger than 3 μm, and the eutectic structure does not have a strong effect on yield behavior. This is because failure in the eutectic phases occurs just before final fracture. In situ failure observation during tensile testing is performed using microstructural and lattice characteristics. From the experimental results obtained, models of failure during tensile loading are proposed.

  15. Impact of Interlayer Dwell Time on Microstructure and Mechanical Properties of Nickel and Titanium Alloys

    Science.gov (United States)

    Foster, B. K.; Beese, A. M.; Keist, J. S.; McHale, E. T.; Palmer, T. A.

    2017-09-01

    Path planning in additive manufacturing (AM) processes has an impact on the thermal histories experienced at discrete locations in simple and complex AM structures. One component of path planning in directed energy deposition is the time required for the laser or heat source to return to a given location to add another layer of material. As structures become larger and more complex, the length of this interlayer dwell time can significantly impact the resulting thermal histories. The impact of varying dwell times between 0 and 40 seconds on the microstructural and mechanical properties of Inconel® 625 and Ti-6Al-4V builds has been characterized. Even though these materials display different microstructures and solid-state phase transformations, the addition of an interlayer dwell generally led to a finer microstructure in both materials that impacted the resulting mechanical properties. With the addition of interlayer dwell times up to 40 seconds in the Inconel® 625 builds, finer secondary dendrite arm spacing values, produced by changes in the thermal history, correspond to increased yield and tensile strengths. These mechanical properties did not appear to change significantly, however, for dwell times greater than 20 seconds in the Inconel® 625 builds, indicating that longer dwell times have a minimal impact. The addition of interlayer dwell times in Ti-6Al-4V builds resulted in a slight decrease in the measured alpha lath widths and a much more noticeable decrease in the width of prior beta grains. In addition, the yield and tensile values continued to increase, nearly reaching the values observed in the rolled plate substrate material with dwell times up to 40 seconds.

  16. Deformation mechanisms in the San Andreas Fault zone - a comparison between natural and experimentally deformed microstructures

    Science.gov (United States)

    van Diggelen, Esther; Holdsworth, Robert; de Bresser, Hans; Spiers, Chris

    2010-05-01

    The San Andreas Fault (SAF) in California marks the boundary between the Pacific plate and the North American plate. The San Andreas Fault Observatory at Depth (SAFOD) is located 9 km northwest of the town of Parkfield, CA and provide an extensive set of samples through the SAF. The SAFOD drill hole encountered different lithologies, including arkosic sediments from the Salinian block (Pacific plate) and claystones and siltstones from the Great Valley block (North American plate). Fault deformation in the area is mainly by a combination of micro-earthquakes and fault creep. Deformation of the borehole casing indicated that the SAFOD drill hole cross cuts two actively deforming strands of the SAF. In order to determine the deformation mechanisms in the actively creeping fault segments, we have studied thin sections obtained from SAFOD phase 3 core material using optical and electron microscopy, and we have compared these natural SAFOD microstructures with microstructures developed in simulated fault gouges deformed in laboratory shear experiments. The phase 3 core material is divided in three different core intervals consisting of different lithologies. Core interval 1 consists of mildly deformed Salinian rocks that show evidence of cataclasis, pressure solution and reaction of feldspar to form phyllosilicates, all common processes in upper crustal rocks. Most of Core interval 3 (Great Valley) is also only mildly deformed and very similar to Core interval 1. Bedding and some sedimentary features are still visible, together with limited evidence for cataclasis and pressure solution, and reaction of feldspar to form phyllosilicates. However, in between the relatively undeformed rocks, Core interval 3 encountered a zone of foliated fault gouge, consisting mostly of phyllosilicates. This zone is correlated with one of the zones of localized deformation of the borehole casing, i.e. with an actively deforming strand of the SAF. The fault gouge zone shows a strong, chaotic

  17. Microstructure and failure mechanisms of refill friction stir spot welded 7075-T6 aluminum alloy joints

    International Nuclear Information System (INIS)

    Shen, Zhikang; Yang, Xinqi; Zhang, Zhaohua; Cui, Lei; Li, Tielong

    2013-01-01

    Highlights: ► There is a correlation between the void in the weld and the joint strength. ► The preferable mechanical properties can be obtained by lowering rotational speed. ► The alclad has an adverse effect on the mechanical properties. -- Abstract: In this paper, the microstructure and mechanical properties of 7075-T6 aluminum alloy joints joined by refill friction stir spot welding (RFSSW) were investigated. The keyhole was refilled successfully, and the microstructure of the weld exhibited variations in the grain sizes in the width and the thickness directions. There existed defects (hook, voids, bonding ligament, etc.) associated to the material flow in the weld. Mechanical properties of the joint have been investigated in terms of hardness and tensile/shear and cross-tension test, and the fracture mechanisms were observed by SEM (scanning electron microscope). The hardness profile of the weld exhibited a W-shaped appearance in the macroscopic level, which reached the minimum at the boundary of the sleeve and the clamping ring. The variation laws between tensile/shear and cross-tension strength and processing parameters were rather complicated. The void in the weld played an important role in determining the strength of the joint. On the whole, the preferable strength can be obtained at lower rotational speed. Shear fracture mode was observed under tensile–shear loadings, and nugget debonding, plug type fracture (on the upper sheet) and plug type fracture (on the lower sheet) modes were observed under cross-tension loadings. It was also observed that the main feature affecting the mechanical properties of the joint is the alclad between the upper and lower sheets and the connecting qualities between the stir zone and thermo-mechanically affected zone.

  18. Influence of particle shape on the microstructure evolution and the mechanical properties of granular materials

    Science.gov (United States)

    Tian, Jianqiu; Liu, Enlong; Jiang, Lian; Jiang, Xiaoqiong; Sun, Yi; Xu, Ran

    2018-06-01

    In order to study the influence of particle shape on the microstructure evolution and the mechanical properties of granular materials, a two-dimensional DEM analysis of samples with three particle shapes, including circular particles, triangular particles, and elongated particles, is proposed here to simulate the direct shear tests of coarse-grained soils. For the numerical test results, analyses are conducted in terms of particle rotations, fabric evolution, and average path length evolution. A modified Rowe's stress-dilatancy equation is also proposed and successfully fitted onto simulation data.

  19. Microstructure and Mechanical Property of SiCf/SiC and Cf/SiC Composites

    International Nuclear Information System (INIS)

    Lee, S P; Cho, K S; Lee, H U; Lee, J K; Bae, D S; Byun, J H

    2011-01-01

    The mechanical properties of SiC based composites reinforced with different types of fabrics have been investigated, in conjunction with the detailed analyses of their microstructures. The thermal shock properties of SiC f /SiC composites were also examined. All composites showed a dense morphology in the matrix region. Carbon coated PW-SiC f /SiC composites had a good fracture energy, even if their strength was lower than that of PW-C f /SiC composites. SiC f /SiC composites represented a great reduction of flexural strength at the thermal shock temperature difference of 300 deg. C.

  20. A parametric study of the microstructural, mechanical and tribological properties of PACVD TiN coatings

    DEFF Research Database (Denmark)

    Mogensen, K.S.; Thomsen, N.B.; Eskildsen, S.S.

    1998-01-01

    deposition chamber were investigated. The process parameters, i.e, voltage, pressure, and flows of H-2, Ar, N, and TiCl4, were varied. The microstructural, mechanical and tribological properties of the coatings were investigated using X-ray diffraction, scanning electron microscopy, transmission electron...... microscopy, nanoindentation, pin-on-disc measurements and Rutherford backscattering spectrometry. The residual stress level and hardness varied significantly with changes in the process parameters, whereas the tribological properties displayed only minor variations. (C) 1998 Elsevier Science S.A....

  1. Microstructure and mechanical properties of metallic high-temperature materials. Research report

    International Nuclear Information System (INIS)

    Mughrabi, H.; Gottstein, G.; Mecking, H.; Riedel, H.; Toboloski, J.

    1999-01-01

    This volume contains 38 lectures of research studies performed in the course of the Priority Programme 'Microstructure and Mechanical Properties of Metallic High-Temperature Materials' supported by the Deutsche Forschungsgemeinschaft (DFG) over a period of six years from 1991 to 1997. The four materials selected were: 1. light metal PM-aluminium and titanium base alloys; 2. ferritic chromium and austenitic alloy 800 steels; 3. (monocrystalline) nickel-base superalloys; and 4. nickel- and iron-base oxide-dispersion-strengthened superalloys. All papers have been abstracted separately for the ENERGY database

  2. Mechanical and microstructural characterization of the nickel base alloy (Alloy 600) after heat treatment

    International Nuclear Information System (INIS)

    Fernandes, Stela Maria de Carvalho

    1993-01-01

    The characterization of microstructural and mechanical properties of cold rolled and heat treated alloys 600 made in Brazil were investigated. The recovery and recrystallization behavior as well as solubilization and aging have been studied using optical, scanning electron and transmission electron microscopy. Microhardness and tensile testing have been carried out. The recovery process of the cold rolled alloy 600 occurred until 600 deg C and the recrystallization stage was situated between 600 and 850 deg C. The primary recrystallization temperature was obtained at 850 deg C after 1 hour (isochronal heat treatments). The aged alloy 600 shows carbide precipitation on grains bu with ductility maintenance. (author)

  3. Microstructure and Mechanical Properties of ASTM A743 CA6NM Steel Welded by FCAW Process

    OpenAIRE

    Silva, Rafael de Paula; Faria, Maria Ismenia Sodero Toledo; Almeida, Luiz Fernando Cursino Briet de; Nunes, Carlos Angelo; Vieira, Décio; Borges Júnior, Wanderlei

    2017-01-01

    CA6NM steel is widely used in the manufacture of hydraulic turbines metallic parts, due to its resistance to corrosion and cavitation damage, combined with good weldability and fatigue properties. However, welding of this type of steel is complex and to ensure a minimum residual stress after welding it is necessary perform a post welding heat treatment (PWHT) of the part. This study aims to analyze the effect of a PWHT on the microstructure and mechanical properties of CA6NM steel weld joint ...

  4. Study on mechanical and microstructure behavior of submerged arc welding flux using red mud

    Science.gov (United States)

    Dewangan, Rishi; Pandey, Pankaj K.; Upadhyay, Renu

    2018-05-01

    This paper emphasis on utilization of Red Mud for preparing submerged arc welding flux and study its mechanical and microstructure behavior. Among the six fluxes prepared in the laboratory, Flux no. 1 (basicity 1.106) found to be best due to its running performance, micro hardness and Brinell hardness. The hardness value (HV) of the fluxes was varying from 165.70 to 217.15 at a load of 1000gm respectively. From the micrograph of welded metal, acicular ferrite found to be optimum which helps in increasing the ductility and hardness of the welded material.

  5. Thermo-mechanically induced texture evolution and micro-structural change of aluminum metallization

    DEFF Research Database (Denmark)

    Brincker, Mads; Walter, Thomas; Kristensen, Peter Kjær

    2018-01-01

    During operation of high power electronic chips the topside metallization is subjected to cyclic compressive and tensile stresses leading to unwanted thermo-mechanical fatigue of the metallization layer. The stress is caused by the difference in the thermal expansion coefficients...... are not yet fully understood. In this work, we investigate the microstructural evolution of an Al metallization on high power diode chips subjected to passive thermal cycling between 20 and 100ºC. The texture of the Al film is analyzed ex-situ by a combination of electron backscatter diffraction and X...

  6. Effect of scandium additions on microstructure and mechanical properties of Al-Zn-Mg alloy welds

    International Nuclear Information System (INIS)

    Dev, Selvi; Stuart, A. Archibald; Kumaar, R.C. Ravi Dev; Murty, B.S.; Rao, K. Prasad

    2007-01-01

    The microstructure and mechanical properties of fusion zones of medium strength Al-Zn-Mg alloy (RDE-40) welds obtained by using different fillers containing various amount of scandium was investigated. It was observed that addition of scandium led to very significant grain refinement in the fusion zone especially for scandium levels greater than the eutectic composition (0.55 wt%). The grain refinement led to the reduction in solidification cracking and improved the tensile properties of fusion zone compared to the ones obtained by the commercial AA5556 filler

  7. Mechanical Properties and Microstructure of Fast – Fired Clinker Tiles Based on Wierzbka I Raw Material

    OpenAIRE

    Gajek M.; Rapacz-Kmita A.; Dudek M.; Partyka J.

    2016-01-01

    The article presents results of research on microstructural and mechanical properties of floor tiles clinker manufactured on the basis of Wierzbka I raw material, which is part of the deposit Wierzbka, near Suchedniów. Wierzbka I clay was added in various volume fractions to the standard tile compositions used in industrial practice. The samples were pressed in a range of from 21 MPa to 42 MPa and fired in the laboratory furnace at 1130°C to 1190°C. Selected compositions were pressed at 28 MP...

  8. Microstructural and Mechanical Property Characterization of Shear Formed Aerospace Aluminum Alloys

    Science.gov (United States)

    Troeger, Lillianne P.; Domack, Marcia S.; Wagner, John A.

    2000-01-01

    Advanced manufacturing processes such as near-net-shape forming can reduce production costs and increase the reliability of launch vehicle and airframe structural components through the reduction of material scrap and part count and the minimization of joints. The current research is an investigation of the processing-microstructure-property relationships for shear formed cylinders of the Al-Cu-Li-Mg-Ag alloy 2195 for space applications and the Al-Cu-Mg-Ag alloy C415 for airframe applications. Cylinders which had undergone various amounts of shear-forming strain were studied to correlate the grain structure, texture, and mechanical properties developed during and after shear forming.

  9. Microstructure and Mechanical Properties of n-irradiated Fe-Cr Model Alloys

    International Nuclear Information System (INIS)

    Matijasevic, Milena; Al Mazouzi, Abderrahim

    2008-01-01

    High chromium ( 9-12 wt %) ferritic/martensitic steels are candidate structural materials for future fusion reactors and other advanced systems such as accelerator driven systems (ADS). Their use for these applications requires a careful assessment of their mechanical stability under high energy neutron irradiation and in aggressive environments. In particular, the Cr concentration has been shown to be a key parameter to be optimized in order to guarantee the best corrosion and swelling resistance, together with the least embrittlement. In this work, the characterization of the neutron irradiated Fe-Cr model alloys with different Cr % with respect to microstructure and mechanical tests will be presented. The behavior of Fe-Cr alloys have been studied using tensile tests at different temperature range ( from -160 deg. C to 300 deg. C). Irradiation-induced microstructure changes have been studied by TEM for two different irradiation doses at 300 deg. C. The density and the size distribution of the defects induced have been determined. The tensile test results indicate that Cr content affects the hardening behavior of Fe-Cr binary alloys. Hardening mechanisms are discussed in terms of Orowan type of approach by correlating TEM data to the measured irradiation hardening. (authors)

  10. Study of microstructure evolution and strengthening mechanisms in novel TiZrAlB alloy

    Energy Technology Data Exchange (ETDEWEB)

    Liu, S.G.; Feng, Z.H.; Xia, C.Q.; Zhang, Z.G.; Zhang, X.; Zhang, X.Y., E-mail: xyzhang@ysu.edu.cn; Ma, M.Z.; Liu, R.P., E-mail: riping@ysu.edu.cn

    2017-04-24

    In this paper, the microstructural evolution and mechanical properties of the as-cast Ti-χZr-4Al-0.005B (TχZAB and χ=0, 10, 20, 30, 40 wt%) alloys were systematically investigated. Only the α phase was detected from the X-ray diffraction patterns of the as-cast TχZAB quaternary alloy series. As the Zr content increased, the average size and length-diameter ratio of the α grains were decreased from 69.8 μm to 17.1 µm and 37.5 to 8.4, respectively. The analysis of the results from the tensile and microhardness tests demonstrated that both the strength and hardness increased significantly as the Zr content increased (from 0 wt% to 40 wt%). Nevertheless, the ductility exhibited an opposite trend. The fracture mode of the ductile-brittle transfer was consistent with the ductility alteration. The as-cast Ti-40Zr-4Al-0.005B alloys demonstrated the highest tensile strength (σ{sub b}=1134 MPa), which increased by 53% compared to the Ti-4Al-0.005B alloys, whereas the lowest elongation-to-failure was of 6.77%. The mechanical properties of the TχZAB alloy series were discussed based on the microstructural evolution and the solid solution strengthening mechanisms.

  11. The effect of phosphorus on the microstructure and mechanical properties of ATI 718Plus alloy

    International Nuclear Information System (INIS)

    Wang, Minqing; Du, Jinhui; Deng, Qun; Tian, Zhiling; Zhu, Jing

    2015-01-01

    Since the discovery in the 1990s of the abnormal improvement produced by phosphorus in the stress rupture and creep life of Inconel 718 (hereafter referred to as 718), a great deal of additional research followed. However, the mechanism of the action of phosphorous in 718 is still in question. This paper details an experimental study that was intended to determine how phosphorus acts upon the microstructure and mechanical properties of Ni–Fe based alloy 718Plus. The results show that phosphorus has little effect on the strength and ductility of alloy 718Plus, but can significantly improve the stress rupture life. Phase constituents such as the δ and γ′ phases were quantitatively analyzed using electrolytic phase isolation and micro-chemical and XRD analysis as the phosphorous content of the alloy was increased. A full atom mapping of the distribution of phosphorus in the 718Plus alloy was quantitatively determined using APT (Atom Probe Tomography) technique. The results showed that there is no significant segregation of phosphorus at the γ′/γ and γ′/γ′ interface, but it significantly segregates at the grain boundaries and δ/γ interface. It was found that phosphorus is extremely depleted in the δ phase, which is believed to inhibit δ-phase precipitation by preventing δ phase nucleation and growth in the 718Plus alloy. Finally, the influence of phosphorus on the microstructure and mechanical properties of the 718Plus alloy was discussed

  12. Effect of chemical composition and microstructure on the mechanical behavior of fish scales from Megalops Atlanticus.

    Science.gov (United States)

    Gil-Duran, S; Arola, D; Ossa, E A

    2016-03-01

    This paper presents an experimental study of the composition, microstructure and mechanical behavior of scales from the Megalops Atlanticus (Atlantic tarpon). The microstructure and composition were evaluated by Scanning Electron Microscopy (SEM) and RAMAN spectroscopy, respectively. The mechanical properties were evaluated in uniaxial tension as a function of position along the length of the fish (head, mid-length and tail). Results showed that the scales are composed of collagen and hydroxyapatite, and these constituents are distributed within three well-defined layers from the bottom to the top of the scale. The proportion of these layers with respect to the total scale thickness varies radially. The collagen fibers are arranged in plies with different orientations and with preferred orientation in the longitudinal direction of the fish. Results from the tensile tests showed that scales from Megalops Atlanticus exhibit variations in the elastic modulus as a function of body position. Additional testing performed with and without the highly mineralized top layers of the scale revealed that the mechanical behavior is anisotropic and that the highest strength was exhibited along the fish length. Furthermore, removing the top mineralized layers resulted in an increase in the tensile strength of the scale. Copyright © 2015 Elsevier Ltd. All rights reserved.

  13. Microstructural evolution and mechanical properties of Inconel 718 after thermal exposure

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Z.S., E-mail: yuzaisong@tpri.com.cn [State Key Laboratory for Mechanical Behavior of Materials, Xi’an Jiaotong University, No. 28, Xianning West Road, Xi’an 710049 (China); Xi' an Thermal Power Research Institute Co. Ltd., No. 136, Xingqing Road, Xi’an 710032 (China); Zhang, J.X. [State Key Laboratory for Mechanical Behavior of Materials, Xi’an Jiaotong University, No. 28, Xianning West Road, Xi’an 710049 (China); Yuan, Y.; Zhou, R.C.; Zhang, H.J.; Wang, H.Z. [Xi' an Thermal Power Research Institute Co. Ltd., No. 136, Xingqing Road, Xi’an 710032 (China)

    2015-05-14

    Inconel 718 was subjected to various heat treatments, i.e., solution heat treatment, standard ageing treatment and standard ageing plus 700 °C thermal exposure. The mechanical properties of the alloys were determined using tensile tests and Charpy pendulum impact tests at 650 °C and room temperature, respectively. The highest yield strength of 988 MPa was attained in the standard aged specimen, whereas a maximum impact toughness of 217 J cm{sup −2} was attained in the solution-treated specimen. After thermal exposure, the mechanical properties of the specimens degrade. Both the yield strength and impact toughness decreased monotonically with increasing thermal exposure time. Subjected to a 10000-h long-term thermal exposure, the yield strength dramatically decreased to 475 MPa (almost 50% of the maximum strength), and the impact toughness reduced to only 18 J cm{sup −2}. The microstructures of the specimens were characterized using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Coarsening of γ′ and γ″ and the transformation of γ″ to δ-Ni{sub 3}Nb was observed after thermal exposure. However, a complete transformation from metastable γ″ to δ-Ni{sub 3}Nb was never accomplished, even after the 10000-h long-term thermal exposure. Based on the obtained experimental results, the effects of the microstructural evolution on the mechanical properties are discussed.

  14. The effect of phosphorus on the microstructure and mechanical properties of ATI 718Plus alloy

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Minqing, E-mail: minqingw@yahoo.com [Central Iron and Steel Research Institute, Beijing 100081 (China); School of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China); Beijing Key Laboratory of Advanced High Temperature Materials, Beijing 100081 (China); Du, Jinhui; Deng, Qun [Central Iron and Steel Research Institute, Beijing 100081 (China); Beijing Key Laboratory of Advanced High Temperature Materials, Beijing 100081 (China); Tian, Zhiling [Central Iron and Steel Research Institute, Beijing 100081 (China); Zhu, Jing, E-mail: jzhu@mail.tsinghua.edu.cn [School of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China)

    2015-02-25

    Since the discovery in the 1990s of the abnormal improvement produced by phosphorus in the stress rupture and creep life of Inconel 718 (hereafter referred to as 718), a great deal of additional research followed. However, the mechanism of the action of phosphorous in 718 is still in question. This paper details an experimental study that was intended to determine how phosphorus acts upon the microstructure and mechanical properties of Ni–Fe based alloy 718Plus. The results show that phosphorus has little effect on the strength and ductility of alloy 718Plus, but can significantly improve the stress rupture life. Phase constituents such as the δ and γ′ phases were quantitatively analyzed using electrolytic phase isolation and micro-chemical and XRD analysis as the phosphorous content of the alloy was increased. A full atom mapping of the distribution of phosphorus in the 718Plus alloy was quantitatively determined using APT (Atom Probe Tomography) technique. The results showed that there is no significant segregation of phosphorus at the γ′/γ and γ′/γ′ interface, but it significantly segregates at the grain boundaries and δ/γ interface. It was found that phosphorus is extremely depleted in the δ phase, which is believed to inhibit δ-phase precipitation by preventing δ phase nucleation and growth in the 718Plus alloy. Finally, the influence of phosphorus on the microstructure and mechanical properties of the 718Plus alloy was discussed.

  15. Microstructure, Mechanical, and Fatigue Strength of Ti-54M Processed by Rotary Swaging

    Science.gov (United States)

    Al-Khazraji, Hasan; El-Danaf, Ehab; Wollmann, Manfred; Wagner, Lothar

    2015-05-01

    TIMETAL 54M is a newly developed (α + β) titanium alloy with nominal composition Ti-5Al-4V-0.6Mo-0.4Fe. The alloy can provide a cost benefit over Ti-6Al-4V due to improved machinability and formability. In the present work, evolution of mechanical properties in terms of tensile and hardness values is investigated as a function of deformation degrees imposed via rotary swaging (RS). Microstructure, mechanical properties, and fatigue performance of Ti-54M are investigated after severe plastic deformation by RS conducted at 850 °C and after being subjected to two different post-swaging annealing conditions. Optical microscopy and scanning electron microscopy using electron back scatter diffraction were utilized to document the evolution of the microstructure. Tensile tests were conducted to characterize mechanical properties. RS, to a true strain of 3.0, is found to lead to a marked ultrafine-grained structure of about 1 μm grain size with low content of high angle grain boundaries (HAGBs). Post-swaging heat treatment at 800 °C followed by air cooling did not change the grain size but exhibited high content of HAGBs. Post-swaging heat treatment at 940 °C followed by furnace cooling resulted in a grain size of about 5 μm and enhanced work-hardening capability and ductility, which resulted in less fatigue notch sensitivity, but at the same time lower fatigue strength at 107 cycles.

  16. Elemental, microstructural, and mechanical characterization of high gold orthodontic brackets after intraoral aging.

    Science.gov (United States)

    Hersche, Sepp; Sifakakis, Iosif; Zinelis, Spiros; Eliades, Theodore

    2017-02-01

    The purpose of the present study was to investigate the elemental composition, the microstructure, and the selected mechanical properties of high gold orthodontic brackets after intraoral aging. Thirty Incognito™ (3M Unitek, Bad Essen, Germany) lingual brackets were studied, 15 brackets as received (control group) and 15 brackets retrieved from different patients after orthodontic treatment. The surface of the wing area was examined by scanning electron microscopy (SEM). Backscattered electron imaging (BEI) was performed, and the elemental composition was determined by X-ray EDS analysis (EDX). After appropriate metallographic preparation, the mechanical properties tested were Martens hardness (HM), indentation modulus (EIT), elastic index (ηIT), and Vickers hardness (HV). These properties were determined employing instrumented indentation testing (IIT) with a Vickers indenter. The results were statistically analyzed by unpaired t-test (α=0.05). There were no statistically significant differences evidenced in surface morphology and elemental content between the control and the experimental group. These two groups of brackets showed no statistically significant difference in surface morphology. Moreover, the mean values of HM, EIT, ηIT, and HV did not reach statistical significance between the groups (p>0.05). Under the limitations of this study, it may be concluded that the surface elemental content and microstructure as well as the evaluated mechanical properties of the Incognito™ lingual brackets remain unaffected by intraoral aging.

  17. Control of microstructure and mechanical properties of laser solid formed Inconel 718 superalloy by electromagnetic stirring

    Science.gov (United States)

    Liu, Fencheng; Cheng, Hongmao; Yu, Xiaobin; Yang, Guang; Huang, Chunping; Lin, Xin; Chen, Jing

    2018-02-01

    The coarse columnar grains and special interface in laser solid formed (LSFed) Inconel 718 superalloy workpieces seriously affect their mechanical properties. To improve the microstructure and mechanical properties of LSFed Inconel 718 superalloy, electromagnetic stirring (EMS) was introduced to alter the solidification process of the molten pool during LSF. The results show that EMS could not completely eliminate the epitaxially growing columnar grains, however, the strong convection of liquid metals can effectively influence the solid-liquid interface growing mode. The segregation of alloying elements on the front of solid-liquid interface is inhibited and the degree of constitutional supercooling decreases correspondingly. Comparing the microstructures of samples formed under different process parameters, the size and amount of the γ+Laves eutectic phases formed in interdendritic area decrease along with the increasing magnetic field intensity, resulting in more uniformly distributed alloying elements. The residual stress distribution is proved to be more uniform, which is beneficial to the grain refinement after recrystallilzaiton. Mechanical properties testing results show an improvement of 100 MPa in tensile strength and 22% in elongation was obtained after EMS was used. The high cycle fatigue properties at room temperature was also improved from 4.09 × 104 cycles to 8.21 × 104 cycles for the as-deposited samples, and from 5.45 × 104 cycles to 12.73 × 104 cycles for the heat treated samples respectively.

  18. Heat-affected zone microstructure and mechanical properties evolution for laser remanufacturing 35CrMoA axle steel

    Science.gov (United States)

    Feng, Xiangyi; Dong, Shiyun; Yan, Shixing; Liu, Xiaoting; Xu, Binshi; Pan, Fusheng

    2018-03-01

    In this article, by using orthogonal test the technological test was conducted and the optimum processing of the remanufacturing35CrMoA axle were obtained. The evolution of microstructure and mechanical property of HAZ were investigated. The microstructure of HAZ was characterized by means of OM and SEM. Meanwhile hardness distribution in HAZ and tensile property of cladding-HAZ-substrate samples were measured. The microstructure of cladding and HAZ were observed. The microsturcture evoltion and the mechanism of harden in the HAZ was discussed and revealed. The results indicated that the remanufacturing part has excellent strength due to grain refining and dispersive distribution of nanoscale cementite. The remanufacturing part will have uniform microstructure and hardness matching with that of 35CrMoA axle by using stress-relieving annealing at 580°.

  19. Biofilm-mediated Antibiotic-resistant Oral Bacterial Infections: Mechanism and Combat Strategies.

    Science.gov (United States)

    Kanwar, Indulata; Sah, Abhishek K; Suresh, Preeti K

    2017-01-01

    Oral diseases like dental caries and periodontal disease are directly associated with the capability of bacteria to form biofilm. Periodontal diseases have been associated to anaerobic Gram-negative bacteria forming a subgingival plaque (Porphyromonas gingivalis, Actinobacillus, Prevotella and Fusobacterium). Biofilm is a complex bacterial community that is highly resistant to antibiotics and human immunity. Biofilm communities are the causative agents of biological developments such as dental caries, periodontitis, peri-implantitis and causing periodontal tissue breakdown. The review recapitulates the latest advancements in treatment of clinical biofilm infections and scientific investigations, while these novel anti-biofilm strategies are still in nascent phases of development, efforts dedicated to these technologies could ultimately lead to anti-biofilm therapies that are superior to the current antibiotic treatment. This paper provides a review of the literature focusing on the studies on biofilm in the oral cavity, formation of dental plaque biofilm, drug resistance of bacterial biofilm and the antibiofilm approaches as biofilm preventive agents in dentistry, and their mechanism of biofilm inhibition. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

  20. Microstructure and Mechanical Properties of the Dactylopodites of the Chinese Mitten Crab (Eriocheir sinensis

    Directory of Open Access Journals (Sweden)

    Ying Wang

    2018-04-01

    Full Text Available The dactylopodites of the Chinese mitten crab (Eriocheir sinensis have evolved extraordinary resistance to wear and impact loading after direct contact with rough surfaces or clashing with hard materials. In this study, the microstructure, components, and mechanical properties of the dactylopodites of the Chinese mitten crab were investigated. Images from a scanning electron microscope show that the dactylopodites’ exoskeleton was multilayered, with an epicuticle, exocuticle, and endocuticle. Cross sections and longitudinal sections of the endocuticle revealed a Bouligand structure, which contributes to the dactylopodites’ mechanical properties. The main organic constituents of the exoskeleton were chitin and protein, and the major inorganic compound was CaCO3, crystallized as calcite. Dry and wet dactylopodites were brittle and ductile, respectively, characteristics that are closely related to their mechanical structure and composition. The findings of this study can be a reference for the bionic design of strong and durable structural materials.

  1. Microstructure and mechanical properties of 304L steel fabricated by arc additive manufacturing

    Directory of Open Access Journals (Sweden)

    Ji Lei

    2017-01-01

    Full Text Available For 304L large structural parts used in nuclear power, it is hard and costly to fabricate and machine traditionally. Wire arc additive manufacturing (WAAM has low cost and high material utilization, which provides an efficient way to fabricate the large structural parts. So in this study, WAAM is used to fabricate the parts of 304L stainless steel. Through the tensile test and metallographic analysis, the mechanical properties and microstructure of the 304L stainless steel fabricated by WAAM were explored. The results indicate that with the layers depositing, the cooling rate becomes slower, the dendrites become thicker and the morphology becomes more stable. Due to the existence of dendrites, the grain boundary strengthening effect is different between the transverse direction and longitudinal direction, and resulting in anisotropy of mechanical properties. However, the mechanical properties of the parts correspond to the forged piece, which lays the foundation for future applications.

  2. Effect of brief heat-curing on microstructure and mechanical properties in fresh cement based mortars

    International Nuclear Information System (INIS)

    Ballester, P.; Hidalgo, A.; Marmol, I.; Morales, J.; Sanchez, L.

    2009-01-01

    The effect of temperature on fresh mortar and cement paste was evaluated by simulating the curing conditions of external buildings plastering applied under extremely hot weather. The specimens were heated at controlled temperatures in the 40-80 o C range by exposure to IR radiation over short periods. The effect of soaking for a short time was also examined. The results of compressive strength tests, scanning electron microscopy, infrared spectroscopy and mercury porosimetry helped to characterize the mechanical and physico-chemical properties of the studied sample. Early age behaviour (28 days) in neat cement was barely affected by the temperature. By contrast, exposure to high temperatures caused significant microstructural changes in the mortar. However, successive soaking over short periods was found to reactivate the mechanism of curing and restore the expected mechanical properties. Based on the results, application of cement based mortar at high temperatures is effective when followed by a short, specific soaking process.

  3. Characterization of mechanical properties and microstructure of highly irradiated SS 316

    Energy Technology Data Exchange (ETDEWEB)

    Karthik, V., E-mail: karthik@igcar.gov.in [Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102 (India); Kumar, RanVijay; Vijayaragavan, A.; Venkiteswaran, C.N.; Anandaraj, V.; Parameswaran, P.; Saroja, S.; Muralidharan, N.G.; Joseph, Jojo; Kasiviswanathan, K.V.; Jayakumar, T.; Raj, Baldev [Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102 (India)

    2013-08-15

    Cold worked austenitic stainless steel type AISI 316 is used as the material for fuel cladding and wrapper of the Fast Breeder Test Reactor (FBTR), India. The evaluation of mechanical properties of these core structurals is very essential to assess its integrity and ensure safe and productive operation of FBTR to very high burn-ups. The changes in the mechanical properties of these core structurals are associated with microstructural changes caused by high fluence neutron irradiation and temperatures of 673–823 K. Remote tensile testing has been used for evaluating the tensile properties of irradiated clad tubes and shear punch test using small disk specimens for evaluating the properties of irradiated hexagonal wrapper. This paper will highlight the methods employed for evaluating the mechanical properties of the irradiated cladding and wrapper and discuss the trends in properties as a function of dpa (displacement per atom) and irradiation temperature.

  4. Microstructural characterization of titanium dental implants by electron microscopy and mechanical tests

    International Nuclear Information System (INIS)

    Helfenstein, B.; Muniz, N.O.; Dedavid, B.A.; Gehrke, S.A.; Vargas, A.L.M.

