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Sample records for alloys fracture mechanics

  1. Fracture mechanics behaviour of neutron irradiated Alloy A-286

    International Nuclear Information System (INIS)

    The effect of fast-neutron irradiation on the fatigue-crack propagation and fracture toughness behaviour of Alloy A-286 was characterized using fracture mechanics techniques. The fracture toughness was found to decrease continuously with increasing irradiation damage at both 24 deg. C and 427 deg. C. In the unirradiated and low fluence conditions, specimens displayed appreciable plasticity prior to fracture, and equivalent Ksub(Ic) values were determined from Jsub(Ic) fracture toughness results. At high irradiation exposure levels, specimens exhibited a brittle Ksub(Ic) fracture mode. The 427 deg. C fracture toughness fell from 129 MPa√m in the unirradiated condition to 35 MPa√m at an exposure of 16.2 dpa (total fluence of 5.2x1022n/cm2). Room temperature fracture toughness values were consistently 40 to 60 percent higher than the 427 deg. C values. Electron fractography revealed that the reduction in fracture resistance was attributed to a fracture mechanism transition from ductile microvoid coalescence to channel fracture. Fatigue-crack propagation tests were conducted at 427 deg. C on specimens irradiated at 2.4 dpa and 16.2 dpa. Crack growth rates at the lower exposure level were comparable to those in unirradiated material, while those at the higher exposure were slightly higher than in unirradiated material. (author)

  2. Influence of ageing, inclusions and voids on ductile fracture mechanism in commercial Al-alloys

    Indian Academy of Sciences (India)

    A Chennakesava Reddy; S Sundar Rajan

    2005-02-01

    The objective of the paper is to study the effect of ageing, inclusions and voids on the mechanism of fracture and resultant toughness. It has been found that the voids are initiated at only a fraction of the larger inclusions present. The initiation of voids at small particles in the ductile fracture process appears to have little effect on fracture toughness. The strain hardening capacity has a marked effect on void size, and is an indicator of fracture toughness in the commercial Al alloy.

  3. Correlation of fracture features with mechanical properties as a function of strain rate in zirconium alloys

    Energy Technology Data Exchange (ETDEWEB)

    Das, Arpan; Chakravartty, Jayanta Kumar [Bhabha Atomic Research Centre (Department of Atomic Energy), Trombay, Mumbai, Maharashtra (India). Mechanical Metallurgy Div.

    2016-02-15

    Two dimensional fracture features (i. e., dimple diameter, extent of tearing ridges etc.) quantified from the tensile fractographs are investigated to predict the nature of variation in mechanical properties with strain rates in zirconium alloys tested under ambient temperature where the initial inclusion or other second phase particle contents were kept unaltered. It has been possible to reasonably estimate the strength and ductility properties of an alloy from a systematic analysis of fractographic features.

  4. Fracture mechanics of pseudoelastic NiTi alloys: review of the research activities carried out at University of Calabria

    Directory of Open Access Journals (Sweden)

    E. Sgambitterra

    2013-01-01

    Full Text Available This paper reports a brief review of the research activities on fracture mechanics of nickel-titanium based shape memory alloys carried out at University of Calabria. In fact, this class of metallic alloys show a unusual fracture response due to the reversible stress-induced and thermally phase transition mechanisms occurring in the crack tip region as a consequence of the highly localized stresses. The paper illustrates the main results concerning numerical, analytical and experimental research activities carried out by using commercial NiTi based pseudoelastic alloys. Furthermore, the effect of several thermo-mechanical loading conditions on the fracture properties of NiTi alloys are illustrated.

  5. Mechanical Behavior and Fracture Properties of NiAl Intermetallic Alloy with Different Copper Contents

    Directory of Open Access Journals (Sweden)

    Tao-Hsing Chen

    2016-03-01

    Full Text Available The deformation behavior and fracture characteristics of NiAl intermetallic alloy containing 5~7 at% Cu are investigated at room temperature under strain rates ranging from 1 × 10−3 to 5 × 103 s−1. It is shown that the copper contents and strain rate both have a significant effect on the mechanical behavior of the NiAl alloy. Specifically, the flow stress increases with an increasing copper content and strain rate. Moreover, the ductility also improves as the copper content increases. The change in the mechanical response and fracture behavior of the NiAl alloy given a higher copper content is thought to be the result of the precipitation of β-phase (Ni,CuAl and γ'-phase (Ni,Cu3Al in the NiAl matrix.

  6. The microstructural, mechanical, and fracture properties of austenitic stainless steel alloyed with gallium

    Science.gov (United States)

    Kolman, D. G.; Bingert, J. F.; Field, R. D.

    2004-11-01

    The mechanical and fracture properties of austenitic stainless steels (SSs) alloyed with gallium require assessment in order to determine the likelihood of premature storage-container failure following Ga uptake. AISI 304 L SS was cast with 1, 3, 6, 9, and 12 wt pct Ga. Increased Ga concentration promoted duplex microstructure formation with the ferritic phase having a nearly identical composition to the austenitic phase. Room-temperature tests indicated that small additions of Ga (less than 3 wt pct) were beneficial to the mechanical behavior of 304 L SS but that 12 wt pct Ga resulted in a 95 pct loss in ductility. Small additions of Ga are beneficial to the cracking resistance of stainless steel. Elastic-plastic fracture mechanics analysis indicated that 3 wt pct Ga alloys showed the greatest resistance to crack initiation and propagation as measured by fatigue crack growth rate, fracture toughness, and tearing modulus. The 12 wt pct Ga alloys were least resistant to crack initiation and propagation and these alloys primarily failed by transgranular cleavage. It is hypothesized that Ga metal embrittlement is partially responsible for increased embrittlement.

  7. Mechanical properties and microstructure of an α+β titanium alloy with high strength and fracture toughness

    Institute of Scientific and Technical Information of China (English)

    YU Yang; HUI Songxiao; YE Wenjun; XIONG Baiqing

    2009-01-01

    The Ti-Al-Sn-Zr-Cr-Mo-V-Si (Ti-62A) alloy, an alpha-beta alloy with high strength and fracture toughness, is currently used as an advanced structural material in aerospace and non-aerospace applications. Thermo-mechanical processes can be used to optimize the relationship be-twcen its strength and fracture toughness. A Ti-62A alloy bar can be machined through a transus β-forged plus α+β solution treated and aged specimen with a lamellar alpha microstructure. The effects of heat treatment on the mechanical properties were discussed. Heat treatment provided a practical balance of strength, fracture toughness, and fatigue crack growth resistance. A comparison of the Ti-62A alloy with the Ti-62222S alloy under the same thermo-mechanical processing conditions showed that their properties are at the same level.

  8. Fracture Mechanics

    CERN Document Server

    Zehnder, Alan T

    2012-01-01

    Fracture mechanics is a vast and growing field. This book develops the basic elements needed for both fracture research and engineering practice. The emphasis is on continuum mechanics models for energy flows and crack-tip stress- and deformation fields in elastic and elastic-plastic materials. In addition to a brief discussion of computational fracture methods, the text includes practical sections on fracture criteria, fracture toughness testing, and methods for measuring stress intensity factors and energy release rates. Class-tested at Cornell, this book is designed for students, researchers and practitioners interested in understanding and contributing to a diverse and vital field of knowledge. Alan Zehnder joined the faculty at Cornell University in 1988. Since then he has served in a number of leadership roles including Chair of the Department of Theoretical and Applied Mechanics, and Director of the Sibley School of Mechanical and Aerospace Engineering.  He teaches applied mechanics and his research t...

  9. Damage and fracture mechanism of 6063 aluminum alloy under three kinds of stress states

    Institute of Scientific and Technical Information of China (English)

    ZHU Hao; ZHU Liang; CHEN Jianhong

    2008-01-01

    To study the damage and fracture mechanism of 6063 aluminum alloy under different stress states,three kinds of representative triaxial stress states have been adopted,namely smooth tensile,notch tensile,and pure shear.The results of the study indicate the following.During the notch tensile test,a relatively higher stress triaxiality appears in the root of the notch.With the applied loading increasing,the volume fraction of microvoids in the root of the notch increases continuously.When it reaches the critical volume fraction of microvoids,the specimen fractures.During the pure shear test,the stress triaxiality almost equals to zero,and there is almost no microvoids but a shear band at the center of the butterfly specimen.The shear band results from nonuniform deformation constantly under the shear stress.With stress concentration,cracks are produced within the shear band and are later coalesced.When the equivalent plastic strain reaches the critical value (equivalent plastic fracture strain),the butterfly specimen fractures.During the smooth tensile test,the stress triaxiality in the gauge of the specimen remains constant at 0.33.Thus,the volume of microvoids of the smooth tensile test is less than that of the notch tensile test and the smooth specimen fractures due to shearing between microvoids.The G-T-N damage model and Johnson-Cook model are used to simulate the notch tensile and shear test,respectively.The simulated engineering stress-strain curves fit the measured engineering stress-strain curves very well.In addition,the empirical damage evolution equation for the notch specimen is obtained from the experimental data and FEM simulations.

  10. Friction Stir-Welded Titanium Alloy Ti-6Al-4V: Microstructure, Mechanical and Fracture Properties

    Science.gov (United States)

    Sanders, D. G.; Edwards, P.; Cantrell, A. M.; Gangwar, K.; Ramulu, M.

    2015-05-01

    Friction stir welding (FSW) has been refined to create butt welds from two sheets of Ti-6Al-4V alloy to have an ultra-fine grain size. Weld specimen testing was completed for three different FSW process conditions: As welded, stress relieved, stress relieved and machined, and for the un-welded base material. The investigation includes macrostructure, microstructure, microhardness, tensile property testing, notched bar impact testing, and fracture toughness evaluations. All experiments were conducted in accordance with industry standard testing specifications. The microstructure in the weld nugget was found to consist of refined and distorted grains of alpha in a matrix of transformed beta containing acicular alpha. The enhanced fracture toughness of the welds is a result of increased hardness, which is attributed to an increase in alpha phase, increase in transformed beta in acicular alpha, and grain refinement during the weld process. The noted general trend in mechanical properties from as welded, to stress relieved, to stress relieved and machined conditions exhibited a decrease in ultimate tensile strength, and yield strength with a small increase in ductility and a significant increase in fracture toughness.

  11. Nanoindentation and micro-mechanical fracture toughness of electrodeposited nanocrystalline Ni–W alloy films

    International Nuclear Information System (INIS)

    Nanocrystalline nickel–tungsten alloys have great potential in the fabrication of components for microelectromechanical systems. Here the fracture toughness of Ni–12.7 at.%W alloy micro-cantilever beams was investigated. Micro-cantilevers were fabricated by UV lithography and electrodeposition and notched by focused ion beam machining. Load was applied using a nanoindenter and fracture toughness was calculated from the fracture load. Fracture toughness of the Ni–12.7 at.%W was in the range of 1.49–5.14 MPa √m. This is higher than the fracture toughness of Si (another important microelectromechanical systems material), but considerably lower than that of electrodeposited nickel and other nickel based alloys. - Highlights: ► Micro-scale cantilevers manufactured by electro-deposition and focused ion beam machining. ► Nanoindenter used to perform micro-scale fracture test on Ni-13at%W micro-cantilevers. ► Calculation of fracture toughness of electrodeposited Ni-13at%W thin films. ► Fracture toughness values lower than that of nanocrystalline nickel.

  12. Nanoindentation and micro-mechanical fracture toughness of electrodeposited nanocrystalline Ni-W alloy films

    Energy Technology Data Exchange (ETDEWEB)

    Armstrong, D.E.J., E-mail: david.armstrong@materials.ox.ac.uk [Department of Materials, University of Oxford, Parks Road, Oxford, OX1 3PH (United Kingdom); Haseeb, A.S.M.A. [Department of Mechanical Engineering, University of Malaya, 50603 Kuala Lumpur (Malaysia); Roberts, S.G.; Wilkinson, A.J. [Department of Materials, University of Oxford, Parks Road, Oxford, OX1 3PH (United Kingdom); Bade, K. [Institut fuer Mikrostrukturtechnik (IMT), Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen (Germany)

    2012-04-30

    Nanocrystalline nickel-tungsten alloys have great potential in the fabrication of components for microelectromechanical systems. Here the fracture toughness of Ni-12.7 at.%W alloy micro-cantilever beams was investigated. Micro-cantilevers were fabricated by UV lithography and electrodeposition and notched by focused ion beam machining. Load was applied using a nanoindenter and fracture toughness was calculated from the fracture load. Fracture toughness of the Ni-12.7 at.%W was in the range of 1.49-5.14 MPa {radical}m. This is higher than the fracture toughness of Si (another important microelectromechanical systems material), but considerably lower than that of electrodeposited nickel and other nickel based alloys. - Highlights: Black-Right-Pointing-Pointer Micro-scale cantilevers manufactured by electro-deposition and focused ion beam machining. Black-Right-Pointing-Pointer Nanoindenter used to perform micro-scale fracture test on Ni-13at%W micro-cantilevers. Black-Right-Pointing-Pointer Calculation of fracture toughness of electrodeposited Ni-13at%W thin films. Black-Right-Pointing-Pointer Fracture toughness values lower than that of nanocrystalline nickel.

  13. MECHANISM ANALYSIS OF THICKNESS EFFECT ON MIXED MODE Ⅰ/Ⅱ FRACTURE OF LC4-CS ALUMINUM ALLOY

    Institute of Scientific and Technical Information of China (English)

    H.R. Dong; W.L. Guo

    2004-01-01

    Mixed mode Ⅰ/Ⅱ fracture experiments of LC4-CS aluminum alloy were conducted by using tension-shear specimens with thicknesses of 2, 4, 8 and 14mm. Fracture mechanisms of thickness effect on mixed mode Ⅰ/Ⅱ fracture were first examined from fracture surface morphology to correlate with the macroscopic fracture behavior and stress state. It is found that specimen thickness has a strong influence on mixed mode fracture. As thickness varies from thin to thick the macroscopic fracture surfaces appear the characteristics of plane stress state (2mm, 4mm-thick specimen), threedimensional stress state (8mm-thick specimens), and plane strain state (14mm-thick specimens), respectively. The specimens of all kinds of thicknesses are typical of tensile type failure under mode I loading condition and shear type failure under mode Ⅱloading condition. Two distinct features coexist on the fracture surfaces under mixed mode loading conditions, and the corresponding proportion varies with loading mixity. Void-growth processes are the failure mechanism in both predominately tensileand shear-type fractures. The size and depth of dimples on the fracture surface vary greatly with thickness. Therefore, it is extraordinary necessary to take into account the thickness effect when a mixed mode fracture criterion is being established.

  14. Tensile and fracture behavior of AA6061-T6 aluminum alloys: micro-mechanical approach

    International Nuclear Information System (INIS)

    The AA6061-T6 aluminum alloy was chosen as the material for the core vessel of the future Jules Horowitz testing reactor (JHR). The objective of this thesis is to understand and model the tensile and fracture behavior of the material, as well as the origin of damage anisotropy. A micro-mechanical approach was used to link the microstructure and mechanical behavior. The microstructure of the alloy was characterized on the surface via Scanning Electron Microscopy and in the 3D volume via synchrotron X-ray tomography and laminography. The damage mechanism was identified by in-situ SEM tensile testing, ex-situ X-ray tomography and in-situ laminography on different levels of triaxiality. The observations have shown that damage nucleated at lower strains on Mg2Si coarse precipitates than on iron rich intermetallics. The identified scenario and the in-situ measurements were then used to develop a coupled GTN damage model incorporating nucleation, growth and coalescence of cavities formed by coarse precipitates. The relationship between the damage and the microstructure anisotropies was explained and simulated. (author)

  15. Characterization of the Microstructure, Fracture, and Mechanical Properties of Aluminum Alloys 7085-O and 7175-T7452 Hollow Cylinder Extrusions

    Science.gov (United States)

    Benoit, Samuel G.; Chalivendra, Vijaya B.; Rice, Matthew A.; Doleski, Robert F.

    2016-06-01

    Microstructural, tensile, and fracture characterizations of cylindrically forged forms of aluminum alloys AA7085-O and AA7175-T7452 were performed. Mechanical and fracture properties were investigated along radial, circumferential, and longitudinal directions to determine directional dependency. American Society for Testing and Materials (ASTM) test methods (ASTM E8-04 and ASTM E1820) were employed for both the tensile and fracture characterizations, respectively. The tensile and fracture properties were related to microstructure in each direction. The strength, elongation at break, and ultimate tensile strength of AA7085-O were higher than those of AA7175-T7452. AA7175-T7452 alloy failed in a brittle manner during fracture studies. AA7085-O outperformed AA7175-T7452 on fracture energy in all of the orientations studied. Smaller grain sizes on the planes normal to circumferential and longitudinal directions showed improvement in both elongation at break and fracture energy values compared to those of radial direction. Scanning electron microscopy images demonstrated cleavage fracture in AA7175-T7452 and transgranular fracture in AA7085-O.

  16. Evaluation of Stress Corrosion Cracking Susceptibility Using Fracture Mechanics Techniques, Part 1. [environmental tests of aluminum alloys, stainless steels, and titanium alloys

    Science.gov (United States)

    Sprowls, D. O.; Shumaker, M. B.; Walsh, J. D.; Coursen, J. W.

    1973-01-01

    Stress corrosion cracking (SSC) tests were performed on 13 aluminum alloys, 13 precipitation hardening stainless steels, and two titanium 6Al-4V alloy forgings to compare fracture mechanics techniques with the conventional smooth specimen procedures. Commercially fabricated plate and rolled or forged bars 2 to 2.5-in. thick were tested. Exposures were conducted outdoors in a seacoast atmosphere and in an inland industrial atmosphere to relate the accelerated tests with service type environments. With the fracture mechanics technique tests were made chiefly on bolt loaded fatigue precracked compact tension specimens of the type used for plane-strain fracture toughness tests. Additional tests of the aluminum alloy were performed on ring loaded compact tension specimens and on bolt loaded double cantilever beams. For the smooth specimen procedure 0.125-in. dia. tensile specimens were loaded axially in constant deformation type frames. For both aluminum and steel alloys comparative SCC growth rates obtained from tests of precracked specimens provide an additional useful characterization of the SCC behavior of an alloy.

  17. Fracture mechanical studies on high temperature alloys between room temperature and 9000C

    International Nuclear Information System (INIS)

    As a contribution to the fracture mechanics characterization of the three solid-solution hardened alloys X10NiCrAlTi 32 20, NiCr 22 Co 12 Mo and NiCr 22 W 12 Si, (material No. 1.4876, No. 2.4663 and No. 2.4972) investigations of the J-integral concept in room temperature tests, of creep crack growth at 800 and 8500C and of fatigue crack growth at 700-9000C were carried out. Standard compact tension test pieces (1/2 inch and 1 inch) were used. In order to assess the transferability of crack growth relationships determined on standardized specimens to component geometries, fatigue crack growth tests were carried out on thick-walled tubes with external circumferential notches. The measurement of crack length was accomplished using the d. c. potential drop method which was further developed and optimized for these particular experimental conditions. The creep crack growth was described using the stress intensity (KI), the energy rate integral (C*) and the net stress (σnet) concepts. For description (ΔKI) could be applied. Because no dependence of fatigue crack growth on either specimen size or on specimen geometry (CT specimen, tube specimen) was found, fatigue crack growth data determined on CT specimens are transferable to tubes with circumferential notches. (orig./IHOE)

  18. The role of stress state on the fracture toughness and toughening mechanisms of wrought molybdenum and molybdenum alloys

    International Nuclear Information System (INIS)

    Rolling unalloyed molybdenum, molybdenum alloys, and Oxide Dispersion Strengthened (ODS) molybdenum into sheet produces microstructures with elongated, pancake shaped grains that can result in anisotropic mechanical properties. In this work, unalloyed molybdenum, molybdenum alloys, and ODS molybdenum are rolled to thinner sheet and then subjected to tensile and fracture toughness testing and examination of the toughening mechanism. The ductile laminate toughening mechanism observed for wrought molybdenum results from a lower toughness in the short-transverse orientation that leads to separation of the layers of sheet-like grains of the microstructure along the grain boundaries in the regions of stress concentration. This splitting of the microstructure results in the formation of ligaments of grains, or non-constrained laminates, that are stretched to failure under a plane stress-state with large amounts of plastic deformation. The thinner specimens exhibit higher fracture toughness values and lower Ductile to Brittle Transition Temperature (DBTT) values than for thicker specimens machined from thicker starting material from the same alloy. The lower constraint of the thinner specimens tested in this work results in higher toughness and lower DBTT values. The finer grain size, finer precipitate size, and state of plane stress achieved for the thinner sheet specimens appears to enhance the ductile laminate toughening to result in higher fracture toughness and lower DBTT values. The detrimental effect of crack initiation from brittle carbides, oxides, and second phases is also observed to be diminished under a stress-state of plane stress.