    2010-01-01

    Mini screw types for titanium implants, with differentiated design, were tested for traction and torsion for behavior analysis of the shape relative to the requirements of ASTM F136. All implants showed mechanical tensile strength above by the standard requirement, being that 83.3% of them broke above the doughnut, in support of the prosthesis. Distinct morphologies in ruptured by mechanical tests, were obtained. However, both fracture surfaces showed fragile comportments. Metallographic tests, x-ray diffraction (XRD) and microhardness were used for microstructural characterization of material, before and after heat treatment. The presences of β phase in screw surface after quenching treatment proves that the thermal treatment can contribute for mechanical resistance in surface implants. (author)

  5. Microstructures and mechanical properties of Ti5553 alloy processed by high-pressure torsion

    Science.gov (United States)

    Jiang, B. Z.; Emura, S.; Tsuchiya, K.

    2014-08-01

    In the present research, the effects of high-pressure torsion (HPT) processing on the microstructure and mechanical properties of Ti-5Al-5Mo-5V-3Cr (Ti5553) alloy were studied. HPT processing produced a white etching layer (WEL) in the middle section of the cross-section and numerous shear bands in the surface region of the cross-section. And the thickness of the WEL increased with increasing the HPT revolutions. TEM observation of the WEL revealed an ultrafine-grained structure with high degree of lattice distortions. The mechanical properties measurements showed that the hardness and ultimate tensile strength increased by HPT processing, accompanied with a decrease in the elongation to failure. It is considered that the mechanical properties of HPT processed Ti5553 alloy are mostly dominated by the shear banded region and the WEL where have the finest grain size and high density of dislocations.

  6. Microstructures and mechanical properties of Ti5553 alloy processed by high-pressure torsion

    International Nuclear Information System (INIS)

    Jiang, B Z; Emura, S; Tsuchiya, K

    2014-01-01

    In the present research, the effects of high-pressure torsion (HPT) processing on the microstructure and mechanical properties of Ti-5Al-5Mo-5V-3Cr (Ti5553) alloy were studied. HPT processing produced a white etching layer (WEL) in the middle section of the cross-section and numerous shear bands in the surface region of the cross-section. And the thickness of the WEL increased with increasing the HPT revolutions. TEM observation of the WEL revealed an ultrafine-grained structure with high degree of lattice distortions. The mechanical properties measurements showed that the hardness and ultimate tensile strength increased by HPT processing, accompanied with a decrease in the elongation to failure. It is considered that the mechanical properties of HPT processed Ti5553 alloy are mostly dominated by the shear banded region and the WEL where have the finest grain size and high density of dislocations

  7. Scale Dependence of the Mechanical Properties and Microstructure of Crustaceans Thin Films as Biomimetic Materials

    Science.gov (United States)

    Verma, Devendra; Qu, Tao; Tomar, Vikas

    2015-04-01

    The exoskeletons of crustacean species in the form of thin films have been investigated by several researchers to better understand the role played by the exoskeletal structure in affecting the functioning of species such as shrimps, crabs, and lobsters. These species exhibit similar designs in their exoskeleton microstructure, such as a Bouligand pattern (twisted plywood structure), layers of different thickness across cross section, change in mineral content through the layers, etc. Different parts of crustaceans exhibit a significant variation in mechanical properties based on the variation in the above-mentioned parameters. This change in mechanical properties has been analyzed by using imaging techniques such as scanning electron microscopy and energy-dispersive x-ray spectroscopy, and by using mechanical characterization techniques such as nanoindentation and atomic force microscopy. In this article, the design principles of these biological composites are discussed based on two shrimp species: Rimicaris exoculata and Pandalus platyceros.

  8. Microstructure and mechanical properties of as-cast Zr-Nb alloys.

    Science.gov (United States)

    Kondo, Ryota; Nomura, Naoyuki; Suyalatu; Tsutsumi, Yusuke; Doi, Hisashi; Hanawa, Takao

    2011-12-01

    On the basis of the microstructures and mechanical properties of as-cast Zr-(0-24)Nb alloys the effects of phase constitution on the mechanical properties and magnetic susceptibility are discussed in order to develop Zr alloys for use in magnetic resonance imaging (MRI). The microstructures were evaluated using an X-ray diffractometer, an optical microscope, and a transmission electron microscope; the mechanical properties were evaluated by a tensile test. The α' phase was dominantly formed with less than 6 mass% Nb content. The ω phase was formed in Zr-(6-20)Nb alloys, but disappeared from Zr-22Nb. The β phase dominantly existed in Zr-(9-24)Nb alloys. The mechanical properties as well as the magnetic susceptibility of the Zr-Nb alloys varied depending on the phase constitution. The Zr-Nb alloys consisting of mainly α' phase showed high strength, moderate ductility, and a high Young's modulus, retaining low magnetic susceptibility. Zr-Nb alloys containing a larger volume of ω phase were found to be brittle and, thus, should be avoided, despite their low magnetic susceptibility. When the Zr-Nb alloys consisted primarily of β phase the effect of ω phase weakened the mechanical properties, thereby leading to an increase in ductility, even with an increase in magnetic susceptibility. The minimum value of Young's modulus was obtained for Zr-20Nb, because this composition was the phase boundary between the β and ω phases. However, the magnetic susceptibility of the alloy was half that of Ti-6Al-4V alloys. Zr-Nb alloys consisting of α' or β phase have excellent mechanical properties with low magnetic susceptibility and, thus, these alloys could be useful for medical devices used in MRI. Copyright © 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  9. Microstructures and Mechanical Properties of Co-Cr Dental Alloys Fabricated by Three CAD/CAM-Based Processing Techniques

    Directory of Open Access Journals (Sweden)

    Hae Ri Kim

    2016-07-01

    Full Text Available The microstructures and mechanical properties of cobalt-chromium (Co-Cr alloys produced by three CAD/CAM-based processing techniques were investigated in comparison with those produced by the traditional casting technique. Four groups of disc- (microstructures or dumbbell- (mechanical properties specimens made of Co-Cr alloys were prepared using casting (CS, milling (ML, selective laser melting (SLM, and milling/post-sintering (ML/PS. For each technique, the corresponding commercial alloy material was used. The microstructures of the specimens were evaluated via X-ray diffractometry, optical and scanning electron microscopy with energy-dispersive X-ray spectroscopy, and electron backscattered diffraction pattern analysis. The mechanical properties were evaluated using a tensile test according to ISO 22674 (n = 6. The microstructure of the alloys was strongly influenced by the manufacturing processes. Overall, the SLM group showed superior mechanical properties, the ML/PS group being nearly comparable. The mechanical properties of the ML group were inferior to those of the CS group. The microstructures and mechanical properties of Co-Cr alloys were greatly dependent on the manufacturing technique as well as the chemical composition. The SLM and ML/PS techniques may be considered promising alternatives to the Co-Cr alloy casting process.

  10. Mechanical properties and microstructure of long term thermal aged WWER 440 RPV steel

    Energy Technology Data Exchange (ETDEWEB)

    Kolluri, M., E-mail: kolluri@nrg.eu [Nuclear Research & Consultancy Group (NRG), P.O. Box 25, 1755 ZG Petten (Netherlands); Kryukov, A. [Scientific and Engineering Centre for Nuclear and Radiation Safety, 107140 Moscow (Russian Federation); Magielsen, A.J. [Nuclear Research & Consultancy Group (NRG), P.O. Box 25, 1755 ZG Petten (Netherlands); Hähner, P. [European Commission, Joint Research Centre, Directorate G – Nuclear Safety and Security, P.O. Box 2, 1755 ZG Petten (Netherlands); Petrosyan, V. [Armenian Scientific Research Institute for Nuclear Plant Operation (ARMATOM), 0027 Yerevan (Armenia); Sevikyan, G. [Armenian Nuclear Power Plant (ANPP), 0911, Metsamor, Armavir Marz (Armenia); Szaraz, Z. [European Commission, Joint Research Centre, Directorate G – Nuclear Safety and Security, P.O. Box 2, 1755 ZG Petten (Netherlands)

    2017-04-01

    The integrity assessment of the Reactor Pressure Vessel (RPV) is essential for the safe and Long Term Operation (LTO) of a Nuclear Power Plant (NPP). Hardening and embrittlement of RPV caused by neutron irradiation and thermal ageing are main reasons for mechanical properties degradation during the operation of an NPP. The thermal ageing-induced degradation of RPV steels becomes more significant with extended operational lives of NPPs. Consequently, the evaluation of thermal ageing effects is important for the structural integrity assessments required for the lifetime extension of NPPs. As a part of NRG's research programme on Structural Materials for safe-LTO of Light Water Reactor (LWR) RPVs, WWER-440 surveillance specimens, which have been thermal aged for 27 years (∼200,000 h) at 290 °C in a surveillance channel of Armenian-NPP, are investigated. Results from the mechanical and microstructural examination of these thermal aged specimens are presented in this article. The results indicate the absence of significant long term thermal ageing effect of 15Cr2MoV-A steel. No age hardening was detected in aged tensile specimens compared with the as-received condition. There is no difference between the impact properties of as-received and thermal aged weld metals. The upper shelf energy of the aged steel remains the same as for the as-received material at a rather high level of about 120 J. The T{sub 41} value did not change and was found to be about 10 °C. The microstructure of thermal aged weld, consisting carbides, carbonitrides and manganese-silicon inclusions, did not change significantly compared to as-received state. Grain-boundary segregation of phosphorus in long term aged weld is not significant either which has been confirmed by the absence of intergranular fracture increase in the weld. Negligible hardening and embrittlement observed after such long term thermal ageing is attributed to the optimum chemical composition of 15Cr2MoV-A for high

  11. Load-adaptive bone remodeling simulations reveal osteoporotic microstructural and mechanical changes in whole human vertebrae.

    Science.gov (United States)

    Badilatti, Sandro D; Christen, Patrik; Parkinson, Ian; Müller, Ralph

    2016-12-08

    Osteoporosis is a major medical burden and its impact is expected to increase in our aging society. It is associated with low bone density and microstructural deterioration. Treatments are available, but the critical factor is to define individuals at risk from osteoporotic fractures. Computational simulations investigating not only changes in net bone tissue volume, but also changes in its microstructure where osteoporotic deterioration occur might help to better predict the risk of fractures. In this study, bone remodeling simulations with a mechanical feedback loop were used to predict microstructural changes due to osteoporosis and their impact on bone fragility from 50 to 80 years of age. Starting from homeostatic bone remodeling of a group of seven, mixed sex whole vertebrae, five mechanostat models mimicking different biological alterations associated with osteoporosis were developed, leading to imbalanced bone formation and resorption with a total net loss of bone tissue. A model with reduced bone formation rate and cell sensitivity led to the best match of morphometric indices compared to literature data and was chosen to predict postmenopausal osteoporotic bone loss in the whole group. Thirty years of osteoporotic bone loss were predicted with changes in morphometric indices in agreement with experimental measurements, and only showing major deviations in trabecular number and trabecular separation. In particular, although being optimized to match to the morphometric indices alone, the predicted bone loss revealed realistic changes on the organ level and on biomechanical competence. While the osteoporotic bone was able to maintain the mechanical stability to a great extent, higher fragility towards error loads was found for the osteoporotic bones. Copyright © 2016 Elsevier Ltd. All rights reserved.

  12. Microstructure and Thermo-Hydro-Mechanical effects as an explanation for rate dependency during seismic slip

    Science.gov (United States)

    Stefanou, I.; Rattez, H.; Sulem, J.

    2017-12-01

    Rapid shear tests of granulated fault gouges show pronounced rate-dependency. For this reason rate-dependent constitutive laws are frequently used for describing fault friction.Here we propose a micromechanical, physics-based continuum approach by considering the characteristic size of the microstructure and the thermal- and pore-pressure-diffusion mechanisms that take place in the fault gouge during rapid shearing. It is shown that even for rate-independent materials, the apparent, macroscopic behavior of the system is rate-dependent. This is due to the competition of the characteristic lengths and time scales introduced indirectly by the microstructure and the thermal and hydraulic diffusivities.Both weakening and shear band thickness are rate dependent, despite the fact that the constitutive description of the material was considered rate-independent. Moreover the size of the microstructure, which here is identified with the grain size of the fault gouge (D50), plays an important role in the slope of the softening branch of the shear stress-strain response curve and consequently in the transition from aseismic to seismic slip.References Dieterich, J. H. (1979). Modeling of rock friction: 1. Experimental results and constitutive equations. Journal of Geophysical Research, 84(B5), 2161. http://doi.org/10.1029/JB084iB05p02161 Scholz, C. H. (2002). The mechanics of earthquakes and faulting (Second). Cambridge. Sulem, J., & Stefanou, I. (2016). Thermal and chemical effects in shear and compaction bands. Geomechanics for Energy and the Environment, 6, 4-21. http://doi.org/10.1016/j.gete.2015.12.004

  13. Effect of weld spacing on microstructure and mechanical properties of CLAM electron beam welding joints

    Energy Technology Data Exchange (ETDEWEB)

    Zhai, Yutao; Huang, Bo, E-mail: aufa0007@163.com; Zhang, Junyu; Zhang, Baoren; Liu, Shaojun; Huang, Qunying

    2016-11-15

    Highlights: • The welded joints of CLAM steel with different weld spacings have been fabricated with electron beam welding, and a simplified model of CLAM sheet was proposed. • The microstructure and mechanical properties such as microhardness, impact and tensile were investigated at different welding spacing for both conditions of as-welded and post weld heat treatment (PWHT). • The effect of the welding thermal cycle was significantly when the weld spacings were smaller than 4 mm. • When the weld spacing was small enough, the original microstructures would be fragmented with the high heat input. - Abstract: China low activation martensitic (CLAM) steel has been chosen as the primary structural material in the designs of dual function lithium-lead (DFLL) blanket for fusion reactors, China helium cooled ceramic breeder (HCCB) test blanket module (TBM) for ITER and China fusion engineering test reactor (CFETR) blanket. The cooling components of the blankets are designed with high density cooling channels (HDCCs) to remove the high nuclear thermal effectively. Hence, the welding spacing among the channels are small. In this paper, the welded joints of CLAM steel with different weld spacings have been fabricated with electron beam welding (EBW). The weld spacing was designed to be 2 mm, 3 mm, 4 mm, 6 mm and 8 mm. The microstructure and mechanical properties such as microhardness, impact and tensile were investigated at different welding spacing for both conditions of as-welded and post weld heat treatment (PWHT). The PWHT is tempering at 740 °C for 120 min. The results showed that the grain size in the heat affected zone (HAZ) increased with the increasing weld spacing, and the joint with small weld spacing had a better performance after PWHT. This work would give useful guidance to improve the preparation of the cooling components of blanket.

  14. Microstructure and mechanical properties of stainless steel/calcium silicate composites manufactured by selective laser melting

    Energy Technology Data Exchange (ETDEWEB)

    Zheng, Zeng [School of Materials Science and Engineering, Tongji University, Shanghai 201804 (China); Shanghai Key Lab. of D& A for Metal-Functional Materials, Shanghai 201804 (China); Wang, Lianfeng [School of Materials Science and Engineering, Tongji University, Shanghai 201804 (China); Shanghai Aerospace Equipments Manufacturer, Shanghai 200240 (China); Jia, Min [Shanghai Aircraft Manufacturing Co., Ltd, Shanghai 200436 (China); Cheng, Lingyu [Shanghai Aerospace Equipments Manufacturer, Shanghai 200240 (China); Yan, Biao, E-mail: 84016@tongji.edu.cn [School of Materials Science and Engineering, Tongji University, Shanghai 201804 (China); Shanghai Key Lab. of D& A for Metal-Functional Materials, Shanghai 201804 (China)

    2017-02-01

    Selective laser melting (SLM) is raised as one kind of additive manufacturing (AM) which is based on the discrete-stacking concept. This technique can fabricate advanced composites with desirable properties directly from 3D CAD data. In this research, 316L stainless steel (316L SS) and different fractions of calcium silicate (CaSiO{sub 3}) composites (weight fractions of calcium silicate are 0%, 5%,10% and 15%, respectively) were prepared by SLM technique with a purpose to develop biomedical metallic materials. The relative density, tensile, microhardness and elastic modulus of the composites were tested, their microstructures and fracture morphologies were observed using optical microscope (OM), scanning electron microscopy (SEM) and X-ray diffraction (XRD). It was found that the addition of CaSiO{sub 3} particles influenced the microstructure and mechanical properties of specimens significantly. The CaSiO{sub 3} precipitates from the overlap of adjacent tracks and became the origin of the defects. The tensile strength of specimens range 320–722 MPa. The microhardness and elastic modulus are around 250 HV and 215 GPa respectively. These composites were ductile materials and the fracture mode of the composites was mixed mode of ductile and brittle fracture. The 316L SS/CaSiO{sub 3} composites can be a potential biomedical metallic materials in the medical field. - Highlights: • 316L SS/CaSiO{sub 3} composites were fabricated by selective laser melting. • Microstructure, mechanical properties, corrosion resistance of samples was studied. • Composites is a ductile material and mixed mode of ductile and brittle fracture. • Composites is a potential biomedical metallic materials in the medical field.

  15. Microstructures and formation mechanism of W–Cu composite coatings on copper substrate prepared by mechanical alloying method

    International Nuclear Information System (INIS)

    Meng, Yunfei; Shen, Yifu; Chen, Cheng; Li, Yongcan; Feng, Xiaomei

    2013-01-01

    In the present work, high-energy mechanical alloying (MA) method was applied to prepare tungsten–copper composite coatings on pure copper surface using a planetary ball mill. During mechanical alloying process, grains on the surface layer of substrate were refined and the substrate surface was activated as a result of repeated collisions by a large number of flying balls along with powder particles. The repeated ball-to-substrate collisions resulted in the deposition of coatings. The microstructures and elemental and phase composition of mechanically alloyed coatings at different milling durations during mechanical alloying process were studied using scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS). Microhardness tests were carried out to examine the mechanical properties of the coatings. The results showed that the coatings and the substrates were well bonded, and with the increase of the milling duration, multi-layered coatings with different structures were generated and the coatings became denser. The microhardness tests showed that the maximum microhardness of the coatings reached HV 0.1 228, showing a threefold improvement upon the substrate. And the cross-sectional microhardness values of the processed sample changed gradually, which gave a proof for the cushioning and sustaining functions of the multi-layered coatings. A reasonable formation mechanism of coatings on bulk materials with metallic immiscible system by mechanical alloying method was presented.

  16. Influence of Microstructure and Composition Changes on Mechanical Characteristics of Aluminium Alloy After Heating and Cooling Treatment

    International Nuclear Information System (INIS)

    Sigit; Nuraini, E; Martoyo

    1998-01-01

    Influences of microstructure and chemical composition changes on mechanical characteristics of AIMg2 which were heated at 85-500 0 C and cooled with sands, water or air have been studied. Microstructure observation was carried out using optical microscope, while chemical composition determination by atomic absorption spectrophotometry (AAS). AIMg2 which has been heated at the relatively low temperature i. e, 200 0 C during 6 hours and cooled using sands showed a small change microstructure, but those will be clearly observed on the treatment at 300 0 C. The microstructure change is in agreement with the change of mechanical characteristic, I. e., the decreasing of tensile strength and hardness and increasing of elongation. After the temperature of treatment is higher than 300 0 C, the decreasing of the tensile strength was relatively constant, while the hardness increased. The microstructure of AIMg2 resulted from the heat treatment at temperature of 500 0 C was different with that of 300 0 C. Heat treatment at 500 0 C following by cooling in the sands, water or air respectively gave similar microstructure. Those also caused the change of alloying element content which was in agreement with decreasing of mechanical characteristics

  17. Microstructural evolutions and mechanical behaviour of the nickel based alloys 617 and 230 at high temperature

    International Nuclear Information System (INIS)

    Chomette, S.

    2009-11-01

    High Temperature Reactors (HTR), is one of the innovative nuclear reactor designed to be inherently safer than previous generation and to produce minimal waste. The most critical metallic component in that type of reactor is the Intermediate Heat exchanger (IHX). The constraints imposed by the conception and the severe operational conditions (high temperature of 850 C to 950 C, lifetime of 20,000 h) have guided the IHX material selection toward two solid solution nickel base alloys, the Inconel 617 and the Haynes 230. Inconel 617 is the primary candidate alloy thanks to its good high temperature mechanical and corrosion properties and the large data base developed in previous programs. However, its high cobalt content has to be considered as an issue (nuclear activation). The more recent alloy Haynes 230, in which most of the cobalt has been replaced by tungsten, present characteristics similar to the 617 alloy. The objective of this thesis is to study the high temperature mechanical behaviour of both alloys in relation with their microstructural evolutions. The as received microstructural observations have revealed primary carbides (M 6 C). Most of this precipitates are evenly distributed in the materials. Few M 23 C 6 secondary carbides are observed in both alloys in the as received state. Thermal ageing treatments at 850 C lead to an important M 23 C 6 precipitation on slip lines and at grain boundaries. The size of this carbides increases and their number decreases with increasing ageing duration. The intragranular precipitation of secondary carbides at 950 C is more limited and the intergranular evolution more important than at 850 C. The microstructural observations and the hardness evolution of both alloys show that the main microstructural evolutions occur before 1,000 h at both studied temperatures. The mechanical properties of the Inconel 617 and the Haynes 230 have been studied using tensile, creep, fatigue and relaxation-fatigue tests. Particularly, the

  18. Bacteriostatic Effect of Quercetin as an Antibiotic Alternative In Vivo and Its Antibacterial Mechanism In Vitro.

    Science.gov (United States)

    Wang, Shengan; Yao, Jiaying; Zhou, Bo; Yang, Jiaxin; Chaudry, Maria T; Wang, Mi; Xiao, Fenglin; Li, Yao; Yin, Wenzhe

    2018-01-01

    Quercetin, a ubiquitous flavonoid, is known to have antibacterial effects. The purpose of this study was to investigate the effect of quercetin on cecal microbiota of Arbor Acre (AA) broiler chickens in vivo and the bacteriostatic effect and antibacterial mechanism of quercetin in vitro. In vivo, 480 AA broilers (1 day old) were randomly allotted to four treatments (negative control and 0.2, 0.4, or 0.6 g of quercetin per kg of diet) for 42 days. Cecal microbial population and distribution were measured at the end of the experiment. The cecal microflora in these broilers included Proteobacteria, Fimicutes, Bacteroidetes, and Deferribacteres. Compared with the negative control, quercetin significantly decreased the copies of Pseudomonas aeruginosa ( P 0.05). These results suggest that quercetin has potential as an alternative antibiotic feed additive in animal production.

  19. Effect of tempering temperature on the microstructure and mechanical properties of a reactor pressure vessel steel

    Energy Technology Data Exchange (ETDEWEB)

    Li, C.W.; Han, L.Z.; Luo, X.M.; Liu, Q.D.; Gu, J.F., E-mail: gujf@sjtu.edu.cn

    2016-08-15

    The microstructure and mechanical properties of reactor pressure vessel (RPV) steel were investigated after tempering at different temperatures ranging from 580 to 700 °C for 5 h. With increasing tempering temperature, the impact toughness, which is qualified by Charpy V-notch total absorbed energy, initially increases from 142 to 252 J, and then decreases to 47 J, with a maximum value at 650 °C, while the ultimate tensile strength varies in exactly the opposite direction. Comparing the microstructure and fracture surfaces of different specimens, the variations in toughness and strength with the tempering temperature were generally attributed to the softening of the bainitic ferrite, the agminated Fe{sub 3}C carbides that resulted from decomposition of martensite/austenite (M/A) constituents, the precipitation of Mo{sub 2}C carbides, and the newly formed M/A constituents at the grain boundaries. Finally, the correlation between the impact toughness and the volume fraction of the M/A constituents was established, and the fracture mechanisms for the different tempering conditions are explained. - Highlights: • The dependence of the deterioration of impact toughness on tempering temperature has been analysed. • The instrumented Charpy V-notch impact test has been employed to study the fracture mechanism. • The influence of M/A constituents on different fracture mechanisms based on the hinge model has been demonstrated. • A correlation between the mechanical properties and the amount of M/A constituents has been established.

  20. Microstructure and Mechanical Performance of Friction Stir Spot-Welded Aluminum-5754 Sheets

    Science.gov (United States)

    Pathak, N.; Bandyopadhyay, K.; Sarangi, M.; Panda, Sushanta Kumar

    2013-01-01

    Friction stir spot welding (FSSW) is a recent trend of joining light-weight sheet metals while fabricating automotive and aerospace body components. For the successful application of this solid-state welding process, it is imperative to have a thorough understanding of the weld microstructure, mechanical performance, and failure mechanism. In the present study, FSSW of aluminum-5754 sheet metal was tried using tools with circular and tapered pin considering different tool rotational speeds, plunge depths, and dwell times. The effects of tool design and process parameters on temperature distribution near the sheet-tool interface, weld microstructure, weld strength, and failure modes were studied. It was found that the peak temperature was higher while welding with a tool having circular pin compared to tapered pin, leading to a bigger dynamic recrystallized stir zone (SZ) with a hook tip bending towards the upper sheet and away from the keyhole. Hence, higher lap shear separation load was observed in the welds made from circular pin compared to those made from tapered pin. Due to influence of size and hardness of SZ on crack propagation, three different failure modes of weld nugget were observed through optical cross-sectional micrograph and SEM fractographs.

  1. Microstructure and mechanical properties of GTAW welded joints of AA6105 aluminum alloy

    Directory of Open Access Journals (Sweden)

    Minerva Dorta-Almenara

    2016-09-01

    Full Text Available Gas Tungsten Arc Welding (GTAW is one of the most used methods to weld aluminum. This work investigates the influence of welding parameters on the microstructure and mechanical properties of GTAW welded AA6105 aluminum alloy joints. AA6105 alloy plates with different percent values of cold work were joined by GTAW, using various combinations of welding current and speed. The fusion zone, in which the effects of cold work have disappeared, and the heat affected zone of the welded samples were examined under optical and scanning electron microscopes, additionally, mechanical tests and measures of Vickers microhardness were performed. Results showed dendritic morphology with solute micro- and macrosegregation in the fusion zone, which is favored by the constitutional supercooling when heat input increases. When heat input increased and welding speed increased or remained constant, greater segregation was obtained, whereas welding speed decrease produced a coarser microstructure. In the heat affected zone recrystallization, dissolution, and coarsening of precipitates occurred, which led to variations in hardness and strength.

  2. Microstructure and mechanical properties of Ti/TiN film coated on AISI 304 stainless steel

    International Nuclear Information System (INIS)

    Park, Ji Yoon; Kim, Kwan Hyu; Choe, Han Cheol

    1999-01-01

    The microstructure and mechanical properties of Ti/TiN film coated on AISI 304 stainless steels have been studied. AISI 304 stainless steels containing 0.1∼1.0 wt% Ti were fabricated by using vacuum furnace and followed by solutionization treatment at 1050 .deg. C for 1hr. The specimens were coated by Ti and TiN with 1 μm and 2 μm thickness by electron-beam PVD method. The microstructure and phase analysis were carried out by using XRD, WDS and SEM. Mechanical properties such as hardness (micro-Vickers) and wear resistance were examined. Coated films showed fine columnar structure and some defects. Surface roughness increased in all specimens after TiN coating. XRD patterns showed that the TiN(111) peak was major in TiN single-layer and the other peaks were very weak, but TiN(220) and TiN(200) peaks were developed in Ti/TiN double-layer. The hardness of the coating film was higher in Ti/TiN double-layer than in TiN single-layer and not affected by the Ti content of substrate. Ti/TiN double-layer showed better wear resistance than TiN single-layer. The observed wear traces were sheared type in all coated specimens

  3. Effect of Macrosegregation on the Microstructure and Mechanical Properties of a Pressure-Vessel Steel

    Science.gov (United States)

    Yan, Guanghua; Han, Lizhan; Li, Chuanwei; Luo, Xiaomeng; Gu, Jianfeng

    2017-07-01

    Macrosegregation refers to the chemical segregation, which occurs quite commonly in the large forgings such as nuclear reactor pressure vessel. This work assesses the effect of macrosegregation and homogenization treatment on the mechanical properties of a pressure-vessel steel (SA508 Gr.3). It was found that the primary reason for the inhomogeneity of the microstructure was the segregation of Mn, Mo, and Ni. Martensite, and coarse upper bainite with M-A (martensite-austenite) islands have been obtained, respectively, in the positive and negative segregation zone during a simulated quenching process. During tempering, the carbon-rich M-A islands decomposed into a mixture of ferrite and numerous carbides which deteriorated the toughness of the material. The segregation has been substantially minimized by a homogenizing treatment. The results indicate that the material homogenized has a higher impact toughness than the material with segregation, due to the reduction in M-A island in the negative segregation zone. It can be concluded that the microstructure and mechanical properties have been improved remarkably by means of homogenization treatment.

  4. Effect Of Milling Time On Microstructure Of AA6061 Composites Fabricated Via Mechanical Alloying

    Directory of Open Access Journals (Sweden)

    Tomiczek B.

    2015-06-01

    Full Text Available The aim of this work is to determine the effect of manufacturing conditions, especially milling time, on the microstructure and crystallite size of a newly developed nanostructural composite material with the aluminium alloy matrix reinforced with halloysite nanotubes. Halloysite, being a clayey mineral of volcanic origin, is characterized by high porosity and large specific surface area. Thus it can be used as an alternative reinforcement in metal matrix composite materials. In order to obtain this goal, composite powders with fine microstructures were fabricated using high-energy mechanical alloying, cold compacting and hot extrusion techniques. The obtained composite powders of aluminium alloy reinforced with 5, 10 and 15 wt% of halloysite nanotubes were characterized with SEM, TEM and XRD analysis. It has been proven that the use of mechanical alloying leads to a high degree of deformation, which, coupled with a decreased grain size below 100 nm and the dispersion of the refined reinforcing particles–reinforces the material very well.

  5. Microstructural control and high temperature mechanical property of ferritic/martensitic steels for nuclear reactor application

    International Nuclear Information System (INIS)

    Adetunji, G.J.

    1991-04-01

    The materials under study are 9-12% Cr ferritic/martensitic steels, alternative candidate materials for application in core components of nuclear power reactors. This work involves (1) Investigation of high temperature fracture mechanism during slow tensile and limited creep testing at 600 o C (2) Extensive study of solute element segregation both theoretically and experimentally (3) Investigation of effects by thermal ageing and irradiation on microstructural developments in relation to high temperature mechanical behaviour. From (1) the results obtained indicate that the important microstructural characteristics controlling the fracture of 9-12% Cr ferritic/martensitic steels at high temperature are (a) solute segregation to inclusion-matrix interfaces (b) hardness of the martensitic matrix and (c) carbide particle size distribution. From (2) the results indicate a strong concentration gradient of silicon and molybdenum near lath packet boundaries for certain quenching rates from the austenitizing temperature. From (3) high temperature tensile data were obtained for irradiated samples with thermally aged ones as control. (author)

  6. Mechanical properties and microstructure of Ti-35.5Nb-5.7Ta beta alloy.

    Science.gov (United States)

    Bartakova, S; Prachar, P; Dvorak, I; Hruby, V; Vanek, J; Pospichal, M; Svoboda, E; Martikan, A; Konecna, H; Sedlak, I

    2015-01-01

    Titanium and titanium alloys represent generally accepted metallic biomaterials for clinical dentistry and dental implantology. In this paper, we present a Ti-35.5Nb-5.7Ta alloy with a special respect to its microstructure and mechanical characteristics, such as Young modulus of elasticity. Three thermal treatments differing in temperature and time of annealing were used during the Ti-35.5Nb-5.7Ta processing in order to evaluate the effects of ageing, melting annealing, and annealing on mechanical characteristics and microstructure. Using microscopy, the alloy was analyzed and the differences in shares of beta phase grains, alpha particles and precipitates evaluated. The three thermal treatments were evaluated also from technological point of view. The following thermal treatment was found optimal for the Ti-35.5Nb-5.7Ta alloy: melting annealing at 800 °C for 0.5 hour followed by a cold swaging with a 52-79 % deformation, and final hardening at 500 °C for 2 hours in water(Tab. 2, Fig. 3, Ref. 24).

  7. Two-Photon Polymerization Metrology: Characterization Methods of Mechanisms and Microstructures

    Directory of Open Access Journals (Sweden)

    Christopher N. LaFratta

    2017-03-01

    Full Text Available The ability to create complex three-dimensional microstructures has reached an unprecedented level of sophistication in the last 15 years. For the most part, this is the result of a steady development of the additive manufacturing technique named two-photon polymerization (TPP. In a short amount of time, TPP has gone from being a microfabrication novelty employed largely by laser specialists to a useful tool in the hands of scientists and engineers working in a wide range of research fields including microfluidics. When used in combination with traditional microfabrication processes, TPP can be employed to add unique three-dimensional components to planar platforms, thus enabling the realization of lab-on-a-chip solutions otherwise impossible to create. To take full advantage of TPP, an in-depth understanding is required of the materials photochemistry and the fabricated microstructures’ mechanical and chemical properties. Thus, we review methods developed so far to investigate the underling mechanism involved during TPP and analytical methods employed to characterize TPP microstructures. Furthermore, we will discuss potential opportunities for using optofluidics and lab-on-a-chip systems for TPP metrology.

  8. Preliminary evaluation of microstructure and mechanical properties on low activation ferritic steels

    International Nuclear Information System (INIS)

    Hsu, C.Y.; Lechtenberg, T.A.

    1985-01-01

    Radioactive waste disposal has become a primary concern for the selection of materials for the structural components for fusion reactors. One way to minimize this potential environmental problem is to use structural materials in which the induced radioactivity decays quickly to levels that allow for near-surface disposal under 10CFR61 rules. The primary objective of this work is to develop low activation ferritic steels that exhibit mechanical and physical properties approximately equivalent to the HT-9 and 9Cr-1Mo steels, but which only contain elements that would permit near-surface disposal under 10CFR61 after exposure to fusion neutrons. A preliminary evaluation of the microstructure and mechanical properties of a 9Cr-2.5W-0.3V-0.15C (GA3X) low activation ferritic steel has been performed. An optimum heat treatment condition has been defined for GA3X steel. The properties and microstructure of the quenched and tempered specimens were characterized via hardness measurement and optical metallographic observation. The hot-microhardness and ductility parameter measurements were used to estimate the tensile properties at elevated temperatures. The estimated tensile strengths of GA3X steel at elevated temperatures are comparable to both 9Cr-1Mo and the modified 9Cr-1Mo steels. These preliminary results are encouraging in that they suggest that suitable low activation alloys can be successfully produced in this ferritic alloy class

  9. Mechanical properties and microstructure analysis of fly ash geopolymeric recycled concrete.

    Science.gov (United States)

    Shi, X S; Collins, F G; Zhao, X L; Wang, Q Y

    2012-10-30

    Six mixtures with different recycled aggregate (RA) replacement ratios of 0%, 50% and 100% were designed to manufacture recycled aggregate concrete (RAC) and alkali-activated fly ash geopolymeric recycled concrete (GRC). The physical and mechanical properties were investigated indicating different performances from each other. Optical microscopy under transmitted light and scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDX) were carried out in this study in order to identify the mechanism underlying the effects of the geopolymer and RA on concrete properties. The features of aggregates, paste and interfacial transition zone (ITZ) were compared and discussed. Experimental results indicate that using alkali-activated fly ash geopolymer as replacement of ordinary Portland cement (OPC) effectively improved the compressive strength. With increasing of RA contents in both RAC and GRC, the compressive strength decreased gradually. The microstructure analysis shows that, on one hand, the presence of RA weakens the strength of the aggregates and the structure of ITZs; on the other hand, due to the alkali-activated fly ash in geopolymer concrete, the contents of Portlandite (Ca(OH)(2)) and voids were reduced, as well as improved the matrix homogeneity. The microstructure of GRC was changed by different reaction products, such as aluminosilicate gel. Copyright © 2012 Elsevier B.V. All rights reserved.

  10. Effects of nano-silica on mechanical performance and microstructure of ultra-high performance concrete

    Energy Technology Data Exchange (ETDEWEB)

    Mendes, T. M., E-mail: thiagomendes@utfpr.edu.br [Universidade Tecnologica Federal do Parana (UTFPR), Londrina, PR (Brazil). Departamento de Engenharia Ambiental; Repette, W.L., E-mail: wellington.repette@gmail.br [Universidade Federal de Santa Catarina (UFSC), Florianopolis, SC (Brazil). Dept. de Engenharia Civil; Reis, P.J., E-mail: pjlondrina@yahoo.com.br [Univeridade Estadual de Londrina (UEL), PR (Brazil). Lab. de Fisica Nuclear Aplicada

    2017-07-15

    The use of nanoparticles in ultra-high strength concretes can result in a positive effect on mechanical performance of these cementitious materials. This study evaluated mixtures containing 10 and 20 wt% of silica fume, for which the optimum nano-silica content was determined, i.e. the quantity of nano-silica that resulted on the higher gain of strength. The physical characterization of raw materials was done in terms of particle size distribution, density and specific surface area. Chemical and mineralogical compositions of materials were obtained through fluorescence and X-ray diffraction. The mechanical performance was evaluated by compressive strength, flexural strength and dynamic elastic modulus measurements. The microstructural analysis of mixtures containing nano-silica was performed by X-ray diffraction, thermogravimetry, mercury intrusion porosimetry and scanning electron microscopy. Obtained results indicate an optimum content of nano-silica of 0.62 wt%, considering compressive and flexural strengths. This performance improvement was directly related to two important microstructural aspects: the packing effect and pozzolanic reaction of nano-silica. (author)

  11. Effect of boron on the microstructure and mechanical properties of carbidic austempered ductile iron

    International Nuclear Information System (INIS)

    Peng Yuncheng; Jin Huijin; Liu Jinhai; Li Guolu

    2011-01-01

    Highlights: → Boron are applied to carbidic austempered ductile iron (CADI). → Boron microalloying CADI is a new high hardenability of wear-resistant cast iron. → Addition of boron to CADI significantly improves hardenability. → Effect of boron on the CADI grinding ball were investigated. → Optimum property is obtained when boron content at 0.03 wt%. - Abstract: Carbidic austempered ductile iron (CADI) castings provide a unique combination of high hardness and toughness coupled with superior wear resistance properties, but their hardenability restricts their range of applications. The purpose of this study was to investigate the influence of boron on the microstructure and mechanical properties of CADI. The experimental results indicate that the CADI comprises graphite nodules, which are dispersive boron-carbides that are distributed in the form of strips, and the matrix is a typical ausferritic matrix. Microscopic amounts of boron can improve the hardenability of CADI, but higher boron content reduces the hardenability and toughness of CADI. The results are discussed in the context of the influence of boron content on the microstructure and mechanical properties of grinding balls.

  12. Microstructure and mechanical performance of autogenously fibre laser beam welded Ti-6242 butt joints

    Energy Technology Data Exchange (ETDEWEB)

    Kashaev, Nikolai, E-mail: nikolai.kashaev@hzg.de; Pugachev, Dmitry; Ventzke, Volker; Fomin, Fedor; Burkhardt, Irmela; Enz, Josephin; Riekehr, Stefan

    2017-05-10

    This work deals with the effects of laser beam power, focus position and advance speed on the geometry, microstructure and mechanical properties such as the tensile strength and microhardness of autogenously fibre laser beam welded Ti-6Al-2Sn-4Zr-2Mo (denoted as Ti-6242) butt joints used for high temperature applications. The Ti-6242 sheet employed here is characterized by a globular (α+β) microstructure. Laser beam welded butt joints consisted of a martensitic fusion zone, inhomogeneous heat affected zones and equiaxed base materials. The microhardness increased from 330 HV 0.3 in base material to 430 HV 0.3 in fusion zone due to the martensitic transformation. Butt joints showed the base material level of strength in tensile test. The local increase in microhardness provided a shielding effect that protected the Ti-6242 butt joint against mechanical damage during the static tensile load test. The predicted critical total underfill depth that does not reduce the tensile strength of the weld was determined to be 25% of the specimen thickness. - Highlights: • Autogenous fibre LBW of Ti-6242 was successfully achieved. • Butt joints showed low levels of porosity and an appropriate seam geometry. • Base material level of strength achieved for tensile strength. • Predicted critical underfill depth is 25% of the specimen thickness.

  13. Effect of Pr addition on microstructure and mechanical properties of AZ61 magnesium alloy

    Directory of Open Access Journals (Sweden)

    You Zhiyong

    2014-03-01

    Full Text Available To improve the strength, hardness and heat resistance of Mg-6Al-1Zn (AZ61 alloy, the effects of Pr addition on the as-cast microstructure and mechanical properties of AZ61 alloy were investigated at room and elevated temperatures by means of Brinell hardness measurement, optical microscope (OM, scanning electron microscope (SEM, energy dispersive spectroscopy (EDS, X-ray diffractometer (XRD and DNS100 electronic universal testing machine. The results show that the microstructures of Pr-containing AZ61 alloys were refined, with primary β-Mg17Al12 phase distributed homogeneously. When the addition of Pr is up to 1.2wt.%, the β phase becomes finer, and new needle-like or short-rod shaped Al11Pr3 phase and blocky AlPr phase appear. As a result, optimal tensile properties are obtained. However, greater than 1.2wt.% Pr addition leads to poorer mechanical properties due to the aggregation of the needle-like phase and large size of grains. The present research findings provide a new way for strengthening of magnesium alloys at room and elevated temperatures, and a method of producing thermally-stable AZ61 magnesium alloy.

  14. Mechanical and Microstructural Evaluations of Lightweight Aggregate Geopolymer Concrete before and after Exposed to Elevated Temperatures.

    Science.gov (United States)

    Abdulkareem, Omar A; Abdullah, Mohd Mustafa Al Bakri; Hussin, Kamarudin; Ismail, Khairul Nizar; Binhussain, Mohammed

    2013-10-09

    This paper presents the mechanical and microstructural characteristics of a lightweight aggregate geopolymer concrete (LWAGC) synthesized by the alkali-activation of a fly ash source (FA) before and after being exposed to elevated temperatures, ranging from 100 to 800 °C. The results show that the LWAGC unexposed to the elevated temperatures possesses a good strength-to-weight ratio compared with other LWAGCs available in the published literature. The unexposed LWAGC also shows an excellent strength development versus aging times, up to 365 days. For the exposed LWAGC to the elevated temperatures of 100 to 800 °C, the results illustrate that the concretes gain compressive strength after being exposed to elevated temperatures of 100, 200 and 300 °C. Afterward, the strength of the LWAGC started to deteriorate and decrease after being exposed to elevated temperatures of 400 °C, and up to 800 °C. Based on the mechanical strength results of the exposed LWAGCs to elevated temperatures of 100 °C to 800 °C, the relationship between the exposure temperature and the obtained residual compressive strength is statistically analyzed and achieved. In addition, the microstructure investigation of the unexposed LWAGC shows a good bonding between aggregate and mortar at the interface transition zone (ITZ). However, this bonding is subjected to deterioration as the LWAGC is exposed to elevated temperatures of 400, 600 and 800 °C by increasing the microcrack content and swelling of the unreacted silicates.

  15. Microstructure evaluation of Al-Al2O3 composite produced by mechanical alloying method

    International Nuclear Information System (INIS)

    Zebarjad, S.M.; Sajjadi, S.A.

    2006-01-01

    Mechanical alloying process using ball-milling techniques, has received much attention as a powerful tool for fabrication of several advanced materials, including amorphous, quasicrystals, nanocrystalline and composite materials, etc. This research is focused on production of Al-Al 2 O 3 composite materials by mechanical alloying method and on investigation of its microstructure. For this purpose a horizontal ball mill was designed and manufactured. Aluminum and alumina powders, with specified size and weight percent, were added to the mill. The mixed powders were milled at different times. The milled powders were pressed and sintered under argon gas control. Microstructure of produced composite was investigated by scanning electron microscope. The results show that increasing milling time causes to make fine alumina powders as well as uniform distribution within aluminum, also in steady-state stage increasing milling time has not significant effect on their size distribution within aluminum. The results of atomic analysis of initial and milled powders at different times show that at the beginning of milling, the powders will tend to absorb iron and gradually their susceptibility decrease until steady-state condition is prevailed. The result of infrared spectroscopy does not show any evidence of compounds except alumina

  16. Study on microstructure and mechanical characteristics of low-carbon steel and ferritic stainless steel joints

    Energy Technology Data Exchange (ETDEWEB)

    Sarkari Khorrami, Mahmoud; Mostafaei, Mohammad Ali; Pouraliakbar, Hesam, E-mail: hpouraliakbar@alum.sharif.edu; Kokabi, Amir Hossein

    2014-07-01

    In this work, examinations on the microstructure and mechanical properties of plain carbon steel and AISI 430 ferritic stainless steel dissimilar welds are carried out. Welding is conducted in both autogenous and using ER309L austenitic filler rod conditions through gas tungsten arc welding process. The results indicate that fully-ferritic and duplex ferritic–martensitic microstructures are formed for autogenous and filler-added welds, respectively. Carbide precipitation and formation of martensite at ferrite grain boundaries (intergranular martensite) as well as grain growth occur in the heat affected zone (HAZ) of AISI 430 steel. It is found that weld heat input can strongly affect grain growth phenomenon along with the amount and the composition of carbides and intergranular martensite. Acquired mechanical characteristics of weld in the case of using filler metal are significantly higher than those of autogenous one. Accordingly, ultimate tensile strength (UTS), hardness, and absorbed energy during tensile test of weld metal are increased from 662 MPa to 910 MPa, 140 Hv to 385 Hv, and 53.6 J m{sup −3} to 79 J m{sup −3}, respectively by filler metal addition. From fracture surfaces, predominantly ductile fracture is observed in the specimen welded with filler metal while mainly cleavage fracture occurs in the autogenous weld metal.

  17. Microstructural changes in ground 3Y-TZP and their effect on mechanical properties

    Energy Technology Data Exchange (ETDEWEB)

    Munoz-Tabares, J.A., E-mail: j.a.munoz.tabares@gmail.com [Departament de Ciencia dels Materials i Enginyeria Metallurgica, Universitat Politecnica de Catalunya, Avda. Diagonal 647 (ETSEIB), 08028 Barcelona (Spain); Jimenez-Pique, E. [Departament de Ciencia dels Materials i Enginyeria Metallurgica, Universitat Politecnica de Catalunya, Avda. Diagonal 647 (ETSEIB), 08028 Barcelona (Spain); Centre de Recerca en Nanoenginyeria (CRnE), C. Pascual i Vila 15, 08028 Barcelona (Spain); Reyes-Gasga, J. [Instituto de Fisica, Universidad Nacional Autonoma de Mexico, Circuito de la Investigacion Cientifica s/n, Cd Universitaria, 04510 Mexico DF (Mexico); Anglada, M. [Departament de Ciencia dels Materials i Enginyeria Metallurgica, Universitat Politecnica de Catalunya, Avda. Diagonal 647 (ETSEIB), 08028 Barcelona (Spain); Centre de Recerca en Nanoenginyeria (CRnE), C. Pascual i Vila 15, 08028 Barcelona (Spain)

    2011-10-15

    In the present work we studied the changes in the microstructure and mechanical properties that are produced by grinding of tetragonal polycrystalline zirconia doped with 3 mol.% yttria (3Y-TZP). It is shown that the X-ray diffraction spectrum of ground 3Y-TZP presents asymmetric broadening of the (1 1 1) tetragonal peak, reversal of the intensity of the (0 0 2) and (2 0 0) tetragonal peaks, and tetragonal to monoclinic (t-m) phase transformation. The in-depth monoclinic phase distribution obtained by micro-Raman spectroscopy has been related with the compression residual stresses profile generated during grinding. These compressive residual stresses are also responsible for the observed increase in mechanical properties (strength and apparent fracture toughness). The subsurface microstructure of ground specimens has been analyzed by transmission electron microscopy and three different regions were found from the interior to the surface: (1) a t-m phase transformation zone in the deeper region, (2) a plastically deformed zone, with dynamically recovered dislocation cells, and (3) a surface recrystallized zone with grains of {approx}20 nm in diameter, resulting from in situ recrystallization. In addition, microcracking is concentrated on the sides of the grinding grooves, corresponding to the zone of maximum tensile stress during contact with an abrasive particle.

  18. Microstructure evolution of the oxide dispersion strengthened CLAM steel during mechanical alloying process

    Energy Technology Data Exchange (ETDEWEB)

    Song, Liangliang [Key Laboratory of Neutronics and Radiation Safety, Institute of Nuclear Energy Safety Technology, Chinese Academy of Science, Hefei, Anhui, 230031 (China); University of Science and Technology of China, Hefei, Anhui, 230031 (China); Liu, Shaojun, E-mail: shaojun.liu@fds.org.cn [Key Laboratory of Neutronics and Radiation Safety, Institute of Nuclear Energy Safety Technology, Chinese Academy of Science, Hefei, Anhui, 230031 (China); Mao, Xiaodong [Key Laboratory of Neutronics and Radiation Safety, Institute of Nuclear Energy Safety Technology, Chinese Academy of Science, Hefei, Anhui, 230031 (China)

    2016-11-15

    Highlights: • A nano-sized oxides dispersed ODS-CLAM steel was obtained by MA and HIP. • A minimum saturated grain size of down to 30 nm was achieved by varying the milling time from 0 to 100 h. • Solution of W in the MA powder could be significantly improved by increasing MA rotation speed. - Abstracts: Oxide dispersion strengthened Ferritic/Martensitic steel is considered as one of the most potential structural material for future fusion reactor, owing to its high mechanical properties and good irradiation resistance. The oxide dispersion strengthened China Low Activation Martensitic (ODS-CLAM) steel was fabricated by mechanical alloying (MA) and hot isostatic pressing (HIP). The microstructural evolutions during the process of ball milling and subsequent consolidation were investigated by SEM, XRD and TEM. The results showed that increasing the milling time during the first 36 h milling could effectively decrease the grain size to a value of around 30 nm, over which grain sized remained nearly constant. Increasing the rotation speed promoted the solution of tungsten (W) element obviously and decreased the grain size to a certain degree. Observation on the consolidated and further heat-treated ODS-CLAM steel samples indicated that a martensite microstructure with a high density of nano-particles was achieved.

  19. Influence of Zr addition on the microstructures and mechanical properties of 14Cr ODS steels

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Liye [State Key Lab of Hydraulic Engineering Simulation and Safety, Tianjin key Lab of Composite and Functional Materials, Tianjin University, Tianjin 300072 (China); Yu, Liming, E-mail: lmyu@tju.edu.cn [State Key Lab of Hydraulic Engineering Simulation and Safety, Tianjin key Lab of Composite and Functional Materials, Tianjin University, Tianjin 300072 (China); Liu, Yongchang; Liu, Chenxi; Li, Huijun [State Key Lab of Hydraulic Engineering Simulation and Safety, Tianjin key Lab of Composite and Functional Materials, Tianjin University, Tianjin 300072 (China); Wu, Jiefeng [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China)

    2017-05-17

    Oxide dispersion strengthened (ODS) steel is one of the most promising candidate structural materials for the high-temperature nuclear reactor application. In this study, two compositions of ODS steels (14Cr-ODS and 14Cr-Zr-ODS) were prepared to investigate the influence of Zr addition on the microstructures and mechanical properties of ODS steels. The microstructures, including dispersion morphology and crystal structures of oxide particles, particle-matrix interface coherency and particle-dislocation interactions, were characterized using TEM, HRTEM, and SEM, and the mechanical properties at room and high temperatures were measured using uniaxial tensile tests. Results show that Zr addition leads to the formation of finer precipitated particles, which was identified as rhombohedral Y{sub 4}Zr{sub 3}O{sub 12}, with denser dispersion in the matrix. The calculation results reveal that the lattice misfit, δ, at the interface between particle and matrix increases as the particle size increases. In addition, the strength and elongation of ODS steels are improved with Zr addition due to the stronger interface bonding force between fine particles and matrix as well as the larger pinning effect of small particles to dislocation movements.

  20. Direct laser sintering of metal powders: Mechanism, kinetics and microstructural features

    International Nuclear Information System (INIS)

    Simchi, A.

    2006-01-01

    In the present work, the densification and microstructural evolution during direct laser sintering of metal powders were studied. Various ferrous powders including Fe, Fe-C, Fe-Cu, Fe-C-Cu-P, 316L stainless steel, and M2 high-speed steel were used. The empirical sintering rate data was related to the energy input of the laser beam according to the first order kinetics equation to establish a simple sintering model. The equation calculates the densification of metal powders during direct laser sintering process as a function of operating parameters including laser power, scan rate, layer thickness and scan line spacing. It was found that when melting/solidification approach is the mechanism of sintering, the densification of metals powders (D) can be expressed as an exponential function of laser specific energy input (ψ) as ln(1 - D) = -Kψ. The coefficient K is designated as 'densification coefficient'; a material dependent parameter that varies with chemical composition, powder particle size, and oxygen content of the powder material. The mechanism of particle bonding and microstructural features of the laser sintered powders are addressed

  1. Effects of nano-silica on mechanical performance and microstructure of ultra-high performance concrete

    International Nuclear Information System (INIS)

    Mendes, T. M.; Repette, W.L.; Reis, P.J.

    2017-01-01

    The use of nanoparticles in ultra-high strength concretes can result in a positive effect on mechanical performance of these cementitious materials. This study evaluated mixtures containing 10 and 20 wt% of silica fume, for which the optimum nano-silica content was determined, i.e. the quantity of nano-silica that resulted on the higher gain of strength. The physical characterization of raw materials was done in terms of particle size distribution, density and specific surface area. Chemical and mineralogical compositions of materials were obtained through fluorescence and X-ray diffraction. The mechanical performance was evaluated by compressive strength, flexural strength and dynamic elastic modulus measurements. The microstructural analysis of mixtures containing nano-silica was performed by X-ray diffraction, thermogravimetry, mercury intrusion porosimetry and scanning electron microscopy. Obtained results indicate an optimum content of nano-silica of 0.62 wt%, considering compressive and flexural strengths. This performance improvement was directly related to two important microstructural aspects: the packing effect and pozzolanic reaction of nano-silica. (author)

  2. Effect of boron and carbon addition on microstructure and mechanical properties of Ti-15-3 alloy

    International Nuclear Information System (INIS)

    Sarkar, R.; Ghosal, P.; Muraleedharan, K.; Nandy, T.K.; Ray, K.K.

    2011-01-01

    Highlights: → Development of β Ti alloys with B and C addition for improved mechanical properties. → Detailed characterization of microstructural constituents using electron microscopy. → Microstructure-mechanical property correlation in this new class of alloys. → Strengthening mechanism in β Ti alloy in the presence of hard and non-deformable phases. - Abstract: A detailed microstructure-mechanical property correlation was carried out in beta titanium alloys (Ti-15V-3Al-3Sn-3Cr) with boron and carbon additions. The alloys were prepared by non-consumable vacuum arc melting followed by hot rolling. Microstructural characterization was carried out using an optical microscope, a scanning electron microscope (SEM), a transmission electron microscope (TEM) and a high resolution TEM (HRTEM). Addition of boron and carbon resulted in the precipitation of TiB and TiC, respectively, and these phases acted as reinforcements. Evaluation of mechanical properties in solution treated and solution treated plus aged condition showed strengthening in the boron and carbon containing alloy with respect to the base. Strengthening in solution treated condition was attributed to a synergistic effect of grain refinement and load transfer in the presence of non-deformable phases. On the other hand, higher strength in boron and carbon containing alloys on aging was ascribed to the presence of finer aged microstructures.

  3. Cold deformation effect on the microstructures and mechanical properties of AISI 301LN and 316L stainless steels

    International Nuclear Information System (INIS)

    Silva, Paulo Maria de O.; Abreu, Hamilton Ferreira G. de; Albuquerque, Victor Hugo C. de; Neto, Pedro de Lima; Tavares, Joao Manuel R.S.

    2011-01-01

    As austenitic stainless steels have an adequate combination of mechanical resistance, conformability and resistance to corrosion they are used in a wide variety of industries, such as the food, transport, nuclear and petrochemical industries. Among these austenitic steels, the AISI 301LN and 316L steels have attracted prominent attention due to their excellent mechanical resistance. In this paper a microstructural characterization of AISI 301LN and 316L steels was made using various techniques such as metallography, optical microscopy, scanning electronic microscopy and atomic force microscopy, in order to analyze the cold deformation effect. Also, the microstructural changes were correlated with the alterations of mechanical properties of the materials under study. One of the numerous uses of AISI 301LN and 316L steels is in the structure of wagons for metropolitan surface trains. For this type of application it is imperative to know their microstructural behavior when subjected to cold deformation and correlate it with their mechanical properties and resistance to corrosion. Microstructural analysis showed that cold deformation causes significant microstructural modifications in these steels, mainly hardening. This modification increases the mechanical resistance of the materials appropriately for their foreseen application. Nonetheless, the materials become susceptible to pitting corrosion.

  4. Characterisation and modelling of the microstructural and mechanical evolution of a steam turbine rotor steel

    International Nuclear Information System (INIS)

    Mayer, T.

    2012-01-01

    This dissertation deals with the effective mechanical analysis of steam turbine parts which is not only required for the reliable and safe use of newly built steam turbines, but also for the remaining life assessment of components that have been exposed to service duty over long periods of time. This Thesis aims to develop a physically motivated evolutionary constitutive model for a low-alloy bainitic 2CrMoNiWV (23CrMoNiWV8-8) steam turbine rotor steels. A comprehensive experimental characterisation is performed concerning the mechanical and microstructural evolution of 2CrMoNiWV as subjected to low cycle fatigue (LCF) deformation at elevated temperatures, at different strain rates and for various strain amplitudes. This cyclic plastic deformation causes the rearrangement of dislocations in the microstructure of the steels used for such rotor applications. Symmetric, strain controlled LCF experiments have been carried out in the Laboratory of the High Temperature Integrity Group at the Swiss Federal Laboratories for Materials Science and Technology EMPA. These include mechanical tests in the temperature range between 20 °C to 600 °C at strain rates of 0.001%/s to 1.0%/s and strain amplitudes of ±0.25% to ±1.0%. The LCF experiments reported on comprehensively characterise the temperature, strain rate and strain amplitude dependent cyclic elastic-plastic behaviour of 2CrMoNiWV. Both complete single-specimen endurance tests and interrupted multi-specimen tests have been performed. On the basis of this experimental evidence, an evolutionary formulation of the model is further developed that excellently reproduces the strain amplitude dependent mechanical evolution of 2CrMoNiWV when subjected to LCF loading at different constant strain amplitudes but equal temperature and strain rate. The simulation of benchmark experiments introducing increasing or decreasing strain amplitude steps into the LCF deformation history provide promising results. A further important

  5. Characterisation and modelling of the microstructural and mechanical evolution of a steam turbine rotor steel

    Energy Technology Data Exchange (ETDEWEB)

    Mayer, T.

    2012-07-01

    This dissertation deals with the effective mechanical analysis of steam turbine parts which is not only required for the reliable and safe use of newly built steam turbines, but also for the remaining life assessment of components that have been exposed to service duty over long periods of time. This Thesis aims to develop a physically motivated evolutionary constitutive model for a low-alloy bainitic 2CrMoNiWV (23CrMoNiWV8-8) steam turbine rotor steels. A comprehensive experimental characterisation is performed concerning the mechanical and microstructural evolution of 2CrMoNiWV as subjected to low cycle fatigue (LCF) deformation at elevated temperatures, at different strain rates and for various strain amplitudes. This cyclic plastic deformation causes the rearrangement of dislocations in the microstructure of the steels used for such rotor applications. Symmetric, strain controlled LCF experiments have been carried out in the Laboratory of the High Temperature Integrity Group at the Swiss Federal Laboratories for Materials Science and Technology EMPA. These include mechanical tests in the temperature range between 20 °C to 600 °C at strain rates of 0.001%/s to 1.0%/s and strain amplitudes of ±0.25% to ±1.0%. The LCF experiments reported on comprehensively characterise the temperature, strain rate and strain amplitude dependent cyclic elastic-plastic behaviour of 2CrMoNiWV. Both complete single-specimen endurance tests and interrupted multi-specimen tests have been performed. On the basis of this experimental evidence, an evolutionary formulation of the model is further developed that excellently reproduces the strain amplitude dependent mechanical evolution of 2CrMoNiWV when subjected to LCF loading at different constant strain amplitudes but equal temperature and strain rate. The simulation of benchmark experiments introducing increasing or decreasing strain amplitude steps into the LCF deformation history provide promising results. A further important

  6. Microstructure, mechanical properties, bio-corrosion properties and antibacterial properties of Ti–Ag sintered alloys

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Mian [Key Lab. for Anisotropy and Texture of Materials, Education Ministry of China, Northeastern University, Shenyang 110819 (China); Zhang, Erlin, E-mail: zhangel@atm.neu.edu.cn [Key Lab. for Anisotropy and Texture of Materials, Education Ministry of China, Northeastern University, Shenyang 110819 (China); Zhang, Lan [State Key Laboratory for Mechanical Behavior of Materials, Xi' an Jiaotong University, Xi' an 710049 (China)

    2016-05-01

    In this research, Ag element was selected as an antibacterial agent to develop an antibacterial Ti–Ag alloy by a powder metallurgy. The microstructure, phase constitution, mechanical properties, corrosion resistance and antibacterial properties of the Ti–Ag sintered alloys have been systematically studied by X-ray diffraction (XRD), scanning electron microscope (SEM), compressive test, electrochemical measurements and antibacterial test. The effects of the Ag powder size and the Ag content on the antibacterial property and mechanical property as well as the anticorrosion property have been investigated. The microstructure results have shown that Ti–Ag phase, residual pure Ag and Ti were the mainly phases in Ti–Ag(S75) sintered alloy while Ti{sub 2}Ag was synthesized in Ti–Ag(S10) sintered alloy. The mechanical test indicated that Ti–Ag sintered alloy showed a much higher hardness and the compressive yield strength than cp-Ti but the mechanical properties were slightly reduced with the increase of Ag content. Electrochemical results showed that Ag powder size had a significant effect on the corrosion resistance of Ti–Ag sintered alloy. Ag content increased the corrosion resistance in a dose dependent way under a homogeneous microstructure. Antibacterial tests have demonstrated that antibacterial Ti–Ag alloy was successfully prepared. It was also shown that the Ag powder particle size and the Ag content influenced the antibacterial activity seriously. The reduction in the Ag powder size was benefit to the improvement in the antibacterial property and the Ag content has to be at least 3 wt.% in order to obtain a strong and stable antibacterial activity against Staphylococcus aureus bacteria. The bacterial mechanism was thought to be related to the Ti{sub 2}Ag and its distribution. - Highlights: • Ti–Ag alloy with up to 99% antibacterial rate was developed by powder metallurgy. • The effects of the Ag powder size and the Ag content on the

  7. The microstructure, mechanical stress, texture, and electromigration behavior of Al-Pd alloys

    Science.gov (United States)

    Rodbell, K. P.; Knorr, D. B.; Mis, J. D.

    1993-06-01

    As the minimum feature size of interconnect lines decreases below 0.5 urn, the need to control the line microstructure becomes increasingly important. The alloy content, deposition process, fabrication method, and thermal history all determine the microstructure of an interconnect, which, in turn, affects its performance and reliability. The motivation for this work was to characterize the microstructure of various sputtered Al-Pd alloys (Al-0.3wt.%Pd, Al-2Cu-0.3Pd, and Al-0.3Nb-0.3Pd) vs sputtered Al-Cu control samples (Al-0.5Cu and Al-2Cu) and to assess the role of grain size, mechanical stress, and crystallographic texture on the electromigration behavior of submicrometer wide lines. The grain size, mechanical stress, and texture of blanket films were measured as a function of annealing. The as-deposited film stress was tensile and followed a similar stress history on heating for all of the films; on cooling, however, significant differences were observed between the Al-Pd and Al-Cu films in the shape of their stress-temperature-curves. A strong (111) crystallographic texture was typically found for Al-Cu films deposited on SiO2. A stronger (111) texture resulted when Al-Cu was deposited on 25 nm titanium. Al-0.3Pd films, however, exhibited either a weak (111) or (220) texture when deposited on SiO2, which reverted to a strong (111) texture when deposited on 25 nm titanium. The electromigration lifetimes of passivated, ≈0.7 μm wide lines at 250°C and 2.5 × 106 A/cm2 for both single and multi-level samples (separated with W studs) are reported. The electromigration behavior of Al-0.3Pd was found to be less dependent on film microstructure than on the annealing atmosphere used, i.e. forming gas (90% N2-10%H2) annealed Al-0.3Pd films were superior to all of the alloys investigated, while annealing in only N2 resulted in poor lifetimes.

  8. Investigation on Mechanical Properties and Microstructure of Hydroxyapatite-SiCw Composite Bioceramics

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    Hydroxyapatite-SiCw composite micropowder was synthesized using in-situ composite method,and hydroxyapatite-SiCw composite bioceramics with different content of SiCw were produced by hot pressing sintering method. The microstructures of the materials were analyzed by SEM, and the relative density, bending strength and fracture toughness of the materials were tested. The results show that the mechanical properties of composite material are best when the whisker content is 20-23.7% . The mechanical properties of the material are the best when the tensile stress acted on the composite material is parallel with the hot pressing plane, and they are the worst when the tensile stress acted on the composite material is normal to the hot pressing plane.

  9. Microstructure and mechanical properties of direct metal laser sintered TI-6AL-4V

    Directory of Open Access Journals (Sweden)

    Becker, Thorsten Hermann

    2015-05-01

    Full Text Available Direct metal laser sintering (DMLS is a selective laser melting (SLM manufacturing process that can produce near net shape parts from metallic powders. A range of materials are suitable for SLM; they include various metals such as titanium, steel, aluminium, and cobalt-chrome alloys. This paper forms part of a research drive that aims to evaluate the material performance of the SLM-manufactured metals. It presents DMLS-produced Ti-6Al-4V, a titanium alloy often used in biomedical and aerospace applications. This paper also studies the effect of several heat treatments on the microstructure and mechanical properties of Ti-6Al-4V processed by SLM. It reports the achievable mechanical properties of the alloy, including quasi-static, crack growth behaviour, density and porosity distribution, and post-processing using various heat-treatment conditions.

  10. Microstructure and mechanical properties of selective laser melted Ti6Al4V alloy

    Science.gov (United States)

    Losertová, M.; Kubeš, V.

    2017-11-01

    The present work was focused on the properties of porous Ti6Al4V specimens processed by selective laser melting (SLM) and tested in tension and compression before and after heat treatment. The SLM samples were annealed at 955 °C, water quenched and aged at 600 °C with following air cooling. The values of the mechanical tests showed that the samples exhibited high mechanical properties. The anisotropy of tensile and compressive strength was observed, which was related to the occurrence of voids. The plastic properties of specimens were improved by means of the heat treatment that led to the transformation of martensitic to lamellar structure composed of α + β phases. The microstructure of SLM samples were evaluated before and after the heat treatment. The brittle nature of failures of non-heat treated samples can be explained by synergy of martensite presence, microcracks and residual stresses produced by SLM.

  11. Mechanical, thermal and microstructural characteristics of cellulose fibre reinforced epoxy/organoclay nanocomposites

    KAUST Repository

    Alamri, H.

    2012-10-01

    Epoxy nanocomposites reinforced with recycled cellulose fibres (RCFs) and organoclay platelets (30B) have been fabricated and investigated in terms of WAXS, TEM, mechanical properties and TGA. Results indicated that mechanical properties generally increased as a result of the addition of nanoclay into the epoxy matrix. The presence of RCF significantly enhanced flexural strength, fracture toughness, impact strength and impact toughness of the composites. However, the inclusion of 1 wt.% clay into RCF/epoxy composites considerably increased the impact strength and toughness. The presence of either nanoclay or RCF accelerated the thermal degradation of neat epoxy, but at high temperature, thermal stability was enhanced with increased char residue over neat resin. The failure micromechanisms and energy dissipative processes in these nanocomposites were discussed in terms of microstructural observations. © 2012 Published by Elsevier Ltd. All rights reserved.