  19. High-temperature mechanical properties and fracture mechanisms of Al–Si piston alloy reinforced with in situ TiB2 particles

    International Nuclear Information System (INIS)

    In order to assess the high-temperature performance of aluminum–silicon alloy reinforced with titanium diboride particles as potential piston material, the tensile behaviors and fracture mechanisms of in situ 4 wt% TiB2/Al–Si composite were investigated in the temperature range 25–350 °C. The tensile results revealed that the composite exhibited higher modulus than the matrix alloy at all testing temperatures, but both the matrix alloy and the composite presented similar strength levels above 200 °C. The ductility of the composite was found to be lower than that of the unreinforced matrix alloy at 25 and 200 °C, but no obvious distinction was observed at 350 °C. The effects of temperature and the presence of TiB2 particles on tensile properties of the composite had been evaluated. Fractographic morphology studies were done using scanning electron microscope, which indicated that the fracture of the composite altered from brittle to ductile mode with temperature increasing. At 25 and 200 °C, fracture was dominated by cracked silicon particles and separated TiB2 particles, while decohesion at particle–matrix interface was prevalent at 350 °C. Analysis of the fracture surfaces also showed that regions of clustered TiB2 particles were found to be the locations prone to damage in the composite at both room and high temperatures

  20. High-temperature mechanical properties and fracture mechanisms of Al–Si piston alloy reinforced with in situ TiB{sub 2} particles

    Energy Technology Data Exchange (ETDEWEB)

    Han, Gang [School of Mechanical Engineering, Beijing Institute of Technology, 5 South Zhongguancun Street, Haidian District, Beijing 100081 (China); Zhang, Weizheng, E-mail: zhangwz@bit.edu.cn [School of Mechanical Engineering, Beijing Institute of Technology, 5 South Zhongguancun Street, Haidian District, Beijing 100081 (China); Zhang, Guohua; Feng, Zengjian; Wang, Yanjun [Shandong Binzhou Bohai Piston Co., Ltd., Binzhou 256602 (China)

    2015-05-01

    In order to assess the high-temperature performance of aluminum–silicon alloy reinforced with titanium diboride particles as potential piston material, the tensile behaviors and fracture mechanisms of in situ 4 wt% TiB{sub 2}/Al–Si composite were investigated in the temperature range 25–350 °C. The tensile results revealed that the composite exhibited higher modulus than the matrix alloy at all testing temperatures, but both the matrix alloy and the composite presented similar strength levels above 200 °C. The ductility of the composite was found to be lower than that of the unreinforced matrix alloy at 25 and 200 °C, but no obvious distinction was observed at 350 °C. The effects of temperature and the presence of TiB{sub 2} particles on tensile properties of the composite had been evaluated. Fractographic morphology studies were done using scanning electron microscope, which indicated that the fracture of the composite altered from brittle to ductile mode with temperature increasing. At 25 and 200 °C, fracture was dominated by cracked silicon particles and separated TiB{sub 2} particles, while decohesion at particle–matrix interface was prevalent at 350 °C. Analysis of the fracture surfaces also showed that regions of clustered TiB{sub 2} particles were found to be the locations prone to damage in the composite at both room and high temperatures.

  1. Strengths and Fracture Mechanisms of Al2O3 Short Fiber Reinforced Al-Mg Alloy Matrix Composite at Elevated Temperatures

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Using the experimental and theoretical methods, the tensile strengths and fracture mechanisms of Al2O3 short fiber reinforced Al-Mg alloy matrix composite at elevated temperatures were researched. The interfacial microstructural characteristics and the fracture surfaces of the composite at different temperatures were observed by transmission electron microscope (TEM) and by scanning electron microscope (SEM), respectively. Then, from the results of microscopic observation, the fracture mechanisms of the composite at different temperatures are discussed. Finally,the tensile strengths of the composite at elevated temperatures were predicted by statistical integration average (SIA) method with the consideration of various fracture mechanisms. It was shown that the strengths and fracture mechanisms of the composite at elevated temperature (300 C) were significantly different from those at room temperature due to the variations of interfacial bonding states. The tensile strengths predicted by the SIA method at elevated temperatures agreed well with the experimental results.

  2. Lead induced intergranular fracture in aluminum alloy AA6262

    NARCIS (Netherlands)

    De Hosson, JTM

    2003-01-01

    The influence of lead on the fracture behavior of aluminum alloy AA6262 is investigated. Under certain conditions, the mode of fracture changes from transgranular microvoid coalescence to an intergranular mechanism. Three different intergranular fracture mechanisms are observed: liquid metal embritt

  3. Mechanisms of intergranular fracture

    Energy Technology Data Exchange (ETDEWEB)

    Farkas, D. [Virginia Polytechnic Inst. and State Univ., Blacksburg, VA (United States). Dept. of Materials Science and Engineering

    1999-08-01

    The authors present a study of the atomistic mechanisms of crack propagation along grain boundaries in metals and alloys. The failure behavior showing cleavage crack growth and/or crack-tip dislocation emission is demonstrated using atomistic simulations for an embedded-atom model. The simulations follow the quasi-equilibrium growth of a crack as the stress intensity applied increases. Dislocations emitted from crack tips normally blunt the crack and inhibit cleavage, inducing ductile behavior. When the emitted dislocations stay near the crack tip (sessile dislocations), they do blunt the crack but brittle cleavage can occur after the emission of a sufficient number of dislocations. The fracture process occurs as a combination of dislocation emission/micro-cleavage portions that are controlled by the local atomistic structure of the grain boundary. The grain boundary is shown to be a region where dislocation emission is easier, a mechanism that competes with the lower cohesive strength of the boundary region.

  4. A fracture mechanics approach for estimating fatigue crack initiation in carbon and low-alloy steels in LWR coolant environments

    International Nuclear Information System (INIS)

    A fracture mechanics approach for elastic-plastic materials has been used to evaluate the effects of light water reactor (LWR) coolant environments on the fatigue lives of carbon and low-alloy steels. The fatigue life of such steel, defined as the number of cycles required to form an engineering-size crack, i.e., 3-mm deep, is considered to be composed of the growth of (a) microstructurally small cracks and (b) mechanically small cracks. The growth of the latter was characterized in terms of ΔJ and crack growth rate (da/dN) data in air and LWR environments; in water, the growth rates from long crack tests had to be decreased to match the rates from fatigue S-N data. The growth of microstructurally small cracks was expressed by a modified Hobson relationship in air and by a slip dissolution/oxidation model in water. The crack length for transition from a microstructurally small crack to a mechanically small crack was based on studies on small crack growth. The estimated fatigue S-N curves show good agreement with the experimental data for these steels in air and water environments. At low strain amplitudes, the predicted lives in water can be significantly lower than the experimental values

  5. Study of deformation and fracture micro mechanisms of titanium alloy Ti-6Al-4V using electron microscopy and and X-ray diffraction techniques

    International Nuclear Information System (INIS)

    This present work allowed the study of deformation and fracture micro mechanisms of titanium alloy Ti-6Al-4V, used commercially for the manufacture of metallic biomaterials. The techniques employed for the analysis of the material under study were: scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The study of the influence and behavior of the phases present in titanium alloys is important to evaluate the behavior of cracks in titanium alloys with high mechanical strength, which have fine alpha (α), beta (β) and (α±β) microstructure, linking the presence of the phases with the strength of the material. The evaluation in situ of deformation and fracture micro mechanisms were performed by TEM and was also a study of phase transformations during cooling in titanium alloys, using the techniques of bright field, dark field and diffraction of electrons in the selected area. After heat treatment differences were observed between the amount of in relation to the original microstructure of the β and α phases material for different conditions used in heat treatment applied to the alloy. The presence of lamellar microstructure formed during cooling in the β field was observed, promoting the conversion of part of the secondary alpha structure in β phase, which was trapped between the lamellar of alpha. (author)

  6. Effect of morphology of eutectic silicon crystals on mechanical properties and cleavage fracture toughness of AlSi5Cu1 alloy

    Directory of Open Access Journals (Sweden)

    M. Wierzbińska

    2005-12-01

    Full Text Available Purpose: The purpose of this paper is presentation of the results that concerned the influence of morphology of eutectic silicon crystals on mechanical properties, especially on the cleavage fracture toughness of AlSi5Cu1 alloy.Design/methodology/approach: Microscopic studies – optical microscope NIKON 300 and quantitative analysis of geometrical parameters of microstructure – image analysis program APHELION, tensile and fracture toughness tests – testing machine INSTRON 8810.Findings: The sizes of silicon crystals and values of yield strength, tensile strength and plane strain fracture toughness have been determined. Relationships between mechanical properties and silicon crystals size were described using Hall-Petch equation. It was found that a decrease in silicon crystals causes an increasing in strength and in fracture toughness.Practical implications: This paper is part of the previous author’s investigations which results in modification of the casting technology of turboblower compressor impellers.Originality/value: The microscopic observations indicated that alloy cracking begins with nucleation and growth of micro-cracks in the silicon crystals of large size, in orthogonal plane to tension direction. The hard and brittle silicon crystals are very strong barriers for slip in the stressed alloy.

  7. The role of deformation twinning in the fracture behavior and mechanism of basal textured magnesium alloys

    Energy Technology Data Exchange (ETDEWEB)

    Ando, D., E-mail: dando@material.tohoku.ac.jp; Koike, J.; Sutou, Y.

    2014-04-01

    AZ31 magnesium alloys were deformed to 10% and to failure strain by tensile loading at room temperature. Scribed grids were drawn by a focused ion beam system (FIB) to visualize the local deformation in each grain. This showed that the magnitude of the strain was distributed non-uniformly in each grain. It was found that the low-strain grains accompanied {10–12} twins, while the severely strained grains accompanied {10–11}–{10–12} double twins. Cracks nucleated at the double twins and tended to propagate along {10–12} twin interfaces as well as within grains. Furthermore, fractography revealed three types of microstructural features: dimples, elliptic facets and sheared dimples. Most abundant were the dimples formed by ductile failure. The elliptic facets appeared to be due to crack propagation along the {10–12} twin interfaces. The sheared dimples were frequently observed in connection with localized shear deformation within the double twins. These results led us to conclude that premature and catastrophic failure of Mg alloys is mainly associated with double twins. Prevention of double twinning is essential to improve the ductility of Mg alloys.

  8. A study at understanding the mechanisms governing the high cycle fatigue and final fracture behavior of the titanium alloy: Ti-4Al-2.5V

    International Nuclear Information System (INIS)

    In this research paper, the cyclic stress amplitude-controlled high cycle fatigue properties and fracture behavior of a titanium alloy are presented and discussed. The material chosen for this study is a Ti-Al-V-Fe-O2 alloy that is marketed under the trade name ATI 425TM. This alloy was initially developed and put forth for use as a ballistic material but through the last few years it gained in stature for use in other areas due to a healthy combination of physical and mechanical properties. Test specimens were prepared, in conformance with the ASTM E-8 standard, from the as-received sheet stock, which was cold rolled and mill annealed, with the rolling direction both parallel (longitudinal) and perpendicular (transverse) to the length of the sheet. The test specimens were cyclically deformed at three different load ratios (R = 0.1, R = 0.3 and R = 0.033) and the cycles-to-failure (Nf) was recorded. The fatigue fracture surfaces were examined in a scanning electron microscope to examine the macroscopic fracture mode, the intrinsic features on the fatigue fracture surface and the role of magnitude of applied stress-microstructural feature interactions in governing failure.

  9. Relationship between tensile and impact properties in Al–Si–Cu–Mg cast alloys and their fracture mechanisms

    International Nuclear Information System (INIS)

    An extensive study related to the investigation of the precipitation behavior of the CuAl2 phase in various 319-type alloys containing strontium (Sr), iron (Fe) and phosphorus (P) alloying elements, and its dissolution during solution heat treatment at 490 °C for times up to 100 h was carried out in the present work. Furthermore, the effect of CuAl2 and other intermetallics on the alloy performance under two different heat treatment conditions (i.e. T5 and T6) was also investigated through an examination of the tensile and impact properties. By comparing the experimental results, conclusions were drawn in terms of the optimum alloying elements, solidification parameters and heat treatment conditions (viz., Sr modification, Fe content, cooling rate and T6 condition). The fracture behaviors of the 319 base alloy and the Sr-modified 319 alloy containing ∼1.2% Fe were also compared through a study of the fracture surfaces of the corresponding alloy samples. The results explicitly reveal that solution heat treatment plays a critical role in the dissolution of the CuAl2 phase. Iron addition leads to an increased precipitation of brittle β-Al5FeSi platelets which act as preferred crack sites and dramatically reduce the impact properties, regardless of the value of dendrite arm spacing. Crack initiation usually occurs through the fragmentation of Si particles and β-Al5FeSi platelets, and the crack propagates through the cleavage of β-Al5FeSi platelets. - Highlights: • The addition of Sr leads to the segregation of the copper phase • The addition of Fe results in the dispersion of the CuAl2 • The CuAl2 phase particles are more or less completely dissolved in the Al matrix after 100 h of solution heat treatment • After T6 heat treatment most of the CuAl2 phase particles are dissolved into the aluminum matrix

  10. Fracture mechanics safety approaches

    Energy Technology Data Exchange (ETDEWEB)

    Roos, E.; Schuler, X.; Eisele, U. [Materials Testing Inst. (MPA), Univ. of Stuttgart (Germany)

    2004-07-01

    Component integrity assessments require the knowledge of reliable fracture toughness parameters characterising the initiation of the failure process in the whole relevant temperature range. From a large number of fracture mechanics tests a statistically based procedure was derived allowing to quantify the initiation of fracture toughness as a function of temperature as a closed function as well as the temperature dependence of the cleavage instability parameters. Alternatively to the direct experimental determination one also can use a correlation between fracture toughness and notch impact energy. (orig.)

  11. Fracture of niobium-base silicide coated alloy

    International Nuclear Information System (INIS)

    Mechanical properties and character of fracture of Nb-W-Mo-Zr-C alloy composition with complex by composition and structure silicide coating under different states of stage-by-stage coating are studied. Structural features, character of fracture from ductile to quasibrittle transcrystalline one and, respectively, the composition plasticity level are defined by interrelation of fracture processes in coating, matrix plastic flow and possibility and way of stress relaxation on their boundary

  12. Fracture performance of high strength steels, aluminium and magnesium alloys during plastic deformation

    Directory of Open Access Journals (Sweden)

    Yu Haiyan

    2015-01-01

    Full Text Available A series of uniaxial tension tests were performed for 5052 and 6061 aluminum alloys, AZ31B magnesium alloy, TRIP600 and DP600 steels, to obtain a better understanding of their fracture performance. Scanning electron microscope (SEM observation of the microstructure evolution was conducted. The dimple structure, orientation relationship between the fracture surface and tensile direction, necking behavior were analyzed. The fracture mechanism and fracture mode of each material was discussed in detail. The results show that TRIP600 steel is subject to a typical inter-granular ductile fracture combined by shear fracture. DP600 steel belongs to mainly ductility mixed with normal fracture. Both 5052 and 6061 aluminum alloys are subject to a mixed ductility fracture and brittle fracture. AA5052 and AA6061 belong to a typical shear fracture and a normal fracture, respectively. Magnesium AZ31B is typical of a brittle fracture combined with normal fracture.

  13. Probabilistic fracture mechanics

    International Nuclear Information System (INIS)

    It has been attempted to present the elements of probabilistic fracture mechanics in a self-contained way. First, for brittle fracture, damage theories are discussed which allow for the effects of both size and local strength of the structure on the probability of fracture. Second, combined crack and damage theories are presented. They provide insight into macro-crack formation and take into account the effects of crack orientation and multiaxial states of stress. For fatigue, both the two-phase theory of damage and crack extension as well as the cumulative theory (of damage or of crack extension) are presented. They give estimates for the lifetime of a structure under random load. The effect of random material properties may be included. Finally, an assessment of the probability of failure of reactor pressure vessels is discussed. There, brittle fracture and fatigue are taken into account and both fracture toughness and crack size are considered to be random quantities. (Auth.)

  14. Mechanisms of plastic instability and fracture of compressed and tensile tested Mg-Li alloys investigated using the acoustic emission method

    Directory of Open Access Journals (Sweden)

    A. Pawełek

    2016-01-01

    Full Text Available The results of the investigation of both mechanical and acoustic emission (AE behaviors of Mg4Li5Al alloy subjected to compression and tensile tests at room temperature are compared with the test results obtained using the same alloy and loading scheme but at elevated temperatures. The main aim of the paper is to investigate, to determine and to explain the possible influence of factors related with enhanced internal stresses such as: segregation of precipitates along grain boundaries or solute atoms along dislocations (Cottrell atmospheres or dislocation pile-ups at grain boundaries which create very high stress concentration leading to fracture. The results show that the plastic instabilities are related to the Portevin–Le Châtelier phenomenon (PL effect and they are correlated with the generation of AE peaks. The fractography of breaking samples was analyzed on the basis of light (optical, TEM and SEM images.

  15. Fracture Criterion for Fracture Mechanics of Magnets

    Institute of Scientific and Technical Information of China (English)

    潘灏; 杨文涛

    2003-01-01

    The applicability and limitation of some fracture criteria in the fracture mechanics of magnets are studied.It is shown that the magnetic field intensity factor can be used as a fracture criterion when the crack in a magnet is only affected by a magnetic field. For some magnetostrictive materials in which the components of magnetostriction strain do not satisfy the compatibility equation of deformation, the stress intensity factor can no longer be effectively applicable as a fracture criterion when the crack in a magnet is affected by a magnetic field and mechanical loads simultaneously.

  16. Phase Field Fracture Mechanics.

    Energy Technology Data Exchange (ETDEWEB)

    Robertson, Brett Anthony [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2015-11-01

    For this assignment, a newer technique of fracture mechanics using a phase field approach, will be examined and compared with experimental data for a bend test and a tension test. The software being used is Sierra Solid Mechanics, an implicit/explicit finite element code developed at Sandia National Labs in Albuquerque, New Mexico. The bend test experimental data was also obtained at Sandia Labs while the tension test data was found in a report online from Purdue University.

  17. Fracture Mechanics of Concrete

    DEFF Research Database (Denmark)

    Ulfkjær, Jens Peder

    Chapter 1 Chapter l contains the introduction to this thesis. The scope of the thesis is partly to investigate different numerical and analytical models based on fracture mechanical ideas, which are able to predict size effects, and partly to perform an experimental investigation on high-strength......Chapter 1 Chapter l contains the introduction to this thesis. The scope of the thesis is partly to investigate different numerical and analytical models based on fracture mechanical ideas, which are able to predict size effects, and partly to perform an experimental investigation on high......-strength concrete. Chapter 2 A description of the factors which influence the strength and cracking of concrete and high strength concrete is made. Then basic linear fracture mechanics is outlined followed by a description and evaluation of the models used to describe concrete fracture in tension. The chapter ends...... and the goveming equations are explicit and simple. These properties of the model make it a very powerful tool, which is applicable for the designing engineer. The method is also extended to reinforced concrete, where the results look very promising. The large experimental investigation on high-strength concrete...

  18. Mechanical behaviour of aluminium-lithium alloys

    Indian Academy of Sciences (India)

    N Eswara Prasad; A A Gokhale; P Rama Rao

    2003-02-01

    Aluminium-lithium alloys hold promise of providing a breakthrough response to the crying need for lightweight alloys for use as structurals in aerospace applications. Considerable worldwide research has gone into developing a range of these alloys over the last three decades. As a result, substantial understanding has been developed of the microstructure-based micromechanisms of strengthening, of fatigue and fracture as well as of anisotropy in mechanical properties. However, these alloys have not yet greatly displaced the conventionally used denser Al alloys on account of their poorer ductility, fracture toughness and low cycle fatigue resistance. This review aims to summarise the work pertaining to study of structure and mechanical properties with a view to indicate the directions that have been and can be pursued to overcome property limitations.

  19. Characterization of fracture and deformation mechanism in a high strength beta titanium alloy Ti-10-2-3 using EBSD technique

    International Nuclear Information System (INIS)

    In the present study, fracture toughness tested specimens in longitudinal (LT) and transverse loading (TL) directions of beta titanium alloy have been investigated using Electron Back Scattered Diffraction (EBSD) technique. The orientation images captured at three different locations i.e. machine notch, fatigue pre-crack and final fracture have been compared. The LT sample exhibits with more facets than TL sample. The faceted aspect of the crack is generally associated with quasi-cleavage mechanism. The EBSD analysis clearly points out that in the LT specimen, the hexagonal orientation has moved towards near basal during the test. This may be the reason for the observance of facets in the LT specimen. The cracking in TL specimen might have been taken over by the bcc phase as it is oriented with harder planes of cubic {001} planes. Further, the Schmid factor has also been computed based on the defined loading conditions. Significant variation has been observed in the slip plane orientations and distributions at these three locations. The Schmid analysis has highlighted the significant contribution of different slip systems towards deformation and cracking in LT and TL specimens

  20. Mechanisms and modeling of cleavage fracture in simulated heat-affected zone microstructures of a high-strength low alloy steel

    Science.gov (United States)

    Lambert-Perlade, A.; Sturel, T.; Gourgues, A. F.; Besson, J.; Pineau, A.

    2004-03-01

    The effect of the welding cycle on the fracture toughness properties of high-strength low alloy (HSLA) steels is examined by means of thermal simulation of heat-affected zone (HAZ) microstructures. Tensile tests on notched bars and fracture toughness tests at various temperatures are performed together with fracture surface observations and cross-sectional analyses. The influence of martensite-austenite (M-A) constituents and of “crystallographic” bainite packets on cleavage fracture micromechanisms is, thus, evidenced as a function of temperature. Three weakest-link probabilistic models (the “Master-curve” (MC) approach, the Beremin model, and a “double-barrier” (DB) model) are applied to account for the ductile-to-brittle transition (DBT) fracture toughness curve. Some analogy, but also differences, are found between the MC approach and the Beremin model. The DB model, having nonfitted, physically based scatter parameters, is applied to the martensite-containing HAZ microstructures and gives promising results.

  1. Mechanical alloying in immiscible alloy systems

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    In recent years, mechanical alloying (MA) of immiscible alloy systems characterized by positive heat of mixing has been extensively investigated. The present article reviews the latest progress in MA of immiscible alloy systems including the mechanisms of non-equilibrium phase transformation and metastable phase formation of the MA-driven supersaturated solid solutions, amorphous phases and nanophase composites as well as their mechanical and physical properties related to those metastable phases.

  2. EFFECT OF TESTING ENVIRONMENT ON FRACTURING BEHAVIOR OF Fe3Si BASED ALLOY

    Institute of Scientific and Technical Information of China (English)

    J.H. Peng; G.L. Chen

    2003-01-01

    The mechanical behavior of Fe3Si based alloy with B2 structure was studied by tensionand fracture toughness test in various testing media. The fracture strength σb ofFe3Si alloy decreased in the following order: oxygen, air and hydrogen respectively.The fracture toughness in different testing environment showed that KiC in oxygenis 11.5±0.3MPa. m1/2, and is 8.6±0.4MPa. m1/2 in distilled water. The reductionof fracture toughness is contributed to the environmental reaction of Si with water.Addition of Al element in Fe3Si is not beneficial to improve the intrinsic ductility ofFe-14Si-3Al alloy. The scattering phenomenon of fracture strength was found, andexplained by fracture mechanics. It was found by means of SEM that the fracture modechanged from transgranular in oxygen to intergranular in hydrogen gas and distilledwater.

  3. Mechanical properties of fracture zones

    International Nuclear Information System (INIS)

    Available data on mechanical characteristics of fracture zones are compiled and discussed. The aim is to improve the basis for adequate representation of fracture zones in geomechanical models. The sources of data researched are primarily borehole investigations and case studies in rock engineering, involving observations of fracture zones subjected to artificial load change. Boreholes only yield local information about the components of fracture zones, i.e. intact rock, fractures and various low-strength materials. Difficulties are therefore encountered in evaluating morphological and mechanical properties of fracture zones from borehole data. Although often thought of as macroscopically planar features, available field data consistently show that fracture zones are characterized by geometrical irregularities such as thickness variations, surface undulation and jogs. These irregularities prevail on all scales. As a result, fracture zones are on all scales characterized by large, in-plane variation of strength- and deformational properties. This has important mechanical consequences in terms of non-uniform stress transfer and complex mechanisms of shear deformation. Field evidence for these findings, in particular results from the underground research laboratory in Canada and from studies of induced fault slip in deep mines, is summarized and discussed. 79 refs

  4. Mechanisms of Plastic and Fracture Instabilities for Alloy Development of Fusion Materials. Final Project Report for period July 15, 1998 - July 14, 2003

    Energy Technology Data Exchange (ETDEWEB)

    Ghoniem, N. M.

    2003-07-14

    The main objective of this research was to develop new computational tools for the simulation and analysis of plasticity and fracture mechanisms of fusion materials, and to assist in planning and assessment of corresponding radiation experiments.

  5. Mechanisms of plastic instability and fracture of compressed and tensile tested Mg-Li alloys investigated using the acoustic emission method

    OpenAIRE

    A. Pawełek; A. Piątkowski; W. Wajda; W. Skuza; A. Tarasek; W. Ozgowicz; B. Grzegorczyk; Z. Ranachowski; S. Kúdela; S. Kúdela, Jr.

    2016-01-01

    The results of the investigation of both mechanical and acoustic emission (AE) behaviors of Mg4Li5Al alloy subjected to compression and tensile tests at room temperature are compared with the test results obtained using the same alloy and loading scheme but at elevated temperatures. The main aim of the paper is to investigate, to determine and to explain the possible influence of factors related with enhanced internal stresses such as: segregation of precipitates along grain bound...

  6. Fracture toughness of irradiated stainless steel alloys

    International Nuclear Information System (INIS)

    The postirradiation fracture toughness responses of Types 316 and 304 stainless steel (SS) wrought products, cast CF8 SS and Type 308 SS weld deposit were characterized at 4270C using J/sub R/-curve techniques. Fast-neutron irradiation of these alloys caused an order of magnitude reduction in J/sub c/ and two orders of magnitude reduction in tearing modulus at neutron exposures above 10 dpa, where radiation-induced losses in toughness appeared to saturate. Saturation J/sub c/ values for the wrought materials ranged from 28 to 31 kJ/m2; the weld exhibited a saturation level of 11 kJ/m2. Maximum allowable flaw sizes for highly irradiated stainless steel components stressed to 90% of the unirradiated yield strength are on the order of 3 cm for the wrought material and 1 cm for the weld. Electron fractographic examination revealed that irradiation displacement damage brought about a transition from ductile microvoid coalescence to channel fracture, associated with local separation along planar deformation bands. The lower saturation toughness value for the weld relative to that for the wrought products was attributed to local failure of ferrite particles ahead of the advancing crack which prematurely initiated channel fracture

  7. Finnie's notes on fracture mechanics fundamental and practical lessons

    CERN Document Server

    Dharan, C K H; Finnie, Iain

    2016-01-01

    This textbook consists primarily of notes by Iain Finnie who taught a popular course on fracture mechanics at the University of California at Berkeley. It presents a comprehensive and detailed exposition of fracture, the fundamentals of fracture mechanics and procedures for the safe design of engineering components made from metal alloys, brittle materials like glasses and ceramics, and composites. Interesting and practical problems are listed at the end of most chapters to give the student practice in applying the theory. A solutions manual is provided to the instructor. The text presents a unified perspective of fracture with a strong fundamental foundation and practical applications. In addition to its role as a text, this reference would be invaluable for the practicing engineer who is involved in the design and evaluation of components that are fracture critical. This book also: Presents details of derivations of the basic equations of fracture mechanics and the historical context of the development of f...

  8. The effect of microstructure on the fracture toughness of titanium alloys

    Science.gov (United States)

    Vanstone, R. H.; Low, J. R., Jr.; Shannon, J. L., Jr.

    1974-01-01

    The microstructure of the alpha titanium alloy Ti-5Al-2.5Sn and the metastable beta titanium alloy Beta 3 was examined. The material was from normal and extra low interstitial grade plates which were either air-cooled or furnace-cooled from an annealing treatment. Beta 3 was studied in alpha-aged and omega-aged plates which were heat treated to similar strength levels. Tensile and plane strain fracture toughness tests were conducted at room temperature on the alpha-aged material. The microstructure and fracture mechanisms of alloys were studied using optical metallography, electron microscopy, microprobe analyses, and texture pole figures. Future experiments are described.

  9. Polymer blends formed by the solid state mechanical alloying process

    OpenAIRE

    Farrell, Michael P.

    1994-01-01

    In the early 1970's a new processing technique to produce metallic alloys was developed by Benjamin and co-workers. This novel technique, called Mechanical Alloying (MA), involves the repeated welding, working hardening, and fracture of metallic powders to form an alloy. The research presented in this thesis describes the use of the MA process to form polymer blends. Until recently there has been no published work discussing the possibility of using this technique with polymers...

  10. Continuum damage and fracture mechanics

    CERN Document Server

    Öchsner, Andreas

    2016-01-01

    This textbook offers readers an introduction to damage and fracture mechanics, equipping them to grasp the basic ideas of the presented approaches to modeling in applied mechanics. In the first part, the book reviews and expands on the classical theory of elastic and elasto-plastic material behavior. A solid understanding of these two topics is the essential prerequisite to advancing to damage and fracture mechanics. Thus, the second part of this course provides an introduction to the treatment of damage and fractures in the context of applied mechanics. Wherever possible, the one-dimensional case is first introduced and then generalized in a following step. This departs somewhat from the more classical approach, where first the most general case is derived and then simplified to special cases. In general, the required mathematics background is kept to a minimum.   Tutorials are included at the end of each chapter, presenting the major steps for the solution and offering valuable tips and tricks. The supplem...

  11. Influence of Electric Field on Mechanical Properties of Al-Li Alloy Containing Cerium and Electronic Mechanism

    Institute of Scientific and Technical Information of China (English)

    刘兵; 陈铮; 王永欣; 王西宁

    2001-01-01

    The effect of electric field on the mechanical properties and microstructure of Al-Li alloy containing Ce was investigated, and mechanism was discussed. The experimental results show that the ductility of the alloy is enhanced by the electric field. The fracture features are changed and the precipitates are dispersed under the effect of the electric field. The mechanism discussion reveals that the effects of the electric field on the alloy are due to the change of the electron density in the alloy.

  12. Mechanically Alloyed High Entropy Composite

    Science.gov (United States)

    Popescu, G.; Adrian, M. M.; Csaki, I.; Popescu, C. A.; Mitrică, D.; Vasile, S.; Carcea, I.

    2016-08-01

    In the last years high entropy alloys have been investigated due to their high hardness, high temperature stability and unusual properties that make these alloys to have significant interest. In comparison with traditional alloys that are based on two or three major elements, this new generation alloys consists at least of 5 principal elements, with the concentration between 5 and 35 at.%. The present paper reports synthesis of high entropy alloys (HEA) and high entropy composites (HEC) synthesized by mechanical alloying (MA). The equiatomic AlCrFeNiMn matrix was used for creating the HEA matrix, starting from elemental powders and as reinforcing material for composites was used pure graphite. The mechanical alloying process was carried out at different duration, in a high energy planetary ball mill, under argon atmosphere. The elemental powders alloying began after '5 hours of milling and was complete after 40 hours. The mechanical alloyed matrix and composite was pressed and heat treated under argon protection. The elemental powers were investigated for physical - technological properties, and by X-ray diffraction and scanning electron microscopy. Phase pressing operation was realized with a hydraulic press and the applied pressure was progressive. The sintering process was carried out at 850°C for 2 h. The X-ray diffraction revealed that the MA process resulted in solid solutions formation and also revealed body- centred cubic (BCC) and face-centred cubic (FCC) structures with average grain size around 40 nm. In addition, nanoscale particles were highlighted by scanning electron microscopy, as well as the homogeneity of the chemical composition of the matrix and composite that was confirmed by EDX microanalysis. It was noted that HEA matrix and HEA composites were processed with a high degree of compaction and with a quite large capacity of mixed powder densification (around 70%).

  13. A study of cyclic fatigue, damage initiation, damage propagation, and fracture of welded titanium alloy plate

    International Nuclear Information System (INIS)

    In this paper, the influence of test specimen orientation and microstructure on cyclic stress-amplitude controlled fatigue response, damage initiation, damage propagation and fracture behavior of samples taken from a welded plate of titanium alloy is presented and discussed. Test specimens from the chosen alloy were prepared from an as-welded plate of the material with the stress axis both parallel (longitudinal) and perpendicular (transverse) to the deformed (rolling) direction of the plate. The test specimens were cyclically deformed at different values of maximum stress at a constant load ratio of 0.1, and the resultant cycles-to-failure was recorded. The fracture surfaces of the deformed and failed test specimens were examined in a scanning electron microscope to establish the macroscopic fracture mode, the intrinsic features on the fatigue fracture surface and the role of applied stress-microstructural feature interactions in establishing the microscopic mechanisms governing failure.

  14. Microstructure, tensile properties and fracture behavior of high temperature Al–Si–Mg–Cu cast alloys

    International Nuclear Information System (INIS)

    The high temperature tensile behavior of 354 aluminum cast alloy was investigated in the presence of Zr and Ni. The cast alloys were given a solutionizing treatment followed by artificial aging at 190 °C for 2 h. High temperature tensile tests were conducted at various temperatures from 25 °C to 300 °C. Optical microscopy and electron probe micro-analyzer were used to study the microstructure of different intermetallic phases formed. The fractographic observations of fracture surface were analyzed by scanning electron microscopy to understand the fracture mechanism. The results revealed that the intermetallics phases of (Al, Si)3(Zr, Ti), Al3CuNi and Al9NiFe are the main feature in the microstructures of alloys with Zr and Ni additions. The results also indicated that the tensile strength of alloy decreases with an increase in temperature. The combined addition of 0.2 wt% Zr and 0.2 wt% Ni leads to a 30% increase in the tensile properties at 300 °C compared to the base alloy. Zr and Ni bearing phases played a vital role in the fracture mechanism of the alloys studied

  15. Microstructure, tensile properties and fracture behavior of high temperature Al–Si–Mg–Cu cast alloys

    Energy Technology Data Exchange (ETDEWEB)

    Mohamed, A.M.A., E-mail: madel@uqac.ca [Center for Advanced Materials, Qatar University, Doha (Qatar); Department of Metallurgical and Materials Engineering, Faculty of Petroleum and Mining Engineering, Suez Canal University, Box 43721, Suez (Egypt); Samuel, F.H. [Université du Québec à Chicoutimi, Chicoutimi, QC, Canada G7H 2B1 (Canada); Al Kahtani, Saleh [Industrial Engineering Program, Mechanical Engineering Department, College of Engineering, Salman bin Abdulaziz University, Al Kharj (Saudi Arabia)

    2013-08-10

    The high temperature tensile behavior of 354 aluminum cast alloy was investigated in the presence of Zr and Ni. The cast alloys were given a solutionizing treatment followed by artificial aging at 190 °C for 2 h. High temperature tensile tests were conducted at various temperatures from 25 °C to 300 °C. Optical microscopy and electron probe micro-analyzer were used to study the microstructure of different intermetallic phases formed. The fractographic observations of fracture surface were analyzed by scanning electron microscopy to understand the fracture mechanism. The results revealed that the intermetallics phases of (Al, Si){sub 3}(Zr, Ti), Al{sub 3}CuNi and Al{sub 9}NiFe are the main feature in the microstructures of alloys with Zr and Ni additions. The results also indicated that the tensile strength of alloy decreases with an increase in temperature. The combined addition of 0.2 wt% Zr and 0.2 wt% Ni leads to a 30% increase in the tensile properties at 300 °C compared to the base alloy. Zr and Ni bearing phases played a vital role in the fracture mechanism of the alloys studied.

  16. Fracture Mechanisms in Steel Castings

    Directory of Open Access Journals (Sweden)

    Z. Stradomski

    2013-07-01

    Full Text Available The investigations were inspired with the problem of cracking of steel castings during the production process. A single mechanism of decohesion - the intergranular one - occurs in the case of hot cracking, while a variety of structural factors is decisive for hot cracking initiation, depending on chemical composition of the cast steel. The low-carbon and low-alloyed steel castings crack due to the presence of the type II sulphides, the cause of cracking of the high-carbon tool cast steels is the net of secondary cementite and/or ledeburite precipitated along the boundaries of solidified grains. Also the brittle phosphor and carbide eutectics precipitated in the final stage solidification are responsible for cracking of castings made of Hadfield steel. The examination of mechanical properties at 1050°C revealed low or very low strength of high-carbon cast steels.

  17. Fracture toughness of Alloy 600 and EN82H weld in air and water

    Energy Technology Data Exchange (ETDEWEB)

    Mills, W.J.; Brown, C.M.

    1999-06-01

    The fracture toughness of Alloy 600 and its weld, EN82H, was characterized in 54 C to 338 C air and hydrogenated water. Elastic-plastic J{sub IC} testing was performed due to the inherent high toughness of these materials. Alloy 600 exhibited excellent fracture toughness under all test conditions. While EN82H welds displayed excellent toughness in air and high temperature water, a dramatic toughness degradation occurred in water at temperatures below 149 C. Comparison of the cracking response in low temperature water with that for hydrogen-precharged specimens tested in air demonstrated that the loss in toughness is due to a hydrogen-induced intergranular cracking mechanism. At loading rates about approx. 1000 MPa {radical}m/h, the toughness in low temperature water is improved because there is insufficient time for hydrogen to embrittle grain boundaries. Electron fractographic examinations were performed to correlate macroscopic properties with key microstructural features and operative fracture mechanisms.

  18. Fracture mechanics of mollusc shells

    Energy Technology Data Exchange (ETDEWEB)

    Cortie, Michael B. [Institute for Nanoscale Technology, University of Technology, Sydney (Australia)]. E-mail: michael.cortie@uts.edu.au; McBean, Katie E. [Microstructural Analysis Unit, University of Technology, Sydney (Australia); Elcombe, Margaret M. [Bragg Institute, Australian Nuclear Science and Technology Organisation, PMB 1, NSW (Australia)

    2006-11-15

    The shape and structure of the shells of molluscs has attracted considerable attention. One aspect of interest is the comparatively high resistance to fracture of these shells. It is known that they are composite structures of aragonite, other calcereous materials, and up to 5% by volume of protein 'glue'. A large component of their toughening derives from crack tip blunting, deflection and closure, concepts well-known from the field of fracture mechanics. However, the possibility that they might also derive a measure of toughening from a residual stress distribution has been generally overlooked, although Illert first raised this over a decade ago. The optimum situation would be when the inner surface of the shell is maintained in a state of tensile stress, while the outer layers are in the necessarily counter-balancing compressive state. We have examined this hypothesis using a combination of neutron diffraction and scanning electron microscopy and find that it is certainly feasible. However, a definitive proof will require a diffraction study at higher resolution.

  19. Fracture Mechanics: Inspirations from Nature

    Directory of Open Access Journals (Sweden)

    David Taylor

    2014-10-01

    Full Text Available In Nature there are many examples of materials performing structural functions. Nature requires materials which are stiff and strong to provide support against various forces, including self-weight, the dynamic forces involved in movement, and external loads such as wind or the actions of a predator. These materials and structures have evolved over millions of years; the science of Biomimetics seeks to understand Nature and, as a result, to find inspiration for the creation of better engineering solutions. There has been relatively little fundamental research work in this area from a fracture mechanics point of view. Natural materials are quite brittle and, as a result, they have evolved several interesting strategies for preventing failure by crack propagation. Fatigue is also a major problem for many animals and plants. In this paper, several examples will be given of recent work in the Bioengineering Research Centre at Trinity College Dublin, investigating fracture and fatigue in such diverse materials as bamboo, the legs and wings of insects, and living cells.