  12. Investigation of microstructure and mechanical properties of proton irradiated Zircaloy 2

    Energy Technology Data Exchange (ETDEWEB)

    Sarkar, Apu, E-mail: asarkar@barc.gov.in [Mechanical Metallurgy Division, Bhabha Atomic Reserch Centre, Mumbai, 400 085 (India); Kumar, Ajay [Nuclear Physics Division, Bhabha Atomic Reserch Centre, Mumbai, 400 085 (India); Mukherjee, S.; Sharma, S.K.; Dutta, D.; Pujari, P.K. [Radiochemistry Division, Bhabha Atomic Research Centre, Mumbai, 400 085 (India); Agarwal, A.; Gupta, S.K.; Singh, P. [Ion Accelerator Development Division, Bhabha Atomic Research Centre, Mumbai, 400 085 (India); Chakravartty, J.K. [Mechanical Metallurgy Division, Bhabha Atomic Reserch Centre, Mumbai, 400 085 (India)

    2016-10-15

    Samples of Zircaloy 2 have been irradiated with 4 MeV protons to two different doses. Microstructures of the unirradiated and irradiated samples have been characterized by Electron Back Scatter Diffraction (EBSD), X-ray diffraction line profile analysis (XRDLPA), Positron Annihilation Lifetime Spectroscopy (PALS) and Coincident Doppler Broadening (CDB) Spectroscopy. Tensile tests and micro hardness measurements have been carried out at room temperature to assess the changes in mechanical properties of Zircaloy 2 due to proton irradiation. The correlation of dislocation density, grain size and yield stress of the irradiated samples indicated that an increase in dislocation density due to irradiation is responsible for the change in mechanical behavior of irradiated Zircaloy.

  13. Effects of erbium modification on the microstructure and mechanical properties of A356 aluminum alloys

    Energy Technology Data Exchange (ETDEWEB)

    Shi, Z.M., E-mail: shizm@imut.edu.cn; Wang, Q.; Zhao, G.; Zhang, R.Y.

    2015-02-25

    The effects of erbium (Er) modification on the microstructure and mechanical properties of A356 aluminum alloys were investigated using optical microscope, X-ray diffraction, scanning electronic microscope and mechanical testing. Experimental results show that additions of Er refined the α-Al grains and eutectic Si phases in its as-cast state; the addition of 0.3 wt% of Er has the best effects on them. The Fe-containing Al{sub 3}Er phases were introduced by the modifications; by a T6 treatment, the eutectic Si phases were further sphereodized; the large Al{sub 3}Er and β-Al{sub 5}FeSi phases were changed into fine particles and short rods; which enhanced the hardness of the alloys. The highest strength and elongation were obtained for the 0.3 wt% of Er-modified and T6-treated A356 alloy.

  14. Fabrication, microstructure, and mechanical properties of high strength cobalt sub-micron structures

    International Nuclear Information System (INIS)

    Jin Sumin; Burek, Michael J.; Evans, Robert D.; Jahed, Zeinab; Leung, Michael C.; Evans, Neal D.; Tsui, Ting Y.

    2012-01-01

    The mechanical properties exhibited by sub-micron scale columnar structures of cobalt, fabricated by electron beam lithography and electroplating techniques, were investigated through uniaxial compression. Transmission electron microscopy analyses show these specimens possess a microstructure with sub-micron grains which are elongated and aligned near to the pillar loading axis. In addition, small nanocrystalline cobalt crystals are also present within the columnar structure. These specimens display exceptional mechanical strength comparable with both bulk polycrystalline and nanocrystalline cobalt deposited by electroplating. Size-dependent softening with shrinking sample dimensions is also observed in this work. Additionally, the strength of these sub-micron structures appears to be strain rate sensitive and comparable with bulk nanocrystalline cobalt specimens.

  15. Mechanical and microstructural behaviour of Y{sub 2}O{sub 3} ODS EUROFER 97

    Energy Technology Data Exchange (ETDEWEB)

    Castro, V. de [Departamento de Fisica, Universidad Carlos III de Madrid, 28911 Leganes (Spain)]. E-mail: mvcastro@fis.uc3m.es; Leguey, T. [Departamento de Fisica, Universidad Carlos III de Madrid, 28911 Leganes (Spain); Munoz, A. [Departamento de Fisica, Universidad Carlos III de Madrid, 28911 Leganes (Spain); Monge, M.A. [Departamento de Fisica, Universidad Carlos III de Madrid, 28911 Leganes (Spain); Fernandez, P. [CIEMAT, Avda. Complutense 22, 28040 Madrid (Spain); Lancha, A.M. [CIEMAT, Avda. Complutense 22, 28040 Madrid (Spain); Pareja, R. [Departamento de Fisica, Universidad Carlos III de Madrid, 28911 Leganes (Spain)

    2007-08-01

    Two small ingots of the steel EUROFER 97, one containing 0.25 wt% Y{sub 2}O{sub 3} and the other Y{sub 2}O{sub 3} free, have been produced by consolidating mechanically milled powder by hot isostatic pressing at 1373 K for 2 h under 200 MPa. For comparison, a third ingot was consolidated under identical conditions but using un-milled EUROFER powder. Microhardness, tensile and Charpy tests, along with TEM observations, have been performed on these materials in the as-HIPed condition and after different heat treatments. The mechanical behaviour and the microstructural characteristics of these materials suggest that the origin of the reduced impact properties of the oxide dispersion strengthened EUROFER could be the premature formation of carbides during quenching following the HIP process. This would be enhanced by the high density of structural defects produced by milling, as these favour the fast diffusion and segregation of carbon.

  16. Microstructure and mechanical property of dual-directional-extruded Mg alloy AZ31

    International Nuclear Information System (INIS)

    Lu Liwei; Liu Tianmo; Jiang Shan; Pan Fushen; Liu Qing; Wang Zhongchang

    2010-01-01

    We report microstructure evolution and mechanical property of Mg alloy AZ31 processed by a new deformation technique, dual-directional extrusion (DDE). Using optical microscopy, scanning electron microscopy, and electron back scatter diffraction technique, we attribute the significant refinement of original coarse grains in the DDE-processed alloy to the occurrence of dynamic recrystallization. Moreover, we find that low temperature is crucial for yielding fine grain, which consequently results in high micro-hardness and yield stress, large fracture strain, and enhanced elongation. The improved mechanical properties are comparable or even superior to those of the alloy subjected to other deformation techniques, rendering the DDE a promising way for further tailoring properties of Mg-based alloys.

  17. Microstructural Evolution of Advanced Radiation-Resistant ODS Steel with Different Lengths of Mechanical Alloying Time

    Energy Technology Data Exchange (ETDEWEB)

    Noh, Sanghoon; Kim, Ga Eon; Kang, Suk Hoon; Kim, Tae Kyu [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2015-05-15

    Austenitic stainless steel may be one of the candidates because of good strength and corrosion resistance at the high temperatures, however irradiation swelling well occurred to 120dpa at high temperatures and this leads the decrease of the mechanical properties and dimensional stability. Compared to this, ferritic/ martensitic steel is a good solution because of excellent thermal conductivity and good swelling resistance. Unfortunately, the available temperature range of ferritic/martensitic steel is limited up to 650 .deg. C. ODS steel is the most promising structural material because of excellent creep and irradiation resistance by uniformly distributed nano-oxide particles with a high density which is extremely stable at the high temperature in ferritic/martensitic matrix. In this study, powder properties and microstructures of the ODS steel with different length of mechanical alloying time was investigated. The ODS steel milled 5h showed homogeneous grain structure with the highest hardness.

  18. Microstructure, mechanical properties, and biological response to functionally graded HA coatings

    International Nuclear Information System (INIS)

    Rabiei, Afsaneh; Blalock, Travis; Thomas, Brent; Cuomo, Jerry; Yang, Y.; Ong, Joo

    2007-01-01

    Hydroxyapatite (HA) [Ca 10 (PO 4 ) 6 (OH) 2 ] is the primary mineral content, representing 43% by weight, of bone. Applying a thin layer of HA, to the surface of a metal implant, can promote osseointegration and increase the mechanical stability of the implant. In this study, a biocompatible coating comprising an HA film with functionally graded crystallinity is being deposited on a heated substrate in an Ion Beam Assisted Deposition (IBAD) system. The microstructure of the film was studied using Transmission Electron Microscopy techniques. Finally, initial cell adhesion and cell differentiation on the coating was evaluated using ATCC CRL 1486 human embryonic palatal mesenchymal cell, an osteoblast precursor cell line. The results have shown superior mechanical properties and biological response to the functionally graded HA film

  19. Microstructural Evolution of Advanced Radiation-Resistant ODS Steel with Different Lengths of Mechanical Alloying Time

    International Nuclear Information System (INIS)

    Noh, Sanghoon; Kim, Ga Eon; Kang, Suk Hoon; Kim, Tae Kyu

    2015-01-01

    Austenitic stainless steel may be one of the candidates because of good strength and corrosion resistance at the high temperatures, however irradiation swelling well occurred to 120dpa at high temperatures and this leads the decrease of the mechanical properties and dimensional stability. Compared to this, ferritic/ martensitic steel is a good solution because of excellent thermal conductivity and good swelling resistance. Unfortunately, the available temperature range of ferritic/martensitic steel is limited up to 650 .deg. C. ODS steel is the most promising structural material because of excellent creep and irradiation resistance by uniformly distributed nano-oxide particles with a high density which is extremely stable at the high temperature in ferritic/martensitic matrix. In this study, powder properties and microstructures of the ODS steel with different length of mechanical alloying time was investigated. The ODS steel milled 5h showed homogeneous grain structure with the highest hardness

  20. Mechanical and microstructural characterization of low activation steels as first wall of nuclear fusion reactors

    International Nuclear Information System (INIS)

    Hernandez, M.T.; Lapena, J.; Diego, G. de; Schirra, M.

    1996-01-01

    Currently, the design development of fusion reactors and the possible materials to use in them are being studied in parallel. One of the most critical problems in this research is the structural materials selection for the first wall and blanket. The aim of the present work is to study three low activation alloys designed in Germany in which niobium has been substituted by tantalum or cerium. The mechanical results show that the alloys containing cerium are in the same order of the low activation materials known to date, but the tantalum doped alloy produces TaC 3 precipitation that destabilizes the matrix and provokes large microstructural changes. This causes a decrease of the mechanical properties at about 600 degree centigree. This fact makes this alloy insuitable for the first wall on fusion reactors, because the working temperature is near 550 degree centigree. (Author) 11 refs

  1. Microstructural and mechanical evolutions during the forging step of the COBAPRESS, a casting/forging process

    Science.gov (United States)

    Perrier, Frédéric; Desrayaud, Christophe; Bouvier, Véronique

    Aluminum casting/forging processes are used to produce parts for the automotive industry. In this study, we examined the influence of the forging step on the microstructure and the mechanical properties of an A356 aluminum alloy modified with strontium. Firstly, a design of samples which allows us to test mechanically the alloy before and after forging was created. A finite element analysis with the ABAQUS software predicts a maximum of strain in the core of the specimens. Observations with the EBSD technique confirm a more intense sub-structuration of the dendrite cells in this zone. Yield strength, ultimate tensile strength, elongation and fatigue lives were then improved for the casting/forging samples compared to the only cast specimens. The closure of the porosities and the improvement of the surface quality during the forging step enhance also the fatigue resistance of the samples.

  2. Evaluation of Microstructure and Mechanical Properties in Dissimilar Austenitic/Super Duplex Stainless Steel Joint

    Science.gov (United States)

    Rahmani, Mehdi; Eghlimi, Abbas; Shamanian, Morteza

    2014-10-01

    To study the effect of chemical composition on microstructural features and mechanical properties of dissimilar joints between super duplex and austenitic stainless steels, welding was attempted by gas tungsten arc welding process with a super duplex (ER2594) and an austenitic (ER309LMo) stainless steel filler metal. While the austenitic weld metal had vermicular delta ferrite within austenitic matrix, super duplex stainless steel was mainly comprised of allotriomorphic grain boundary and Widmanstätten side plate austenite morphologies in the ferrite matrix. Also the heat-affected zone of austenitic base metal comprised of large austenite grains with little amounts of ferrite, whereas a coarse-grained ferritic region was observed in the heat-affected zone of super duplex base metal. Although both welded joints showed acceptable mechanical properties, the hardness and impact strength of the weld metal produced using super duplex filler metal were found to be better than that obtained by austenitic filler metal.

  3. The Influence of Duration of Mechanical Activation of Titanium Powder on its Morphology, Microstructure, and Microhardness

    Science.gov (United States)

    Ditenberg, I. A.; Korchagin, M. A.; Pinzhin, Yu. P.; Melnikov, V. V.; Tyumentsev, A. N.; Grinyaev, K. V.; Smirnov, I. V.; Radishevskii, V. L.; Tsverova, A. S.; Sukhanov, I. I.

    2017-10-01

    Using the methods of X-ray diffraction analysis and scanning and transmission electron microscopy, an investigation of the influence of duration of mechanical activation on morphology and structure of titanium powder is performed. In the course of processing the following stages of material transformation are revealed: fragmentation of the initial powder, conglomeration, and ovalization of the conglomerates. It is found that when the duration of mechanical activation increases, the characteristic size of coherent scattering regions is significantly decreased, which is accompanied by an increase in the value of microdistortions and intensive fragmentation of the crystal lattice inside powder particles followed by the formation of highly defective nanostructured states. The transformation of microstructure is accompanied by a considerable increase in microhardness.

  4. Relationship of vibro-mechanical properties and microstructure of wood and varnish interface in string instruments

    Science.gov (United States)

    Sedighi Gilani, Marjan; Pflaum, Johanna; Hartmann, Stefan; Kaufmann, Rolf; Baumgartner, Michael; Schwarze, Francis Willis Mathew Robert

    2016-04-01

    Wood varnish coatings not only are aesthetically important, but also preserve the musical instrument from wear and fluctuations in the ambient humidity. Depending on the thickness, extent of penetration into the wood and the physical and mechanical properties after hardening, varnishes may change the mechanical and also vibro-acoustical properties of the coated wood. Contrary to studies on the chemistry of the varnish and primer used for old and contemporary musical instruments, the physical and mechanical properties of the varnished wood in relation to the geometry of their interface have been poorly studied. We implemented non-destructive test methods, i.e., vibration tests and X-ray tomography, to characterize the hardening-dependent change in the vibrational properties of master grade tone wood specimens after coating with four different varnishes. Two were manufactured in the laboratory, and two were supplied from master violin makers. For a controlled accelerated hardening of the varnish, a UV exposure method was used. It was demonstrated that varnishes increase wood damping, along and perpendicular to the grain directions. Varnishes reduce the sound radiation along the grain, but increase it in the perpendicular direction. Changes in the vibrational properties were discussed together with results of 3D images of wood and varnish microstructure, obtained from a customized tabletop X-ray microtomographic setup. For comparison, the microstructure of the interface of the varnished wood in the laboratory and of specimens from two old violins was analyzed with the same X-ray tomography setup. Laboratory varnishes with various compositions penetrated differently into the wood structure. One varnish of a master grade old violin had a higher density and was also thicker and penetrated weaker into the wood, which is more likely related to a more sophisticated primer and varnish application. The study demonstrates the importance of the vibro-mechanical properties of

  5. Effect of Cu on the microstructural and mechanical properties of as-cast ductile iron

    International Nuclear Information System (INIS)

    Tiwari, Siddhartha; Das, J.; Ray, K.K.; Kumar, Hemant; Bhaduri, A.

    2012-01-01

    The application of ductile cast iron in the heavy engineering components like, cask for the storage and transportation of radioactive materials, demands high strength with improved fracture toughness in as cast condition. The mechanical properties and fracture toughness of as-cast ductile iron (DI) is directly related to its structure property which can be controlled by proper inoculation, alloying elements and cooling rate during solidification. The aim of the present investigation is to study the effect of varying amount of Cu (0.07%, 0.11%, and 0.16%) with 1% Ni in the microstructural development of as-cast ductile iron with emphasis on its mechanical properties and fracture toughness. Three different ductile irons have been prepared using induction furnace in batches of 300 kg following industrial practice. Microstructural features (amount of phases, morphology, size and count of graphite nodules) and mechanical properties (tensile strength and hardness) of prepared DI were determined using standard methods. Dynamic fracture toughness was measured using instrumented Charpy impact test on pre-cracked specimens following the standard ISO-FDIS-26843. Additionally, fracture surfaces of broken tensile and pre-cracked specimens were observed by SEM to study the micro-mechanism of fracture. The pearlite fraction and the nodule count are found to increase with increasing amount of copper in ferritic-pearlitic matrix. The hardness and strength values are found to increase with increasing amount of pearlite whereas fracture toughness decreases. Fractographs of broken specimens exhibited decohesion of graphite, crack propagation from graphite interface and transgranular fracture of ferrite. (author)

  6. Microstructures, mechanical properties and cytotoxicity of low cost beta Ti-Mn alloys for biomedical applications.

    Science.gov (United States)

    Santos, Pedro Fernandes; Niinomi, Mitsuo; Cho, Ken; Nakai, Masaaki; Liu, Huihong; Ohtsu, Naofumi; Hirano, Mitsuhiro; Ikeda, Masahiko; Narushima, Takayuki

    2015-10-01

    The microstructures, mechanical properties and biocompatibility of low cost β-type Ti-(6-18)Mn alloys were investigated after solution treatment. Ti-9 Mn exhibits the best combination of tensile strength and elongation among the fabricated alloys, and its performance is comparable to or superior to those of Ti-6Al-4V ELI (Ti-64 ELI) in terms of every parameter evaluated. A hardness of 338 HV, a Young's modulus of 94 GPa, a 0.2% proof stress of 1023 MPa, an ultimate tensile strength of 1048 MPa and elongation of 19% were obtained for Ti-9 Mn. Furthermore, the cell viability and metallic ion release ratios are comparable to those of commercially pure titanium, making this alloy promising for biomedical applications. The Young's modulus is also lower than that of Ti-64 ELI (110 GPa), which can possibly reduce the stress shielding effect in implanted patients. This study evaluates mechanical and biological performance of low cost solution treated β-type Ti-(6, 9, 13 and 18 mass%)Mn alloys. It includes alloys containing a Mn content range higher than most previously published works (which is around or lower than 8 mass%). Furthermore, the effects of the ω phase and the β phase stability of the alloys over some mechanical properties and microstructures are discussed. Ion release behavior under simulated body fluids and cell viability are also evaluated. For the case of the Ti-9 Mn, a mechanical and biological performance that is comparable to or superior than that of the widely used Ti-6Al-4V ELI and commercially pure Ti was observed. Copyright © 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  7. Production, microstructure and mechanical properties of two different austenitic ODS steels

    Energy Technology Data Exchange (ETDEWEB)

    Gräning, T., E-mail: tim.graening@kit.edu; Rieth, M.; Hoffmann, J.; Möslang, A.

    2017-04-15

    This article is to summarize and examine processing parameters of novel developed austenitic oxide dispersed strengthened (ODS) steels. Comparing hot-rolled and extruded conditions after the same degree of deformation after and before annealing, are just some examples to give insights into the complex processing of austenitic ODS steels. One of the major drawbacks of the material is the more sophisticated production process. Due to a ductile matrix material with an increased stickiness during milling, a two-step milling procedure with the use of ZrO{sub 2} milling balls was applied to raise the production yield and to use the abrasion of the ZrO{sub 2} as an additional element to facilitate the formation of nano-sized precipitates. To get a better understanding how the different powder particle sizes after milling affect final properties, sieving was applied and revealed a serious effect in terms of precipitate size, distribution and mechanical properties. Grain sizes in relation to the precipitate size, annealing time and processing parameters were determined and compared to the mechanical properties. Hardness and tensile test have pointed out, that the precipitate size and number are more important in respect to the ultimate tensile strength than the grain size and that in this study hot-rolled material exhibited the better properties. The investigation of the microstructure illustrated the stability of precipitates during annealing at 1100 °C for 40 h. These heat treatments also led to a consistent grain size, due to the pinning effect of the grain boundaries, caused by precipitates. - Highlights: •Comparison of the microstructure of extruded and hot-rolled ODS. •Two-step mechanical alloying with ZrO{sub 2} milling balls. •Determination of precipitate size distribution depending on chemical composition and annealing times. •Determination of the influence of sieving of mechanical alloyed powder on the near net shape products. •Tensile tests of two

  8. Study on microstructure and strengthening mechanism of AZ91-Y magnesium alloy

    Science.gov (United States)

    Cai, Huisheng; Guo, Feng; Su, Juan; Liu, Liang; Chen, Baodong

    2018-03-01

    AZ91-Y magnesium alloy with different thicknesses were prepared by die casting process. The main existence forms of Y in alloy and the effects of Y on microstructure and mechanical properties of alloy were studied, the main reason for the change of mechanical properties and fracture mechanism were analyzed. The results show that, yttrium exists mainly in the forms of Al2Y phase and trace solid solution in α-Mg. Yttrium can refine the grain of α-Mg, reduce the amount of eutectic β-Mg17Al12 phase and promote its discrete distribution. The room temperature tensile strength and elongation of alloy increased first and then decreased with the increase of Y content. The designed alloys containing 0.6% Y (measured containing 0.63% Y) have better mechanical properties. The change of mechanical properties of alloy is a comprehensive reflection of the effect of solid solution, grain refinement and second phase. The cracking of Al2Y phase and β-Mg17Al12 phase and crack propagation through Al2Y phase and β-Mg17Al12 phase are the main fracture mechanism of magnesium alloy containing yttrium. The cooling rate does not change the trend of the influence of Y, but affects the degree of influence of Y.

  9. Microstructure and Mechanical Properties of Thixowelded AISI D2 Tool Steel

    Directory of Open Access Journals (Sweden)

    M. N. Mohammed

    2018-05-01

    Full Text Available Rigid perpetual joining of materials is one of the main demands in most of the manufacturing and assembling industries. AISI D2 cold work tool steels is commonly known as non-weldable metal that a high quality joint of this kind of material can be hardly achieved and almost impossible by conventional welding. In this study, a novel thixowelding technology was proposed for joining of AISI D2 tool steel. The effect of joining temperature, holding time and post-weld heat treatment on microstructural features and mechanical properties were also investigated. Acceptable joints without defect were achieved through the welding temperature of 1300 °C, while the welding at lower temperature resulted in a series of cracks across the entire joint that led to spontaneous fracture after joining. Tensile test results showed that maximum joint tensile strength of 271 MPa was achieved at 1300 °C and 10 min holding time, which was 35% of that of D2 base metal. Meanwhile, tensile strength of the joined parts after heat treatment showed a significant improvement over the non-heat treated condition with 560 MPa, i.e., about 70% of that of the strength value of the D2 base metal. This improvement in the tensile strength attributed to the dissolution of some amounts of eutectic chromium carbides and changes in the microstructure of the matrix. The joints are fractured at the diffusion zone, and the fracture exhibits a typical brittle characteristic. The present study successfully confirmed that by avoiding dendritic microstructure, as often resulted from the fusion welding, high joining quality components obtained in the semi-solid state. These results can be obtained without complex or additional apparatuses that are used in traditional joining process.

  10. Microstructure, crystallographic texture and mechanical properties of friction stir welded AA2017A

    Energy Technology Data Exchange (ETDEWEB)

    Ahmed, M.M.Z., E-mail: mohamed_ahmed4@s-petrol.suez.edu.eg [Institute for Microstructural and Mechanical Processing Engineering, University of Sheffield (IMMPETUS), Mappin Street, Sheffield S1 3JD (United Kingdom); Department of Metallurgical and Materials Engineering, Suez Canal University, Suez 43721 (Egypt); Wynne, B.P.; Rainforth, W.M. [Institute for Microstructural and Mechanical Processing Engineering, University of Sheffield (IMMPETUS), Mappin Street, Sheffield S1 3JD (United Kingdom); Threadgill, P.L. [TWI LTD, Granta Park, Great Abington, Cambridge CB21 6AL (United Kingdom)

    2012-02-15

    In this study a thick section (20 mm) friction stir welded AA2017A-T451 has been characterized in terms of microstructure, crystallographic texture and mechanical properties. For microstructural analysis both optical and scanning electron microscopes have been used. A detailed crystallographic texture analysis has been carried out using the electron back scattering diffraction technique. Crystallographic texture has been examined in both shoulder and probe affected regions of the weld NG. An entirely weak texture is observed at the shoulder affected region which is mainly explained by the effect of the sequential multi pass deformation experienced by both tool probe and tool shoulder. The texture in the probe dominated region at the AS side of the weld is relatively weak but still assembles the simple shear texture of FCC metals with B/B{sup Macron} and C components existing across the whole map. However, the texture is stronger at the RS than at the AS of the weld, mainly dominated byB/B{sup Macron} components and with C component almost absent across the map. An alternating bands between (B) components and (B{sup Macron }) component are observed only at the AS side of the weld. - Highlights: Black-Right-Pointing-Pointer Detailed investigation of microstructure and crystallographic texture. Black-Right-Pointing-Pointer The grain size is varied from the top to the bottom of the NG. Black-Right-Pointing-Pointer An entirely weak texture is observed at the shoulder affected region. Black-Right-Pointing-Pointer The texture in the probe affected region is dominated by simple shear texture.

  11. Effect of particle size on microstructure and mechanical properties of composites produced by ARB process

    Energy Technology Data Exchange (ETDEWEB)

    Jamaati, Roohollah, E-mail: r.jamaatikenari@ma.iut.ac.ir [Department of Materials Engineering, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Amirkhanlou, Sajjad; Toroghinejad, Mohammad Reza; Niroumand, Behzad [Department of Materials Engineering, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of)

    2011-02-25

    Research highlights: {yields} Microstructure of MMC with larger particles becomes completely uniform, sooner. {yields} When the number of cycles increased, tensile strength for both samples improved. {yields} Up to the seventh cycle, tensile strength of MMC with larger particles was bigger. {yields} First, the tensile elongation of MMCs was decreased, and then it was improved. - Abstract: In the present work, Al/10 vol.% SiC metal matrix composite (MMC) was manufactured by accumulative roll bonding (ARB) process. The silicon carbide particles with two various particle sizes of 40 and 2 {mu}m were used. Effect of particle size on microstructure (by scanning electron microscopy) and mechanical properties (tensile strength and elongation) at various ARB cycles was investigated. It was found that the microstructural evolution in MMC with 40 {mu}m particle size was more salient compared to the MMCs with 2 {mu}m particle size. Also, the composite strip with 40 {mu}m particle size became uniform with high bonding quality and without any porosity sooner than the strip of 2 {mu}m particle size. Moreover, when the number of cycles was increased, the tensile strength for both samples was improved. The tensile strength of the composite strip with 40 {mu}m particle size was more than the composite strip with 2 {mu}m up to the seventh cycle. By increasing the number of cycles after the seventh cycle, the value of tensile strength of MMC with 40 {mu}m particle size became saturated and then decreased, and its tensile strength became less than that of the composite with 2 {mu}m particle size for the ninth and eleventh cycles. Up to the seventh cycle, when the number of ARB cycles was increased, the elongation of composite strips was decreased, but after the ninth cycle, the tensile elongation for both samples was improved.

  12. Effect of particle size on microstructure and mechanical properties of composites produced by ARB process

    International Nuclear Information System (INIS)

    Jamaati, Roohollah; Amirkhanlou, Sajjad; Toroghinejad, Mohammad Reza; Niroumand, Behzad

    2011-01-01

    Research highlights: → Microstructure of MMC with larger particles becomes completely uniform, sooner. → When the number of cycles increased, tensile strength for both samples improved. → Up to the seventh cycle, tensile strength of MMC with larger particles was bigger. → First, the tensile elongation of MMCs was decreased, and then it was improved. - Abstract: In the present work, Al/10 vol.% SiC metal matrix composite (MMC) was manufactured by accumulative roll bonding (ARB) process. The silicon carbide particles with two various particle sizes of 40 and 2 μm were used. Effect of particle size on microstructure (by scanning electron microscopy) and mechanical properties (tensile strength and elongation) at various ARB cycles was investigated. It was found that the microstructural evolution in MMC with 40 μm particle size was more salient compared to the MMCs with 2 μm particle size. Also, the composite strip with 40 μm particle size became uniform with high bonding quality and without any porosity sooner than the strip of 2 μm particle size. Moreover, when the number of cycles was increased, the tensile strength for both samples was improved. The tensile strength of the composite strip with 40 μm particle size was more than the composite strip with 2 μm up to the seventh cycle. By increasing the number of cycles after the seventh cycle, the value of tensile strength of MMC with 40 μm particle size became saturated and then decreased, and its tensile strength became less than that of the composite with 2 μm particle size for the ninth and eleventh cycles. Up to the seventh cycle, when the number of ARB cycles was increased, the elongation of composite strips was decreased, but after the ninth cycle, the tensile elongation for both samples was improved.

  13. Microstructural and mechanical approaches of the selective laser melting process applied to a nickel-base superalloy

    International Nuclear Information System (INIS)

    Vilaro, T.; Colin, C.; Bartout, J.D.; Nazé, L.; Sennour, M.

    2012-01-01

    Highlights: ► We examine the as-fabricated microstructure of the Nimonic 263 processed by selective laser melting. ► We optimized heat treatments to modify the microstructure and improve the mechanical properties. ► We tested through tensile tests the various microstructures in order to compare the effects of the heat treatments. - Abstract: This article aims at presenting the Nimonic 263 as-processed microstructure of the selective laser melting which is an innovative process. Because the melting pool is small and the scanning speed of the laser beam is relatively high, the as-processed microstructure is out-of-equilibrium and very typical to additive manufacturing processes. To match the industrial requirement, the microstructures are modified through heat treatments in order to either produce precipitation hardening or relieve the thermal stresses. Tensile tests at room temperature give rise to high mechanical properties close or above those presented by Wang et al. . However, it is noted a strong anisotropy as a function of the building direction of the samples because of the columnar grain growth.

  14. Structural Studies of Bacterial Enzymes and their Relation to Antibiotic Resistance Mechanisms - Final Paper

    Energy Technology Data Exchange (ETDEWEB)

    Maltz, Lauren [SLAC National Accelerator Lab., Menlo Park, CA (United States)

    2015-08-27

    By using protein crystallography and X-ray diffraction, structures of bacterial enzymes were solved to gain a better understanding of how enzymatic modification acts as an antibacterial resistance mechanism. Aminoglycoside phosphotransferases (APHs) are one of three aminoglycoside modifying enzymes that confer resistance to the aminoglycoside antibiotics via enzymatic modification, rendering many drugs obsolete. Specifically, the APH(2”) family vary in their substrate specificities and also in their preference for the phosphate donor (ADP versus GDP). By solving the structures of members of the APH(2”) family of enzymes, we can see how domain movements are important to their substrate specificity. Our structure of the ternary complex of APH(2”)-IIIa with GDP and kanamycin, when compared to the known structures of APH(2”)-IVa, reveals that there are real physical differences between these two enzymes, a structural finding that explains why the two enzymes differ in their preferences for certain aminoglycosides. Another important group of bacterial resistance enzymes are the Class D β- lactamases. Oxacillinase carbapenemases (OXAs) are part of this enzyme class and have begun to confer resistance to ‘last resort’ drugs, most notably carbapenems. Our structure of OXA-143 shows that the conformational flexibility of a conserved hydrophobic residue in the active site (Val130) serves to control the entry of a transient water molecule responsible for a key step in the enzyme’s mechanism. Our results provide insight into the structural mechanisms of these two different enzymes

  15. The effect of quench rate on the microstructure, mechanical properties, and corrosion behavior of U-6 Wt Pct Nb

    International Nuclear Information System (INIS)

    Eckelmeyer, K.H.; Romiy, A.D.; Weirick, L.J.

    1984-01-01

    The effect of cooling rate on microstructure, mechanical behavior, corrosion resistance, and subsequent age hardenability is discussed. Cooling rates in excess of 20 Ks -1 cause the parent γ-phase to transform martensitically to a niobium supersaturated variant of the α-phase. This phase exhibits low hardness and strength, high ductility, good corrosion resistance, and age hardenability. As cooling rate decreases from 10 Ks -1 to 0.2 Ks -1 , microstructural changes (consistent with spinodal decomposition) occur to an increasing extent. These changes produce increases in hardness and strength and decreases in ductility, corrosion resistance, and age hardenability. At cooling rates less than 0.2 Ks -1 the parent phase undergoes cellular decomposition to a coarse two-phase lamellar microstructure which exhibits intermediate strength and ductility, reduced corrosion resistance, and no age hardenability. An analysis of the cooling rates indicates that fully martensitic microstructures can be obtained in plates as thick as 50 mm

  16. Replication of engine block cylinder bridge microstructure and mechanical properties with lab scale 319 Al alloy billet castings

    International Nuclear Information System (INIS)

    Lombardi, A.; D'Elia, F.; Ravindran, C.; MacKay, R.