  20. Non-alloyed Ni3Al based alloys – preparation and evaluation of mechanical properties

    Directory of Open Access Journals (Sweden)

    J. Malcharcziková

    2013-07-01

    Full Text Available The paper reports on the fabrication and mechanical properties of Ni3Al based alloy, which represents the most frequently used basic composition of nickel based intermetallic alloys for high temperature applications. The structure of the alloy was controlled through directional solidification. The samples had a multi-phase microstructure. The directionally solidified specimens were subjected to tensile tests with concurrent measurement of acoustic emission (AE. The specimens exhibited considerable room temperature ductility before fracture. During tensile testing an intensive AE was observed.

  1. Recent trends in fracture and damage mechanics

    CERN Document Server

    Zybell, Lutz

    2016-01-01

    This book covers a wide range of topics in fracture and damage mechanics. It presents historical perspectives as well as recent innovative developments, presented by peer reviewed contributions from internationally acknowledged authors.  The volume deals with the modeling of fracture and damage in smart materials, current industrial applications of fracture mechanics, and it explores advances in fracture testing methods. In addition, readers will discover trends in the field of local approach to fracture and approaches using analytical mechanics. Scholars in the fields of materials science, engineering and computational science will value this volume which is dedicated to Meinhard Kuna on the occasion of his 65th birthday in 2015. This book incorporates the proceedings of an international symposium that was organized to honor Meinhard Kuna’s contributions to the field of theoretical and applied fracture and damage mechanics.

  2. Physical fracture properties (fracture surfaces as information sources; crackgrowth and fracture mechanisms; exemples of cracks)

    International Nuclear Information System (INIS)

    Fracture surfaces are considered as a useful source of informations: an introduction to fractography is presented; the fracture surface may be observed through X ray microanalysis, and other physical methods such as Auger electron spectroscopy or secundary ion emission. The mechanisms of macroscopic and microscopic crackgrowth and fracture are described, in the case of unstable fracture (cleavage, ductile with shear, intergranular brittleness) and of progressive crack propagation (creep, fatigue). Exemples of cracks are presented in the last chapter

  3. Fracture characteristics of structural aerospace alloys containing deep surface flaws. [aluminum-titanium alloys

    Science.gov (United States)

    Masters, J. N.; Bixler, W. D.; Finger, R. W.

    1973-01-01

    Conditions controlling the growth and fracture of deep surface flaws in aerospace alloys were investigated. Static fracture tests were performed on 7075-T651 and 2219-T87 aluminum, and 6Ai-4V STA titanium . Cyclic flaw growth tests were performed on the two latter alloys, and sustain load tests were performed on the titanium alloy. Both the cyclic and the sustain load tests were performed with and without a prior proof overload cycle to investigate possible growth retardation effects. Variables included in all test series were thickness, flaw depth-to-thickness ratio, and flaw shape. Results were analyzed and compared with previously developed data to determine the limits of applicability of available modified linear elastic fracture solutions.

  4. Effect of alloying addition and microstructural parameters on mechanical properties of 93% tungsten heavy alloys

    Energy Technology Data Exchange (ETDEWEB)

    Ravi Kiran, U., E-mail: uravikiran@gmail.com [Defence Metallurgical Research Laboratory, Kanchanbagh, Hyderabad 500 058 (India); Panchal, A.; Sankaranarayana, M. [Defence Metallurgical Research Laboratory, Kanchanbagh, Hyderabad 500 058 (India); Nageswara Rao, G.V.S. [National Institute of Technology, Warangal 506004 (India); Nandy, T.K. [Defence Metallurgical Research Laboratory, Kanchanbagh, Hyderabad 500 058 (India)

    2015-07-29

    Liquid phase sintering, heat treatment and swaging studies on three tungsten heavy alloys, 93W–4.9Ni–2.1Fe (wt%), 93W–4.2Ni–1.2Fe–1.6Co (wt%) and 93W–4.9Ni–1.9Fe–0.2Re (wt%) were carried out in detail with respect to microstructure, tensile and impact properties. All the alloys were sintered and swaged to 40% deformation. The results indicate that Re addition reduces the grain size of the alloy compared to W–Ni–Fe and W-Ni-Fe-Co alloys. W–Ni–Fe–Re alloy shows superior tensile properties in heat treated condition as compared to W–Ni–Fe and W–Ni–Fe–Co alloys. SEM study of fractured specimens clearly indicates that the failure in case of W–Ni–Fe–Re was due to transgranular cleavage of tungsten grains and W–W de-cohesion. W–Ni–Fe and W–Ni–Fe–Co alloys also failed by mixed mode failure. However, in these cases, ductile dimples corresponding the failure of the matrix phase was rarely seen. Thermo-mechanical processing resulted in significant changes in mechanical properties. While W–Ni–Fe–Re alloy showed the highest tensile strength (1380 MPa), W–Ni–Fe–Co exhibited the highest elongation (12%) to failure. A detailed analysis involving microstructure, mechanical properties and failure behavior was undertaken in order to understand the property trends.

  5. Fracture mechanics of piezoelectric and ferroelectric solids

    CERN Document Server

    Fang, Daining

    2013-01-01

    Fracture Mechanics of Piezoelectric and Ferroelectric Solids presents a systematic and comprehensive coverage of the fracture mechanics of piezoelectric/ferroelectric materials, which includes the theoretical analysis, numerical computations and experimental observations. The main emphasis is placed on the mechanics description of various crack problems such static, dynamic and interface fractures as well as the physical explanations for the mechanism of electrically induced fracture. The book is intended for postgraduate students, researchers and engineers in the fields of solid mechanics, applied physics, material science and mechanical engineering. Dr. Daining Fang is a professor at the School of Aerospace, Tsinghua University, China; Dr. Jinxi Liu is a professor at the Department of Engineering Mechanics, Shijiazhuang Railway Institute, China.

  6. Research of quasi-solid fracture behavior of casting AI-4.5Cu alloys

    Directory of Open Access Journals (Sweden)

    Shengquan DONG

    2005-02-01

    Full Text Available The influencing mechanisms of elements Ti and Ce and their interactions on fracture behaviors of casting alloys AI-4.5Cu-0.6Mn were studied by observing tensile fracture behavior in quasi-solid zone under SEM and EDX instruments.The results indicate that the resistance stress against hot cracking can be improved obviously by addition of Ti, because of its grain refining function. It is also found that, when Ce is added into the alloys, besides its effect in refining crystalline, the mechanical behavior of lower melting point eutectic phase in quasi-solid zone can be improved efficiently by some compounds with Ce formed and deposited between dendrites. Therefore, a colligating effect of Ti and Ce on improving resistance stress against hot cracking is more efficient than that only single alloy element is applied. When hot cracking occurs, grains yield at first, and then crack spreads. Both inter-grain and trans-grain fractures are observed, but the major fracture manner is brittleness.

  7. Effect of interfacial solute segregation on ductile fracture of Al–Cu–Sc alloys

    International Nuclear Information System (INIS)

    Three-dimensional atom probe analysis is employed to characterize the Sc segregation at θ′/α-Al interfaces in Al–2.5 wt.% Cu–0.3 wt.% Sc alloys aged at 473, 523 and 573 K, respectively. The interfacial Sc concentration is quantitatively evaluated and the change in interfacial energy caused by Sc segregation is assessed, which is in turn correlated to yield strength and ductility of the alloys. The strongest interfacial Sc segregation is generated in the 523 K-aged alloy, resulting in an interfacial Sc concentration about 10 times greater than that in the matrix and a reduction of ∼25% in interfacial energy. Experimental results show that the interfacial Sc segregation promotes θ′ precipitation and enhances the strengthening response. A scaling relationship between the interfacial energy and precipitation strengthening increment is proposed to account for the most notable strengthening effect observed in the 523 K-aged alloy, which is ∼2.5 times that in its Sc-free counterpart and ∼1.5 times that in the 473 and 573 K-aged Al–Cu–Sc alloys. The interfacial Sc segregation, however, causes a sharp drop in the ductility when the precipitate radius is larger than ∼200 nm in the 523 K-aged alloy, indicative of a transition in fracture mechanisms. The underlying fracture mechanism for the low ductility regime, revealed by in situ transmission electron microscopy tensile testing, is that interfacial decohesion occurs at the θ′ precipitates ahead of crack tip and favorably aids the crack propagation. A micromechanical model is developed to rationalize the precipitate size-dependent transition in fracture mechanisms by taking into account the competition between interfacial voiding and matrix Al rupture that is tailored by interfacial Sc segregation

  8. Mechanisms of hydraulic fracturing in cohesive soil

    Directory of Open Access Journals (Sweden)

    Jun-jie WANG

    2009-12-01

    Full Text Available Hydraulic fracturing in the soil core of earth-rockfill dams is a common problem affecting the safety of the dams. Based on fracture tests, a new criterion for hydraulic fracturing in cohesive soil was suggested. Using this criterion, the mechanisms of hydraulic fracturing in cubic soil specimens were investigated. The results indicate that the propagation of the crack in a cubic specimen under water pressure occurs in a mixed mode I-II if the crack face is not perpendicular to any of the principal stresses, and the crack most likely to propagate is the one that is perpendicular to the minor principal stress and propagates in mode I.

  9. Mechanisms of hydraulic fracturing in cohesive soil

    OpenAIRE

    Wang, Jun-Jie; Zhang, Hui-ping; Ming-jie ZHAO; Lin, Xin

    2009-01-01

    Hydraulic fracturing in the soil core of earth-rockfill dams is a common problem affecting the safety of the dams. Based on fracture tests, a new criterion for hydraulic fracturing in cohesive soil was suggested. Using this criterion, the mechanisms of hydraulic fracturing in cubic soil specimens were investigated. The results indicate that the propagation of the crack in a cubic specimen under water pressure occurs in a mixed mode I-II if the crack face is not perpendicular to any of the pri...

  10. Effect of titanium addition on fracture toughness behavior of ZL108 alloy

    Institute of Scientific and Technical Information of China (English)

    WENG Yong-gang; LI Zi-jing; LIU Zhi-yong; LIU Wen-cai; WANG Ming-xing; SONG Tian-fu

    2006-01-01

    Two different titanium alloying methods were applied to ZL108 alloy for preparing specimens containing titanium. The specimens were tested on the MTS 810 material test system for studying their behavior of the plane strain fracture toughness KIC. The experimental data were analyzed by the statistical significance tests. The results show that the fracture toughness of the ZL108 alloy containing titanium is superior to that of common ZL108 alloy containing no titanium, but there is no significant difference for different titanium alloying methods. Therefore titanium addition is an effective method for improving the fracture toughness of the alloy ZL108.

  11. Fracture analysis of Ag nanobrazing of NiTi to Ti alloy

    Energy Technology Data Exchange (ETDEWEB)

    Quintino, L., E-mail: lquirino@ist.utl.pt [Universidade Tecnica de Lisboa (IST/UTL) (Portugal). Instituto Superior Tecnico. Dept. de Engenharia Mecanica; Liu, L., E-mail: ray.plasma@gmail.com [Tsinghua Univ., Beijing (China). Dept. of Mechanical Engineering; Hu, A.; Zhou, Y., E-mail: anming.hu@uwaterloo.ca, E-mail: nzhou@uwaterloo.ca [University of Waterloo, Ontario (Canada). Dept. of Mechanical Engineering; Miranda, R.M., E-mail: rmiranda@fct.unl.pt [Universidade Nova de Lisboa (UNIDEMI), Caparica (Portugal). Dept. de Engenharia Mecanica e Industrial

    2013-07-15

    Dissimilar joining of shape memory alloys to Ti alloys has long been attempted by several research groups due to the foreseen potential industrial applications. However, the very dissimilar thermo-physical properties of both materials place several difficulties. Brazing can be a solution since the base materials are subjected to a less sharp thermal cycle. In the present study brazed overlap joints of 1 mm thick plates of equiatomic Ni Ti and Ti6Al4V were produced using nano silver based filler materials. Surfaces were analyzed to asses the type of fracture and the capability of achieving bonding and involved mechanisms are discussed. (author)

  12. Process development for 9Cr nanostructured ferritic alloy (NFA) with high fracture toughness

    Science.gov (United States)

    Byun, Thak Sang; Yoon, Ji Hyun; Hoelzer, David T.; Lee, Yong Bok; Kang, Suk Hoon; Maloy, Stuart A.

    2014-06-01

    This article is to summarize the process development and key characterization results for the newly-developed Fe-9Cr based nanostructured ferritic alloys (NFAs) with high fracture toughness. One of the major drawbacks from pursuing ultra-high strength in the past development of NFAs is poor fracture toughness at high temperatures although a high fracture toughness is essential to prevent cracking during manufacturing and to mitigate or delay irradiation-induced embrittlement in irradiation environments. A study on fracture mechanism using the NFA 14YWT found that the low-energy grain boundary decohesion in fracture process at a high temperature (>200 °C) resulted in low fracture toughness. Lately, efforts have been devoted to explore an integrated process to enhance grain bonding. Two base materials were produced through mechanical milling and hot extrusion and designated as 9YWTV-PM1 and 9YWTV-PM2. Isothermal annealing (IA) and controlled rolling (CR) treatments in two phase region were used to enhance diffusion across the interfaces and boundaries. The PM2 alloy after CR treatments showed high fracture toughness (KJQ) at represented temperatures: 240-280 MPa √m at room temperature and 160-220 MPa √m at 500 °C, which indicates that the goal of 100 MPa √m over possible nuclear application temperature range has been well achieved. Furthermore, it is also confirmed by comparison that the CR treatments on 9YWTV-PM2 result in high fracture toughness similar to or higher than those of the conventional ferritic-martensitic steels such as HT9 and NF616.

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

    Directory of Open Access Journals (Sweden)

    Yuanxin Wang

    2016-03-01

    Full Text Available 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 (KIC 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.

  14. Effect of mechanical alloying on FeCrC reinforced Ni alloys

    Energy Technology Data Exchange (ETDEWEB)

    Yilmaz, S. Osman [Univ. of Namik Kemal, Tekirdag (Turkey); Teker, Tanju [Adiyaman Univ. (Turkey). Dept. of Metallurgical and Materials Engineering; Demir, Fatih [Batman Univ. (Turkey)

    2016-05-01

    Mechanical alloying (MA) is a powder metallurgy processing technique involving cold welding, fracturing and rewelding of powder particles in a high-energy ball mill. In the present study, the intermetallic matrix composites (IMCs) of Ni-Al reinforced by M{sub 7}C{sub 3} were produced by powder metallurgical routes via solid state reaction of Ni, Al and M{sub 7}C{sub 3} particulates by mechanical alloying processes. Ni, Al and M{sub 7}C{sub 3} powders having 100 μm were mixed, mechanical alloyed and the compacts were combusted in a furnace. The mechanically alloyed (MAed) powders were investigated by X-ray diffraction (XRD), microhardness measurement, optic microscopy (OM), scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS). The presence of the carbides depressed the formation of unwanted NiAl intermetallic phases. The mechanical alloyed M{sub 7}C{sub 3} particles were unstable and decomposed partially within the matrix during alloying and sintering, and the morphology of the composites changed with the dissolution ratio of M{sub 7}C{sub 3} and sintering temperature.

  15. Laser treatment of aluminum copper alloys: A mechanical enhancement

    International Nuclear Information System (INIS)

    Aluminum-copper alloys are commonly used as structural components for the car and aircraft industry. They combine low density, high strength, high fracture toughness and good machinability. Moreover, the strength and wear-resistance of the surface of alloys are improved by a high power laser beam. In this way the molten surface will be self-quenched by conduction of heat into the bulk. This technique ensures solidification velocities of 0.01--1 m/s. These high solidification velocities have a significant influence on the size and distribution of the morphology. This work concentrates on Al-Cu alloys, in which the Cu content ranges between 0--40 wt.%, and is aimed at describing the mechanical and microstructural properties of these alloys upon variation of the laser scan velocity in the range of 0.0125 to 0.125 m/s

  16. Influence of microstructure on work-hardening and ductile fracture of aluminium alloys

    International Nuclear Information System (INIS)

    Highlights: • Microstructural effects on work-hardening and fracture of aluminium are studied. • Four alloys with three different processing steps are tested in uniaxial tension. • An experimental–numerical approach is used to determine the work-hardening. • The microstructure has a strong effect on both work-hardening and ductility. • A linear decrease in failure strain with yield stress for the materials is found. - Abstract: The effect of microstructure on the work-hardening and ductile fracture of aluminium alloys was studied using an experimental–numerical approach. Four aluminium alloys with different strength and particle content were tested in uniaxial tension after the following subsequent processing steps: (1) casting and homogenisation, (2) extrusion, and (3) cold rolling followed by heat treatment. The latter processing step was carried out to obtain a recrystallized grain structure with random crystallographic texture. The alloys were two AlFe alloys with different Fe content, one AlMn alloy and one AlMgSi alloy. The grain structure, particle distribution and crystallographic texture were determined for all combinations of alloy and processing route using optical and scanning electron microscopy. Tensile tests were carried out on axisymmetric samples to obtain the true stress–strain curves to failure and the true failure strain of the materials, using a laser-based measuring system. Based on numerical simulations of the tensile tests, the equivalent stress–strain curves were determined to failure, assuming J2 flow theory. The results showed that the microstructure had a marked effect on both work-hardening and ductility, whilst the ductile fracture mechanism remained unchanged. The plastic anisotropy, induced by the extrusion process and not entirely removed by the cold rolling and heat treatment, led to a wide range of fracture modes of the axisymmetric samples. The failure strain was markedly lower for the cast and homogenised

  17. Mechanical Behaviour of Materials Volume II Fracture Mechanics and Damage

    CERN Document Server

    François, Dominique; Zaoui, André

    2013-01-01

    Designing new structural materials, extending lifetimes and guarding against fracture in service are among the preoccupations of engineers, and to deal with these they need to have command of the mechanics of material behaviour. This ought to reflect in the training of students. In this respect, the first volume of this work deals with elastic, elastoplastic, elastoviscoplastic and viscoelastic behaviours; this second volume continues with fracture mechanics and damage, and with contact mechanics, friction and wear. As in Volume I, the treatment links the active mechanisms on the microscopic scale and the laws of macroscopic behaviour. Chapter I is an introduction to the various damage phenomena. Chapter II gives the essential of fracture mechanics. Chapter III is devoted to brittle fracture, chapter IV to ductile fracture and chapter V to the brittle-ductile transition. Chapter VI is a survey of fatigue damage. Chapter VII is devoted to hydogen embrittlement and to environment assisted cracking, chapter VIII...

  18. Mechanical behavior and coupling between mechanical and oxidation in alloy 718: effect of solide solution elements

    International Nuclear Information System (INIS)

    Alloy 718 is the superalloy the most widely used in industry due to its excellent mechanical properties, as well as oxidation and corrosion resistance in wide range of temperatures and solicitation modes. Nevertheless, it is a well-known fact that this alloy is sensitive to stress corrosion cracking and oxidation assisted cracking under loading in the range of temperatures met in service. Mechanisms explaining this phenomenon are not well understood: nevertheless, it is well established that a relation exists between a change in fracture mode and the apparition of plastic instabilities phenomenon. During this study, the instability phenomenon, Portevin-Le Chatelier effect, in alloy 718 was studied by tensile tests in wide ranges of temperatures and strain rates. Different domains of plastic instabilities have been evidenced. Their characteristics suggest the existence of interactions between dislocations and different types of solute elements: interstitials for lower temperatures and substitutionals for higher testing temperatures. Mechanical spectroscopy tests have been performed on alloy 718 and various alloys which composition is comparable to that of alloy 718. These tests prove the mobility of molybdenum atoms in the alloy in the studied temperature range. Specific tests have been performed to study interaction phenomenon between plasticity and oxidation. These results highlight the strong effect of plastic strain rate on both mechanical behavior and intergranular cracking in alloy 718. The subsequent discussion leads to propose hypothesis on coupling effects between deformation mechanisms and oxidation assisted embrittlement in the observed cracking processes. (author)

  19. Bending Strength and Fracture Behavior of Ni50Mn29Ga21 Alloy with Terbium

    Institute of Scientific and Technical Information of China (English)

    ZHAO Zeng-qi; XIONG Wei; WU Shuang-xia; WANG Xin-lin

    2004-01-01

    The bending strength and fracture behaviors of Ni50Mn29Ga21 alloy with terbium were investigated. The results show that the bending strength of the alloy is increased dramatically with the increase of terbium content. The fracture appearance of the sample without terbium is dominated by grain boundary fracture, while that with terbium is dominated by cleavage fracture with the increase of terbium content.Moreover, the grains are refined obviously and the oxygen content is decreased after adding terbium.

  20. Mechanical properties of low alloy high phosphorus weathering steel

    OpenAIRE

    Jena B.K.; Gupta N; Singh B; Ahoo G.S.

    2015-01-01

    Mechanical behaviour of two low alloy steels (G11 and G12) was studied with respect to different phosphorus contents. Tensile strength and yield strength increased while percentage elongation at fracture decreased on increasing phosphorus content. The SEM and light optical photomicrograph of low phosphorus steel (G11) revealed ferrite and pearlite microstructure. On increasing phosphorus content from 0.25 wt.% to 0.42 wt.%, the morphology of grain changed f...

  1. On the intergranular fracture behavior of high-temperature plastic deformation of 1420 Al-Li alloy

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The tensile deformation hot simulation test of as-cast 1420 Al-Li alloy was performed on Gleeble-1500 Thermal Simulator in the deformation temperature range from 350 to 450 ℃, and the strain rate range from 0.01 to 10.0 s-1.The tensile fracture behavior of the 1420 Al-Li alloy at high temperature was studied experimently. The results show that the tensile fracture mode of the 1420 Al-Li alloy at high temperature is changed from typical transgranular ductile fracture to intergranular brittle fracture with the increase of the deformation temperature and the strain rate. It is made out that the precipitation of LiH is the fundamental reason for the intergranular brittle fracture of the 1420 Al-Li alloy at high temperature. The mechanism of hydrogen embrittlement of the 1420 Al-Li alloy at high temperature was discussed, and it was proposed that the hydrogen embrittlement at high temperature is an integrated function of the dynamic and the static force, which enrichs the theories of hydrogen embrittlement.

  2. Investigation on mechanical behaviour of AM60 magnesium alloys

    Directory of Open Access Journals (Sweden)

    C. Yan

    2008-12-01

    Full Text Available Purpose: In this work, tension, impact, bend and fatigue tests were conducted in an AM60 magnesium alloy. The effects of environmental temperature and loading rates on impact and tension behavior of the alloy were also investigated.Design/methodology/approach: The tests were conducted using an Instron universal testing machine. The loading speed was changed from 1 mm/min to 300 mm/min to gain a better understanding of the effect of strain rate. To understand the failure behavior of this alloy at different environmental temperatures, Charpy impact test was conducted in a range of temperatures (-40~35°C. Plane strain fracture toughness (KIC was evaluated using compact tension (CT specimen. To gain a better understanding of the failure mechanisms, all fracture surfaces were observed using scanning electron microscopy (SEM. In addition, fatigue behavior of this alloy was estimated using tension test under tension-tension condition at 30 Hz. The stress amplitude was selected in the range of 20~50 MPa to obtain the S-N curve.Findings: The tensile test indicated that the mechanical properties were not sensitive to the strain rates applied (3.3x10-4~0.1 and the plastic deformation was dominated by twining mediated slip. The impact energy is not sensitive to the environmental temperature. The plane strain fracture toughness and fatigue limit were evaluated and the average values were 7.6 MPa.m1/2 and 25 MPa, respectively. Practical implications: Tested materials AM60 Mg alloy can be applied among others in automotive industry aerospace, communication and computer industry.Originality/value: Many investigations have been conducted to develop new Mg alloys with improved stiffness and ductility. On the other hand, relatively less attention has been paid to the failure mechanisms of Mg alloys, such as brittle fracture and fatigue, subjected to different environmental or loading conditions. In this work, tension, impact, bend and fatigue tests were conducted

  3. The Origin of Fracture in the I-ECAP of AZ31B Magnesium Alloy

    Science.gov (United States)

    Gzyl, Michal; Rosochowski, Andrzej; Boczkal, Sonia; Qarni, Muhammad Jawad

    2015-11-01

    Magnesium alloys are very promising materials for weight-saving structural applications due to their low density, comparing to other metals and alloys currently used. However, they usually suffer from a limited formability at room temperature and low strength. In order to overcome those issues, processes of severe plastic deformation (SPD) can be utilized to improve mechanical properties, but processing parameters need to be selected with care to avoid fracture, very often observed for those alloys during forming. In the current work, the AZ31B magnesium alloy was subjected to SPD by incremental equal-channel angular pressing (I-ECAP) at temperatures varying from 398 K to 525 K (125 °C to 250 °C) to determine the window of allowable processing parameters. The effects of initial grain size and billet rotation scheme on the occurrence of fracture during I-ECAP were investigated. The initial grain size ranged from 1.5 to 40 µm and the I-ECAP routes tested were A, BC, and C. Microstructures of the processed billets were characterized before and after I-ECAP. It was found that a fine-grained and homogenous microstructure was required to avoid fracture at low temperatures. Strain localization arising from a stress relaxation within recrystallized regions, namely twins and fine-grained zones, was shown to be responsible for the generation of microcracks. Based on the I-ECAP experiments and available literature data for ECAP, a power law between the initial grain size and processing conditions, described by a Zener-Hollomon parameter, has been proposed. Finally, processing by various routes at 473 K (200 °C) revealed that route A was less prone to fracture than routes BC and C.

  4. Application of microstatistical fracture mechanics to dynamic fracture problems

    International Nuclear Information System (INIS)

    This chapter presents a microstatistical treatment of shear bands. Describes the microstatistical fracture mechanics (MSFM) approach by illustrating its use in the case of shock-induced ductile voids in steel. Shows that the microstatistical approach merges with the continuum approach. Computes the behavior of a macrocrack propagating in a DCB specimen by using MSFM and the data generated in the shock wave experiments. Discusses shockwave-induced ductile fractures; plate impact experiments; data analysis; progress in MSFM and required research efforts; and macrocrack propagation. Points out that although continuum treatments have the advantage of simplicity and low cost, the more complex and expensive MSFM treatment may be the only viable approach when detailed information is needed such as size, velocity, and trajectory distributions of fragments ejected from a plate of armor steel after impact

  5. Influence of annealing on stain hardening behaviour and fracture properties of a cryorolled Al 2014 alloy

    International Nuclear Information System (INIS)

    The influence of annealing on strength, ductility, strain hardening, plastic instability and fracture behaviour are studied in the present work on a cryorolled Al 2014 alloy by tensile test, transmission electron microscopy, macrograph analysis and fractography study. Investigations on the cryorolled alloy have been done for different annealing temperatures in the range of 100–400 °C and the results obtained are correlated with the microstructural evolution, precipitation behaviour and post failure analysis. Study reveals a complex trend in ductility and strain hardening behaviour as a result of simultaneous occurrence of dislocation annihilation, recrystallization and precipitation evolution during annealing. By investigations of fractured samples, dominant mode of fracture is found to be shear deformation and upon annealing the fracture mechanism is affected jointly by propagation of microvoids and shear deformation due to combined action of precipitation and microstructural evolution. Yield strength is increased by 4 times after cryorolling and retained after annealing up to 100 °C. It even remains higher than the base material up to 350 °C, due to the combined effect of precipitation hardening and thermal stability of microstructure

  6. Influence of annealing on stain hardening behaviour and fracture properties of a cryorolled Al 2014 alloy

    Energy Technology Data Exchange (ETDEWEB)

    Dhal, A.; Panigrahi, S.K., E-mail: skpanigrahi@iitm.ac.in; Shunmugam, M.S.

    2015-10-01

    The influence of annealing on strength, ductility, strain hardening, plastic instability and fracture behaviour are studied in the present work on a cryorolled Al 2014 alloy by tensile test, transmission electron microscopy, macrograph analysis and fractography study. Investigations on the cryorolled alloy have been done for different annealing temperatures in the range of 100–400 °C and the results obtained are correlated with the microstructural evolution, precipitation behaviour and post failure analysis. Study reveals a complex trend in ductility and strain hardening behaviour as a result of simultaneous occurrence of dislocation annihilation, recrystallization and precipitation evolution during annealing. By investigations of fractured samples, dominant mode of fracture is found to be shear deformation and upon annealing the fracture mechanism is affected jointly by propagation of microvoids and shear deformation due to combined action of precipitation and microstructural evolution. Yield strength is increased by 4 times after cryorolling and retained after annealing up to 100 °C. It even remains higher than the base material up to 350 °C, due to the combined effect of precipitation hardening and thermal stability of microstructure.

  7. Study on strength and fracture toughness of Al-Zn-Mg-Cu-Ti(-Sn alloys

    Directory of Open Access Journals (Sweden)

    Yan A.

    2015-01-01

    Full Text Available The strength and fracture toughness of Al-Zn-Mg-Cu-Ti(-Sn alloys were investigated by performing tensile and plane strain fracture toughness (KIC tests. Detailed observations with optical, scanning electron and transmission electron microscopy were conducted to analyze microstructure and fracture surfaces of the alloys. The results revealed that addition of Sn refined the solution-aging grain size of matrix and reduced coarsening rate of precipitate during aging. Narrower precipitation free zones and more discontinuous distribution of grain boundary precipitates were observed to be displayed in the Sn-containing alloy. Small size second phase particles Mg2Sn were observed to form in the Sn-containing alloy and distribute in the fine dimples of fracture surface. These features of microstructure were believed to impart higher strength and fracture toughness of the Sn-containing alloy on overaging.

  8. Mechanical alloying of biocompatible Co-28Cr-6Mo alloy.

    Science.gov (United States)

    Sánchez-De Jesús, F; Bolarín-Miró, A M; Torres-Villaseñor, G; Cortés-Escobedo, C A; Betancourt-Cantera, J A

    2010-07-01

    We report on an alternative route for the synthesis of crystalline Co-28Cr-6Mo alloy, which could be used for surgical implants. Co, Cr and Mo elemental powders, mixed in an adequate weight relation according to ISO Standard 58342-4 (ISO, 1996), were used for the mechanical alloying (MA) of nano-structured Co-alloy. The process was carried out at room temperature in a shaker mixer mill using hardened steel balls and vials as milling media, with a 1:8 ball:powder weight ratio. Crystalline structure characterization of milled powders was carried out by X-ray diffraction in order to analyze the phase transformations as a function of milling time. The aim of this work was to evaluate the alloying mechanism involved in the mechanical alloying of Co-28Cr-6Mo alloy. The evolution of the phase transformations with milling time is reported for each mixture. Results showed that the resultant alloy is a Co-alpha solid solution, successfully obtained by mechanical alloying after a total of 10 h of milling time: first Cr and Mo are mechanically prealloyed for 7 h, and then Co is mixed in for 3 h. In addition, different methods of premixing were studied. The particle size of the powders is reduced with increasing milling time, reaching about 5 mum at 10 h; a longer time promotes the formation of aggregates. The morphology and crystal structure of milled powders as a function of milling time were analyzed by scanning electron microscopy and XR diffraction. PMID:20364362

  9. Numerical methods in dynamic fracture mechanics

    International Nuclear Information System (INIS)

    A review of numerical methods for the solution of dynamic problems of fracture mechanics is presented. Finite difference, finite element and boundary element methods as applied to linear elastic or viscoelastic and non-linear elastoplastic or elastoviscoplastic dynamic fracture mechanics problems are described and critically evaluated. Both cases of stationary cracks and rapidly propagating cracks of simple I, II, III or mixed modes are considered. Harmonically varying with time or general transient dynamic disturbances in the form of external loading or incident waves are taken into account. Determination of the dynamic stress intensity factor for stationary cracks or moving cracks with known velocity history as well as determination of the crack-tip propagation history for given dynamic fracture toughness versus crack velocity relation are described and illustrated by means of certain representative examples. Finally, a brief assessment of the present state of knowledge is made and research needs are identified

  10. Geometry, mechanics and transmissivity of rock fractures

    International Nuclear Information System (INIS)

    This thesis work investigates methods and tools for characterising, testing and modelling the behaviour of rock fractures. Using a 3D-laser-scanning technique, the topography of the surfaces and their position with respect to one another are measured. From the fracture topography, fracture roughness, angularity and aperture are quantified; the major features used for characterisation. The standard deviations for the asperity heights, surface slopes and aperture are determined. These statistical parameters usually increase/decrease according to power laws of the sampling size, and sometimes reach a sill beyond which they become constant. Also the number of contact spots with a certain area decreases according to a power-law function of the area. These power-law relations reveal the self affine fractal nature of roughness and aperture. Roughness is 'persistent' while aperture varies between 'persistent' and 'anti-persistent' probably depending on the degree of match of the fracture walls. The fractal models for roughness, aperture and contact area are used to develop a constitutive model, based on contact mechanics, for describing the fracture normal and shear deformability. The experimental testing results of normal deformability are simulated well by the model whereas fracture shear deformability is not as well modelled. The model predicts well fracture dilation but is too stiff compared to rock samples. A mathematical description of the aperture pattern during shearing is also formulated. The mean value and covariance of the aperture in shearing is calculated and verifies reported observations. The aperture map of samples is inserted in a numerical program for flow calculation. The 'integral transform method' is used for solving the Reynolds' equation; it transforms the fracture transmissivity pattern into a frequency-based function. This closely resembles the power laws that describe fractals. This function can be described directly from the fractal properties of

  11. Corrosion and mechanical properties of AM50 magnesium alloy after being modified by 1 wt.% rare earth element gadolinium

    Institute of Scientific and Technical Information of China (English)

    杨淼; 刘耀辉; 刘家安; 宋雨来

    2014-01-01

    In order to improve the corrosion and mechanical properties of AM50 magnesium alloy, 1 wt.% Gd was used to modify the AM50 magnesium alloy. The microstructure, corrosion and mechanical properties were evaluated by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), electrochemical and mechanical stretch methods. The results indicated that β-Mg17Al12 phase decreased and Al2Gd3 and Al0.4GdMn1.6 phase existed after Gd addition. Because of the Gd addition, the grain of AM50 magnesium alloy was refined significantly, which improved the tensile strength of AM50 magnesium al-loy. The decreasing ofβ phase improved the corrosion resistance of the magnesium alloy. The fracture mechanism of the Gd modified AM50 magnesium alloy was quasi-cleavage fracture. The corrosion residual strength (CRS) of AM50 magnesium alloy was im-proved after 1 wt.% Gd addition.

  12. Interrelation of material microstructure, ultrasonic factors, and fracture toughness of two phase titanium alloy

    Science.gov (United States)

    Vary, A.; Hull, D. R.

    1982-01-01

    The pivotal role of an alpha-beta phase microstructure in governing fracture toughness in a titanium alloy, Ti-662, is demonstrated. The interrelation of microstructure and fracture toughness is demonstrated using ultrasonic measurement techniques originally developed for nondestructive evaluation and material property characterization. It is shown that the findings determined from ultrasonic measurements agree with conclusions based on metallurgical, metallographic, and fractographic observations concerning the importance of alpha-beta morphology in controlling fracture toughness in two phase titanium alloys.

  13. Microstructural features of intergranular brittle fracture and cold cracking in high strength aluminum alloys

    NARCIS (Netherlands)

    Lalpoor, M.; Eskin, D. G.; ten Brink, Gert; Katgerman, L.

    2010-01-01

    Intergranular brittle fracture has been mainly observed and reported in steel alloys and precipitation hardened At-alloys where intergranular precipitates cover a major fraction of the grain boundary area. 7xxx series aluminum alloys suffer from this problem in the as-cast condition when brittle int

  14. Fractures and Rock Mechanics, Phase 1

    DEFF Research Database (Denmark)

    Krogsbøll, Anette; Jakobsen, Finn; Madsen, Lena

    1997-01-01

    The main objective of the project is to combine geological descriptions of fractures, chalk types and rock mechanical properties in order to investigate whether the chosen outcrops can be used as analogues to reservoir chalks. This report deals with 1) geological descriptions of outcrop locality ...

  15. Fractures and Rock Mechanics, Phase 1

    DEFF Research Database (Denmark)

    Havmøller, Ole; Krogsbøll, Anette

    1997-01-01

    The main objectives of the project are to combine geological description of fractures, chalk types and rock mechanical properties, and to investigate whether the chosen outcrops can be used as analogues to reservoir chalks. Five chalk types, representing two outcrop localities: Stevns and...

  16. Effects of Magnetic Field on Fracture of Al-Li Alloy Containing Cerium

    Institute of Scientific and Technical Information of China (English)

    刘兵; 王西宁; 陈铮

    2003-01-01

    The effects of magnetic field on fracture feature and microstructure of Al-Li alloys containing Ce were investigated. Experiment results show that the fracture features and the microstructures are changed with the magnetic field. The fracture surface of the alloys is mainly quasi-cleavage without applying magnetic field. With a magnetic field, the fracture of quasi-cleavage changes to more secondary cracks and less quasi-cleavage plates on fracture surface. Grains become thinner and uniform with applying magnetic field. The influence of magnetic field on atom diffusion was discussed.

  17. Fractographic features of W-Ni-Fe (90:7:3) alloy fractures. Review

    Energy Technology Data Exchange (ETDEWEB)

    Minakova, R.V.; Vojtenko, V.L.; Verkhovodov, P.A.; Nedelyaeva, L.P.; Kalinyuk, N.N. (AN Ukrainskoj SSR, Kiev. Inst. Problem Materialovedeniya)

    1985-02-01

    Fractographic peculiarities of W-Ni-Fe (90:7:3) alloy fractures are considered as well as their correlation with mechanical properties depending on thermal treatment conditions after liquid phase sintering and conditions of mechanical tests. It is shown that intergranular and transcrystallite failure of structural components occurs on the stages of crack formation and propagation. Tungsten-base refractory component may transcrystallitically fail forming fan and herring-bone patterns. Nickel-base ..gamma..-solid solution may fail transcrystallitically and on grain-colonies boundaries. The main failure varieties are established on boundaries of basic structural components. Their formation is associated with variation of adhesion strength of the boundary and geometry of ..gamma..-solid solution (grain body and near-boundary volumes) depending on conditions of thermal treatment after liquid phase sintering. It is shown that the greatest plasticity and strength at room temperature is peculiar for the alloy where transcrystallitic failure is predominant for both components.

  18. Fracture mechanics of collagen fibrils

    DEFF Research Database (Denmark)

    Svensson, Rene B; Mulder, Hindrik; Kovanen, Vuokko;

    2013-01-01

    technique to measure the mechanical behavior of individual collagen fibrils loaded to failure. Fibrils from human patellar tendons, rat-tail tendons (RTTs), NaBH₄ reduced RTTs, and tail tendons of Zucker diabetic fat rats were tested. We found a characteristic three-phase stress-strain behavior in the human...... fibrils is limited. The presence of covalent enzymatic cross-links between collagen molecules is an important factor that has been shown to influence mechanical behavior of the tendons. To improve our understanding of how molecular bonds translate into tendon mechanics, we used an atomic force microscopy...... and the plateau continued until failure. The importance of cross-link lability was investigated by NaBH₄ reduction of the rat-tail fibrils, which did not alter their behavior. These findings shed light on the function of cross-links at the fibril level, but further studies will be required to establish...

  19. Comparison of fracture behavior for low-swelling ferritic and austenitic alloys irradiated in the Fast Flux Test Facility (FFTF) to 180 DPA

    International Nuclear Information System (INIS)

    Fracture toughness testing was conducted to investigate the radiation embrittlement of high-nickel superalloys, modified austenitic steels and ferritic steels. These materials have been experimentally proven to possess excellent resistance to void swelling after high neutron exposures. In addition to swelling resistance, post-irradiation fracture resistance is another important criterion for reactor material selection. By means of fracture mechanics techniques the fracture behavior of those highly irradiated alloys was characterized in terms of irradiation and test conditions. Precipitation-strengthened alloys failed by channel fracture with very low postirradiation ductility. The fracture toughness of titanium-modified austenitic stainless steel D9 deteriorates with increasing fluence to about 100 displacement per atom (dpa), the fluence level at which brittle fracture appears to occur. Ferritic steels such as HT9 are the most promising candidate materials for fast and fusion reactor applications. The upper-shelf fracture toughness of alloy HT9 remained adequate after irradiation to 180 dpa although its ductile- brittle transition temperature (DBTT) shift by low temperature irradiation rendered the material susceptible to brittle fracture at room temperature. Understanding the fracture characteristics under various irradiation and test conditions helps reduce the potential for brittle fracture by permitting appropriate measure to be taken

  20. Computational simulation methods for composite fracture mechanics

    Science.gov (United States)

    Murthy, Pappu L. N.