    2014-01-01

    In recent years, aluminum alloy gasoline engine blocks have in large part successfully replaced nodular cast iron engine blocks, resulting in improved vehicle fuel efficiency. However, because of the inadequate wear resistance properties of hypoeutectic Al–Si alloys, gray iron cylinder liners are required. These liners cause the development of large tensile residual stress along the cylinder bores and necessitate the maximization of mechanical properties in this region to prevent premature engine failure. The aim of this study was to replicate the engine cylinder bridge microstructure and mechanical properties following TSR treatment (which removes the sand binder to enable easy casting retrieval) using lab scale billet castings of the same alloy composition with varying cooling rates. Comparisons in microstructure between the engine block and the billet castings were carried out using optical and scanning electron microscopy, while mechanical properties were assessed using tensile testing. The results suggest that the microstructure at the top and middle of the engine block cylinder bridge was successfully replicated by the billet castings. However, the microstructure at the bottom of the cylinder was not completely replicated due to variations in secondary phase morphology and distribution. The successful replication of engine block microstructure will enable the future optimization of heat treatment parameters. - Highlights: • A method to replicate engine block microstructure was developed. • Billet castings will allow cost effective optimization of heat treatment process. • The replication of microstructure in the cylinder region was mostly successful. • Porosity was more clustered in the billet castings compared to the engine block. • Mechanical properties were lower in billet castings due to porosity and inclusions

  17. Replication of engine block cylinder bridge microstructure and mechanical properties with lab scale 319 Al alloy billet castings

    Energy Technology Data Exchange (ETDEWEB)

    Lombardi, A., E-mail: a2lombar@ryerson.ca [Centre for Near-net-shape Processing of Materials, Ryerson University, 101 Gerrard Street East, Toronto, Ontario M5B2K3 (Canada); D' Elia, F.; Ravindran, C. [Centre for Near-net-shape Processing of Materials, Ryerson University, 101 Gerrard Street East, Toronto, Ontario M5B2K3 (Canada); MacKay, R. [Nemak of Canada Corporation, 4600 G.N. Booth Drive, Windsor, Ontario N9C4G8 (Canada)

    2014-01-15

    In recent years, aluminum alloy gasoline engine blocks have in large part successfully replaced nodular cast iron engine blocks, resulting in improved vehicle fuel efficiency. However, because of the inadequate wear resistance properties of hypoeutectic Al–Si alloys, gray iron cylinder liners are required. These liners cause the development of large tensile residual stress along the cylinder bores and necessitate the maximization of mechanical properties in this region to prevent premature engine failure. The aim of this study was to replicate the engine cylinder bridge microstructure and mechanical properties following TSR treatment (which removes the sand binder to enable easy casting retrieval) using lab scale billet castings of the same alloy composition with varying cooling rates. Comparisons in microstructure between the engine block and the billet castings were carried out using optical and scanning electron microscopy, while mechanical properties were assessed using tensile testing. The results suggest that the microstructure at the top and middle of the engine block cylinder bridge was successfully replicated by the billet castings. However, the microstructure at the bottom of the cylinder was not completely replicated due to variations in secondary phase morphology and distribution. The successful replication of engine block microstructure will enable the future optimization of heat treatment parameters. - Highlights: • A method to replicate engine block microstructure was developed. • Billet castings will allow cost effective optimization of heat treatment process. • The replication of microstructure in the cylinder region was mostly successful. • Porosity was more clustered in the billet castings compared to the engine block. • Mechanical properties were lower in billet castings due to porosity and inclusions.

  18. Mechanical properties and deformation mechanism of Mg-Al-Zn alloy with gradient microstructure in grain size and orientation

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Liu; Yuan, Fuping; Jiang, Ping; Xie, Jijia; Wu, Xiaolei, E-mail: xlwu@imech.ac.cn

    2017-05-10

    The surface mechanical attrition treatment was taken to fabricate the gradient structure in AZ31 magnesium alloy sheet. Microstructural investigations demonstrate the formation of dual gradients with respect to grain size and orientation, where the microstructural sizes decreased from several microns to about 200 nm from center area to treated surface, while the c-axis gradually inclined from being vertical to treated plane towards parallel with it. According to tensile results, the gradient structured sample has yield strength of 305 MPa in average, which is increased by about 4 times when compared with its coarse-grained counterpart. Meanwhile, contrary to quickly failure after necking in most traditional magnesium alloys, the failure process of gradient structure appears more gently, which makes it has 6.5% uniform elongation but 11.5% total elongation. The further comparative tensile tests for separated gradient layers and corresponding cores demonstrate that the gradient structured sample has higher elongation either in uniform or in post-uniform stages. In order to elucidate the relationship between mechanical properties and deformation mechanisms for this dual gradient structure, the repeated stress relaxation tests and pole figure examinations via X-ray diffraction were conducted in constituent gradient layer and corresponding core, as well as gradient structured sample. The results show that the pyramidal dislocations in dual gradient structure are activated through the whole thickness of sample. Together with the contribution of grain-size gradient, more dislocations are activated in dual gradient structure under tensile loading, which results in stronger strain hardening and hence higher tensile ductility.

  19. Mechanical properties and deformation mechanism of Mg-Al-Zn alloy with gradient microstructure in grain size and orientation

    International Nuclear Information System (INIS)

    Chen, Liu; Yuan, Fuping; Jiang, Ping; Xie, Jijia; Wu, Xiaolei

    2017-01-01

    The surface mechanical attrition treatment was taken to fabricate the gradient structure in AZ31 magnesium alloy sheet. Microstructural investigations demonstrate the formation of dual gradients with respect to grain size and orientation, where the microstructural sizes decreased from several microns to about 200 nm from center area to treated surface, while the c-axis gradually inclined from being vertical to treated plane towards parallel with it. According to tensile results, the gradient structured sample has yield strength of 305 MPa in average, which is increased by about 4 times when compared with its coarse-grained counterpart. Meanwhile, contrary to quickly failure after necking in most traditional magnesium alloys, the failure process of gradient structure appears more gently, which makes it has 6.5% uniform elongation but 11.5% total elongation. The further comparative tensile tests for separated gradient layers and corresponding cores demonstrate that the gradient structured sample has higher elongation either in uniform or in post-uniform stages. In order to elucidate the relationship between mechanical properties and deformation mechanisms for this dual gradient structure, the repeated stress relaxation tests and pole figure examinations via X-ray diffraction were conducted in constituent gradient layer and corresponding core, as well as gradient structured sample. The results show that the pyramidal dislocations in dual gradient structure are activated through the whole thickness of sample. Together with the contribution of grain-size gradient, more dislocations are activated in dual gradient structure under tensile loading, which results in stronger strain hardening and hence higher tensile ductility.

  20. Microstructure, mechanical and tribological behavior of hot-pressed mechanically alloyed Al–Zn–Mg–Cu powders

    International Nuclear Information System (INIS)

    Azimi, A.; Fallahdoost, H.; Nejadseyfi, O.

    2015-01-01

    Highlights: • Nanocrystalline Al7050 alloy was synthesized by mechanical alloying. • Longer milling time led to increasing porosity in hot-pressed samples. • Significant improvement in strength and wear resistance was obtained by increasing the milling time up to 40 h. - Abstract: This research focuses on the preparation of Al7050 alloy via mechanical alloying and hot pressing techniques. The effect of milling time on the microstructure and densification response was investigated by X-ray diffraction (XRD) and scanning electron microscope (SEM). Furthermore, the mechanical properties of the samples including microhardness, compression strength, and wear resistance were examined as a function of milling time. The results of the experiments proved that by increasing the milling time the crystallite size was reduced, which has a significant effect on improving the mechanical properties. In addition, porosity formation increased when the milling time was increased due to reduction of the compressibility of finer particles. By increasing the milling time to more than 40 h, a relatively invariable crystallite size was obtained and it was observed that the porosities expanded in the samples. Therefore, the compressive strength, hardness, and wear resistance were enhanced up to 40 h milling time and then the strengthening effect was relatively diminished. On observing surfaces with SEM, the dominant wear mechanism was recognized as abrasion, delamination and adhesion

  1. Microstructural Characteristics and Mechanical Properties of an Electron Beam-Welded Ti/Cu/Ni Joint

    Science.gov (United States)

    Zhang, Feng; Wang, Ting; Jiang, Siyuan; Zhang, Binggang; Feng, Jicai

    2018-05-01

    Electron beam welding experiments of TA15 titanium alloy to GH600 nickel superalloy with and without a copper sheet interlayer were carried out. Surface appearance, microstructure and phase constitution of the joint were examined by optical microscopy, scanning electron microscopy and x-ray diffraction analysis. Mechanical properties of Ti/Ni and Ti/Cu/Ni joint were evaluated based on tensile strength and microhardness tests. The results showed that cracking occurred in Ti/Ni electron beam weldment for the formation of brittle Ni-Ti intermetallics, while a crack-free electron beam-welded Ti/Ni joint can be obtained by using a copper sheet as filler metal. The addition of copper into the weld affected the welding metallurgical process of the electron beam-welded Ti/Ni joint significantly and was helpful for restraining the formation of Ti-Ni intermetallics in Ti/Ni joint. The microstructure of the weld was mainly characterized by a copper-based solid solution and Ti-Cu interfacial intermetallic compounds. Ti-Ni intermetallic compounds were almost entirely suppressed. The hardness of the weld zone was significantly lower than that of Ti/Ni joint, and the tensile strength of the joint can be up to 282 MPa.

  2. Effect of Cold Forging on Microstructure and MechanicalProperties of Al/SiC Composites

    Science.gov (United States)

    Hanamantraygouda, M. B.; Shivakumar, B. P., Dr; Siddappa, P. N.; Sampathkumar, L.; Prashanth, L.

    2018-02-01

    The objective of this work was to investigate the effect of cold forging on mechanical properties and microstructural study of Al MMCs, at different wt% of SiC and forging cycle. The Al-SiC composite material was fabricated by stir casting method at different weight percentage of SiC such as 2.5, 5, 7.5 and 10%. Further, the deformation characteristics during open-die forging of Al-SiC composite at cold conditions was investigated. Cast and forged composite material was subjected to hardness test, tensile test and impact test. The grain size, microstructure behaviour was investigated using optical microscope. The results show that hardness and strength of Al-SiC composite increases and ductility decreases as compared to Al alloy in both as-cast and forged conditions. Optical microscope images showed that the distribution of SiC in Al matrix was more homogeneous in a forged composite as compared to cast one and reduction of porosity was found. Further, it showed that due to forging cycle the grain size was reduced by 30% to 35% from initial size.

  3. TiC-Maraging stainless steel composite: microstructure, mechanical and wear properties

    Institute of Scientific and Technical Information of China (English)

    Akhtar Farid; GUO Shiju; FENG Peizhong; Khadijah Ali Shah; Syed Javid Askari

    2006-01-01

    Particulate TiC reinforced 17-4PH and 465 maraging stainless steel matrix composites were processed by conventional powder metallurgy (P/M). TiC-maraging stainless steel composites with theoretical density >97% were produced using conventional P/M. The microstructure, and mechanical and wear properties of the composites were evaluated. The microstructure of the composites consisted of (core-rim structure) spherical and semi-spherical TiC particles depending on the wettability of the matrix with TiC particles. In TiC-maraging stainless steel composites, 465 stainless steel binder phase showed good wettability with TiC particles. Some microcracks appeared in the composites, indicating the presence of tensile stresses in the composites produced during sintering. The typical properties, hardness, and bend strength were reported for the composites. After heat treatment and aging, an increase in hardness was observed. The increase in hardness was attributed to the aging reaction in maraging stainless steel. The specific wear behavior of the composites strongly depends on the content of TiC particles and their interparticle spacing, and on the heat treatment of the maraging stainless steel.

  4. Influence of microstructure on the mechanical properties of a Zr-4.6 wt.% Al alloy

    International Nuclear Information System (INIS)

    Raman, V.; Mukhopadhyay, P.; Banerjee, S.

    1978-01-01

    The influence of microstructure on the room temperature mechanical properties of a Zr-4.6 wt.% Al alloy was investigated. Quenching from the beta phase produced a significant solid solution hardening. On aging the alloy at low temperatures for short periods aluminium rejection from the solid solution occurred and a fine dispersion of a metastable Zr 3 Al phase (DO 19 structure) formed. The strengthening caused by the presence of these ordered particles was found to more than compensate the softening brought about by decreasing supersaturation. The high strength corresponding to this structure could be explained in terms of the contributions from the coherency strains associated with and the state of order within the metastable particles. Aging at these temperatures for longer periods or at higher temperatures gave rise to a lamellar distribution of the α-zirconium (aluminium) and the equilibrium Zr 3 Al (Ll 2 structure) phases. The strength associated with this lamellar structure was found to be appreciably lower and to be strongly dependent on the interlamellar spacing. Investigations of the fracture surfaces showed that the modes of fracture associated with these different microstructures were different. An attempt was made to rationalize the observed strength properties in terms of existing theoretical models. (Auth.)

  5. Microstructure and mechanical behavior of pulsed laser surface melted AISI D2 cold work tool steel

    International Nuclear Information System (INIS)

    Yasavol, N.; Abdollah-zadeh, A.; Ganjali, M.; Alidokht, S.A.

    2013-01-01

    Highlights: ► Melted zone contained fine dendrites in the bottom and equiaxed grains on the top. ► Microstructural refinements of PLSM led to microhardness enhancement. ► Higher scanning rate and lower laser energy were more effective to refine the microstructure. - Abstract: D2 cold work tool steel (CWTS) was subjected to pulse laser surface melting (PLSM) at constant frequency of 20 Hz Nd: YAG laser with different energies, scanning rate and pulse durations radiated to the surface. Characterizing the PLSM, with optical and field emission scanning electron microscopy, electron backscattered diffraction and surface hardness mapping technique was used to evaluate the microhardness and mechanical behavior of different regions of melting pool. Increasing laser energy and reducing the laser scanning rate results in deeper melt pool formation. Moreover, PLSM has led to entirely dissolution of the carbides and re-solidification of cellular/dendritic structure of a fine scale surrounded by a continuous interdendritic network. This caused an increase in surface microhardness, 2–4 times over that of the base metal.

  6. Microstructure and mechanical behavior of pulsed laser surface melted AISI D2 cold work tool steel

    Energy Technology Data Exchange (ETDEWEB)

    Yasavol, N. [Department of Materials Engineering, Tarbiat Modares University, P.O. Box 14115-143, Tehran (Iran, Islamic Republic of); Abdollah-zadeh, A., E-mail: zadeh@modares.ac.ir [Department of Materials Engineering, Tarbiat Modares University, P.O. Box 14115-143, Tehran (Iran, Islamic Republic of); Ganjali, M. [Materials and Energy Research Center, P.O. Box 14155-4777, Karaj (Iran, Islamic Republic of); Alidokht, S.A. [Department of Materials Engineering, Tarbiat Modares University, P.O. Box 14115-143, Tehran (Iran, Islamic Republic of)

    2013-01-15

    Highlights: Black-Right-Pointing-Pointer Melted zone contained fine dendrites in the bottom and equiaxed grains on the top. Black-Right-Pointing-Pointer Microstructural refinements of PLSM led to microhardness enhancement. Black-Right-Pointing-Pointer Higher scanning rate and lower laser energy were more effective to refine the microstructure. - Abstract: D2 cold work tool steel (CWTS) was subjected to pulse laser surface melting (PLSM) at constant frequency of 20 Hz Nd: YAG laser with different energies, scanning rate and pulse durations radiated to the surface. Characterizing the PLSM, with optical and field emission scanning electron microscopy, electron backscattered diffraction and surface hardness mapping technique was used to evaluate the microhardness and mechanical behavior of different regions of melting pool. Increasing laser energy and reducing the laser scanning rate results in deeper melt pool formation. Moreover, PLSM has led to entirely dissolution of the carbides and re-solidification of cellular/dendritic structure of a fine scale surrounded by a continuous interdendritic network. This caused an increase in surface microhardness, 2-4 times over that of the base metal.

  7. Influence of Austempering Heat Treatment on Microstructure and Mechanical Properties of Medium Carbon High Silicon Steel

    Science.gov (United States)

    Palaksha, P. A.; Ravishankar, K. S.

    2017-08-01

    In the present investigation, the influence of austempering heat treatment on the microstructure and mechanical properties of medium carbon high silicon steel was evaluated. The test specimens were machined from the as-received steel and were first austenitised at 900 °C for 45 minutes, followed by austempering heat treatment in salt bath at various temperatures 300 °C, 350 °C and 400 °C for a fixed duration of two hours, after that those specimens were air-cooled to room temperature. The characterization studies were carried out using optical microscope, scanning electron microscope (SEM) and x-ray diffractometer (XRD) and then correlated to the hardness and tensile properties. Results indicate that, the specimens austempered at lower temperature i.e. at 300 °C, which offered high hardness, tensile strength and lower ductility (1857 MPa and 13.3 %) due to the presence of acicular bainite i.e. lower bainite and also some martensite in the microstructure. At 350 °C, reduction in the tensile strength and hardness was observed, but comparatively higher ductility, which was favored by the presence of bainite laths i.e. upper bainitic structure along with higher retained austenite content. Finally at 400 °C, reduction in both ductility and tensile strength was observed, which is due to the precipitation of carbides between the banite laths, however good strain hardening response was observed at austempering temperatures of 350 °C and 400 °C.

  8. Microstructural evaluation and flexural mechanical behavior of pultruded glass fiber composites

    International Nuclear Information System (INIS)

    Chacon, Y.G.; Paciornik, S.; D'Almeida, J.R.M.

    2010-01-01

    Research highlights: → Mosaic images fully characterize the microstructure of heterogeneous materials. → Mosaic images have advantages over microscopy techniques using single fields. → UV and water immersion aging are minimized at the fibers' direction. → UV radiation produced marked changes on the composite surface. - Abstract: The microstructure of a pultruded glass fiber-reinforced composite was fully characterized using digital image analysis. A mosaic technique was used to analyze the entire thickness along specimens' cross-sections, enabling the visualization of the fiber, resin and filler spatial distribution. The advantages of this technique over the usual analysis on single fields, is presented and discussed. The fiber spatial distribution was correlated with flexural mechanical properties as a function of the specimens' position along the length and across the cross section of the composite. The influence of aging by immersion in distilled water and by UV radiation on flexural properties was also analyzed. Minor variation due to aging occurred when longitudinal specimens were tested. Transversally to the fibers, the matrix-dominated composite properties were more affected.

  9. Microstructures and mechanical properties of directionally solidified Ni-25%Si full lamellar in situ composites

    International Nuclear Information System (INIS)

    Zhang, Binggang; Li, Xiaopeng; Wang, Ting; Liu, Zheng

    2016-01-01

    Directional solidification experiments have been performed on Ni-25 at% Si alloy using electron beam floating zone method. A fully regular eutectic microstructures consisting of Ni, γ-Ni 31 Si 12 and β 1 -Ni 3 Si have been obtained. The influences of the directional solidification rate on the microstructures and properties of the full lamellar structures have been studied. The results show that the relationship between the mean interphase spacing (λ) and withdrawal rate (v) meets λ=29.9v −0.65 . The hardness increases with the increasing of growth rate (v) and decreasing of the interlamellar spacing (λ) which meets the relationship of H V =445.2v 0.14 and H V =910λ −0.21 . The maximum compressive strength, 2576 MPa, for DS samples is obtained by 10 mm/h. The average fracture toughness value found for 5 mm/h, 7 mm/h, 10 mm/h is 28.3 MPa m 1/2 , 29.1 MPa m 1/2 and 35.9 MPa m 1/2 , respectively. The crack bridging and crack deflection/interface debonding are the main toughening mechanism of Ni-25 at% Si with full lamellar structures.

  10. Cryogenic treatments on AISI 420 stainless steel: Microstructure and mechanical properties

    International Nuclear Information System (INIS)

    Prieto, G.; Ipiña, J.E. Perez; Tuckart, W.R.

    2014-01-01

    Cryogenic treatments have been employed over the last three decades in both tool and high-alloy steels to improve wear resistance, mainly through the transformation of retained austenite and the precipitation of fine carbides. The application of these treatments to low-alloy steels and even to non-ferrous materials is becoming the subject of several investigations, due to their potentiality to reduce wear. This study was aimed at analyzing the microstructural changes and the effect of cryogenic treatments on hardness and impact toughness in martensitic AISI 420 stainless steel. X-ray diffraction (XRD) was employed for phase analysis and characterization, while carbide volume fraction, size and composition evaluation was measured by using scanning electron microscopy (SEM-EDX) and Energy Dispersive Spectrometry (EDS). Hardness was assessed with Vickers technique and the impact toughness was measured by means of Charpy's V-notch tests. Fracture surfaces were analyzed by scanning electron microscopy to evaluate the fracture micromechanisms. In this study, it has been experimentally demonstrated that cryogenic treatments favors the precipitation of small carbides, which also present a more homogeneous size distribution. It was observed that this microstructural feature is responsible for the improvement in the mechanical properties of the material

  11. Microstructure and mechanical characteristics of a laser welded joint in SA508 nuclear pressure vessel steel

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Wei, E-mail: wei.guo-2@manchester.ac.uk [Laser Processing Research Centre, School of Mechanical, Aerospace and Civil Engineering, University of Manchester, Sackville Street, Manchester, M13 9 PL (United Kingdom); Dong, Shiyun [Laser Processing Research Centre, School of Mechanical, Aerospace and Civil Engineering, University of Manchester, Sackville Street, Manchester, M13 9 PL (United Kingdom); Institute of Laser Engineering, Beijing University of Technology, Beijing 100124 (China); Guo, Wei; Francis, John A.; Li, Lin [Laser Processing Research Centre, School of Mechanical, Aerospace and Civil Engineering, University of Manchester, Sackville Street, Manchester, M13 9 PL (United Kingdom)

    2015-02-11

    SA508 steels are typically used in civil nuclear reactors for critical components such as the reactor pressure vessel. Nuclear components are commonly joined using arc welding processes, but with design lives for prospective new build projects exceeding 60 years, new welding technologies are being sought. In this exploratory study, for the first time, autogenous laser welding was carried out on 6 mm thick SA508 Cl.3 steel sheets using a 16 kW fiber laser system operating at a power of 4 kW. The microstructure and mechanical properties (including microhardness, tensile strength, elongation, and Charpy impact toughness) were characterized and the microstructures were compared with those produced through arc welding. A three-dimensional transient model based on a moving volumetric heat source model was also developed to simulate the laser welding thermal cycles in order to estimate the cooling rates included by the process. Preliminary results suggest that the laser welding process can produce welds that are free of macroscopic defects, while the strength and toughness of the laser welded joint in this study matched the values that were obtained for the parent material in the as-welded condition.

  12. Morphology, microstructure, and mechanical properties of laser-welded joints in GH909 alloy

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Chunming; Cai, Yuanzheng; Hu, Chongjing; Zhang, Xiong; Yan, Fei; Hu, Xiyuan [Huazhong University of Science and Technology, Wuhan (China)

    2017-05-15

    The experimental laser welding of GH909 alloy was conducted in this study. The morphology, microstructure, and mechanical properties of laser-welded joints were analyzed by scanning electron microscopy, energy diffraction spectroscopy, and other techniques. Results revealed that the microstructure of the welded joints mainly consisted of tiny cellular structures, dendritic structures, and equiaxed crystals. Pores appeared in the interdendritic regions because of the insufficient local feeding of molten metal during solidification. Nb segregation in the heat-affected zone caused liquation cracking, whereas C segregation further induced the formation of carbide precipitates along the grain boundaries during the welding thermal cycle. The instability of the keyhole significantly promoted the escape of the metal vapor/plasma from the hole; as a result, porosity defects formed in the weld. The average tensile strength of the test joints was 756 MPa, which is 93.1 % of that of the base metal. The average microhardness of the weld zone (250 HV) was higher than that of the GH909 alloy substrate (208 HV), peaking at 267 HV. Microcracks appeared along the grain boundaries, proving that the grain boundaries were the weakest areas in the joint.

  13. Microstructure and mechanical properties of stainless steel/calcium silicate composites manufactured by selective laser melting.

    Science.gov (United States)

    Zheng, Zeng; Wang, Lianfeng; Jia, Min; Cheng, Lingyu; Yan, Biao

    2017-02-01

    Selective laser melting (SLM) is raised as one kind of additive manufacturing (AM) which is based on the discrete-stacking concept. This technique can fabricate advanced composites with desirable properties directly from 3D CAD data. In this research, 316L stainless steel (316L SS) and different fractions of calcium silicate (CaSiO 3 ) composites (weight fractions of calcium silicate are 0%, 5%,10% and 15%, respectively) were prepared by SLM technique with a purpose to develop biomedical metallic materials. The relative density, tensile, microhardness and elastic modulus of the composites were tested, their microstructures and fracture morphologies were observed using optical microscope (OM), scanning electron microscopy (SEM) and X-ray diffraction (XRD). It was found that the addition of CaSiO 3 particles influenced the microstructure and mechanical properties of specimens significantly. The CaSiO 3 precipitates from the overlap of adjacent tracks and became the origin of the defects. The tensile strength of specimens range 320-722MPa. The microhardness and elastic modulus are around 250HV and 215GPa respectively. These composites were ductile materials and the fracture mode of the composites was mixed mode of ductile and brittle fracture. The 316L SS/CaSiO 3 composites can be a potential biomedical metallic materials in the medical field. Copyright © 2016. Published by Elsevier B.V.

  14. Selective laser melting of carbon/AlSi10Mg composites: Microstructure, mechanical and electronical properties

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Xiao; Song, Bo, E-mail: bosong@hust.edu.cn; Fan, Wenrui; Zhang, Yuanjie; Shi, Yusheng

    2016-04-25

    Carbon nanotubes/AlSi10Mg composites has drawn lots of attention in structural engineering and functional device applications due to its extraordinary high elastic modulus and mechanical strength as well as excellent electrical and thermal conductivities. In this study, the CNTs/AlSi10Mg composites was firstly prepared and then processed by selective laser melting. The powder preparation, SLM process, and microstructure evolution, properties were clarified. The results showed that CNTs were decomposed due to the direct interaction with the laser beam. The SLMed composites displayed a similar microstructure to that of SLMed AlSi10Mg. The common brittleness phase Al{sub 4}C{sub 3} didn't form, and the carbon dispersion strengthening was observed. The electrical resistivity of the composites was reduced significantly and the hardness was improved. - Highlights: • Carbon nanotubes/AlSi10Mg powder were prepared by slurry ball milling process. • Carbon nanotubes/AlSi10Mg composites were firstly prepared by SLM. • The electrical resistivity of the composites was significantly reduced and hardness was improved.

  15. Rapid Tempering of Martensitic Stainless Steel AISI420: Microstructure, Mechanical and Corrosion Properties

    Science.gov (United States)

    Abbasi-Khazaei, Bijan; Mollaahmadi, Akbar

    2017-04-01

    In this research, the effect of rapid tempering on the microstructure, mechanical properties and corrosion resistance of AISI 420 martensitic stainless steel has been investigated. At first, all test specimens were austenitized at 1050 °C for 1 h and tempered at 200 °C for 1 h. Then, the samples were rapidly reheated by a salt bath furnace in a temperature range from 300 to 1050 °C for 2 min and cooled in air. The tensile tests, impact, hardness and electrochemical corrosion were carried out on the reheated samples. Scanning electron microscopy was used to study the microstructure and fracture surface. To investigate carbides, transmission electron microscopy and also scanning electron microscopy were used. X-ray diffraction was used for determination of the retained austenite. The results showed that the minimum properties such as the tensile strength, impact energy, hardness and corrosion resistance were obtained at reheating temperature of 700 °C. Semi-continuous carbides in the grain boundaries were seen in this temperature. Secondary hardening phenomenon was occurred at reheating temperature of 500 °C.

  16. Cryogenic treatments on AISI 420 stainless steel: Microstructure and mechanical properties

    Energy Technology Data Exchange (ETDEWEB)

    Prieto, G., E-mail: german.prieto@uns.edu.ar [Tribology Group, Universidad Nacional del Sur/CONICET, Av. Alem 1253, 8000 Bahía Blanca (Argentina); Ipiña, J.E. Perez [GMF UNComa/CONICET, Buenos Aires 1400, 8300 Neuquén (Argentina); Tuckart, W.R. [Tribology Group, Universidad Nacional del Sur/CONICET, Av. Alem 1253, 8000 Bahía Blanca (Argentina)

    2014-05-01

    Cryogenic treatments have been employed over the last three decades in both tool and high-alloy steels to improve wear resistance, mainly through the transformation of retained austenite and the precipitation of fine carbides. The application of these treatments to low-alloy steels and even to non-ferrous materials is becoming the subject of several investigations, due to their potentiality to reduce wear. This study was aimed at analyzing the microstructural changes and the effect of cryogenic treatments on hardness and impact toughness in martensitic AISI 420 stainless steel. X-ray diffraction (XRD) was employed for phase analysis and characterization, while carbide volume fraction, size and composition evaluation was measured by using scanning electron microscopy (SEM-EDX) and Energy Dispersive Spectrometry (EDS). Hardness was assessed with Vickers technique and the impact toughness was measured by means of Charpy's V-notch tests. Fracture surfaces were analyzed by scanning electron microscopy to evaluate the fracture micromechanisms. In this study, it has been experimentally demonstrated that cryogenic treatments favors the precipitation of small carbides, which also present a more homogeneous size distribution. It was observed that this microstructural feature is responsible for the improvement in the mechanical properties of the material.

  17. Microstructure and mechanical properties in cast magnesium-neodymium binary alloys

    International Nuclear Information System (INIS)

    Yan Jingli; Sun Yangshan; Xue Feng; Xue Shan; Tao Weijian

    2008-01-01

    The microstructure, tensile properties and creep behavior of three binary magnesium-neodymium (Mg-Nd) based alloys were investigated. The microstructure of all the alloys consists of the dendritic α-Mg matrix and a divorced eutectic Mg 12 Nd. With the increase of neodymium addition, the volume fraction of the Mg 12 Nd phase increases and an interphase network is visible with 4 wt% of neodymium addition. The addition of Nd to Mg causes significant improvement of creep properties and the creep resistance increases with the increase of Nd addition, which is account for by the combination of precipitation and solid solution hardening. For the Mg-2 wt%Nd alloy, a stress exponent of 4.5 and an apparent activation energy of 151.8 kJ/mol were obtained at 175 deg. C/50-90 MPa and 150-225 deg. C/70 MPa, respectively, suggesting that the mechanism responsible for creep in the present investigation is dislocation climb

  18. Effect of Hot Rolling on the Microstructure and Mechanical Properties of Nitrogen Alloyed Austenitic Stainless Steel

    Science.gov (United States)

    Chenna Krishna, S.; Karthick, N. K.; Jha, Abhay K.; Pant, Bhanu; Cherian, Roy M.

    2018-05-01

    In the present investigation, the effect of multi-pass hot rolling in the temperature range of 700-1000 °C on the microstructure and mechanical properties of nitrogen alloyed austenitic stainless steel was studied with the aid of optical microscopy, tensile testing and x-ray diffraction measurements. The microstructural changes that occurred in the hot rolled specimens were elongation of grains in rolling direction, nucleation of new grains at the grain boundaries of elongated grains and growth of nucleated grains to form fully recrystallized grains. Elongated grains formed at lower rolling temperature (700-800 °C) due to inadequate strain/temperature for the initiation of dynamic recrystallization. At higher rolling temperature (900-1000 °C), fine grains formed due to dynamic recrystallization. Tensile properties showed strong dependency on the rolling temperature. Tensile strength increased with the decrease in the rolling temperature at the cost of ductility. Maximum strength was observed in samples hot rolled at 700 °C with yield strength of 917 MPa and ductility of 25%. This variation in the tensile properties with the rolling temperature is attributed to changes in the dislocation density and grain structure. The estimated yield strength from the dislocation density, solid solution and grain boundary strengthening closely matched with experimentally determined yield strength confirming the role of dislocation density and grain size in the strengthening.

  19. INFLUENCE OF REPAINTING ON THE MECHANICAL PROPERTIES, SURFACE TOPOGRAPHY AND MICROSTRUCTURE OF POLYESTER POWDER COATINGS

    Directory of Open Access Journals (Sweden)

    Mirosław Szala

    2017-06-01

    This study examined three different electrostatic spray epoxy coatings with matt, silk gloss and fine structure-matt finish. Test panels were prepared as single- and double-layer paint coatings on the aluminum alloy 6060 substrate. Hence, six test sets of coatings were deposited. Each set contained six samples. The microstructure of the cross section of coating was investigated by scanning electron microscopy (SEM and light optical microscopy (metallographic and stereoscopy microscope. The chemical composition of coating was analyzed by the SEM-EDS method. The 2D surface roughness of single- and double-layer coatings and 3D surface topography maps were examined using a profile measurement gauge. The mechanical properties of coatings were measured by cupping, bending, impact, adhesion to substrate tests run according to standard procedures. As a result, the influence of repainting of polyester powder coatings on their properties was determined. The results demonstrate that repainting has no effect on the microstructure and coating adhesion to substrate as well as the bending test results and roughness of matt and silk gloss coatings. It has been found that repainting affects the results of impact and cupping tests as well as the roughness of samples with fine structure surface finish.

  20. Effect of vibration on microstructures and mechanical properties of 304 stainless steel GTA welds

    Science.gov (United States)

    Hsieh, Chih-Chun; Lai, Chien-Hong; Wu, Weite

    2013-07-01

    This study investigates the microstructures and mechanical properties of 304 stainless steel at various vibration frequencies during simultaneous vibration welding. The experimental results demonstrated that simultaneous vibration welding could accelerate the nucleation and grain refinement of the microstructures. The effect of the grain refinement was more evident at the resonant frequency (375 Hz) and a minimum content of residual δ-ferrite (4.0%). The γ phase grew in the preferential orientation of the (111) direction with and without vibration. The full width at half maximum of the diffraction peak widened after the vibration, which was attributed to the grain refinement. The residual stress could be efficiently removed through simultaneous vibration welding when the amplitude of the vibration was increased. Furthermore, the lowest residual stress (139 MPa) was found when the vibration frequency was 375 Hz. The hardness and Young's modulus exhibited slight increases with low and medium frequencies. The hardness values were increased by 7.6% and Young's modulus was increased by 15% when the vibration frequency was resonant (375 Hz).

  1. Effects of Bamboo Shoot Dietary Fiber on Mechanical Properties, Moisture Distribution, and Microstructure of Frozen Dough

    Directory of Open Access Journals (Sweden)

    Hua Zhang

    2017-01-01

    Full Text Available In this paper, the effects of Bamboo shoot dietary fiber (BSDF on the mechanical properties, moisture distribution, and microstructure of frozen dough were investigated. The state and distribution of water in frozen dough was determined by differential scanning calorimetry (DSC and low-field nuclear magnetic resonance (LNMR spectroscopy. The microstructure of frozen dough was studied. The structure of the gluten protein network found in wheat flour dough was studied by scanning electron microscopy (SEM. The result showed that the BSDF could significantly improve the viscoelasticity and extensibility of frozen dough after thawing in a dose-dependent manner. It was significantly improved with the increase in the addition amount of BSDF (P<0.05. DSC analysis showed that the freezable water content and thermal stability of frozen dough were increased after the addition of BSDF. LNMR analysis showed that the appropriate (<0.1% addition amount of BSDF could significantly (P<0.05 decline the contents of bound water. Meanwhile, the loose bound water and free water were raised significantly (P<0.05 after the addition of BSDF. Moreover, the addition of BSDF induces arrangement of starch granule and gluten network in frozen dough. BSDF can be used as a novel quality improver of frozen dough.