    1988-01-01

    Structural integrity, durability, and damage tolerance of advanced composites are assessed by studying damage initiation at various scales (micro, macro, and global) and accumulation and growth leading to global failure, quantitatively and qualitatively. In addition, various fracture toughness parameters associated with a typical damage and its growth must be determined. Computational structural analysis codes to aid the composite design engineer in performing these tasks were developed. CODSTRAN (COmposite Durability STRuctural ANalysis) is used to qualitatively and quantitatively assess the progressive damage occurring in composite structures due to mechanical and environmental loads. Next, methods are covered that are currently being developed and used at Lewis to predict interlaminar fracture toughness and related parameters of fiber composites given a prescribed damage. The general purpose finite element code MSC/NASTRAN was used to simulate the interlaminar fracture and the associated individual as well as mixed-mode strain energy release rates in fiber composites.

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

    International Nuclear Information System (INIS)

    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. Use of fracture mechanics parameters to characterize comminution

    OpenAIRE

    Hao, Bin

    1996-01-01

    This report is to investigate the use of fracture mechanics parameters (fracture toughness, specific work of fracture) to characterize comminution process. Comminution is a very important industrial process and is extremely low in efficiency. Establishment of a crushing index based on fracture mechanics principles is of great significance for improved machine design and enhanced efficiency. Single particle fracture study has been reviewed because it is considered the most eleme...

  3. Fracture criterion for predicting surface cracking of Ti40 alloy in hot forming processes

    Institute of Scientific and Technical Information of China (English)

    ZHANG Xue-min; ZENG Wei-dong; SHU Ying; ZHOU Yi-gang; ZHAO Yong-qing; WU Huan; YU Han-qing

    2009-01-01

    Hot compression tests were conducted on Ti40 burn resistant titanium alloy in the temperature range of 900-1 100 ℃ and strain rate range of 0.01-10 s-1 to investigate its fracture behavior and critical fracture conditions in hot forming. It was observed that the failure of Ti40 alloy is attributed to longitudinal surface cracking due to severe oxidation of element V and the secondary tensile stresses. The critical fracture strain increases with increasing temperature and decreasing strain rate. From these observations and parallel FEM simulations, it was concluded that the critical fracture strain is a function of a single argument Zener-Hollomon parameter, and there is a linear relationship between them. An Oyane criterion successfully predicted the location of crack initiation. The critical fracture values also exhibit a liner relationship with lnZ. Based on these results, a new fracture criterion of Ti40 alloy based on Zener-Hollomon parameter was established.

  4. Effects of irradiation to 4 dpa at 390 C on the fracture toughness of vanadium alloys

    Energy Technology Data Exchange (ETDEWEB)

    Gruber, E.E.; Galvin, T.M.; Chopra, O.K. [Argonne National Lab., IL (United States)

    1998-09-01

    Fracture toughness J-R curve tests were conducted at room temperature on disk-shaped compact-tension DC(T) specimens of three vanadium alloys having a nominal composition of V-4Cr-4Ti. The alloys in the nonirradiated condition showed high fracture toughness; J{sub IC} could not be determined but is expected to be above 600 kJ/m{sup 2}. The alloys showed very poor fracture toughness after irradiation to 4 dpa at 390 C, e.g., J{sub IC} values of {approx}10 kJ/m{sup 2} or lower.

  5. Environmentally induced fracture of nickel alloys: a comparison of hydrogen and mercury embrittlement with respect to temperature

    International Nuclear Information System (INIS)

    Previous studies have compared electrolytic hydrogen embrittlement (HE) and liquid metal embrittlement (LME) by mercury for numerous nickel alloys. All alloys tested exhibited embrittlement to some degree with HE and LME having similar fractographies. This study examines the effect of temperature on He and LME of Monel 400 over the range -30 and 800C. Slow strain rate tensile tests were conducted at two strain rates, 1.6 x 10-5s-1 and 1.6 x 10-3s-1, and two grain sizes, 35 μm and 250 μm. Behavior of Monel 400 is compared with previously studied nickel alloys. Results showed that intergranular, tranogranular, and microvoid-coalescence fractures can be obtained in both hydrogen and mercury. Fracture mode is governed by strain at fracture. Embrittlement ceases below -200 in both environment, believed due to lack of mobility of adsorbed hydrogen and lack of wetting by mercury. LME is more severe than HE because hydrogen blunts cracks by promoting plasticity. HE ceases at about 800C because excess plasticity promotes crack blunting and inhibits initiation. LME fractures remain brittle to 800C. An incubation period is normally needed for adsorption of the embrittler or for penetration of the crack through the plane stress surface zone. Otherwise ductile failures in mercury often exhibit longitudinal splitting, believed to be due to the combination of high normal stress, low shear stress, and a clean surface. The existence of a temperature window for LME can be explained on the basis of strain activated localized wetting. Results of this study are consistent with a decohesion mechanism producing intergranular fracture; competing with an enhanced dislocation nucleation mechanism producing transgranular fracture. Monel 400 exhibited the range of features observed for other nickel base alloys at appropriate conditions of temperature, strain rate, and grain size

  6. A Study On Critical Thinning In Thin-walled Tube Bending Of Al-Alloy 5052O Via Coupled Ductile Fracture Criteria

    Science.gov (United States)

    Li, Heng; Yang, He; Zhan, Mei

    2010-06-01

    Thin-walled tube bending(TWTB) method of Al-alloy tube has attracted wide applications in aerospace, aviation and automobile,etc. While, under in-plane double tensile stress states at the extrados of bending tube, the over-thinning induced ductile fracture is one dominant defect in Al-alloy tube bending. The main objective of this study is to predict the critical wall-thinning of Al-alloy tube bending by coupling two ductile fracture criteria(DFCs) into FE simulation. The DFCs include Continuum Damage Mechanics(CDM)-based model and GTN porous model. Through the uniaxial tensile test of the curved specimen, the basic material properties of the Al-alloy 5052O tube is obtained; via the inverse problem solution, the damage parameters of both the two fracture criteria are interatively determined. Thus the application study of the above DFCs in the TWTB is performed, and the more reasonable one is selected to obtain the critical thinning of Al-alloy tube in bending. The virtual damage initiation and evolution (when and where the ductile fracture occurs) in TWTB are investigated, and the fracture mechanisms of the voided Al-alloy tube in tube bending are consequently discussed.

  7. Effects of cooling rate on the fracture properties of TA15 ELI alloy plates

    Institute of Scientific and Technical Information of China (English)

    LI Shikai; XIONG Baiqing; HUI Songxiao

    2007-01-01

    The effects of cooling rate on the mechanical properties and the fatigue crack growth behavior of TA15 ELI alloy plates with different microstructures were investigated at room temperature. The results indicate that the cooling rate (water quench, air cooling, and furnace cooling) has a pronounced influence on the mechanical properties and on the fatigue crack growth,especially for air cooling and furnace cooling.Optical microstructure observation and scanning electron microscopy of tensile fracture surfaces were performed to gain an insight into the mechanism of properties.The dependence of mechanical properties and fatigue crack growth behavior on the cooling rate can be attributed to the α lamellae width and the α colony size,which induce the change in slip length. The microstructure produced by air cooling shows the best damage tolerance behavior when compared with water quench and furnace cooling.

  8. Strengthening of Aluminum Alloy 2219 by Thermo-mechanical Treatment

    Science.gov (United States)

    Li, Xifeng; Lei, Kun; Song, Peng; Liu, Xinqin; Zhang, Fei; Li, Jianfei; Chen, Jun

    2015-10-01

    Strengthening of aluminum alloy 2219 by thermo-mechanical treatment has been compared with artificial aging. Three simple deformation modes including pre-stretching, compression, and rolling have been used in thermo-mechanical treatment. The tensile strength, elongation, fracture feature, and precipitated phase have been investigated. The results show that the strengthening effect of thermo-mechanical treatment is better than the one of artificial aging. Especially, the yield strength significantly increases with a small decrease of elongation. When the specimen is pre-stretched to 8.0%, the yield strength reaches 385.0 MPa and increases by 22.2% in comparison to the one obtained in aging condition. The maximum tensile strength of 472.4 MPa is achieved with 4.0% thickness reduction by compression. The fracture morphology reveals locally ductile and brittle failure mechanism, while the coarse second-phase particles distribute on the fracture surface. The intermediate phases θ″ or θ' orthogonally precipitate in the matrix after thermo-mechanical treatment. As compared to artificial aging, the cold plastic deformation increases distribution homogeneity and the volume fraction of θ'' or θ' precipitates. These result in a better strengthening effect.

  9. Crack propagation in fracture mechanical graded structures

    Directory of Open Access Journals (Sweden)

    B. Schramm

    2015-10-01

    Full Text Available The focus of manufacturing is more and more on innovative and application-oriented products considering lightweight construction. Hence, especially functional graded materials come to the fore. Due to the application-matched functional material gradation different local demands such as absorbability, abrasion and fatigue of structures are met. However, the material gradation can also have a remarkable influence on the crack propagation behavior. Therefore, this paper examines how the crack propagation behavior changes when a crack grows through regions which are characterized by different fracture mechanical material properties (e.g. different threshold values KI,th, different fracture toughness KIC. In particular, the emphasis of this paper is on the beginning of stable crack propagation, the crack velocity, the crack propagation direction as well as on the occurrence of unstable crack growth under static as well as cyclic loading. In this context, the developed TSSR-concept is presented which allows the prediction of crack propagation in fracture mechanical graded structures considering the loading situation (Mode I, Mode II and plane Mixed Mode and the material gradation. In addition, results of experimental investigations for a mode I loading situation and numerical simulations of crack growth in such graded structures confirm the theoretical findings and clarify the influence of the material gradation on the crack propagation behavior.

  10. Microstructures and Mechanical Properties of Al/Mg Alloy Multilayered Composites Produced by Accumulative Roll Bonding

    Institute of Scientific and Technical Information of China (English)

    H.S.Liu; B.Zhang; G.P.Zhang

    2011-01-01

    Al/Mg alloy multilayered composites were produced successfully at the lower temperature (280℃) by accumulative roll bonding (ARB) processing technique. The microstructures of Al and Mg alloy layers were characterized by scanning electron microscopy and transmission electron microscopy. Vickers hardness and three-point bending tests were conducted to investigate mechanical properties of the composites. It is found that Vickers hardness, bending strength and stiffness modulus of the Al/Mg alloy multilayered composite increase with increasing the ARB pass. Delamination and crack propagation along the interface are the two main failure modes of the multilayered composite subjected to bending load. Strengthening and fracture mechanisms of the composite are analyzed.

  11. Effect of laser peening with different energies on fatigue fracture evolution of 6061-T6 aluminum alloy

    Science.gov (United States)

    Sheng, J.; Huang, S.; Zhou, J. Z.; Lu, J. Z.; Xu, S. Q.; Zhang, H. F.

    2016-03-01

    To deeply understand the effect of laser peening (LP) with different laser pulse energies on 6061-T6 aluminum alloy, the fatigue fracture morphologies evolution process at various fatigue crack growth (FCG) stages and the corresponding strengthen mechanism were investigated. At the initial stage of FCG, more fatigue micro-cliffs were found after LP, while the fatigue striation spacing simultaneously reduced. A "stop-continue" phenomenon of crack propagation was discovered for laser peened samples. The fatigue striation spacing at the middle stage of FCG increased significantly while compared with that at the initial stage, in addition, the fatigue striation spacing decreased with an increase in laser pulse energy. Fracture morphologies in transition region of laser peened samples exhibit a mixing fracture characteristic of striations and dimples. The laser peened sample with laser pulse energy of 7 J presents more circuitous growing paths. Due to the complex stress state induced by LP, dimples with different sizes appeared in the final fracture region.

  12. High-temperature mechanical properties of aluminium alloys reinforced with boron carbide particles

    Energy Technology Data Exchange (ETDEWEB)

    Onoro, J. [Dept. Ingenieria y Ciencia de los Materiales, ETSI Industriales, Universidad Politecnica de Madrid, c/Jose Gutierrez Abascal 2, 28006 Madrid (Spain)], E-mail: javier.onoro@upm.es; Salvador, M.D. [Dept. Ingenieria Mecanica y de Materiales, ETSI Industriales, Universidad Politecnica de Valencia, Camino de Vera s/n, 46071 Valencia (Spain); Cambronero, L.E.G. [Dept. Ingenieria de Materiales, ETSI Minas, Universidad Politecnica de Madrid, c/Rios Rosas 21, 28003 Madrid (Spain)

    2009-01-15

    The mechanical properties of particulate-reinforced metal-matrix composites based on aluminium alloys (6061 and 7015) at high temperatures were studied. Boron carbide particles were used as reinforcement. All composites were produced by hot extrusion. The tensile properties and fracture analysis of these materials were investigated at room temperature and at high temperature to determine their ultimate strength and strain to failure. The fracture surface was analysed by scanning electron microscopy.

  13. Combined effects of phosphorus segregation and partial intergranular fracture on the ductile-brittle transition temperature in structural alloy steels

    International Nuclear Information System (INIS)

    Research highlights: → Effective P segregation was proposed by segregated P and intergranular fracture. → The DBTT of aged and irradiated steel was analyzed by effective P segregation. → The DBTT of two classes of steels are controlled by differing mechanisms. → Hardening strongly influenced the embrittling potency of segregated P. - Abstract: This article introduced effective P segregation in terms of the product of the amount of segregated P and partial intergranular fracture to account for the combined effects on the ductile-brittle transition temperature (DBTT) measured by dynamic and static notched bar tests on several alloy steels. Effective P segregation characterized a DBTT shift caused by thermal ageing and/or neutron irradiation in various A533B and 2.25Cr-1Mo steels, while P segregation controlled the DBTT independent of the fraction of intergranular fracture in thermally aged 3.5Ni-1.7Cr steels with and without Mo and V. These DBTT behaviors of the two classes of steels are related to differing brittle fracture mechanisms. The present analysis enables one to investigate how the embrittling potency of segregated P in association with partial intergranular fracture is influenced by the differing plasticity and the addition of several alloying elements under dynamic and static loading conditions.

  14. Fracture behavior of reinforced aluminum alloy matrix composites using thermal imaging tools

    Science.gov (United States)

    Avdelidis, N. P.; Exarchos, D.; Vazquez, P.; Ibarra-Castanedo, C.; Sfarra, S.; Maldague, X. P. V.; Matikas, T. E.

    2016-05-01

    In this work the influence of the microstructure at the vicinity of the interface on the fracture behavior of particulate-reinforced aluminum alloy matrix composites (Al/SiCp composites) is studied by using thermographic tools. In particular, infrared thermography was used to monitor the plane crack propagation behavior of the materials. The deformation of solid materials is almost always accompanied by heat release. When the material becomes deformed or is damaged and fractured, a part of the energy necessary to initiate and propagate the damage is transformed in an irreversible way into heat. The thermal camera detects the heat wave, generated by the thermo-mechanical coupling and the intrinsic dissipated energy during mechanical loading of the sample. By using an adapted detector, thermography records the two dimensional "temperature" field as it results from the infrared radiation emitted by the object. The principal advantage of infrared thermography is its noncontact, non-destructive character. This methodology is being applied to characterise the fracture behavior of the particulate composites. Infrared thermography is being used to monitor the plane crack propagation behavior of such materials. Furthermore, an innovative approach to use microscopic measurements using IR microscopic lenses was attempted, in order to enable smaller features (in the micro scale) to be imaged with accuracy and assurance.

  15. Fracture performance of computer-aided manufactured zirconia and alloy crowns

    NARCIS (Netherlands)

    M. Rosentritt; M. Behr; C. Thaller; H. Rudolph; A.J. Feilzer

    2009-01-01

    Objective: To compare the fracture resistance and fracture performance of CAD/CAM zirconia and alloy crowns. Method and Materials: One electrophoretic deposition alumina ceramic (Wolceram, Wolceram) and 4 zirconia-based systems (ce.novation, ce.novation; Cercon, DeguDent; Digizon, Amann Girrbach; an

  16. Mechanic behavior of unloading fractured rock mass

    Institute of Scientific and Technical Information of China (English)

    YIN Ke; ZHANG Yongxing; WU Hanhui

    2003-01-01

    Under tension and shear conditions related to unloading of rock mass, a jointed rock mass model of linear elastic fracture mechanics is established. According to the model, the equations of stresses, strains and displacements of the region influenced by the crack but relatively faraway the crack (the distance between the research point and the center of the crack is longer than the length of crack) are derived. They are important for evaluating the deformation of cracked rock. It is demonstrated by the comparison between computational results of these theoretical equations and the observed data from unloading test that they are applicable for actual engineering.

  17. Effect of N on microstructure and mechanical properties of as-cast Ti-6Al alloy

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    In-situ titanium matrix composites with N content of 0. 045-0. 27 wt% have been produced by a casting method. The microstructure and mechanical properties of as-cast materials have been observed and tested.The results show that when N content in Ti-6Al alloy is between 0. 045 wt% and 0. 27 wt%, the reinforcement is a compound of Ti, Al and N, and volume fraction of reinforcements increases with an increase of N content.The hardness, compressive strength and elastic modulus are all higher than that of the matrix alloy. With the increase of N content, the compressive strength, the hardness and the elastic modulus increase. Fracture surface analysis has also shown that the matrix alloy fractures in a ductile model and the composites fracture in a cleavage brittle model with characteristics of dimple and cleavage surface.

  18. Numerical Fracture Analysis of Cryogenically Treated Alloy Steel Weldments

    Science.gov (United States)

    Rasool Mohideen, S.; Thamizhmanii, S.; Fatah, M. M. Muhammed Abdul; Saidin, W. Najmuddin W.

    2016-02-01

    Cryogenic treatment is being used commercially in the industries in the last two decades for improving the life of many engineering component such as bearings and cutting tools. Though their influence in improving the wear resistance of tool materials is well established, the effect of treatment on weldments is not much investigated. In the present work, a two dimensional finite element analysis was carried out on the compact tension specimen model for simulating the treatment process and to study the fracture behaviour. The weldments were modelled by thermo- mechanical coupled field analysis for simulating he temperature distribution in the model during weld pool cooling and introducing thermal stresses due to uneven contraction and cooling. The model was subjected to cryogenic treatment by adopting radiation effect. The fracture analysis was carried out using Rice's J- Integral approach. The analysis produced a similar outcome of experimental results i.e. Increase in the fracture toughness of the specimen after cryogenic treatment in the heat affected zone of weldment.

  19. Stress Concentration and Fracture at Inter-variant Boundaries in an Al-Li Alloy

    Science.gov (United States)

    Crooks, Roy; Tayon, Wes; Domack, Marcia; Wagner, John; Beaudoin, Armand

    2009-01-01

    Delamination fracture has limited the use of lightweight Al-Li alloys. Studies of secondary, delamination cracks in alloy 2090, L-T fracture toughness samples showed grain boundary failure between variants of the brass texture component. Although the adjacent texture variants, designated B(sub s1) and B(sub s2), behave similarly during rolling, their plastic responses to mechanical tests can be quite different. EBSD data from through-thickness scans were used to generate Taylor factor maps. When a combined boundary normal and shear tensor was used in the calculation, the delaminating grains showed the greatest Taylor Factor differences of any grain pairs. Kernel Average Misorientation (KAM) maps also showed damage accumulation on one side of the interface. Both of these are consistent with poor slip accommodation from a crystallographically softer grain to a harder one. Transmission electron microscopy was used to confirm the EBSD observations and to show the role of slip bands in the development of large, interfacial stress concentrations. A viewgraph presentation accompanies the provided abstract.

  20. Fracture toughness of TiAl-Cr-Nb-Mo alloys produced via centrifugal casting

    Directory of Open Access Journals (Sweden)

    A. Brotzu

    2012-10-01

    Full Text Available Fracture toughness of a TiAl base intermetallic alloy has been investigated at room temperature. The Ti-48Al-2.5Cr-0.5Nb-2Mo (at. % alloy produced via centrifugal casting exhibits fine nearly lamellar microstructures, consisting mainly of fine lamellar grains, together with a very small quantity of residual β phases along lamellar colony boundaries. In order to determine the alloy fracture toughness compact tension specimens were tested and the results were compared with those available in literature.

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

    International Nuclear Information System (INIS)

    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 Al3Mg2 and Mg17Al12 formed in the Al/Mg interface and resulted in the fracture of the joint

  2. Mechanical properties of ({alpha}+{beta})-titanium alloy at cryogenic temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Ivasishin, O.M. [Institute for Metal Physics, 36 Vernadsky str, Kiev 252142 (Ukraine); Markovsky, P.E. [Institute for Metal Physics, 36 Vernadsky str, Kiev 252142 (Ukraine); Pakharenko, G.A. [Institute for Metal Physics, 36 Vernadsky str, Kiev 252142 (Ukraine); Shevchenko, A.V. [Institute for Metal Physics, 36 Vernadsky str, Kiev 252142 (Ukraine)

    1995-06-15

    The influence of microstructure, fine surface stress concentrators and weak surface gas saturation on the mechanical properties of high-strength ({alpha}+{beta})-titanium alloy at cryogenics temperatures was studied. The results are discussed in terms of a new microcleavage model of brittle fracture. (orig.)

  3. Patterns and perspectives in applied fracture mechanics

    Energy Technology Data Exchange (ETDEWEB)

    Merkle, J.G.

    1994-12-31

    This lecture begins with a overview of applied fracture mechanics pertinent to safety of pressure vessels. It then progresses to a chronological panorama of experimental and analytical results. To be useful and dependable in safety analysis of real structures, new analysis developments must be physically realistic, which means that they must accurately describe physical cause and effect. Consequently, before mathematical modeling can begin, cause and effect must be established from experimental data. This can be difficult and time consuming, but worth the effort. Accordingly, the theme of this paper is that the search for patterns is constant and vital. This theme is illustrated by the development of small, single-specimen, fracture toughness testing techniques. It is also illustrated by the development, based on two different published large-strain, elastic-plastic, three-dimensional finite-element analyses, of a hypothesis concerning three-dimensional loss of constraint. When a generalization of Irwin`s thickness-normalized plastic-zone parameter, reaches a value close to 2{pi}, the through-thickness contraction strain at the apex of the near-tip logarithmic-spiral slip-line region becomes the dominant negative strain accommodating crack opening. Because slip lines passing from the midplane to the stress-free side surfaces do not have to curve, once these slip lines are established, stresses near the crack tip are only elevated by strain hardening and constraint becomes significantly relaxed. This hypothesis, based on published three-dimensional elastic-plastic analyses, provides a potentially valuable means for gaining additional insight into constraint effects on fracture toughness by considering the roles played by the plastic strains as well as the stresses that develop near a crack tip.

  4. The fracture resistance of 1420 and 1421 Al-Mg-Li alloys

    International Nuclear Information System (INIS)

    Aluminum-magnesium-lithium alloy 1420 was developed in the form USSR as a lightweight, weldable, corrosion resistant alloy for aerospace applications. The alloy is primarily strengthened upon aging by the homogeneous precipitation of metastable δ' (Al3Li). The equilibrium T-phase (Al2MgLi) also precipitated during aging on grain boundaries and dislocations but does not contribute to strength and can have deleterious effects on fracture toughness. The addition of scandium, which refines the ingot grain structure, led to the evolution of alloy 1421 which exhibits higher strength and superior weldability compared to the earlier 1420 alloy. Zirconium is added to both alloys and forms a coherent precipitate, β' (Al3Zr), which acts as a recrystallization inhibitor. The fracture resistance of alloys 1420 and 1421 in the T6 temper has been examined by R-curve determination and the observed behavior has been compared with Al alloy, 2219-T87. The center-cracked (M(T)) sheet panels tested in this study were of sufficient width to produce stable crack growth to a Δa of ∼ 25 mm and the R-curves that were generated allowed for a comparison to be made of the stable crack growth resistance between the alloys in accordance with ASTM E561-86. The data presented are part of an extensive collaborative test program involving both private industry and government laboratories to evaluate the 1420 and 1421 alloys

  5. Tensile Fracture Location Characterizations of Friction Stir Welded Joints of Different Aluminum Alloys

    Institute of Scientific and Technical Information of China (English)

    Huijie LIU; Hidetoshi FUJII; Masakatsu MAEDA; Kiyoshi NOGI

    2004-01-01

    The tensile fracture location characterizations of the friction stir welded joints of the AA1050-H24 and AA6061-T6Al alloys were evaluated in this study. The experimental results show that the fracture locations of the joints are different for the different Al alloys, and they are affected by the FSW parameters. When the joints are free of welding defects, the AA1050-H24 joints are fractured in the HAZ and TMAZ on the AS and the fracture parts undergo a large amount of plastic deformation, while the AA6061-T6 joints are fractured in the HAZ on the RS and the fracture surfaces are inclined a certain degree to the bottom surfaces of the joints. When some welding defects exist in the joints, the AA1050-H24 joints are fractured on the RS or AS, the AA6061-T6 joints are fractured on the RS, and all the fracture locations are near to the weld center. The fracture locations of the joints are dependent on the internal structures of the joints and can be explained by the microhardness profiles and defect morphologies of the joints.

  6. Fatigue fracture of high-strength Al-Zn-Mg-Cu alloy

    Institute of Scientific and Technical Information of China (English)

    JIAN Hai-gen; JIANG Feng; WEN Kang; JIANG Long; HUANG Hong-feng; WEI Li-li

    2009-01-01

    X-ray diffractometry(XRD), optical microscopy(OM), scanning electron microscopy(SEM) were used to study the fatigue fracture of the T7451 Al-Zn-Mg-Cu alloy (470 ℃, 60 min+115 ℃, 8 h+165 ℃, 16 h). The study reveals mainly the microscopic structure of the alloy in the process of crack formation and crack growth. The fatigue fracture is characterized by three zones: fatigue crack source zone, fatigue crack propagation zone and fatigue fracture zone. The fatigue damage preferably incubates at the fractured inclusion particles at or near (about 25 μm) the specimen free surfaces, and these brittle Fe-rich intermetallic inclusion particles are (7-10) μm×(11-14) μm in size. Some features such as "feather-like", "river and range" and boundary extrusions can be observed in the fatigue propagation zone, and in the fatigue fracture zone the surface is rough and uneven.

  7. Mechanical Properties of Niobium Alloyed Gray Iron

    OpenAIRE

    Hanna, Ivil

    2011-01-01

    The influence of adding an amount of 0.1% and 0.3% niobium to the gray iron alloy used for brake discs, these disc materials are called disc 16 respective 17, have been investigated at RT (room temperature). That is together with two other alloys, the reference disc which contains 0.32% molybdenum but lacks niobium and another one with neither niobium nor molybdenum in it, this is called disc material 15. Focus in this thesis work is on the mechanical properties of the studied materials and f...

  8. Effect of the build orientation on the mechanical properties and fracture modes of SLM Ti–6Al–4V

    International Nuclear Information System (INIS)

    Recent research on the additive manufacturing (AM) of Ti alloys has shown that the mechanical properties of the parts are affected by the characteristic microstructure that originates from the AM process. To understand the effect of the microstructure on the tensile properties, selective laser melted (SLM) Ti–6Al–4V samples built in three different orientations were tensile tested. The investigated samples were near fully dense, in two distinct conditions, as-built and stress relieved. It was found that the build orientation affects the tensile properties, and in particular the ductility of the samples. The mechanical anisotropy of the parts was discussed in relation to the crystallographic texture, phase composition and the predominant fracture mechanisms. Fractography and electron backscatter diffraction (EBSD) results indicate that the predominant fracture mechanism is intergranular fracture present along the grain boundaries and thus provide and explain the typical fracture surface features observed in fracture AM Ti–6Al–4V

  9. Effect of the build orientation on the mechanical properties and fracture modes of SLM Ti–6Al–4V

    Energy Technology Data Exchange (ETDEWEB)

    Simonelli, M., E-mail: M.Simonelli@lboro.ac.uk [Department of Materials, Loughborough University, Loughborough LE11 3TU (United Kingdom); Tse, Y.Y. [Department of Materials, Loughborough University, Loughborough LE11 3TU (United Kingdom); Tuck, C. [Additive Manufacturing and 3D Printing Research Group, Faculty of Engineering, The University of Nottingham, Nottingham NG7 2RD (United Kingdom)

    2014-10-20

    Recent research on the additive manufacturing (AM) of Ti alloys has shown that the mechanical properties of the parts are affected by the characteristic microstructure that originates from the AM process. To understand the effect of the microstructure on the tensile properties, selective laser melted (SLM) Ti–6Al–4V samples built in three different orientations were tensile tested. The investigated samples were near fully dense, in two distinct conditions, as-built and stress relieved. It was found that the build orientation affects the tensile properties, and in particular the ductility of the samples. The mechanical anisotropy of the parts was discussed in relation to the crystallographic texture, phase composition and the predominant fracture mechanisms. Fractography and electron backscatter diffraction (EBSD) results indicate that the predominant fracture mechanism is intergranular fracture present along the grain boundaries and thus provide and explain the typical fracture surface features observed in fracture AM Ti–6Al–4V.

  10. Hydrogen pickup mechanism of zirconium alloys

    Science.gov (United States)

    Couet, Adrien

    Although the optimization of zirconium based alloys has led to significant improvements in hydrogen pickup and corrosion resistance, the mechanisms by which such alloy improvements occur are still not well understood. In an effort to understand such mechanisms, a systematic study of the alloy effect on hydrogen pickup is conducted, using advanced characterization techniques to rationalize precise measurements of hydrogen pickup. The hydrogen pick-up fraction is accurately measured for a specially designed set of commercial and model alloys to investigate the effects of alloying elements, microstructure and corrosion kinetics on hydrogen uptake. Two different techniques to measure hydrogen concentrations were used: a destructive technique, Vacuum Hot Extraction, and a non-destructive one, Cold Neutron Prompt Gamma Activation Analysis. The results indicate that hydrogen pickup varies not only from alloy to alloy but also during the corrosion process for a given alloy. For instance Zircaloy type alloys show high hydrogen pickup fraction and sub-parabolic oxidation kinetics whereas ZrNb alloys show lower hydrogen pickup fraction and close to parabolic oxidation kinetics. Hypothesis is made that hydrogen pickup result from the need to balance charge during the corrosion reaction, such that the pickup of hydrogen is directly related to (and indivisible of) the corrosion mechanism and decreases when the rate of electron transport or oxide electronic conductivity sigmao xe through the protective oxide increases. According to this hypothesis, alloying elements (either in solid solution or in precipitates) embedded in the oxide as well as space charge variations in the oxide would impact the hydrogen pick-up fraction by modifying sigmaox e, which drives oxidation and hydriding kinetics. Dedicated experiments and modelling were performed to assess and validate these hypotheses. In-situ electrochemical impedance spectroscopy (EIS) experiments were performed on Zircaloy-4 tubes

  11. Enhancement of Impact Toughness by Delamination Fracture in a Low-Alloy High-Strength Steel with Al Alloying

    Science.gov (United States)

    Sun, Junjie; Jiang, Tao; Liu, Hongji; Guo, Shengwu; Liu, Yongning

    2016-09-01

    The effect of delamination toughening of martensitic steel was investigated both at room and low temperatures [253 K and 233 K (-20 °C and -40 °C)]. Two low-alloy martensitic steels with and without Al alloying were both prepared. Layered structure with white band and black matrix was observed in Al alloyed steel, while a homogeneous microstructure was displayed in the steel without Al. Both steels achieved high strength (tensile strength over 1600 MPa) and good ductility (elongation over 11 pct), but they displayed stark contrasts on impact fracture mode and Charpy impact energy. Delamination fracture occurred in Al alloyed steel and the impact energies were significantly increased both at room temperature (from 75 to 138 J, i.e., nearly improved up to 2 times) and low temperatures [from 47.9 to 71.3 J at 233 K (-40 °C)] compared with the one without Al. Alloying with Al promotes the segregation of Cr, Mn, Si and C elements to form a network structure, which is martensite with higher carbon content and higher hardness than that of the matrix. And this network structure evolved into a band structure during the hot rolling process. The difference of yield stress between the band structure and the matrix gives rise to a delamination fracture during the impact test, which increases the toughness greatly.

  12. Experimental and finite element analysis of fracture criterion in general yielding fracture mechanics

    Indian Academy of Sciences (India)

    D M Kulkarni; Ravi Prakash; A N Kumar

    2002-12-01

    Efforts made over the last three decades to understand the fracture behaviour of structural materials in elastic and elasto-plastic fracture mechanics are numerous, whereas investigations related to fracture behaviour of materials in thin sheets or general yielding fracture regimes are limited in number. Engineering simulative tests are being used to characterize formability and drawability of sheet metals. However, these tests do not assure consistency in quality of sheet metal products. The prevention of failure in stressed structural components currently requires fracture mechanics based design parameters like critical load, critical crack-tip opening displacement or fracture toughness. The present attempt would aim to fulfill this gap and generate more information thereby increased understanding on fracture behaviour of sheet metals. In the present investigation, using a recently developed technique for determining fracture criteria in sheet metals, results are generated on critical CTOD and fracture toughness. Finite element analysis was performed to support the results on various fracture parameters. The differences are within 1 to 4%. At the end it is concluded that magnitude of critical CTOD and/or critical load can be used as a fracture criterion for thin sheets.

  13. Thermal stability and mechanical properties of Gd-Co-Al bulk glass alloys

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The glass forming ability of Gd-Co-Al ternary alloy systems with a composition ranging from 50% to 70% (molar fraction)for Gd and from 5% to 40% (molar fraction) for Al were investigated by copper mold casting and Gd60Co25Al15 bulk glass alloy cylinders with the maximum diameter of 5 mm were obtained. The reduced glass transformation temperature (Tg/Tm) and the distance of supercooling region △Tx are 0.616 and 45 K, respectively for this Gd-Co-Al alloy. The compressive fracture strength (σf) and elastic modulus (E) of Gd-Co-Al glassy alloys are 1 170-1 380 MPa and 59-70 GPa, respectively. The Gd-Al-Co bulk glassy alloys with high glass forming ability and good mechanical properties are promising for the future development as a new type function materials.

  14. Mechanical properties of low alloy high phosphorus weathering steel

    Directory of Open Access Journals (Sweden)

    Jena B.K.

    2015-01-01

    Full Text Available Mechanical behaviour of two low alloy steels (G11 and G12 was studied with respect to different phosphorus contents. Tensile strength and yield strength increased while percentage elongation at fracture decreased on increasing phosphorus content. The SEM and light optical photomicrograph of low phosphorus steel (G11 revealed ferrite and pearlite microstructure. On increasing phosphorus content from 0.25 wt.% to 0.42 wt.%, the morphology of grain changed from equiaxed shape to pan-cake shape and grain size also increased. The Charpy V notch (CVN impact energy of G11 and G12 steel at room temperature was 32 J and 4 J respectively and their fractographs revealed brittle rupture with cleavage facets for both the steels. However, the fractograph of G11 steel after tensile test exhibited ductile mode of fracture with conical equiaxed dimple while that of G12 steel containing 0.42 wt. % P exhibited transgranular cleavage fracture. Based on this study, G11 steel containing 0.25 wt. % P could be explored as a candidate material for weathering application purpose where the 20°C toughness requirement is 27 J as per CSN EN10025-2:2004 specification.

  15. Flow and fracture of alloys in the fusion environment

    International Nuclear Information System (INIS)

    The present paper examines both ductile and brittle fracture models of steels and assesses the impact of the fusion reactor environment on the fracture processes. In particular, the connections between plastic flow properties and fracture modes are reviewed for both ductile and brittle crack propagation. Highly radiation-hardened materials exhibit extreme flow location resulting in channel fracture. Physical models for this phenomon are developed and an estimate for the associated fracture toughness is given. The impact of radiation-hardening and ductility loss on fatigue crack growth is examined. Next, models describing the chemical effects on fatigue and fracture are briefly discussed. Finally, fracture design criteria are proposed for first wall structures in fusion reactors. (orig.)

  16. Effects of grain size on fracture toughness in transition temperature region of Mn-Mo-Ni low-alloy steels

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Sangho; Lee, Sunghak; Lee, Bong Sang

    2003-10-25

    An investigation was conducted into the effect of grain size on fracture toughness in the transition temperature region of Mn-Mo-Ni low-alloy steels used for nuclear pressure vessels. Three kinds of steels with different austenite grain sizes (AGS) were fabricated by varying the contents of Al and N, and their microstructures and mechanical properties were examined. Elastic-plastic cleavage fracture toughness, K{sub Jc}, was determined by three-point bend tests of precracked Charpy V-notch (PCVN) specimens according to ASTM E1921 standard test method. When the AGS decreased, the total number of carbides increased, while the size and the aspect ratio of carbides decreased. Local fracture stresses, estimated from a theoretical stress distribution in front of a crack tip, were found to be mainly determined by the 92nd% size of carbides. Cross-sectional areas beneath fracture surfaces were observed to understand microstructural features to affect the cleavage crack propagation behavior. The results showed that measured cleavage fracture units were smaller than AGSs, indicating that packet boundaries as well as austenite grain boundaries played an important role in the cleavage crack propagation. Based on the electron back-scatter diffraction (EBSD) results, the cleavage fracture units could also be matched with the effective grain sizes determined by the misorientation tolerance angle of 25 deg.

  17. Relationship between grain size and fracture toughness in transition region of Mn-Mo-Ni low-alloy steels

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Sang Ho; Lee, Sung Hak [Pohang Univ. of Science and Technology, Pohang (Korea, Republic of); Oh, Yong Jun [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2002-03-01

    The present study aims at interpreting the effect of grain size on fracture toughness in the transition region of Mn-Mo-Ni low-alloy steels. Three kinds of steels with different austenite grain sizes were fabricated, and their microstructures and mechanical properties were examined. Elastic-plastic cleavage fracture toughness, K{sub Jc}, was determined by 3-point bend tests of precracked Charpy V-notch (PCVN) specimens according to ASTM E1921 standard test method. When the austenite grain size decreased, the total number of carbides increased, while the size and the aspect ratio of carbides decreased. Local fracture stresses, estimated from a theoretical stress distribution in front of a crack tip, were found to be mainly determined by the 92%th size of carbides. Cross-sectional areas beneath fracture surfaces were observed to understand microstructural features to affect the cleavage crack propagation behavior. The results showed that measured cleavage fracture units were smaller than austenite grain sizes, indicating that packet boundaries as well as austenite grain boundaries played an important role in the cleavage crack propagation. Based on the electron back-scatter diffraction (EBSD) results, the cleavage fracture units could also be matched with the effective grain sizes determined by the misorientation tolerance angle of 25 degree.

  18. Influence of Al-Ti-B addition on the microstructure and mechanical properties of A356 alloys

    Institute of Scientific and Technical Information of China (English)

    ZHU Man; YANG Gencang; YAO Lijuan; CHENG Suling; ZHOU Yaohe

    2009-01-01

    The mechanical properties (σb, σ0.2, and δ) and fracture behavior of tensile specimens of the refined A356 alloys were investigated as a func-tion of the addition level of Al-Ti-B master alloy under both as-cast and T6 hot-treated conditions. The results show that as the addition level of Al-5Ti- 1B master alloy increases from 0.1 wt.% to 5.0 wt.%, the mechanical properties of refined A356 alloys improve steadily and then decrease slightly under both as-cast and T6 heat-treated conditions. Also, they display excellent mechanical properties with σb = 231.30-258.30 Mpa, σ0.2 = 134.00-155.50 Mpa, and δ= 8.5%-11.75% at T6 heat-treated state. The excellent mechanical properties of refined A356 alloys are ascribed to the formation of a-Al equiaxed dendrites, the improvement of eutectic structure from needle/plate-like to short-lathy/block-shaped, and the Mg2Si aging precipitation phase after T6 heat treatment. The fracture surface examined by SEM exhibits a mixed fracture mode of refined A356 alloys at as-cast state, while it reveals a ductile fracture mode after T6 heat treatment.

  19. Solution-adaptive finite element method in computational fracture mechanics

    Science.gov (United States)

    Min, J. B.; Bass, J. M.; Spradley, L. W.