  2. Microstructural Characteristics and Mechanical Properties of 2205/AZ31B Laminates Fabricated by Explosive Welding

    Directory of Open Access Journals (Sweden)

    Yan Li

    2017-04-01

    Full Text Available A bimetal composite of 2205 duplex stainless steel and AZ31B magnesium alloy was cladded successfully through the method of explosive welding. The microstructural characteristics and mechanical properties of 2205/AZ31B bimetal composite are discussed. The interface of 2205/AZ31B bimetallic composite was a less regular wavy morphology with locally melted pockets. Adiabatic shear bands occurred only in the AZ31B side near explosive welding interface. The microstructure observed with EBSD showed a strong refinement near the interface zones. Line scan confirmed that the interface had a short element diffusion zone which would contribute to the metallurgical bonding between 2205 duplex stainless steel and AZ31B magnesium alloy. The value of micro-hardness near the bonding interface of composite plate increased because of work hardening and grain refinement. The tensile shear strength of bonding interface of 2205/AZ31B composite was 105.63 MPa. Tensile strength of 2205/AZ31B composite material was higher than the base AZ31B. There were two abrupt drops in stress in the stress–strain curves of the 2205/AZ31B composite materials.

  3. Influence of Lanthanum on Solidification, Microstructure, and Mechanical Properties of Eutectic Al-Si Piston Alloy

    Science.gov (United States)

    Ahmad, R.; Asmael, M. B. A.

    2016-07-01

    The effects of Lanthanum (La) concentration on the solidification parameters of the α-Al, Al-Si, and Al-Cu phases and on the microstructure, tensile, and hardness properties of eutectic Al-Si-Cu-Mg alloy were systematically investigated. The solidification parameters were examined using computer-aided cooling curve thermal analysis (CA-CCTA). The cooling curve and microstructure analysis showed that La altered the Si structure. The nucleation and growth temperatures of eutectic Si decreased when 0.3 wt.% La was added, and a high depression temperature was obtained with 1.0 wt.% La. High amounts of La considerably modified the Si structure and decreased the area and aspect ratio by 69.9 and 51%, respectively. The thermal analysis result recorded a faster freezing time with the La addition and a 36% alteration in the secondary dendrite arm spacing. Two secondary or ternary La-rich intermetallic phases were formed with needle- and plate-like structures. Furthermore, the mechanical properties were investigated by hardness and tensile tests with different La concentrations. The addition of small amounts of La (0.1 wt.%) significantly improved the ultimate tensile strength and quality index of the Al-Si-Cu-Mg alloy. In addition, the hardness value of Al-11Si-Cu increased by 7-8% with the increasing amount of La added.

  4. Microstructural characterization and mechanical properties of Excel alloy pressure tube material

    Science.gov (United States)

    Sattari, Mohammad

    Microstructural characterization and mechanical properties of Excel (Zr-3.5%Sn-0.8%Mo-0.8%Nb), a dual phase alphaZr -hcp and betaZr-bcc pressure tube material, is discussed in the current study which is presented in manuscript format. Chapter 3 discusses phase transformation temperatures using different techniques such as quantitative metallography, differential scanning calorimetry (DSC), and electrical resistivity. It was found that the alphaZr → alphaZr+beta Zr and alphaZr+betaZr → betaZr transformation temperatures are in the range of 600-690°C and 960-970°C respectively. Also it was observed that upon quenching from temperatures below ˜860°C the martensitic transformation of betaZr to alpha'--hcp is halted and instead the microstructure transforms into retained Zr with o hexagonal precipitates inside betaZr grains. Chapter 4 deals with aging response of Excel alloy. Precipitation hardening was observed in samples water-quenched from high in the alphaZr+beta Zr or betaZr regions followed by aging. The optimum aging conditions were found to be 450°C for 1 hour. Transmission electron microscopy (TEM) showed dispersion of fine precipitates (˜10nm) inside the martensitic phase. Energy dispersive X-ray spectroscopy (EDS) showed the chemical composition of precipitates to be Zr-30wt%Mo-25wt%Nb-2wt%Fe. Electron crystallography using whole pattern symmetry of the convergent beam electron diffraction (CBED) patterns together with selected area diffraction (SAD) polycrystalline ring patterns, suggests the -6m2 point group for the precipitates belonging to hexagonal crystal structure, with a= 2.936 A and c=4.481 A, i.e. c/a =1.526. Crystallographic texture and high temperature tensile properties as well as creep-rupture properties of different microstructures are discussed in Chapter 5. Texture analysis showed that solution treatment high in the alpha Zr+betaZr or betaZr regions followed by water quenching or air cooling results in a more random texture compared

  5. Effects of Sm addition on microstructure and mechanical properties of a Mg-10Y alloy

    Directory of Open Access Journals (Sweden)

    Li Quanan

    2014-01-01

    Full Text Available To further increase the mechanical properties, 0.5wt.% Sm was introduced to a Mg-10Y alloy in this study. The effects of Sm addition on the microstructures and mechanical properties of the Mg-10Y alloy, especially the aged Mg-10Y alloy, were investigated. The microstructure observation and tensile tests were performed by using an optical microscopy, a scanning electron microscopy and a universal material testing machine, respectively. The phase analysis was performed using X-ray diffractometer. The results show that the 0.5wt.% Sm addition can not only promote the formation of fine and dispersed Mg24Y5 phases, but also improve their morphology and distribution; it also increases the thermal stability of Mg24Y5 phases. Sm addition is seen to increase the ultimate tensile strength of Mg-10Y alloy at elevated temperatures (200, 250, 300 and 350 ℃, while decrease the elongation. But the elongation is still up to 7.5% even at 350 ℃. In the range of 250 ℃ to 300℃, the ultimate tensile strength of the alloy reaches its maximum (with a range average of 235 MPa and is not sensitive to the temperature change, which is very useful to the application of heat-resistant magnesium alloys. Even at 350 ℃, the ultimate tensile strength of Mg-10Y-0.5Sm is still up to 155 MPa. Considering both of the ultimate tensile strength and elongation, the maximum application temperature of the Mg-10Y-0.5Sm alloy can be up to 300 ℃. The strengthening mechanisms of Mg-10Y-0.5Sm alloy are mainly attributed to dispersion strengthening of Mg24Y5 phase particles with a certain solubility of Sm and grain refinement strengthening of α-Mg matrix.

  6. Effect of Organic Material on Mechanical, Hydrological, and Microstructural Properties of Mudstones

    Science.gov (United States)

    Altobelli, M. A.; Reece, J. S.

    2016-12-01

    In this research we analyze the influence of organic material on the mechanical and flow properties of mudstones. We uniformly mix peat, milled and harvested by Bord na Móna from the surface of bogs in Ireland, with natural mudstone from Site C0011 in the Nankai Trough, offshore Japan, obtained during Integrated Ocean Drilling Program Expedition 322. The mudstone had previously been disaggregated into a homogeneous dry powder of clay- and silt-sized particles. The peat is ground and dry-sieved to achieve a similar particle size distribution as the mudstone (mechanical and hydrological processes affected by peat, we prepare dry peat-mudstone mixtures with three different peat concentrations: 0 wt%, 5 wt%, and 10 wt%. Then, these peat - mudstone mixtures are saturated with deionized water at a water content of 109%, formed into stable slurries, and uniaxially compressed to an axial stress of 100 kPa using resedimentation, a method that simulates the natural behavior of deposition and burial in the laboratory under controlled conditions. How the organic material interacts with the mudstone matrix and pore fluid under compression influences the physical properties of the mudstones such as porosity, compressibility, and permeability; all of which are measured in the resedimentation experiments. We will also analyze the microstructural changes as a function of peat concentration using a petrographic microscope and scanning electron microscope. Due to the fibrous and absorbent nature of peat, we anticipate the peat to force tightly packed clay particles in the mudstone apart resulting in a looser microstructure and increased porosity, and thus, a higher compressibility and permeability. Understanding the controls on the mechanical and flow properties of hydrocarbon-bearing, fine-grained formations is crucial for exploration and successful production from hydrocarbon reservoirs. Additionally, this study has large implications for soil water storage and soil amendment to

  7. Microstructure, mechanical analysis and optimal selection of 7075 aluminum alloy based composite reinforced with alumina nanoparticles

    International Nuclear Information System (INIS)

    Ezatpour, H.R.; Torabi Parizi, M.; Sajjadi, S.A.; Ebrahimi, G.R.; Chaichi, A.

    2016-01-01

    Aluminum metal-matrix nanocomposites (AMMNCs) fabricated by conventional stir-casting process usually show high porosity and poor distribution of nanoparticles within the matrix. In the current study, for the improvement of nanoparticles distribution in the aluminum matrix and enhancement of the mechanical properties, a mixture of Al/nano-Al 2 O 3 powders were injected by pure argon gas into the molten 7075 aluminum alloy and this mixture was extruded at high temperature. Mechanical behavior of the final product was investigated by tensile and compression tests, hardness measurements, Scanning Electron Microscopy (SEM), High Resolution Transmission Electron Microscopy (HRTEM) and Optical Microscopy. This nanocomposite exhibited some superior properties such as a fine grain microstructure and a reasonable uniform distribution of nanoparticles in the matrix. Mechanical experiments results confirmed that the addition of Al 2 O 3 nanoparticles and the extrusion process effectively improved ultimate tensile strength, compression strength and hardness. In next step, we used a Preference Selection Index (PSI) materials selection method to select best combination of strength and workability of Al7075−Al 2 O 3 nanocomposites. By this method, extruded Al7075/0.4 and 0.8 wt % Al 2 O 3 has best combination of strength and workability. - Highlights: • Injection Al/Al 2 O 3 powder is benefit way for improving nanoparticles distribution. • Nanocomposites present superior mechanical properties. • Extrusion process improved significantly mechanical properties of nanocomposites. • Preference Selection Index is a simple and benefit method in material selection.

  8. Fracture mechanics of ceramics. Vol. 8. Microstructure, methods, design, and fatigue

    International Nuclear Information System (INIS)

    Bradt, R.C.; Evans, A.G.; Hasselman, D.P.H.; Lange, F.F.

    1986-01-01

    This paper presents information on the following topics: fracture mechanics and microstructures; non-lubricated sliding wear of Al 2 O 3 , PSZ and SiC; mixed-mode fracture of ceramics; some fracture properties of alumina-containing electrical porcelains; transformation toughening in the Al 2 O 3 -Cr 2 O 3 /ZrO 2 -HfO 2 system; strength toughness relationships for transformation toughened ceramics; tensile strength and notch sensitivity of Mg-PSZ; fracture mechanisms in lead zirconate titanate ceramics; loading-unloading techniques for determining fracture parameters of brittle materials utilizing four-point bend, chevron-notched specimens; application of the potential drop technique to the fracture mechanics of ceramics; ceramics-to-metal bonding from a fracture mechanics perspective; observed changes in fracture strength following laser irradiation and ion beam mixing of Ni overlayers on sintered alpha-SiC; crack growth in single-crystal silicon; a fracture mechanics and non-destructive evaluation investigation of the subcritical-fracture process in rock; slow crack growth in sintered silicon nitride; uniaxial tensile fatigue testing of sintered silicon carbide under cyclic temperature change; and effect of surface corrosion on glass fracture

  9. Investigations into the Mechanical Properties and Microstructural Behavior of Foreign and Locally Fabricated Brake Disc

    Directory of Open Access Journals (Sweden)

    Basil Olufemi Akinnuli

    2017-11-01

    Full Text Available The present work reports investigations on mechanical and microstructural properties of foreign and locally fabricated brake disc. From safety point of view, brake disc is a crucial component of the braking system. Foreign brake disc (FBD are known for their long life span and better mechanical properties under service condition. However, locally fabricated brake disc (LFBD may possess similar or better mechanical properties than the foreign one. Therefore, the need to investigate their mechanical properties in order to determine which brake disc has better mechanical properties under the same service condition. It was observed that a high machinability index occurs in the locally fabricated brake disc as compared with the foreign brake disc, noticeable in the softness and weak graphite flakes formation in the matrix. Higher resistance to indentation was noticeable in the foreign brake disc as compared to the locally fabricated disc. The locally fabricated brake disc however, witnesses about 22% reduction in toughness compared to the foreign brake disc. An offshoot from this research will enhance the choice of material selection in the manufacturing of brake disc and assurance of locally made spare parts at affordable prices, and the provision of employment opportunities by establishing spare-parts production and allied industries

  10. Microstructure and mechanical properties of commercially pure aluminum processed by accumulative back extrusion

    International Nuclear Information System (INIS)

    Haghdadi, N.; Zarei-Hanzaki, A.; Abou-Ras, D.

    2013-01-01

    Accumulative back extrusion (ABE), as a new severe plastic deformation (SPD) method, was applied on a commercially pure aluminum, resulting in an ultrafine microstructure. The grain refinement was attributed to the shearing and/or to the mechanical partitioning of the initial coarse grains as well as different dynamic recrystallization mechanisms (i.e., discontinues and continues ones). The effects of imposing several passes along with the strain reversal path method during consecutive ABE passes were discussed. Mechanical characterization revealed that the yield and ultimate strength of pure Al were significantly increased through applying ABE. This was related to grain boundary and dislocation strengthening, as well as to Orowan dislocation bowing mechanisms. The elongation, however, was deteriorated after ABE processing. This was interpreted through the lack of ability of the material to accommodate the ABE-induced strain, inhomogeneous distribution of strain across the ABE-processed workpieces, and the reduced work hardening capacity of the fine-grained aluminum. The formability index and static toughness were also considered to verify the overall mechanical performance of the ABE-processed pure Al

  11. [Optimizing antibiotics policy in the Netherlands. VI. SWAB advice: no selective decontamination of intensive care patients on mechanical ventilation

    NARCIS (Netherlands)

    Bonten, M.J.; Kullberg, B.J.; Filius, P.M.

    2001-01-01

    The Working Party on Antibiotic Policy (Dutch acronym is SWAB) has issued a guideline in which the pro and cons of the routine use of selective decontamination (SD) in patients in intensive care (IC) on mechanical ventilation are compared in order to decide whether SD is indicated. The effectiveness

  12. Casting and stress-strain simulations of a cast ductile iron component using microstructure based mechanical behavior

    International Nuclear Information System (INIS)

    Olofsson, Jakob; Svensson, Ingvar L

    2012-01-01

    The industrial demand for increased component performance with concurrent reductions in component weight, development times and verifications using physical prototypes drives the need to use the full potential of casting and Finite Element Method (FEM) simulations to correctly predict the mechanical behavior of cast components in service. The mechanical behavior of the component is determined by the casting process, and factors as component geometry and casting process parameters are known to affect solidification and microstructure formation throughout the component and cause local variations in mechanical behavior as well as residual stresses. Though residual stresses are known to be an important factor in the mechanical behavior of the component, the importance of local mechanical behavior is not well established and the material is typically considered homogeneous throughout the component. This paper deals with the influence of solidification and solid state transformation on microstructure formation and the effect of local microstructure variations on the mechanical behavior of the cast component in service. The current work aims to investigate the coupling between simulation of solidification, microstructure and local variations in mechanical behavior and stress-strain simulation. This is done by performing several simulations of a ductile iron component using a recently developed simulation strategy, a closed chain of simulations for cast components, able to predict and describe the local variations in not only elastic but also plastic behavior throughout the component by using microstructural parameters determined by simulations of microstructural evolution in the component during the casting process. In addition the residual stresses are considered. The results show that the FEM simulation results are significantly affected by including microstructure based mechanical behavior. When the applied load is low and the component is subjected to stress levels

  13. Revealing microstructural and mechanical characteristics of cold-drawn pearlitic steel wires undergoing simulated galvanization treatment

    Energy Technology Data Exchange (ETDEWEB)

    Fang Feng, E-mail: fangfeng@seu.edu.cn [School of Materials Science and Engineering, Southeast University, Nanjing 211189 (China); Hu Xianjun [School of Materials Science and Engineering, Southeast University, Nanjing 211189 (China); Jiangsu Sha-Steel Group, Zhangjiagang City, Jiangsu Province 215625 (China); Chen Shaohui [Jiangsu Sha-Steel Group, Zhangjiagang City, Jiangsu Province 215625 (China); Xie Zonghan [School of Engineering, Edith Cowen University, Joondalup, WA 6027 (Australia); Jiang Jianqing [School of Materials Science and Engineering, Southeast University, Nanjing 211189 (China)

    2012-06-15

    Highlights: Black-Right-Pointing-Pointer Annealing time on microstructure and mechanical properties of cold-drawn steel wires were studied. Black-Right-Pointing-Pointer Exothermic peak in cold-drawn wire was resulting from the spheroidization of lamellar cementite. Black-Right-Pointing-Pointer Spheroidization of lamellar cementite is the main effect for torsion property of wires after annealing. - Abstract: Spheroidization of lamellar cementite often occurs in cold-drawn pearlitic steel wires during galvanizing treatment, leading to the degradation of mechanical properties. Therefore, it is important to understand effects of galvanization process on microstructure and mechanical properties of cold-drawn wires. In this paper, cold-drawn steel wires were fabricated by cold drawing pearlitic steel rods from 13 mm to 6.9 mm in diameter. Thermal annealing at 450 Degree-Sign C was used to simulate galvanizing treatment of steel wires. Tensile strength, elongation and torsion laps of steel rods and wires with, and without, annealing treatment were determined. Microstructure was observed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). In addition, differential scanning calorimetry (DSC) was used to probe the spheroidization temperature of cementite. Experimental results showed that tensile strength of wires increased from 1780 MPa to 1940 MPa for annealing <5 min, and then decreased. Tensile strength became constant for annealing >10 min. Elongation of wires decreased for annealing <2.5 min, and then recovered slightly. It approached a constant value for annealing >5 min. Tensile strength and elongation of wires were both influenced by the strain age hardening and static recovery processes. Notably, torsion laps of wires hardly changed when annealing time was less than 2.5 min, and then decreased rapidly. Its value became constant when the hold time is greater than 10 min. Lamellar cementite began to spheroidize at annealing >2.5 min

  14. Effect of rapid solidification on the microstructure and mechanical properties of hot-pressed Al-20Si-5Fe alloys

    International Nuclear Information System (INIS)

    Rajabi, M.; Vahidi, M.; Simchi, A.; Davami, P.

    2009-01-01

    The aim of this work is to study the effect of cooling rate and subsequent hot consolidation on the microstructural features and mechanical strength of Al-20Si-5Fe-2X (X = Cu, Ni and Cr) alloys. Powder and ribbons were produced by gas atomization and melt spinning processes at two different cooling rates of 1 x 10 5 K/s and 5 x 10 7 K/s. The microstructure of the products was examined using optical microscopy, scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. The particles were consolidated by hot pressing at 400 deg. C/250 MPa/1 h under a high purity argon atmosphere and the microstructure, hardness and compressive strength of the compacts were evaluated. Results showed a profound effect of the cooling rate, consolidation stage, and transition metals on the microstructure and mechanical strength of Al-20Si-5Fe alloys. While microstructural refining was obtained at both cooling rates, the microstructure of the atomized powder exhibited the formation of fine primary silicon (∼ 1 μm), eutectic Al-Si phase with eutectic spacing of ∼ 300 nm, and δ-iron intermetallic. Supersaturated Al matrix containing 5-7 at.% silicon and nanometric Si precipitates (20-40 nm) were determined in the microstructure of the melt-spun ribbons. The hot consolidation resulted in coarsening of Si particles in the atomized particles, and precipitation of Si and Fe-containing intermetallics from the supersaturated Al matrix in the ribbons. The consolidated ribbons exhibited higher mechanical strength compared to the atomized powders, particularly at elevated temperatures. The positive influence of the transition metals on the thermal stability of the Al-20Si-5Fe alloy was noticed, particularly in the Ni-containing alloy.

  15. Enantioseparation and chiral recognition mechanism of new chiral derivatives of xanthones on macrocyclic antibiotic stationary phases.

    Science.gov (United States)

    Fernandes, Carla; Tiritan, Maria Elizabeth; Cass, Quezia; Kairys, Visvaldas; Fernandes, Miguel Xavier; Pinto, Madalena

    2012-06-08

    A chiral HPLC method using four macrocyclic antibiotic chiral stationary phases (CSPs) has been investigated for determination of the enantiomeric purity of fourteen new chiral derivatives of xanthones (CDXs). The separations were performed with the CSPs Chirobiotic T, Chirobiotic TAG, Chirobiotic V and Chirobiotic R under multimodal elution conditions (normal-phase, reversed-phase and polar ionic mode). The analyses were performed at room temperature in isocratic mode and UV and CD detection at a wavelength of 254 nm. The best enantioselectivity and resolution were achieved on Chirobiotic R and Chirobiotic T CSPs, under normal elution conditions, with R(S) ranging from 1.25 to 2.50 and from 0.78 to 2.06, respectively. The optimized chromatographic conditions allowed the determination of the enantiomeric ratio of eight CDXs, always higher than 99%. In order to better understand the chromatographic behavior at a molecular level, and the structural features associated with the chiral recognition mechanism, computational studies by molecular docking were carried out using VDock. These studies shed light on the mechanisms involved in the enantioseparation for this important class of chiral compounds. Copyright © 2012 Elsevier B.V. All rights reserved.

  16. Microstructure and Mechanical Properties of Inconel 625 Alloy on Low Carbon Steel by Heat Treatment after Overlay Welding

    International Nuclear Information System (INIS)

    Kim, Seungpil; Jang, Jaeho; Kim, Jungsoo; Kim, Byung Jun; Sohn, Keun Yong; Nam, Dae-Geun

    2016-01-01

    Overlay welding technique is one of methods used to improve metal mechanical properties such as strength, toughness and corrosion resistance. Generally, Inconel 625 alloy is used for overlay welding layer on low carbon steels for economic consideration. However, the method produces some problems in the microstructure of the cast structure and some defects, caused by the elevated temperatures of the overlay process. To resolve these problems, heat treatments are required. In this study, Inconel 625 alloy was welded on a low carbon steel by the overlay welding process to investigate the resulting microstructure and mechanical properties. A double heat treatment was performed to improve the mechanical properties of the welding and substrate layers. It was found that Inconel 625 alloy had an austenite microstructure after the first heat treatment, but the low carbon steel had a ferrite-pearlite microstructure after the second heat treatment. After the double heat treatment, the sample showed the optimum hardness because of grain refinement and homogenization of the microstructure.

  17. Microstructure and Mechanical Properties of Inconel 625 Alloy on Low Carbon Steel by Heat Treatment after Overlay Welding

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Seungpil; Jang, Jaeho; Kim, Jungsoo; Kim, Byung Jun; Sohn, Keun Yong; Nam, Dae-Geun [Korea Institute of Industrial Technology, Busan (Korea, Republic of)

    2016-08-15

    Overlay welding technique is one of methods used to improve metal mechanical properties such as strength, toughness and corrosion resistance. Generally, Inconel 625 alloy is used for overlay welding layer on low carbon steels for economic consideration. However, the method produces some problems in the microstructure of the cast structure and some defects, caused by the elevated temperatures of the overlay process. To resolve these problems, heat treatments are required. In this study, Inconel 625 alloy was welded on a low carbon steel by the overlay welding process to investigate the resulting microstructure and mechanical properties. A double heat treatment was performed to improve the mechanical properties of the welding and substrate layers. It was found that Inconel 625 alloy had an austenite microstructure after the first heat treatment, but the low carbon steel had a ferrite-pearlite microstructure after the second heat treatment. After the double heat treatment, the sample showed the optimum hardness because of grain refinement and homogenization of the microstructure.

  18. Experimental Evolution of Diverse Strains as a Method for the Determination of Biochemical Mechanisms of Action for Novel Pyrrolizidinone Antibiotics.

    Science.gov (United States)

    Beabout, Kathryn; McCurry, Megan D; Mehta, Heer; Shah, Akshay A; Pulukuri, Kiran Kumar; Rigol, Stephan; Wang, Yanping; Nicolaou, K C; Shamoo, Yousif

    2017-11-10

    The continuing rise of multidrug resistant pathogens has made it clear that in the absence of new antibiotics we are moving toward a "postantibiotic" world, in which even routine infections will become increasingly untreatable. There is a clear need for the development of new antibiotics with truly novel mechanisms of action to combat multidrug resistant pathogens. Experimental evolution to resistance can be a useful tactic for the characterization of the biochemical mechanism of action for antibiotics of interest. Herein, we demonstrate that the use of a diverse panel of strains with well-annotated reference genomes improves the success of using experimental evolution to characterize the mechanism of action of a novel pyrrolizidinone antibiotic analog. Importantly, we used experimental evolution under conditions that favor strongly polymorphic populations to adapt a panel of three substantially different Gram-positive species (lab strain Bacillus subtilis and clinical strains methicillin-resistant Staphylococcus aureus MRSA131 and Enterococcus faecalis S613) to produce a sufficiently diverse set of evolutionary outcomes. Comparative whole genome sequencing (WGS) between the susceptible starting strain and the resistant strains was then used to identify the genetic changes within each species in response to the pyrrolizidinone. Taken together, the adaptive response across a range of organisms allowed us to develop a readily testable hypothesis for the mechanism of action of the CJ-16 264 analog. In conjunction with mitochondrial inhibition studies, we were able to elucidate that this novel pyrrolizidinone antibiotic is an electron transport chain (ETC) inhibitor. By studying evolution to resistance in a panel of different species of bacteria, we have developed an enhanced method for the characterization of new lead compounds for the discovery of new mechanisms of action.

  19. Microstructures and mechanical properties of friction stir welded dissimilar steel-copper joints

    Energy Technology Data Exchange (ETDEWEB)

    Jafari, M.; Abbasi, M.; Poursina, D.; Gheysarian, A. [University of Kashan, Kashan (Iran, Islamic Republic of); Bagheri, B. [Amirkabir University of Technology, Tehran (Iran, Islamic Republic of)

    2017-03-15

    Welding dissimilar metals by fusion welding is challenging. It results in welding defects. Friction stir welding (FSW) as a solid-state joining method can overcome these problems. In this study, 304L stainless steel was joined to copper by FSW. The optimal values of the welding parameters traverse speed, rotational speed, and tilt angle were obtained through Response surface methodology (RSM). Under optimal welding conditions, the effects of welding pass number on the microstructures and mechanical properties of the welded joints were investigated. Results indicated that appropriate values of FSW parameters could be obtained by RSM and grain size refinement during FSW mainly affected the hardness in the weld regions. Furthermore, the heat from the FSW tool increased the grain size in the Heat-affected zones (HAZs), especially on the copper side. Therefore, the strength and ductility decreased as the welding pass number increased because of grain size enhancement in the HAZs as the welding pass number increased.

  20. Rare earth effect on microstructure, mechanical and tribological properties of CoCrW coatings

    International Nuclear Information System (INIS)

    Zhang Zhenyu; Lu Xinchun; Han Baolei; Luo Jianbin

    2007-01-01

    Eight different CoCrW coatings doped with rare earth oxide were deposited by supersonic plasma spraying (SPS). Environmental scanning electron microscopy, microhardness tester, X-ray diffractometer, and self-developed tribometer for high temperature were employed to investigate the properties of sprayed coatings. The results show that rare earth can refine the microstructure effectively, and make the element distribution uniform, which leads to the increase of average microhardness and the corresponding decrease of fluctuation range of sectioned surface of SPS coatings. Furthermore, the rare earth can reduce the friction coefficient between the SPS coating and glass during the sliding process at about 973 K largely, and the mechanism of anti-friction is also discussed

  1. Interfacial microstructure and mechanical properties of brazed aluminum / stainless steel - joints

    Science.gov (United States)

    Fedorov, V.; Elßner, M.; Uhlig, T.; Wagner, G.

    2017-03-01

    Due to the demand of mass and cost reduction, joints based on dissimilar metals become more and more interesting. Especially there is a high interest for joints between stainless steel and aluminum, often necessary for example for automotive heat exchangers. Brazing offers the possibilities to manufacture several joints in one step at, in comparison to fusion welding, lower temperatures. In the recent work, aluminum / stainless steel - joints are produced by induction brazing using an AlSi10 filler and a non-corrosive flux. The mechanical properties are determined by tensile shear tests as well as fatigue tests at ambient and elevated temperatures. The microstructure of the brazed joints and the fracture surfaces of the tested samples are investigated by SEM.

  2. ZK60 alloy processed by ECAP: Microstructural, physical and mechanical characterization

    Energy Technology Data Exchange (ETDEWEB)

    Dumitru, F.-D., E-mail: dianadumitru1986@yahoo.com [Materials Science and Engineering Faculty, Politehnica University of Bucharest, Splaiul Independentei 313, 060042 Bucharest (Romania); Higuera-Cobos, O.F., E-mail: osfahico@gmail.com [Departamento de Ciencia de los Materiales e Ingeniería Metalúrgica, ETSEIB – Universidad Politécnica de Cataluña, Av. Diagonal 647, 08028 Barcelona (Spain); Facultad de Ingeniería Mecánica, Universidad Tecnológica de Pereira, Vereda La Julita, Pereira (Colombia); Cabrera, J.M., E-mail: jose.maria.cabrera@upc.es [Departamento de Ciencia de los Materiales e Ingeniería Metalúrgica, ETSEIB – Universidad Politécnica de Cataluña, Av. Diagonal 647, 08028 Barcelona (Spain); Fundació CTM Centre Tecnológic, Plaça de la Ciència 2, 08243 Manresa (Spain)

    2014-01-31

    Lately, magnesium alloys have been extensively investigated through severe plastic deformation (SPD) methods in order to extend their application to structural components. In the present work, as-extruded ZK60 magnesium alloy samples were subjected to 4 passes of equal-channel angular pressing (ECAP) at a processing temperature of 250 °C, following route Bc. The microstructural evolution of the deformed grains was analyzed using electron back-scattered diffraction (EBSD). The Orientation Imaging Microscopy (OIM) maps, together with the grain boundary misorientation distribution showed a reduction in the grain size accompanied by a large proportion of high angle grain boundaries. Calorimetric analysis showed a slight increase in the recrystallization temperature of the ECAPed magnesium samples. Mechanical tests showed an improvement in the elongation-to-failure after 4 ECAP passes, which were about 2 times higher than in the as-extruded sample. Also a brittle to ductile transition was observed.

  3. ZK60 alloy processed by ECAP: Microstructural, physical and mechanical characterization

    International Nuclear Information System (INIS)

    Dumitru, F.-D.; Higuera-Cobos, O.F.; Cabrera, J.M.

    2014-01-01

    Lately, magnesium alloys have been extensively investigated through severe plastic deformation (SPD) methods in order to extend their application to structural components. In the present work, as-extruded ZK60 magnesium alloy samples were subjected to 4 passes of equal-channel angular pressing (ECAP) at a processing temperature of 250 °C, following route Bc. The microstructural evolution of the deformed grains was analyzed using electron back-scattered diffraction (EBSD). The Orientation Imaging Microscopy (OIM) maps, together with the grain boundary misorientation distribution showed a reduction in the grain size accompanied by a large proportion of high angle grain boundaries. Calorimetric analysis showed a slight increase in the recrystallization temperature of the ECAPed magnesium samples. Mechanical tests showed an improvement in the elongation-to-failure after 4 ECAP passes, which were about 2 times higher than in the as-extruded sample. Also a brittle to ductile transition was observed

  4. Effect of yttrium addition on the microstructure and mechanical properties of ODS RAF steels

    International Nuclear Information System (INIS)

    Auger, M.A.; Castro, V. de; Leguey, T.; Tarcísio-Costa, J.; Monge, M.A.; Muñoz, A.; Pareja, R.

    2014-01-01

    An oxide dispersion strengthened (ODS) alloy with nominal composition Fe–14Cr–2W–0.3Ti–0.24Y (wt.%) was produced by mechanical alloying using elemental powders, and subsequent hot isostatic pressing. The microstructure of the material and characteristics of the oxide particle dispersion were investigated by electron microscopy. The effect of heat treatments on the microhardness and tensile properties at room temperature was also studied. The results show that a fine dispersion of Y–O-rich nanoparticles is achieved, together with larger (Cr, Ti)-rich precipitates. The absence of Ti is apparent in the majority of these nanoparticles, in contrast with reported results for ODS Ti-modified steels processed with Y 2 O 3 addition

  5. Determination of Microstructural Parameters of Nanocrystalline Hydroxyapatite Prepared by Mechanical Alloying Method

    Science.gov (United States)

    Joughehdoust, Sedigheh; Manafi, Sahebali

    2011-12-01

    Hydroxyapatite [HA, Ca10(PO4)6(OH)2] is chemically similar to the mineral component of bones and hard tissues. HA can support bone ingrowth and osseointegration when used in orthopaedic, dental and maxillofacial applications. In this research, HA nanostructure was synthesized by mechanical alloying method. Phase development, particle size and morphology of HA were investigated by X-ray diffraction (XRD) pattern, zetasizer instrument, scanning electron microscopy (SEM), respectively. XRD pattern has been used to determination of the microstructural parameters (crystallite size, lattice parameters and crystallinity percent) by Williamson-Hall equation, Nelson-Riley method and calculating the areas under the peaks, respectively. The crystallite size and particle size of HA powders were in nanometric scales. SEM images showed that some parts of HA particles have agglomerates. The ratio of lattice parameters of synthetic hydroxyapatite (c/a = 0.73) was determined in this study is the same as natural hydroxyapatite structure.

  6. Effect of Sphere Properties on Microstructure and Mechanical Performance of Cast Composite Metal Foams

    Directory of Open Access Journals (Sweden)

    Matias Garcia-Avila

    2015-05-01

    Full Text Available Aluminum-steel composite metal foams (Al-S CMF are manufactured using steel hollow spheres, with a variety of sphere carbon content, surface roughness, and wall porosity, embedded in an Aluminum matrix through gravity casting technique. The microstructural and mechanical properties of the material were studied using scanning electron microscopy, energy dispersive spectroscopy, and quasi-static compressive testing. Higher carbon content and surface roughness in the sphere wall were responsible for an increase in formation of intermetallic phases which had a strengthening effect at lower strain levels, increasing the yield strength of the material by a factor of 2, while higher sphere wall porosity resulted in a decrease on the density of the material and improving its cushioning and ductility maintaining its energy absorption capabilities.

  7. New Mechanistic Models of Long Term Evolution of Microstructure and Mechanical Properties of Nickel Based Alloys

    Energy Technology Data Exchange (ETDEWEB)

    Kruzic, Jamie J. [Oregon State Univ., Corvallis, OR (United States); Evans, T. Matthew [Oregon State Univ., Corvallis, OR (United States); Greaney, P. Alex [Univ. of California, Riverside, CA (United States)

    2018-05-15

    The report describes the development of a discrete element method (DEM) based modeling approach to quantitatively predict deformation and failure of typical nickel based superalloys. A series of experimental data, including microstructure and mechanical property characterization at 600°C, was collected for a relatively simple, model solid solution Ni-20Cr alloy (Nimonic 75) to determine inputs for the model and provide data for model validation. Nimonic 75 was considered ideal for this study because it is a certified tensile and creep reference material. A series of new DEM modeling approaches were developed to capture the complexity of metal deformation, including cubic elastic anisotropy and plastic deformation both with and without strain hardening. Our model approaches were implemented into a commercially available DEM code, PFC3D, that is commonly used by engineers. It is envisioned that once further developed, this new DEM modeling approach can be adapted to a wide range of engineering applications.

  8. Microstructure and mechanical properties of the superalloy ATI Allvac 718Plus

    International Nuclear Information System (INIS)

    Zickler, Gerald A.; Schnitzer, Ronald; Radis, Rene; Hochfellner, Rainer; Schweins, Ralf; Stockinger, Martin; Leitner, Harald

    2009-01-01

    ATI Allvac 718Plus is a novel nickel-based superalloy, which was designed for heavy-duty applications in aerospace turbines. In the present study the high-resolution investigation techniques, atom probe tomography, electron microscopy and in situ high-temperature small-angle neutron scattering were used for a comprehensive microstructural characterization. The alloy contains nanometer-sized spherical γ' phase precipitates (Ni 3 (Al,Ti)) and plate-shaped δ phase precipitates (Ni 3 Nb) of micrometer size. The precipitation kinetics of the γ' phase can be described by a classical model for coarsening. The precipitation strongly influences the mechanical properties and is of high scientific and technological interest.

  9. Microstructure and properties in Al-C-Cu system produced by mechanical milling

    International Nuclear Information System (INIS)

    Goytia-Reyes, R.; Gallegos-Orozco, V.; Flores-Zuniga, H.; Alvarado-Hernandez, F.; Huirache-Acuna, R.; Martinez-Sanchez, R.; Santos-Beltran, A.

    2009-01-01

    Different amounts of C and C-Cu mixtures were employed to produce Al-C and Al-C-Cu powder composites by mechanical milling. In order to determine the Cu effect, hardness tests were carried out in the as-milled samples and at different sintering temperatures. Also, X-ray analyses using Rietveld program, transmission electron microscopy and calorimetry were used for the microstructural characterization. In agreement with the results, the Cu powder acts as carrier in the incorporation of graphite into the Al matrix. Also, due to the presence of graphite particles together with Al 4 C 3 precipitation, hardness values remain stable even at elevated temperatures for these Al-based composites.

  10. Effect of large plastic deformation on microstructure and mechanical properties of a TWIP steel

    International Nuclear Information System (INIS)

    Yanushkevich, Z; Belyakov, A; Kaibyshev, R; Molodov, D

    2014-01-01

    The effect of cold rolling on the microstructure evolution and mechanical properties of a cold rolled Fe-0.3C-17Mn-1.5AI TWIP steel was studied. The plate samples were cold rolled with reductions of 20, 40, 60 and 80%. The structural changes were associated with the development of deformation twinning and shear bands. The average spacing between twin boundaries in the transverse section of the rolled plates decreased from ∼190 to 36 nm with an increase in the rolling reduction from 20 to 40%. Upon further rolling to 80% reduction the twin spacing remained at about 30 nm. The cold rolling resulted in significant increase in strength as revealed by tensile tests at an ambient temperature. The offset yield stress approached 1440 MPa, and the ultimate tensile strength increased to 1630 MPa after rolling reduction of 80%. Such significant strengthening was attributed to the development of specific structure consisting of deformation nanotwins with high dislocation density

  11. Effect of yttrium addition on the microstructure and mechanical properties of ODS RAF steels

    Energy Technology Data Exchange (ETDEWEB)

    Auger, M.A., E-mail: maria.auger@materials.ox.ac.uk [Departamento de Física, Universidad Carlos III de Madrid, Av Universidad 30, 28911 Leganés (Spain); Department of Materials, University of Oxford, Parks Road, OX1 3PH Oxford (United Kingdom); Castro, V. de; Leguey, T.; Tarcísio-Costa, J.; Monge, M.A.; Muñoz, A.; Pareja, R. [Departamento de Física, Universidad Carlos III de Madrid, Av Universidad 30, 28911 Leganés (Spain)

    2014-12-15

    An oxide dispersion strengthened (ODS) alloy with nominal composition Fe–14Cr–2W–0.3Ti–0.24Y (wt.%) was produced by mechanical alloying using elemental powders, and subsequent hot isostatic pressing. The microstructure of the material and characteristics of the oxide particle dispersion were investigated by electron microscopy. The effect of heat treatments on the microhardness and tensile properties at room temperature was also studied. The results show that a fine dispersion of Y–O-rich nanoparticles is achieved, together with larger (Cr, Ti)-rich precipitates. The absence of Ti is apparent in the majority of these nanoparticles, in contrast with reported results for ODS Ti-modified steels processed with Y{sub 2}O{sub 3} addition.

  12. Mechanisms of joint and microstructure formation in high power ultrasonic spot welding 6111 aluminium automotive sheet

    International Nuclear Information System (INIS)

    Bakavos, D.; Prangnell, P.B.

    2010-01-01

    Resistance spot welding (RSW) is difficult to apply to aluminium automotive alloys. High power ultrasonic spot welding (HP-USW) is a new alternative method which is extremely efficient, using ∼2% of the energy of RSW. However, to date there have been few studies of the mechanisms of bond formation and the material interactions that take place with this process. Here, we report on a detailed investigation where we have used X-ray tomography, high resolution SEM, and EBSD, and dissimilar alloy welds, to track the interface position and characterise the stages of weld formation, and microstructure evolution, as a function of welding energy. Under optimum conditions high quality welds are produced, showing few defects. Welding proceeds by the development and spread of microwelds, until extensive plastic deformation occurs within the weld zone, where the temperature reaches ∼380 deg. C. The origin of the weld interface 'flow features' characteristic of HP-USW are discussed.

  13. TIG and MIG welding of 6061 and 7020 aluminium alloys. Microstructural studies and mechanical properties

    International Nuclear Information System (INIS)

    Gomez de Salazar, J.M.; Urena, A.; Villauriz, E.; Manzanedo, S.; Barrena, I.

    1998-01-01

    The aluminium alloys of the 6XXX and 7XXX series, are actually considered of medium and high strength, and are been profusely used in different industries such as aeronautical, automotive, etc.However, its wide application as structural material needs of the proper development of their joining process. The present work describes the results obtained from the microstructural evaluation, both with optical and scanning electronic micros copies (OM) and SEM), and of the mechanical one (hardness changes) of the weld produced in the alloys using different arc welding techniques: FTAW (TIG) and GMAW (MIG). For the last one, a filler metal with a composition of Al-5Mg, AWS denomination A5.10-92 (AA5356), has been used. (Author) 5 refs

  14. Effect of hydrogen on the microstructure, mechanical properties and phase transformations in austenitic steels

    International Nuclear Information System (INIS)

    Li, Y.Y.; Xing, Z.S.

    1989-01-01

    Effect of high-pressure hydrogen charging on the microstructure, mechanical properties and phase transformations in austenitic steels has been investigated and discussed. The results show that the strength and impact toughness of the steels increase slightly and that the ductility decreases after hydrogen charging. The existence of δ-ferrite deteriorates the resistance to hydrogen embrittlement (HE) of the steels. The occurrence of carbide in the steel resulted from aging reduces the ductility of the steel and makes the steel sensitive to HE. The existence of sufficient hydrogen promotes the ε-martensitic transformation and suppresses the α'-martensitic transformation. The permeabilities and diffusivities of hydrogen in the steels have also been determined. (orig.)

  15. Effect of microstructure on mechanical properties and machinability of spheroidal graphite cast iron

    International Nuclear Information System (INIS)

    Kubota, Satoru; Iio, Chinori; Yamaguchi, Shoji; Naito, Daiki; Tomota, Yo; Stefanus, Harjo

    2013-01-01

    Tensile properties, fatigue strength and machinability of spheroidal graphite cast irons with different microstructures were studied. Work-hardening and tensile strength increased with increasing pearlite volume fraction. In situ neutron diffraction during tensile deformation revealed that phase stresses and intergranular stresses are generated with deformation resulting in high work-hardening and high tensile strength with increasing pearlite volume fraction. It was found that graphite grains bear almost no stress, and strongly influence fatigue crack initiation as well as propagation. Therefore graphite refinement is very effective to realize high fatigue strength. The tool life for cutting becomes shorter with increasing pearlite volume fraction. The balance of mechanical properties and machinability was considered. (author)

  16. Effect of cobalt on microstructural parameters and mechanical properties of Ni-base single crystal superalloys

    International Nuclear Information System (INIS)

    Suzuki, Takanobu; Imai, Hachiro; Yokokawa, Tadaharu; Kobayashi, Toshiharu; Koizumi, Yutaka; Harada, Hiroshi

    2007-01-01

    The alloying effect of Cobalt (Co) to microstructural parameters and mechanical properties, such as partitioning ratios of alloying elements and creep strength, of Re-bearing Ni-base single crystal superalloys have been investigated. The second generation single crystal superalloys, TMS-82+, Ni-7.8Co-4.9Cr-1.9Mo-8.7W-5.3Al-6.0Ta-2.4Re-0.1Hf, in mass% (8Co) was compared to a Co-free (0Co) and 15 mass% Co (15Co) alloy which had the same chemical composition as TMS-82+ except that Co was changed. It was shown that the partitioning ratios of alloying elements trend to k(=X γ /X' γ )=1, as the content of Co was increased. Furthermore, it was found that there was suitable content of Co for the creep strength under various temperature-stress conditions. (author)

  17. Correlations between operating conditions, microstructure and mechanical properties of twin wire arc sprayed steel coatings

    International Nuclear Information System (INIS)

    Jandin, G.; Liao, H.; Feng, Z.Q.; Coddet, C.

    2003-01-01

    An experimental design matrix was set up in which carbon steel coatings were deposited with a twin wire arc spray gun (TAFA 9000 TM ), using either compressed air or nitrogen as spraying gas. The coating's mechanical properties were studied. Some correlations were made between these properties, spraying conditions and the microstructure of the deposits. Young's modulus was estimated by the single beam method using finite element modeling. Results show that direct relationships do exist between spray conditions, oxide content in the coating and microhardness. Young's modulus of the coatings depends on the lamella thickness and the oxide content. When increasing the compressed air flow rate, Young's modulus increases at first because smaller particles and finer lamellae were made and it decreases later because of a higher oxide content. The increase of nitrogen flow rate lowers the oxide content and increases Young's modulus

  18. Effect of Sc addition on microstructure and mechanical properties of 1460 alloy

    Directory of Open Access Journals (Sweden)

    Juan Ma

    2014-02-01

    Full Text Available The effect of minor addition of Sc on microstructure, age hardening behavior, tensile properties and fracture morphology of 1460 alloy have been studied. It is found that Sc content increase from 0.11 wt% to 0.22 wt% is favorable for grain refinement in as-cast alloy but results in a coarsening of Cu-rich particles. The alloy with 0.11 wt% Sc exhibits enhanced mechanical properties and age hardening effect. Transmission electron microscopy (TEM investigations on the alloy with 0.11 wt% Sc have suggested that a large amount of Al3(Sc, Zr particles precipitated at the earlier aging may inhibit recrystallization effectively.

  19. Microstructure, Mechanical and Corrosion Properties of Friction Stir-Processed AISI D2 Tool Steel

    Science.gov (United States)

    Yasavol, Noushin; Jafari, Hassan

    2015-05-01

    In this study, AISI D2 tool steel underwent friction stir processing (FSP). The microstructure, mechanical properties, and corrosion resistance of the FSPed materials were then evaluated. A flat WC-Co tool was used; the rotation rate of the tool varied from 400 to 800 rpm, and the travel speed was maintained constant at 385 mm/s during the process. FSP improved mechanical properties and produced ultrafine-grained surface layers in the tool steel. Mechanical properties improvement is attributed to the homogenous distribution of two types of fine (0.2-0.3 μm) and coarse (1.6 μm) carbides in duplex ferrite-martensite matrix. In addition to the refinement of the carbides, the homogenous dispersion of the particles was found to be more effective in enhancing mechanical properties at 500 rpm tool rotation rate. The improved corrosion resistance was observed and is attributed to the volume fraction of low-angle grain boundaries produced after friction stir process of the AISI D2 steel.

  20. Microstructure and Mechanical Properties of Zn-Ni-Al2O3 Composite Coatings

    Directory of Open Access Journals (Sweden)

    Yang Bai

    2018-05-01

    Full Text Available Zn-Ni-Al2O3 composite coatings with different Ni contents were fabricated by low-pressure cold spray (LPCS technology. The effects of the Ni content on the microstructural and mechanical properties of the coatings were investigated. According to X-ray diffraction patterns, the composite coatings were primarily composed of metallic-phase Zn and Ni and ceramic-phase Al2O3. The energy-dispersive spectroscopy results show that the Al2O3 content of the composite coatings gradually decreased with increasing of Ni content. The cross-sectional morphology revealed thick, dense coatings with a wave-like stacking structure. The process of depositing Zn and Ni particles and Al2O3 particles by the LPCS method was examined, and the deposition mechanism was demonstrated to be mechanical interlocking. The bond strength, micro hardness and friction coefficient of the coatings did not obviously change when the Ni content varied. The presence of Al2O3 and Ni increased the wear resistance of the composite coatings, which was higher than that of pure Zn coatings, and the wear mechanism was abrasive and adhesive wear.

  1. Comparative Evaluations and Microstructure: Mechanical Property Relations of Sintered Silicon Carbide Consolidated by Various Techniques

    Science.gov (United States)

    Barick, Prasenjit; Chatterjee, Arya; Majumdar, Bhaskar; Saha, Bhaskar Prasad; Mitra, Rahul

    2018-04-01

    A comparative evaluation between pressureless or self-sintered silicon carbide (SSiC), hot-pressed silicon carbide (HP-SiC), and spark plasma-sintered silicon carbide (SPS-SiC) has been carried out with emphasis on examination of their microstructures and mechanical properties. The effect of sample dimensions on density and properties of SPS-SiC has been also examined. Elastic modulus, flexural strength, and fracture toughness measured by indentation or testing of single-edge notched beam specimens have been found to follow the following trend, HP-SiC > SSiC > SPS-SiC. The SPS-SiC samples have shown size-dependent densification and mechanical properties, with the smaller sample exhibiting superior properties. The mechanical properties of sintered SiC samples appear to be influenced by relative density, grain size, and morphology, as well as the existence of intergranular glassy phase. Studies of fracture surface morphologies have revealed the mechanism of failure to be transgranular in SSiC or HP-SiC, and intergranular in case of SPS-SiC, indicating the dominating influence of grain size and α-SiC formation with high aspect ratio.

  2. Microstructural and hardness behavior of graphene-nanoplatelets/aluminum composites synthesized by mechanical alloying

    International Nuclear Information System (INIS)

    Pérez-Bustamante, R.; Bolaños-Morales, D.; Bonilla-Martínez, J.; Estrada-Guel, I.; Martínez-Sánchez, R.

    2014-01-01

    Highlights: • Pure aluminum was reinforced with graphene-platelets by using mechanical milling. • The composites were studied after sintering condition. • Milling time and graphene-platelet enhance the mechanical behavior of the composites. - Abstract: Graphene can be considered as an ideal reinforcement for the production of composites due to its outstanding mechanical properties. These characteristics offer an increased opportunity for their study in the production of metal matrix composites (MMCs). In this research, the studied composites were produced by mechanical alloying (MA). The employed milling times were of 1, 3 and 5 h. GNPs were added in 0.25, 0.50 and 1.0 wt% into an aluminum powder matrix. Milled powders were cold consolidated and subsequently sintered. Composites were microstructurally characterized with Raman spectroscopy and electron microscopy and X-ray diffraction. The hardness behavior in composites was evaluated with a Vickers micro-hardness test. A homogeneous dispersion of graphene during MA and the proper selection of sintering conditions were considered to produce optimized composites. The obtained results with electron microscopy indicate a homogeneous dispersion of GNPs into the aluminum matrix. Analyses showed GNPs edges where the structure of the graphene layers conserved after MA is observed

  3. Effect of strain rate on the mechanical properties of a gum metal with various microstructures

    International Nuclear Information System (INIS)

    Liu, Silu; Pan, Z.L.; Zhao, Y.H.; Topping, T.; Valiev, R.Z.; Liao, X.Z.; Lavernia, E.J.; Zhu, Y.T.; Wei, Q.

    2017-01-01

    In this work, a bulk gum metal (GM) was fabricated via arc melting from high purity powders. The ingots were first extruded using a conventional route followed by equal channel angular pressing (ECAP). The mechanical behavior of the extruded GM and ECAP-processed GM was studied under both quasi-static and high strain rate compression conditions to evaluate the influence of strain rate. In addition, the associated mechanical anisotropy, or the lack thereof, was investigated through loading in different orientations with respect to the extrusion or ECAP direction. Precipitous stress drops were observed under dynamic compression of both extruded and ECAP-processed GM specimens when loading perpendicular to the extrusion direction. Adiabatic shear banding (ASB) was found to be associated with the precipitous stress drops on the dynamic stress-strain curves. The details of the ASBs were characterized by optical and scanning electron microscopy, with emphasis on electron backscattered diffraction (EBSD). The mechanisms responsible for the formation of ASB were examined both from thermal softening and geometrical softening perspectives. Significant microstructure refinement within ASBs was established, and a possible grain refinement mechanism was proposed.

  4. Effects of heat treatments on the microstructure and mechanical properties of a 6061 aluminium alloy

    International Nuclear Information System (INIS)

    Maisonnette, D.; Suery, M.; Nelias, D.; Chaudet, P.; Epicier, T.

    2011-01-01

    Research highlights: → Description of the mechanical behavior of AA6061-T6 at RT after various thermal histories. → A fast-heating device has been designed to reproduce those thermal histories on tensile specimens. → The thermal loadings are representative of the temperature change observed in the HAZ during welding. → The variation of mechanical properties is the result of metallurgical evolution observed by TEM. → The yield stress at RT decreases with the maximum temperature reached during the thermal cycle. - Abstract: This paper describes the mechanical behavior of the 6061-T6 aluminium alloy at room temperature for various previous thermal histories representative of an electron beam welding. A fast-heating device has been designed to control and apply thermal loadings on tensile specimens. Tensile tests show that the yield stress at ambient temperature decreases if the maximum temperature reached increases or if the heating rate decreases. This variation of the mechanical properties is the result of microstructural changes which have been observed by Transmission Electron Microscopy (TEM).

  5. Microstructure and Mechanical Property of Glutaraldehyde-Treated Porcine Pulmonary Ligament.

    Science.gov (United States)

    Chen, Huan; Zhao, Xuefeng; Berwick, Zachary C; Krieger, Joshua F; Chambers, Sean; Kassab, Ghassan S

    2016-06-01

    There is a significant need for fixed biological tissues with desired structural and material constituents for tissue engineering applications. Here, we introduce the lung ligament as a fixed biological material that may have clinical utility for tissue engineering. To characterize the lung tissue for potential clinical applications, we studied glutaraldehyde-treated porcine pulmonary ligament (n = 11) with multiphoton microscopy (MPM) and conducted biaxial planar experiments to characterize the mechanical property of the tissue. The MPM imaging revealed that there are generally two families of collagen fibers distributed in two distinct layers: The first family largely aligns along the longitudinal direction with a mean angle of θ = 10.7 ± 9.3 deg, while the second one exhibits a random distribution with a mean θ = 36.6 ± 27.4. Elastin fibers appear in some intermediate sublayers with a random orientation distribution with a mean θ = 39.6 ± 23 deg. Based on the microstructural observation, a microstructure-based constitutive law was proposed to model the elastic property of the tissue. The material parameters were identified by fitting the model to the biaxial stress-strain data of specimens, and good fitting quality was achieved. The parameter e0 (which denotes the strain beyond which the collagen can withstand tension) of glutaraldehyde-treated tissues demonstrated low variability implying a relatively consistent collagen undulation in different samples, while the stiffness parameters for elastin and collagen fibers showed relatively greater variability. The fixed tissues presented a smaller e0 than that of fresh specimen, confirming that glutaraldehyde crosslinking increases the mechanical strength of collagen-based biomaterials. The present study sheds light on the biomechanics of glutaraldehyde-treated porcine pulmonary ligament that may be a candidate for tissue engineering.

  6. Microstructures, mechanical properties and corrosion resistance of Hastelloy C22 coating produced by laser cladding

    International Nuclear Information System (INIS)

    Wang, Qin-Ying; Zhang, Yang-Fei; Bai, Shu-Lin; Liu, Zong-De

    2013-01-01

    Highlights: ► Hastelloy C22 coatings were prepared by diode laser cladding technique. ► Higher laser speed resulted in smaller grain size. ► Size-effect played the key role in the hardness measurements by different ways. ► Coating with higher laser scanning speed displayed higher nano-scratch resistance. ► Small grain size was beneficial for improvement of coating corrosion resistance. -- Abstract: The Hastelloy C22 coatings H1 and H2 were prepared by laser cladding technique with laser scanning speeds of 6 and 12 mm/s, respectively. Their microstructures, mechanical properties and corrosion resistance were investigated. The microstructures and phase compositions were studied by metallurgical microscope, scanning electron microscope and X-ray diffraction analysis. The hardness and scratch resistance were measured by micro-hardness and nanoindentation tests. The polarization curves and electrochemical impedance spectroscopy were tested by electrochemical workstation. Planar, cellular and dendritic solidifications were observed in the coating cross-sections. The coatings metallurgically well-bonded with the substrate are mainly composed of primary phase γ-nickel with solution of Fe, W, Cr and grain boundary precipitate of Mo 6 Ni 6 C. The hardness and corrosion resistance of steel substrate are significantly improved by laser cladding Hastelloy C22 coating. Coating H2 shows higher micro-hardness than that of H1 by 34% and it also exhibits better corrosion resistance. The results indicate that the increase of laser scanning speed improves the microstuctures, mechanical properties and corrosion resistance of Hastelloy C22 coating

  7. Mechanical Properties and Microstructure of Neutron Irradiated Cold-worked Al-1050 and Al-6063 Alloys

    International Nuclear Information System (INIS)

    Munitz, A.; Cotler, A; Talianker, M.

    1998-01-01

    The impact of neutron irradiation on the internal microstructure, mechanical properties and fracture morphology of cold-worked Al-1050 and Al-6063 alloys was studied, using scanning and transmission electron microscopy, and tensile measurements. Specimens consisting of 50 mm long and 6 mm wide gauge sections, were punched out from Al-1050 and Al-6063 23% cold-worked tubes. They were exposed to prolonged neutron irradiation of up to 4.5x10 25 and 8x10 25 thermal neutrons/m 2 (E -3 s -1 . In general, the uniform and total elongation, the yield stress, and the ultimate tensile strength increase as functions of fluence. However, for Al-1050 a decrease in the ultimate tensile strength and yield stress was observed up to a fluence of 1x10 25 thermal neutrons/m 2 which then increase with thermal neutrons fluence. Metallographic examination and fractography for Al-6063 revealed a decrease in the local area reduction of the final fracture necking. This reduction is accompanied by a morphology transition from ductile transgranular shear rupture to a combination of transgranular shear with intergranular dimpled rupture. The intergranular rupture area increases with fluence. In contrast, for Al-1050, fracture morphology remains ductile transgranular shear rupture and the final local area reduction remains almost constant No voids could be observed in either alloy up to the maximum fluence. The dislocation density of cold-worked Al was found to decrease with the thermal neutron fluence. Prolonged annealing of unirradiated cold-worked Al-6063 at 52 degree led to similar results. Thus, it appears that, under our irradiation conditions, whereby the temperature encompassing the samples increases the exposure to this thermal field is the major factor influencing the mechanical properties and microstructure of aluminum alloys

  8. Strain Rate and Anisotropic Microstructure Dependent Mechanical Behaviors of Silkworm Cocoon Shells.

    Directory of Open Access Journals (Sweden)

    Jun Xu

    Full Text Available Silkworm cocoons are multi-layered composite structures comprised of high strength silk fiber and sericin, and their mechanical properties have been naturally selected to protect pupas during metamorphosis from various types of external attacks. The present study attempts to gain a comprehensive understanding of the mechanical properties of cocoon shell materials from wild silkworm species Antheraea pernyi under dynamic loading rates. Five dynamic strain rates from 0.00625 s-1 to 12.5 s-1 are tested to show the strain rate sensitivity of the cocoon shell material. In the meantime, the anisotropy of the cocoon shell is considered and the cocoon shell specimens are cut along 0°, 45° and 90° orientation to the short axis of cocoons. Typical mechanical properties including Young's modulus, yield strength, ultimate strength and ultimate strain are extracted and analyzed from the stress-strain curves. Furthermore, the fracture morphologies of the cocoon shell specimens are observed under scanning electron microscopy to help understand the relationship between the mechanical properties and the microstructures of the cocoon material. A discussion on the dynamic strain rate effect on the mechanical properties of cocoon shell material is followed by fitting our experimental results to two previous models, and the effect could be well explained. We also compare natural and dried cocoon materials for the dynamic strain rate effect and interestingly the dried cocoon shells show better overall mechanical properties. This study provides a different perspective on the mechanical properties of cocoon material as a composite material, and provides some insight for bio-inspired engineering materials.

  9. Effect of cryogenic treatment on microstructure, mechanical and wear behaviors of AISI H13 hot work tool steel

    Science.gov (United States)

    Koneshlou, Mahdi; Meshinchi Asl, Kaveh; Khomamizadeh, Farzad

    2011-01-01

    This paper focuses on the effects of low temperature (subzero) treatments on microstructure and mechanical properties of H13 hot work tool steel. Cryogenic treatment at -72 °C and deep cryogenic treatment at -196 °C were applied and it was found that by applying the subzero treatments, the retained austenite was transformed to martensite. As the temperature was decreased more retained austenite was transformed to martensite and it also led to smaller and more uniform martensite laths distributed in the microstructure. The deep cryogenic treatment also resulted in precipitation of more uniform and very fine carbide particles. The microstructural modification resulted in a significant improvement on the mechanical properties of the H13 tool steel.

  10. Influence of Size on the Microstructure and Mechanical Properties of an AISI 304L Stainless Steel—A Comparison between Bulk and Fibers

    Directory of Open Access Journals (Sweden)

    Francisco J. Baldenebro-Lopez

    2015-01-01

    Full Text Available In this work, the mechanical properties and microstructural features of an AISI 304L stainless steel in two presentations, bulk and fibers, were systematically studied in order to establish the relationship among microstructure, mechanical properties, manufacturing process and effect on sample size. The microstructure was analyzed by XRD, SEM and TEM techniques. The strength, Young’s modulus and elongation of the samples were determined by tensile tests, while the hardness was measured by Vickers microhardness and nanoindentation tests. The materials have been observed to possess different mechanical and microstructural properties, which are compared and discussed.

  11. Microstructure and mechanical properties of reactor pressure vessel mock-up material treated by intercritical heat treatment

    International Nuclear Information System (INIS)

    Kim, M. C.; Lee, B. S.; Hong, J. H.; Lee, H. J.; Park, S. D.; Kim, K. B.; Yoon, J. H.; Kim, J. S.; Oh, J. M.

    2003-12-01

    The mechanical properties and microstructures of base metal and weld HAZ (Heat-Affected Zone) of a Mn-Mo-Ni low alloy steels treated by intercritical heat treatment were investigated to evaluate effects of intercritical heat treatment on mechanical properties. In order to clarify the effects of intercritical heat treatment, two types of specimen were prepared by CHT(Conventional Heat Treatment) and IHT(CHT+Intercritical Heat Treatment). Tensile test, charpy impact test and vickers hardness test were carried out to evaluate the mechanical properties. It is found that impact toughness and hardness were improved by intercritical heat treatment. Mean size of precipitates and effective grain were quantitatively analysed as microstructural factors. It is found that precipitate size was decreased and shape of precipitate was spherodized by intercritical heat treatment and grain size was also decreased. So, it is thought that these microstructural changes cause the improvement of mechanical properties by intercritical heat treatment. The simulated specimen using a Gleeble thermal simulator system was used to evaluate the mechanical properties of HAZ. It is well known that IRHAZ and SRHAZ have lower toughness than base metal. However, in the case of IHT, impact toughness of IRHAZ and SRHAZ were slightly higher than that of base metal. It is obvious that this improvement of fracture toughness in IRHAZ and SRHAZ region was closely related to the microstructural changes, such as spheroidization of precipitate and decreases of precipitate size and grain size

  12. Predicting the in-reactor mechanical behavior of Zr-2.5Nb pressure tubes from postirradiation microstructural examination data

    International Nuclear Information System (INIS)

    Griffiths, M.; Davies, P.H.; Davies, W.G.; Sagat, S.

    2002-01-01

    Postirradiation microstructure examinations of Zr-2.5Nb pressure tubes removed from service in CANDU reactors have shown clear trends in the dislocation structure and the state of the β-phase, as a function of operating temperature, neutron flux, and time. These microstructural parameters correlate well with changes in the mechanical properties. For example, the rapid increase in dislocation loop density in the early stages of irradiation corresponds with a rapid increase in tensile strength and DHC velocity, and a corresponding decrease in fracture toughness. There is also a strong negative correlation between the degree of β-phase decomposition and DHC velocity. In addition to the effects of microstructure evolution on the mechanical properties, changes in the a-type and c-component dislocation loop densities also affect irradiation deformation (creep and growth). Statistical analyses of the irradiation microstructure data have been used to derive empirical relationships between dislocation densities and β-phase structure with temperature, flux, and time. The relationships thus derived are useful in predicting where the mechanical properties are most affected by the in-reactor operating conditions. The predictions are compared with mechanical test data for samples from various axial and circumferential locations of 42 pressure tubes removed from operating CANDU reactors. The results are discussed in terms of the mechanisms controlling tensile strength, fracture, delayed-hydride-cracking, and in-reactor deformation. (author)

  13. Developing strong concurrent multiphysics multiscale coupling to understand the impact of microstructural mechanisms on the structural scale

    Energy Technology Data Exchange (ETDEWEB)

    Foulk, James W. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Alleman, Coleman N. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Mota, Alejandro [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Lim, Hojun [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Littlewood, David John [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Bergel, Guy Leshem [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Popova, Evdokia [Georgia Inst. of Technology, Atlanta, GA (United States). Woodruff School of Mechanical Engineering; Montes de Oca Zapiain, David [Georgia Inst. of Technology, Atlanta, GA (United States). Woodruff School of Mechanical Engineering; Kalidindi, Suryanarayana Raju [Georgia Inst. of Technology, Atlanta, GA (United States). Woodruff School of Mechanical Engineering; Ernst, Corey [Elemental Technologies, Provo, UT (United States)

    2017-09-01

    The heterogeneity in mechanical fields introduced by microstructure plays a critical role in the localization of deformation. To resolve this incipient stage of failure, it is therefore necessary to incorporate microstructure with sufficient resolution. On the other hand, computational limitations make it infeasible to represent the microstructure in the entire domain at the component scale. In this study, the authors demonstrate the use of concurrent multi- scale modeling to incorporate explicit, finely resolved microstructure in a critical region while resolving the smoother mechanical fields outside this region with a coarser discretization to limit computational cost. The microstructural physics is modeled with a high-fidelity model that incorporates anisotropic crystal elasticity and rate-dependent crystal plasticity to simulate the behavior of a stainless steel alloy. The component-scale material behavior is treated with a lower fidelity model incorporating isotropic linear elasticity and rate-independent J 2 plas- ticity. The microstructural and component scale subdomains are modeled concurrently, with coupling via the Schwarz alternating method, which solves boundary-value problems in each subdomain separately and transfers solution information between subdomains via Dirichlet boundary conditions. Beyond cases studies in concurrent multiscale, we explore progress in crystal plastic- ity through modular designs, solution methodologies, model verification, and extensions to Sierra/SM and manycore applications. Advances in conformal microstructures having both hexahedral and tetrahedral workflows in Sculpt and Cubit are highlighted. A structure-property case study in two-phase metallic composites applies the Materials Knowledge System to local metrics for void evolution. Discussion includes lessons learned, future work, and a summary of funded efforts and proposed work. Finally, an appendix illustrates the need for two-way coupling through a single degree of

  14. Effect of microstructural evolution and elevated temperature on the mechanical properties of Ni–Cr–Mo alloys

    International Nuclear Information System (INIS)

    Karaköse, Ercan; Keskin, Mustafa

    2015-01-01

    Highlights: • A ternary Ni–Cr–Mo alloy is the crucial for many industrial applications. • Microstructure of Ni–25Cr–18Mo alloy mostly depends upon the undercooling rate. • Increasing the applied undercooling range the average dendrite arm thickness decreases from 5 to 0.5 μm. - Abstract: This paper characterizes the impact of solidification rate on the morphology and type of microstructural and mechanical properties of a nickel-based superalloy with a nominal composition of Ni–25Cr–18Mo (at.%) in a wide cooling range (5–100 K/s). The microstructures of the alloys were identified by scanning electron microscopy (SEM) and the phase composition was examined by X-ray diffractometry (XRD). The phase transitions during the solidification process were investigated by differential thermal analysis (DTA) under an Ar atmosphere. It was found that the final microstructure of Ni–25Cr–18Mo alloy mostly depends upon the solidification rate; the microstructures evolve from a coarse dendritic structure to a refined dendritic structure. The mechanical properties of Ni–25Cr–18Mo alloys were examined by using Vickers and Rockwell hardness tests at room temperature and at elevated temperatures from 400 °C to 800 °C. It was found that the hardness values of the samples were connected with the cooling rate and test temperatures

  15. Effect of microstructural evolution and elevated temperature on the mechanical properties of Ni–Cr–Mo alloys

    Energy Technology Data Exchange (ETDEWEB)

    Karaköse, Ercan, E-mail: ekarakose@karatekin.edu.tr [Karatekin University, Faculty of Sciences, Department of Physics, 18100 Çankırı (Turkey); Keskin, Mustafa [Erciyes University, Faculty of Sciences, Department of Physics, 38039 Kayseri (Turkey)

    2015-01-15

    Highlights: • A ternary Ni–Cr–Mo alloy is the crucial for many industrial applications. • Microstructure of Ni–25Cr–18Mo alloy mostly depends upon the undercooling rate. • Increasing the applied undercooling range the average dendrite arm thickness decreases from 5 to 0.5 μm. - Abstract: This paper characterizes the impact of solidification rate on the morphology and type of microstructural and mechanical properties of a nickel-based superalloy with a nominal composition of Ni–25Cr–18Mo (at.%) in a wide cooling range (5–100 K/s). The microstructures of the alloys were identified by scanning electron microscopy (SEM) and the phase composition was examined by X-ray diffractometry (XRD). The phase transitions during the solidification process were investigated by differential thermal analysis (DTA) under an Ar atmosphere. It was found that the final microstructure of Ni–25Cr–18Mo alloy mostly depends upon the solidification rate; the microstructures evolve from a coarse dendritic structure to a refined dendritic structure. The mechanical properties of Ni–25Cr–18Mo alloys were examined by using Vickers and Rockwell hardness tests at room temperature and at elevated temperatures from 400 °C to 800 °C. It was found that the hardness values of the samples were connected with the cooling rate and test temperatures.

  16. Effect of Cu addition on microstructure and mechanical properties of 15%Cr super martensitic stainless steel

    International Nuclear Information System (INIS)

    Ye, Dong; Li, Jun; Jiang, Wen; Su, Jie; Zhao, Kunyu

    2012-01-01

    Highlights: ► Cu contributes to refine the grains. ► Cu solutes in matrix under quenching and precipitates as ε-Cu during tempering. ► Cu promotes the kinetics of reversed austenite formation. ► Mechanical properties are significantly influenced by austenite amount. ► Cu alloyed super martensitic stainless steel exhibits greatly improved mechanical properties. -- Abstract: The effect of adding different content of Cu (0 wt.%, 1.5 wt.% and 3 wt.%) to the 15%Cr super martensitic stainless steel (SMSS) was investigated using optical microscope, scanning electron microscope (SEM), transmission electron microscope (TEM) and X-ray diffraction (XRD). Its consequence on mechanical properties was examined to clarify the role of Cu in the tested steels. The experimental results indicate that the microstructures of three tested steels are tempered martensite, retained austenite and reversed austenite; two kinds of austenites are dispersedly distributed among martensite matrix. Cu can solute in matrix under quenching condition and can precipitate as Cu-rich nanometer phase (ε-Cu) during tempering. Cu is helpful for the grain refinement and to promote the formation of reversed austenite during tempering. The maximum volume fraction of austenite is 55.9% in the steel with 3 wt.% Cu, which is responsible for the improvement of ductility. The results of the mechanical properties tests reveal that the mechanical properties are significantly influenced by the volume fraction of austenite. Cu can cause solid solution strengthening, precipitation strengthening and grain refinement strengthening in SMSS. Cu alloyed super martensitic stainless steel exhibits greatly improved mechanical properties.

  17. Microstructure and Mechanical Properties of J55ERW Steel Pipe Processed by On-Line Spray Water Cooling

    Directory of Open Access Journals (Sweden)

    Zejun Chen

    2017-04-01

    Full Text Available An on-line spray water cooling (OSWC process for manufacturing electric resistance welded (ERW steel pipes is presented to enhance their mechanical properties and performances. This technique reduces the processing needed for the ERW pipe and overcomes the weakness of the conventional manufacturing technique. Industrial tests for J55 ERW steel pipe were carried out to validate the effectiveness of the OSWC process. The microstructure and mechanical properties of the J55 ERW steel pipe processed by the OSWC technology were investigated. The optimized OSWC technical parameters are presented based on the mechanical properties and impact the performance of steel pipes. The industrial tests show that the OSWC process can be used to efficiently control the microstructure, enhance mechanical properties, and improve production flexibility of steel pipes. The comprehensive mechanical properties of steel pipes processed by the OSWC are superior to those of other published J55 grade steels.

  18. Effect of friction stir welding parameters on microstructure and mechanical properties of DSS–Cu joints

    Energy Technology Data Exchange (ETDEWEB)

    Shokri, V., E-mail: v.shokri@modares.ac.ir [Department of Mechanical Engineering, Tarbiat Modarres University, Tehran (Iran, Islamic Republic of); Sadeghi, A. [School of Mechanical Engineering, College of Engineering, University of Tehran, Tehran (Iran, Islamic Republic of); Sadeghi, M.H. [Department of Mechanical Engineering, Tarbiat Modarres University, Tehran (Iran, Islamic Republic of)

    2017-05-02

    Dissimilar joining of copper to duplex stainless steel (DSS) is challenging at high temperatures of fusion welding owing to the large difference in physical properties of the base metals. To reduce negative effects of welding at high temperatures, solid state welding at lower temperatures has been proposed. To study different effects of welding parameters (rotation speed, travel speed and tool offset) on weld zone microstructure and mechanical properties butt joints of a copper alloy and duplex stainless steel (DSS) were produced by friction stir welding (FSW). It has been found that heat input generated by the interaction of different welding conditions has a significant effect on the formation of a brittle intermetallic at the interface and eventually the final mechanical properties. At low heat inputs, mixing of the two sides is insufficient and metallurgical bonding is weak; while at high heat inputs, the thickness of the formed intermetallic is too thick which causes stress concentration at the interface and premature failure. An optimum welding condition was found (rotation speed of 1200 rpm, travel speed of 30 mm/min and tool offset of 0.5 mm) which almost reached the mechanical properties of the Cu-alloy monolayer.

  19. Microstructure and mechanical analysis of W/P91 steel HIP-joint with Ti interlayer

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Ji-chao [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei, 230031 (China); Science Island Branch of Graduate School, University of Science & Technology of China, Hefei, 230031 (China); Wang, Wanjing, E-mail: wjwang@ipp.ac.cn [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei, 230031 (China); Sun, Zhaoxuan; Wang, Xingli; Wei, Ran [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei, 230031 (China); Science Island Branch of Graduate School, University of Science & Technology of China, Hefei, 230031 (China); Xie, Chunyi; Li, Qiang [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei, 230031 (China); Luo, Guang-nan [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei, 230031 (China); Science Island Branch of Graduate School, University of Science & Technology of China, Hefei, 230031 (China); Hefei Center for Physical Science and Technology, Hefei, 230022 (China); Hefei Science Center of Chinese Academy of Sciences, Hefei, 230027 (China)

    2016-11-15

    Highlights: • W and P91 steel can be joined successfully using the Hot Isostatic Pressing (HIP) method with Ti interlayer. • The experiment was conducted at 760 °C below the P91 steel austenitizing temperature with the pressure 150 MPa for 4 h. • The residual stress concentration is responsible for the fracture of HIP joints under low joining temperature. • Low temperature can reduce the reaction products and improve the mechanical properties of W/Ti/P91 steel joints. - Abstract: W and P91 steel were joined by using the Hot Isostatic Pressing method with Ti interlayer, and the experiments were conducted at 760 °C. The mechanical property, bonding quality and interface microstructure were tested by the Torsion test, Non-Destructive Test, Scanning Electron Microscope and Nano-indentation test. The minimum shear strength of joints was 225 MPa and the failure occurred at the W/Ti interfaces. Metallographic analysis revealed good bonding quality across bonding lines. Almost no reaction products were found in the diffusion region and the Nano-indentation test demonstrated that the solid solution strengthening was caused by inter-diffusion in the diffusion zone. The effect of low joining temperature on reducing reaction products and improving mechanical properties of W/Ti/Steel diffusion bonding were investigated in this paper.

  20. Fe–Al–Mn–C lightweight structural alloys: a review on the microstructures and mechanical properties

    Directory of Open Access Journals (Sweden)

    Hansoo Kim, Dong-Woo Suh and Nack J Kim

    2013-01-01

    Full Text Available Adding a large amount of light elements such as aluminum to steels is not a new concept recalling that several Fe–Al–Mn–C alloys were patented in 1950s for replacement of nickel or chromium in corrosion resistance steels. However, the so-called lightweight steels or low-density steels were revisited recently, which is driven by demands from the industry where steel has served as a major structural material. Strengthening without loss of ductility has been a triumph in steel research, but lowering the density of steel by mixing with light elements will be another prospect that may support the competitiveness against emerging alternatives such as magnesium alloys. In this paper, we review recent studies on lightweight steels, emphasizing the concept of alloy design for microstructures and mechanical properties. The influence of alloying elements on the phase constituents, mechanical properties and the change of density is critically reviewed. Deformation mechanisms of various lightweight steels are discussed as well. This paper provides a reason why the success of lightweight steels is strongly dependent on scientific achievements even though alloy development is closely related to industrial applications. Finally, we summarize some of the main directions for future investigations necessary for vitalizing this field of interest.

  1. Microstructure and mechanical properties of annealed SUS 304H austenitic stainless steel with copper

    Energy Technology Data Exchange (ETDEWEB)

    Sen, Indrani [Department of Materials Engineering, Indian Institute of Science, Bangalore 560012 (India); Amankwah, E. [Department of Materials Engineering, Indian Institute of Science, Bangalore 560012 (India); Department of Materials Science, African University of Science and Technology, Abuja (Nigeria); Kumar, N.S. [Department of Materials Engineering, Indian Institute of Science, Bangalore 560012 (India); Fleury, E. [Center for High Temperature Energy Materials, Korea Institute of Science and Technology, Seoul 136-791 (Korea, Republic of); Oh-ishi, K.; Hono, K. [National Institute for Materials Science, 1-2-1 Sengen, Tsukuba 305-0047 (Japan); Ramamurty, U., E-mail: ramu@materials.iisc.ernet.in [Department of Materials Engineering, Indian Institute of Science, Bangalore 560012 (India)

    2011-05-25

    Research highlights: {yields} SUS 304H austenitic stainless steel containing 3 wt.% Cu was annealed at 700 deg. C for up to 100 h. {yields} Microstructure and mechanical properties of annealed alloys are examined. {yields} Nano-sized Cu-rich precipitation upon annealing. {yields} Strength of the alloy remains invariant with annealing whereas ductility improves. {yields} Fatigue crack growth threshold of 3 wt.% Cu added alloy increases with annealing. - Abstract: An experimental investigation into the effect of Cu on the mechanical properties of 0 and 3 wt.% Cu added SUS 304H austenitic stainless steel upon annealing at 700 deg. C for up to 100 h was conducted. Optical microscopy reveals grain coarsening in both the alloys upon annealing. Observations by transmission electron microscopy revealed the precipitation of nanometer-sized spherical Cu particles distributed within the austenitic grains and the presence of carbides at the dislocations. Both the yield and ultimate tensile strengths of the alloys were found to remain invariant with annealing. Tensile ductility and the threshold stress intensity factor range for fatigue crack growth for 3 wt.% Cu added alloy increase with annealing. These are attributed to the grain coarsening with annealing. In all, the addition of Cu to SUS 304H does not affect the mechanical performance adversely while improving creep resistance.

  2. Effect of Cu addition on the microstructure and mechanical properties of Al–30 wt% Zn alloy

    International Nuclear Information System (INIS)

    Abd El-Rehim, A.F.; Sakr, M.S.; El-Sayed, M.M.; Abd El-Hafez, M.

    2014-01-01

    Highlights: • This paper describes a novel work on the effect of Cu addition on the Al–30 wt% Zn alloy. • The 1 wt% Cu alloy revealed the best hardness of the alloys. • The results indicated two deformation temperature regions (below and above 548 K). - Abstract: The effect of 0.5, 1, 1.5 and 2 wt% Cu addition on the microstructure and mechanical properties of Al–30 wt% Zn alloy has been investigated by stress–strain tests carried out in the temperature range from 508 to 608 K. The work-hardening parameters of the test alloys decreased with increasing the deformation temperature and exhibited discontinuity at 548 K, resulting two deformation temperature regions, the low-temperature region (below 548 K) and high-temperature region (above 548 K). The activation energy of fracture mechanisms has been calculated and found to be 19.6 and 33.2 kJ/mol at the low and high temperature regions respectively. The operating mechanisms of work-hardening of the test alloys were confirmed by the analysis of X-ray diffraction patterns

  3. An Experimental Study on Mechanical Modeling of Ceramics Based on Microstructure

    Directory of Open Access Journals (Sweden)

    Ya-Nan Zhang

    2015-11-01

    Full Text Available The actual grinding result of ceramics has not been well predicted by the present mechanical models. No allowance is made for direct effects of materials microstructure and almost all the mechanical models were obtained based on crystalline ceramics. In order to improve the mechanical models of ceramics, surface grinding experiments on crystalline ceramics and non-crystalline ceramics were conducted in this research. The normal and tangential grinding forces were measured to calculate single grit force and specific grinding energy. Grinding surfaces were observed. For crystalline alumina ceramics, the predictive modeling of normal force per grit fits well with the experimental result, when the maximum undeformed chip thickness is less than a critical depth, which turns out to be close to the grain size of alumina. Meanwhile, there is a negative correlation between the specific grinding energy and the maximum undeformed chip thickness. With the decreasing maximum undeformed chip thickness, the proportions of ductile removal and transgranular fracture increase. However, the grinding force models are not applicable for non-crystalline ceramic fused silica and the specific grinding energy fluctuates irregularly as a function of maximum undeformed chip thickness seen from the experiment.

  4. Microstructural evolution of ferritic steel powder during mechanical alloying with iron oxide

    Energy Technology Data Exchange (ETDEWEB)

    Wen, Yuren; Liu, Yong; Liu, Donghua; Tang, Bei [Central South Univ., State Key Lab. of Powder Metallurgy, Changsha (China); Liu, C.T. [The Hong Kong Polytechnic Univ., Dept. of Mechanical Engineering, Hong Kong (China)

    2011-02-15

    Mechanical alloying of mixed powders is of great importance for preparing oxide dispersion strengthened ferritic steels. In this study, the microstructural evolution of ferritic steel powder mixed with TiH{sub x}, YH{sub 2} and Fe{sub 2}O{sub 3} in the process of mechanical alloying is systematically investigated by using X-ray diffraction analysis, scanning electron microscopy, transmission electron microscopy and microhardness tests. It is found that titanium, yttrium hydrides and iron oxide are completely dissolved during milling, and homogeneous element distribution can be achieved after milling for 12 h. The disintegration of the composite powder particles occurs at 24 h and reaches the balance of welding and fracturing after 36 h. The oxygen content increases sharply with the disintegration of powder particles due to the absorption of oxygen at the solid/gas interface from the milling atmosphere, which is the main source of extra oxygen in the milled powder. Grain refinement down to nanometer level occurs due to the severe plastic deformation of particles; however, the grain size does not change much with further disintegration of particles. The hardness increases with milling time and then becomes stable during further milling. The study indicates that the addition of iron oxide and hydrides may be more beneficial for the dispersion and homogenization of chemical compositions in the powder mixture, thus shortening the mechanical alloying process. (orig.)

  5. Microstructure Evolution and Mechanical Properties Improvement in Liquid-Phase-Sintered Hydroxyapatite by Laser Sintering

    Directory of Open Access Journals (Sweden)

    Songlin Duan

    2015-03-01

    Full Text Available CaO-Al2O3-SiO2 (CAS as a liquid phase was introduced into hydroxyapatite (HAp to prepare bone scaffolds. The effects of the CAS content (1, 2, 3, 4 and 5 wt% on microstructure and mechanical properties of HAp ceramics were investigated. The optimal compression strength, fracture toughness and Vickers hardness reached 22.22 MPa, 1.68 MPa·m1/2 and 4.47 GPa when 3 wt% CAS was added, which were increased by 105%, 63% and 11% compared with those of HAp ceramics without CAS, respectively. The improvement of the mechanical properties was attributed to the improved densification, which was caused by the solid particle to rearrange during liquid phase sintering. Moreover, simulated body fluid (SBF study indicated the HAp ceramics could maintain the mechanical properties and form a bone-like apatite layer when they were immersed in SBF. Cell culture was used to evaluate biocompatibility of the HAp ceramics. The results demonstrated MG-63 cells adhered and spread well.

  6. Microstructure and mechanical analysis of W/P91 steel HIP-joint with Ti interlayer

    International Nuclear Information System (INIS)

    Wang, Ji-chao; Wang, Wanjing; Sun, Zhaoxuan; Wang, Xingli; Wei, Ran; Xie, Chunyi; Li, Qiang; Luo, Guang-nan

    2016-01-01

    Highlights: • W and P91 steel can be joined successfully using the Hot Isostatic Pressing (HIP) method with Ti interlayer. • The experiment was conducted at 760 °C below the P91 steel austenitizing temperature with the pressure 150 MPa for 4 h. • The residual stress concentration is responsible for the fracture of HIP joints under low joining temperature. • Low temperature can reduce the reaction products and improve the mechanical properties of W/Ti/P91 steel joints. - Abstract: W and P91 steel were joined by using the Hot Isostatic Pressing method with Ti interlayer, and the experiments were conducted at 760 °C. The mechanical property, bonding quality and interface microstructure were tested by the Torsion test, Non-Destructive Test, Scanning Electron Microscope and Nano-indentation test. The minimum shear strength of joints was 225 MPa and the failure occurred at the W/Ti interfaces. Metallographic analysis revealed good bonding quality across bonding lines. Almost no reaction products were found in the diffusion region and the Nano-indentation test demonstrated that the solid solution strengthening was caused by inter-diffusion in the diffusion zone. The effect of low joining temperature on reducing reaction products and improving mechanical properties of W/Ti/Steel diffusion bonding were investigated in this paper.

  7. Mechanical and microstructure of reinforced hydroxyapatite/calcium silicate nano-composites materials

    International Nuclear Information System (INIS)

    Beheri, Hanan H.; Mohamed, Khaled R.; El-Bassyouni, Gehan T.

    2013-01-01

    Highlights: ► Nano sized of HA and CS powders were prepared. ► Mechanical of HACS composites enhanced with content of CS. ► The apatite formation onto the composites is proved. -- Abstract: In this study, the nano sized hydroxyapatite (HA) and calcium silicate (CS) powders prepared by both chemical precipitation and sol–gel methods respectively. Biphasic nano-composites materials containing different ratios of HA and CS were fabricated and assessed using X-ray diffraction (XRD), Fourier transmission infrared reflectance (FT-IR), transmission electron microscopy (TEM) and scanning electron microscopy (SEM) techniques. The effect of variation of ratios between HA and CS on mechanical properties, microstructure and in vitro study was studied. The results proved that the mechanical properties were enhanced with increasing the CS ratio in the composite. In vitro study proved the formation and nucleation of apatite onto composites surfaces which contain low content of CS after one week of immersion. Finally, it is concluded that the HACS composites containing high HA content at the expense of CS content will be promising for bone substitute’s applications, especially in load bearing sites.

  8. Mechanical and Microstructural Behavior of Cold-Sprayed Titanium- and Nickel-Based Coatings

    Science.gov (United States)

    Cavaliere, P.; Silvello, A.

    2015-12-01

    Cold spraying is a coating technology that can deposit materials with unique properties. The coating forms through intensive plastic deformation of particles impacting on a substrate at temperature well below the melting point of the sprayed material. Recently, various studies have been published regarding the microstructural and mechanical evolution of metal-matrix composite coatings produced by cold spraying. Herein, we describe the principal results of the available literature in the field of cold-sprayed composites. It is shown that more research is required to solve various questions in this field, for example, the different deformation modes of the material exhibited for various processing conditions, the reinforcing percentage of different material combinations, and the mechanical properties resulting from these complex systems. In the present study, this issue is approached and described for cold-sprayed Ni- and Ti-based composites. Materials were produced with varying ceramic phase (BN and TiAl3) fraction. The variation of the grain size, adhesion strength, porosity, and hardness of the deposits as a function of the ceramic phase fraction and processing parameters (impacting particle speed) is described. The interaction mechanisms between the cold-sprayed particles and the metal matrix during the coating process are presented and described. The results demonstrate a beneficial effect on grain size and porosity with increasing reinforcing phase percentage, as well as narrow processing parameter ranges to achieve the optimal properties with respect to the pure parent materials.

  9. Microstructure, mechanical and corrosion properties of Mg-Dy-Gd-Zr alloys for medical applications.

    Science.gov (United States)

    Yang, L; Huang, Y; Feyerabend, F; Willumeit, R; Mendis, C; Kainer, K U; Hort, N

    2013-11-01

    In previous investigations, a Mg-10Dy (wt.%) alloy with a good combination of corrosion resistance and cytocompatibility showed great potential for use as a biodegradable implant material. However, the mechanical properties of Mg-10Dy alloy are not satisfactory. In order to allow the tailoring of mechanical properties required for various medical applications, four Mg-10(Dy+Gd)-0.2Zr (wt.%) alloys were investigated with respect to microstructure, mechanical and corrosion properties. With the increase in Gd content, the number of second-phase particles increased in the as-cast alloys, and the age-hardening response increased at 200°C. The yield strength increased, while the ductility reduced, especially for peak-aged alloys with the addition of Gd. Additionally, with increasing Gd content, the corrosion rate increased in the as-cast condition owing to the galvanic effect, but all the alloys had a similar corrosion rate (~0.5 mm year(-1)) in solution-treated and aged condition. Copyright © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  10. Fe–Al–Mn–C lightweight structural alloys: a review on the microstructures and mechanical properties

    Science.gov (United States)

    Kim, Hansoo; Suh, Dong-Woo; Kim, Nack J

    2013-01-01

    Adding a large amount of light elements such as aluminum to steels is not a new concept recalling that several Fe–Al–Mn–C alloys were patented in 1950s for replacement of nickel or chromium in corrosion resistance steels. However, the so-called lightweight steels or low-density steels were revisited recently, which is driven by demands from the industry where steel has served as a major structural material. Strengthening without loss of ductility has been a triumph in steel research, but lowering the density of steel by mixing with light elements will be another prospect that may support the competitiveness against emerging alternatives such as magnesium alloys. In this paper, we review recent studies on lightweight steels, emphasizing the concept of alloy design for microstructures and mechanical properties. The influence of alloying elements on the phase constituents, mechanical properties and the change of density is critically reviewed. Deformation mechanisms of various lightweight steels are discussed as well. This paper provides a reason why the success of lightweight steels is strongly dependent on scientific achievements even though alloy development is closely related to industrial applications. Finally, we summarize some of the main directions for future investigations necessary for vitalizing this field of interest. PMID:27877553

  11. Fe-Al-Mn-C lightweight structural alloys: a review on the microstructures and mechanical properties.

    Science.gov (United States)

    Kim, Hansoo; Suh, Dong-Woo; Kim, Nack J

    2013-02-01

    Adding a large amount of light elements such as aluminum to steels is not a new concept recalling that several Fe-Al-Mn-C alloys were patented in 1950s for replacement of nickel or chromium in corrosion resistance steels. However, the so-called lightweight steels or low-density steels were revisited recently, which is driven by demands from the industry where steel has served as a major structural material. Strengthening without loss of ductility has been a triumph in steel research, but lowering the density of steel by mixing with light elements will be another prospect that may support the competitiveness against emerging alternatives such as magnesium alloys. In this paper, we review recent studies on lightweight steels, emphasizing the concept of alloy design for microstructures and mechanical properties. The influence of alloying elements on the phase constituents, mechanical properties and the change of density is critically reviewed. Deformation mechanisms of various lightweight steels are discussed as well. This paper provides a reason why the success of lightweight steels is strongly dependent on scientific achievements even though alloy development is closely related to industrial applications. Finally, we summarize some of the main directions for future investigations necessary for vitalizing this field of interest.

  12. Microstructure, mechanical properties and chemical degradation of brazed AISI 316 stainless steel/alumina systems

    International Nuclear Information System (INIS)

    Paiva, O.C.; Barbosa, M.A.

    2008-01-01

    The main aims of the present study are simultaneously to relate the brazing parameters with: (i) the correspondent interfacial microstructure, (ii) the resultant mechanical properties and (iii) the electrochemical degradation behaviour of AISI 316 stainless steel/alumina brazed joints. Filler metals on such as Ag-26.5Cu-3Ti and Ag-34.5Cu-1.5Ti were used to produce the joints. Three different brazing temperatures (850, 900 and 950 deg. C), keeping a constant holding time of 20 min, were tested. The objective was to understand the influence of the brazing temperature on the final microstructure and properties of the joints. The mechanical properties of the metal/ceramic (M/C) joints were assessed from bond strength tests carried out using a shear solicitation loading scheme. The fracture surfaces were studied both morphologically and structurally using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction analysis (XRD). The degradation behaviour of the M/C joints was assessed by means of electrochemical techniques. It was found that using a Ag-26.5Cu-3Ti brazing alloy and a brazing temperature of 850 deg. C, produces the best results in terms of bond strength, 234 ± 18 MPa. The mechanical properties obtained could be explained on the basis of the different compounds identified on the fracture surfaces by XRD. On the other hand, the use of the Ag-34.5Cu-1.5Ti brazing alloy and a brazing temperature of 850 deg. C produces the best results in terms of corrosion rates (lower corrosion current density), 0.76 ± 0.21 μA cm -2 . Nevertheless, the joints produced at 850 deg. C using a Ag-26.5Cu-3Ti brazing alloy present the best compromise between mechanical properties and degradation behaviour, 234 ± 18 MPa and 1.26 ± 0.58 μA cm -2 , respectively. The role of Ti diffusion is fundamental in terms of the final value achieved for the M/C bond strength. On the contrary, the Ag and Cu distribution along the brazed interface seem to

  13. Micro Mechanics and Microstructures of Major Subsurface Hydraulic Barriers: Shale Caprock vs Wellbore Cement

    Science.gov (United States)

    Radonjic, M.; Du, H.

    2015-12-01

    Shale caprocks and wellbore cements are two of the most common subsurface impermeable barriers in the oil and gas industry. More than 60% of effective seals for geologic hydrocarbon bearing formations as natural hydraulic barriers constitute of shale rocks. Wellbore cements provide zonal isolation as an engineered hydraulic barrier to ensure controlled fluid flow from the reservoir to the production facilities. Shale caprocks were deposited and formed by squeezing excess formation water and mineralogical transformations at different temperatures and pressures. In a similar process, wellbore cements are subjected to compression during expandable tubular operations, which lead to a rapid pore water propagation and secondary mineral precipitation within the cement. The focus of this research was to investigate the effect of wellbore cement compression on its microstructure and mechanical properties, as well as a preliminary comparison of shale caprocks and hydrated cement. The purpose of comparative evaluation of engineered vs natural hydraulic barrier materials is to further improve wellbore cement durability when in contact with geofluids. The micro-indentation was utilized to evaluate the change in cement mechanical properties caused by compression. Indentation experiments showed an overall increase in hardness and Young's modulus of compressed cement. Furthermore, SEM imaging and Electron Probe Microanalysis showed mineralogical alterations and decrease in porosity. These can be correlated with the cement rehydration caused by microstructure changes as a result of compression. The mechanical properties were also quantitatively compared to shale caprock samples in order to investigate the similarities of hydraulic barrier features that could help to improve the subsurface application of cement in zonal isolation. The comparison results showed that the poro-mechanical characteristics of wellbore cement appear to be improved when inherent pore sizes are shifted to

  14. Influence of Processing Techniques on Microstructure and Mechanical Properties of a Biodegradable Mg-3Zn-2Ca Alloy

    Czech Academy of Sciences Publication Activity Database

    Doležal, P.; Zapletal, J.; Fintová, Stanislava; Trojanová, Z.; Greger, M.; Roupcová, Pavla; Podrábský, T.

    2016-01-01

    Roč. 9, č. 11 (2016), s. 1-15, č. článku 880. ISSN 1996-1944 Institutional support: RVO:68081723 Keywords : biodegradable magnesium alloy * Mg-Zn-Ca * squeeze casting * ECAP processing * microstructure * mechanical properties Subject RIV: JP - Industrial Processing Impact factor: 2.654, year: 2016 http://www.mdpi.com/1996-1944/9/11/880

  15. Tempering of martensitic steel for fasteners : Effects of micro-alloying on microstructure and mechanical property evolution

    NARCIS (Netherlands)

    Öhlund, C.E.I.C.

    2015-01-01

    The research presented in this thesis aims to deepen our understanding of the effect of micro-alloying on the microstructure and mechanical property evolution during tempering of martensitic steel for fasteners. The ongoing trend of engine down-sizing has led to the need for stronger and more

  16. SYSTEM ANALYSIS OF INTERRELATIONS BETWEEN SPECTRAL CHARACTERISTICS OF THE STEEL MICROSTRUCTURE PICTURE AND ITS MECHANICAL CHARACTERISTICS IN METALLURGICAL PRODUCTION

    Directory of Open Access Journals (Sweden)

    A. N. Chichko

    2009-01-01

    Full Text Available It is shown that spectral characteristics of functions of closeness of the pearlite inter-plate distances, determined by image of the rolled wire samples microstructures, correlate with its mechanical characteristics and also with characteristics of wire, produced of it.

  17. Effect of Heat Treatment on Microstructure and Mechanical Properties of Laser Additively Manufactured AISI H13 Tool Steel

    Science.gov (United States)

    Chen, ChangJun; Yan, Kai; Qin, Lanlan; Zhang, Min; Wang, Xiaonan; Zou, Tao; Hu, Zengrong

    2017-11-01

    The effect of heat treatment on microstructure and mechanical properties (microhardness, wear resistance and impact toughness) of laser additively manufactured AISI H13 tool steel was systemically investigated. To understand the variation of microstructure and mechanical properties under different heat treatments, the as-deposited samples were treated at 350, 450, 550, 600 and 650 °C/2 h, respectively. Microstructure and phase transformation were investigated through optical microscopy, scanning electron microscope and transmission electron microscope. The mechanical properties were characterized by nanoindentation tests, Charpy tests and high-temperature wear tests. The microstructure of as-deposited samples consisted of martensite, ultrafine carbides and retained austenite. After the tempering treatment, the martensite was converted into tempered martensite and some fine alloy carbides which precipitated in the matrix. When treated at 550 °C, the greatest hardness and nanohardness were 600 HV0.3 and 6119.4 MPa due to many needle-like carbides precipitation. The value of hardness increased firstly and then decreased when increasing the temperature. When tempered temperatures exceeded 550 °C, the carbides became coarse, and martensitic matrix recrystallized at the temperature of 650 °C. The least impact energy was 6.0 J at a temperature of 550 °C. Samples tempered at 550 °C had larger wear volume loss than that of others. Wear resistances of all samples under atmospheric condition at 400 °C showed an oxidation mechanism.

  18. Influence of temper condition on microstructure and mechanical properties of semisolid metal processed Al–Si–Mg alloy A356

    CSIR Research Space (South Africa)

    Moller, H

    2009-01-01

    Full Text Available The microstructures and mechanical properties of strontium modified semisolid metal high pressure die cast A356 alloy are presented. The alloy A356-F (as cast) has a globular primary grain structure containing a fine eutectic. Solution treatment...

  19. Microstructure and mechanical properties of friction stir welded 18Cr–2Mo ferritic stainless steel thick plate

    International Nuclear Information System (INIS)

    Han, Jian; Li, Huijun; Zhu, Zhixiong; Barbaro, Frank; Jiang, Laizhu; Xu, Haigang; Ma, Li

    2014-01-01

    Highlights: • We focus on friction stir welding of 18Cr–2Mo ferritic stainless steel thick plate. • We produce high-quality joints with special tool and optimised welding parameters. • We compare microstructure and mechanical properties of steel and joint. • Friction stir welding is a method that can maintain the properties of joint. - Abstract: In this study, microstructure and mechanical properties of a friction stir welded 18Cr–2Mo ferritic stainless steel thick plate were investigated. The 5.4 mm thick plates with excellent properties were welded at a constant rotational speed and a changeable welding speed using a composite tool featuring a chosen volume fraction of cubic boron nitride (cBN) in a W–Re matrix. The high-quality welds were successfully produced with optimised welding parameters, and studied by means of optical microscopy (OM), scanning electron microscopy (SEM), electron back-scattered diffraction (EBSD) and standard hardness and impact toughness testing. The results show that microstructure and mechanical properties of the joints are affected greatly, which is mainly related to the remarkably fine-grained microstructure of equiaxed ferrite that is observed in the friction stir welded joint. Meanwhile, the ratios of low-angle grain boundary in the stir zone regions significantly increase, and the texture turns strong. Compared with the base material, mechanical properties of the joint are maintained in a comparatively high level

  20. Effect of tool pin profile on microstructure and mechanical properties of friction stir welded AZ31B magnesium alloy

    International Nuclear Information System (INIS)

    Motalleb-nejad, P.; Saeid, T.; Heidarzadeh, A.; Darzi, Kh.; Ashjari, M.

    2014-01-01

    Highlights: • FSW conditions for defect free joints of AZ31B magnesium alloy were reached. • The effect of FSW factors such pin design on the features of the welds was studied. • Taper pin caused to finest grains and highest mechanical properties. • The superior properties of the joints were achieved at the condition of ω 2 /υ = 6300. • All the tensile fractures occurred at the interface of the SZ and base metal. - Abstract: In this investigation the effect of friction stir welding pin geometry on the microstructure and mechanical properties of AZ31B magnesium alloy joints is studied. The considered pin geometries are simple cylindrical, screw threaded cylindrical and taper. The joints are friction stir welded at different traverse and rotational speeds. Microstructures of the joints are examined using the optical and scanning electron microscopes. Also, the tensile properties and hardness of the joints are measured. The results show that taper and screw threaded cylindrical pins produce defect free joints. In addition, the taper pin results in finest microstructure and highest mechanical properties. Furthermore, it is found that rotational speed has a more significant role on the final microstructure and mechanical properties of the joints, compared to the traverse speed