    1993-01-01

    Some recent results obtained using solution-adaptive finite element method in linear elastic two-dimensional fracture mechanics problems are presented. The focus is on the basic issue of adaptive finite element method for validating the applications of new methodology to fracture mechanics problems by computing demonstration problems and comparing the stress intensity factors to analytical results.

  20. Fracture mechanics of concrete: Will applications start to emerge?

    NARCIS (Netherlands)

    Van Mier, J.G.M.

    1995-01-01

    Fracture mechanics of concrete has developed into an active field of research in the past decades. It promises a rational solution technique to structural problems in reinforced concrete in the limit state. Numerical tools have been developed on the basis of fracture mechanics theories. The question

  1. Polypropylene–rubber blends: 5. Deformation mechanism during fracture

    NARCIS (Netherlands)

    Wal, van der A.; Gaymans, R.J.

    1999-01-01

    The deformation mechanism of polypropylene–EPDM rubber blends during fracture was studied by post-mortem SEM fractography. The deformation mechanism was determined for various blend morphologies and test conditions. Brittle fracture merely gives rise to voids, which are caused by voiding of the rubb

  2. Identification method of fracture mode based on measurement of microscopic plastic deformation in a Mg cast alloy

    International Nuclear Information System (INIS)

    Plastic deformation under fracture surface in non-combustible magnesium alloy was investigated using electron backscatter diffraction analysis after tensile tests of specimens having a fatigue pre-crack or shrinkage porosity, so that it revealed that the fracture mode of shrinkage porosity of the magnesium alloy can be treated as a crack

  3. Complexity: a new paradigm for fracture mechanics

    Directory of Open Access Journals (Sweden)

    S. Puzzi

    2009-10-01

    Full Text Available The so-called Complexity Sciences are a topic of fast growing interest inside the scientific community. Actually, researchers did not come to a definition of complexity, since it manifests itself in so many different ways [1]. This field itself is not a single discipline, but rather a heterogeneous amalgam of different techniques of mathematics and science. In fact, under the label of Complexity Sciences we comprehend a large variety of approaches: nonlinear dynamics, deterministic chaos theory, nonequilibrium thermodynamics, fractal geometry, intermediate asymptotics, complete and incomplete similarity, renormalization group theory, catastrophe theory, self-organized criticality, neural networks, cellular automata, fuzzy logic, etc. Aim of this paper is at providing insight into the role of complexity in the field of Materials Science and Fracture Mechanics [2-3]. The presented examples will be concerned with the snap-back instabilities in the structural behaviour of composite structures (Carpinteri [4-6], the occurrence of fractal patterns and selfsimilarity in material damage and deformation of heterogeneous materials, and the apparent scaling on the nominal mechanical properties of disordered materials (Carpinteri [7,8]. Further examples will deal with criticality in the acoustic emissions of damaged structures and with scaling in the time-to-failure (Carpinteri et al. [9]. Eventually, results on the transition towards chaos in the dynamics of cracked beams will be reported (Carpinteri and Pugno [10,11].

  4. Effects of consolidation temperature, strength and microstructure on fracture toughness of nanostructured ferritic alloys

    International Nuclear Information System (INIS)

    Fully consolidated nanostructured ferritic alloys (NFAs) were prepared by attritor milling pre-alloyed Fe-14Cr-3W-0.4Ti and 0.3 wt% Y2O3 powders, followed by hot isostatic pressing (HIPing) at 1000 oC or 1150 oC at 200 MPa for 4 h. Transmission electron microscopy (TEM) revealed similar bimodal distributions of fine and coarse ferrite grains in both cases. However, as expected, the alloy microhardness decreased with increasing in HIPing temperature. Three point bend tests on single edge notched specimens, with a nominal root radius ρ = 0.15 mm, were used to measure the notch fracture toughness, K ρ, as a function of test temperature. The K ρ curves were found to be similar for both processing conditions. It appears that the coarser ferrite grains control cleavage fracture, in a way that is independent of alloy strength and HIPing temperature

  5. Effect of thermomechanical treatment on the resistance of low-carbon low-alloy steel to brittle fracture

    Science.gov (United States)

    Schastlivtsev, V. M.; Tabatchikova, T. I.; Yakovleva, I. L.; Del'gado Reina, S. Yu.; Golosienko, S. A.; Pazilova, U. A.; Khlusova, E. I.

    2015-02-01

    Structure and mechanical properties of rolled plates (20-35 mm thick) of low-carbon low-alloy steel subjected to thermomechanical treatment (TMT) according to various regimes under laboratory and industrial conditions have been studied. Structural factors that favor obtaining high mechanical properties have been established. The retarding action of TMT on softening upon tempering has been revealed. The reasons for the decrease in the resistance to brittle fracture of the steel subjected to TMT, repeated quenching from the temperature of the furnace heating, and tempering have been determined.

  6. Substitutional impurities and their effect on fracture peculiarities in W-Ni-Fe-alloy

    Energy Technology Data Exchange (ETDEWEB)

    Minakova, R.V.; Bazhenova, L.G.; Verkhovodov, P.A.; Kolchin, O.P.; Nedelyaeva, L.P.; Tolstunov, A.V. (AN Ukrainskoj SSR, Kiev. Inst. Problem Materialovedeniya)

    1983-11-01

    The paper deals with distribution of admixture elements, shape, size, content, chemical composition, distribution of nonmetal inclusions and their effect on peculiarities of W-Ni-Fe-alloy deformation and fractures. It is established that non-metal inclusions play the part of additional ''notches'' decreasing the size of the slow crack growth area in a refractory component. Segregation of the impurities and the film on the boundaries of nickel base solid solution promote intercrystalline fracture of the alloy.

  7. Effects of cryogenic treatment on mechanical properties of extruded Mg-Gd-Y-Zr(Mn) alloys

    Institute of Scientific and Technical Information of China (English)

    XIONG Chuang-xian; ZHANG Xin-ming; DENG Yun-lai; XIAO Yang; DENG Zhen-zhen; CHEN Bu-xiang

    2007-01-01

    The influence of cryogenic treatment on the mechanical properties of the extruded Mg-Gd-Y-Zr(Mn) alloys was investigated by the tensile tests, scanning electron microscopy(SEM), transmission electron microscopy(TEM), and energy dispersive X-ray spectroscopy (EDS). The results show that the mechanical properties of both alloys are improved greatly during the in situ tensile test by soaking the samples in liquid nitrogen for 10 min. The ultimate tensile strength, yield tensile strength and elongation of cryogenic treated magnesium alloy added with zirconium or manganese are largely elevated. And remarkable microstructure change is observed in both alloys by cryogenic treatment. There are a large number of twins, rod-like, tree-like and chrysanthemum-like precipitated phases in the microstructures and the fracture surfaces exhibit the characteristics of ductile rupture when they are observed at room temperature.

  8. Composite purification technology and mechanism of recycled aluminum alloys

    Institute of Scientific and Technical Information of China (English)

    房文斌; 耿耀宏; 安阁英; 叶荣茂

    2002-01-01

    Iron-rich inclusions in aluminum alloys can be effectively removed by composite purification of sedimentation and filtration technology.The results show that the purposed method has no negative effects on aluminum alloys and obviously improve their mechanical properties.

  9. Metallurgical Mechanisms Controlling Mechanical Properties of Aluminum Alloy 2219 Produced by Electron Beam Freeform Fabrication

    Science.gov (United States)

    Domack, Marcia S.; Tainger, Karen M.

    2006-01-01

    The electron beam freeform fabrication (EBF3) layer-additive manufacturing process has been developed to directly fabricate complex geometry components. EBF3 introduces metal wire into a molten pool created on the surface of a substrate by a focused electron beam. Part geometry is achieved by translating the substrate with respect to the beam to build the part one layer at a time. Tensile properties demonstrated for electron beam deposited aluminum and titanium alloys are comparable to wrought products, although the microstructures of the deposits exhibit cast features. Understanding the metallurgical mechanisms controlling mechanical properties is essential to maximizing application of the EBF3 process. Tensile mechanical properties and microstructures were examined for aluminum alloy 2219 fabricated over a range of EBF3 process variables. Unique microstructures were observed within the deposited layers and at interlayer boundaries, which varied within the deposit height due to microstructural evolution associated with the complex thermal history experienced during subsequent layer deposition. Microstructures exhibited irregularly shaped grains with interior dendritic structures, described based on overall grain size, morphology, distribution, and dendrite spacing, and were correlated with deposition parameters. Fracture features were compared with microstructural elements to define fracture paths and aid in definition of basic processing-microstructure-property correlations.

  10. A study of weldability and fracture modes in electron beam weldments of AZ series magnesium alloys

    Energy Technology Data Exchange (ETDEWEB)

    Chi, C.-T. [Department of Materials Science and Engineering, National Chiao Tung University, Hsinchu 300, Taiwan (China) and System Manufacturing Center, Chung-Shan Institute of Science and Technology, PO Box 90008-14, Sanxia 237, Taipei, Taiwan (China)]. E-mail: joseph.mse92g@nctu.edu.tw; Chao, C.-G. [Department of Materials Science and Engineering, National Chiao Tung University, Hsinchu 300, Taiwan (China)]. E-mail: c_g_chao@hotmail.com; Liu, T.-F. [Department of Materials Science and Engineering, National Chiao Tung University, Hsinchu 300, Taiwan (China)]. E-mail: coe@cc.nctu.edu.tw; Wang, C.-C. [Graduate School of Industrial Design and Architecture, Shih-Chien University, Taipei 104, Taiwan (China)]. E-mail: zcwang@mail.usc.edu.tw

    2006-11-05

    Given the growing need for environmental protection and lightweight construction, electron beam welding (EBW) is becoming the most important welding technology because it can compensate for the poor formability of magnesium alloys. This paper examines interactions between the properties of three AZ series magnesium alloys and welding conditions. The EBW process can yield four kinds of defect in a weld: cavities, the heat-affected zone (HAZ), undercuts, and root concavities. These defects obviously induce stress concentrations in the weld, and may seriously damage its strength. Additionally, the distribution of precipitates ({gamma} phase, Mg{sub 17}Al{sub 12}) in the fusion zone (FZ) changes from a relatively small number of scattered particles to a dense population of dendrites as the Al content of the magnesium alloy increases. Under excessive tensile stress, alloy weldments break in one of two fracture modes: an irregular FZ fracture, or a regular HAZ fracture. AZ31B usually exhibits the former mode and AZ91D the latter, while AZ61A exhibits each mode half the time. The overall weldability, which depends on the random distribution of these precipitates and defects, is found to be greatest for the AZ61A alloy. The best process window, on the other hand, is found for the AZ91D alloy. Finally, we obtain optimum parameters for the EBW process and empirical formulae for the weldment strength as a function of these parameters. These results are closely related to each other.

  11. Fracture of nickel-titanium superelastic alloy in sodium hypochlorite solution

    International Nuclear Information System (INIS)

    Fracture of the Ni-Ti superelastic alloy for endodontic instruments such as files was investigated with a sustained tensile-loading test in sodium hypochlorite (NaOCl) solution of various concentrations. It was found that the time to fracture was reduced when the applied stress exceeded the critical stress for martensite transformation. When the applied stress was higher than the critical stress, the 0.3 mm diameter wires of the Ni-Ti superelastic alloy sometimes fractured within 60 min. From the results of observations of the fracture surface using a scanning electron microscope, it was revealed that the fracture of the Ni-Ti superelastic alloy is significantly influenced by corrosion when the applied stress was higher than the critical stress for martensite transformation. The results of the present study suggest that one of the causes of the fracture of Ni-Ti files during clinical use is corrosion under the applied stress above the critical stress for martensite transformation in NaOCl solution

  12. Evaluation of Microstructure and Mechanical Properties of Nano-Y2O3-Dispersed Ferritic Alloy Synthesized by Mechanical Alloying and Consolidated by High-Pressure Sintering

    Science.gov (United States)

    Karak, Swapan Kumar; Dutta Majumdar, J.; Witczak, Zbigniew; Lojkowski, Witold; Ciupiński, Łukasz; Kurzydłowski, K. J.; Manna, Indranil

    2013-06-01

    In this study, an attempt has been made to synthesize 1.0 wt pct nano-Y2O3-dispersed ferritic alloys with nominal compositions: 83.0 Fe-13.5 Cr-2.0 Al-0.5 Ti (alloy A), 79.0 Fe-17.5 Cr-2.0 Al-0.5 Ti (alloy B), 75.0 Fe-21.5 Cr-2.0 Al-0.5 Ti (alloy C), and 71.0 Fe-25.5 Cr-2.0 Al-0.5 Ti (alloy D) steels (all in wt pct) by solid-state mechanical alloying route and consolidation the milled powder by high-pressure sintering at 873 K, 1073 K, and 1273 K (600°C, 800°C, and 1000°C) using 8 GPa uniaxial pressure for 3 minutes. Subsequently, an extensive effort has been undertaken to characterize the microstructural and phase evolution by X-ray diffraction, scanning and transmission electron microscopy, and energy dispersive spectroscopy. Mechanical properties including hardness, compressive strength, Young's modulus, and fracture toughness were determined using micro/nano-indentation unit and universal testing machine. The present ferritic alloys record extraordinary levels of compressive strength (from 1150 to 2550 MPa), Young's modulus (from 200 to 240 GPa), indentation fracture toughness (from 3.6 to 15.4 MPa√m), and hardness (from13.5 to 18.5 GPa) and measure up to 1.5 through 2 times greater strength but with a lower density (~7.4 Mg/m3) than other oxide dispersion-strengthened ferritic steels (ferritic matrix useful for grain boundary pinning and creep resistance.

  13. Degradation of the Mechanical Properties of Zirconium-base alloys due to Interaction with Hydrogen

    International Nuclear Information System (INIS)

    Security aspects and the purpose to extend the nuclear power plants lifetime motivate the renovated interest on the influence of the environment and radiation on the mechanical properties of in-reactor materials.Zirconium based alloys are the family of alloys most extensively used in nuclear core components.A consequence of the interaction of the in-reactor environment with these alloys is the formation of brittle phase Zr hydride, a process that greatly affects the component integrity.In this work we present a experimental study of the hydrogen influence on the Z ry-4 mechanical properties at different temperatures.As a complement we also present results of a finite elements simulations of the fracture process.We performed standard metallurgical and mechanical characterization in commercial Z ry-4 samples to obtain their basic properties. Different hydrogen pickup techniques were applied to obtain H concentration of charged samples between 10 and 2000 ppm, homogeneous or mainly localized at the crack tip zone.To obtain the fracture toughness of the alloys specimens were tested using elastoplastic fracture mechanics techniques.Specifically we implement J-integral methodology with partial unloading compliance measurements.Tests were performed in a temperature range of 20 to 200 o C.The negative influence of the H content on material toughness probed to be important even at very small concentrations, with an effect that decreases when temperature increases.While there was observed no change in the fracture mechanism in homogeneous charged samples, specimens charged under a superimposed stress field fractured by brittle mode when were tested at 20 to 70 o C. SEM observations of the crack growth, the fracture surface morphology and precipitates content showed the influence of the precipitates on fracture at different H concentrations.At least three stages with different fracture behavior depending on H content were identified.Complementary to the experimental work we

  14. Integration of NDE Reliability and Fracture Mechanics

    Energy Technology Data Exchange (ETDEWEB)

    Becker, F. L.; Doctor, S. R.; Heas!er, P. G.; Morris, C. J.; Pitman, S. G.; Selby, G. P.; Simonen, F. A.

    1981-03-01

    The Pacific Northwest Laboratory is conducting a four-phase program for measuring and evaluating the effectiveness and reliability of in-service inspection (lSI} performed on the primary system piping welds of commercial light water reactors (LWRs). Phase I of the program is complete. A survey was made of the state of practice for ultrasonic rsr of LWR primary system piping welds. Fracture mechanics calculations were made to establish required nondestrutive testing sensitivities. In general, it was found that fatigue flaws less than 25% of wall thickness would not grow to failure within an inspection interval of 10 years. However, in some cases failure could occur considerably faster. Statistical methods for predicting and measuring the effectiveness and reliability of lSI were developed and will be applied in the "Round Robin Inspections" of Phase II. Methods were also developed for the production of flaws typical of those found in service. Samples fabricated by these methods wilI be used in Phase II to test inspection effectiveness and reliability. Measurements were made of the influence of flaw characteristics {i.e., roughness, tightness, and orientation) on inspection reliability. These measurernents, as well as the predictions of a statistical model for inspection reliability, indicate that current reporting and recording sensitivities are inadequate.

  15. Strength and fracture of uranium, plutonium and several their alloys under shock wave loading

    OpenAIRE

    Golubev V.K.

    2012-01-01

    Results on studying the spall fracture of uranium, plutonium and several their alloys under shock wave loading are presented in the paper. The problems of influence of initial temperature in a range of − 196 – 800∘C and loading time on the spall strength and failure character of uranium and two its alloys with molybdenum and both molybdenum and zirconium were studied. The results for plutonium and its alloy with gallium were obtained at a normal temperature and in a temperature range of 40–31...

  16. Preparation of TiMn alloy by mechanical alloying and spark plasma sintering for biomedical applications

    Science.gov (United States)

    Zhang, F.; Weidmann, A.; Nebe, B. J.; Burkel, E.

    2009-01-01

    TiMn alloy was prepared by mechanical alloying and subsequently consolidated by spark plasma sintering (SPS) technique for exploration of biomedical applications. The microstructures, mechanical properties and cytotoxicity of the TiMn alloys were investigated in comparison with the pure Ti and Mn metals. Ti8Mn and Ti12Mn alloys with high relative density (99%) were prepared by mechanical alloying for 60 h and SPS at 700 °C for 5 min. The doping of Mn in Ti has decreased the transformation temperature from α to β phase, increased the relative density and enhanced the hardness of the Ti metal significantly. The Ti8Mn alloys showed 86% cell viability which was comparable to that of the pure Ti (93%). The Mn can be used as a good alloying element for biomedical Ti metal, and the Ti8Mn alloy could have a potential use as bone substitutes and dental implants.

  17. Fracture toughness of copper-base alloys for ITER applications: A preliminary report

    Energy Technology Data Exchange (ETDEWEB)

    Alexander, D.J.; Zinkle, S.J.; Rowcliffe, A.F. [Oak Ridge National Lab., TN (United States)

    1997-04-01

    Oxide-dispersion strengthened copper alloys and a precipitation-hardened copper-nickel-beryllium alloy showed a significant reduction in toughness at elevated temperature (250{degrees}C). This decrease in toughness was much larger than would be expected from the relatively modest changes in the tensile properties over the same temperature range. However, a copper-chromium-zirconium alloy strengthened by precipitation showed only a small decrease in toughness at the higher temperatures. The embrittled alloys showed a transition in fracture mode, from transgranular microvoid coalescence at room temperature to intergranular with localized ductility at high temperatures. The Cu-Cr-Zr alloy maintained the ductile microvoid coalescence failure mode at all test temperatures.

  18. Prediction of Failure Due to Thermal Aging, Corrosion and Environmental Fracture in Amorphous and Titanium Alloys

    Energy Technology Data Exchange (ETDEWEB)

    Farmer, J C

    2003-04-15

    DARPA is exploring a number of advanced materials for military applications, including amorphous metals and titanium-based alloys. Equipment made from these materials can undergo degradation due to thermal aging, uniform corrosion, pitting, crevice corrosion, denting, stress corrosion cracking, corrosion fatigue, hydrogen induced cracking and microbial influenced corrosion. Amorphous alloys have exceptional resistance to corrosion, due in part to the absence of grain boundaries, but can undergo crystallization and other phase instabilities during heating and welding. Titanium alloys are extremely corrosion resistant due to the formation of a tenacious passive film of titanium oxide, but is prone to hydrogen absorption in crevices, and hydrogen induced cracking after hydrogen absorption. Accurate predictions of equipment reliability, necessary for strategic planning, requires integrated models that account for all relevant modes of attack, and that can make probabilistic predictions. Once developed, model parameters must be determined experimentally, and the validity of models must be established through careful laboratory and field tests. Such validation testing requires state-of-the-art surface analytical techniques, as well as electrochemical and fracture mechanics tests. The interaction between those processes that perturb the local environment on a surface and those that alter metallurgical condition must be integrated in predictive models. The material and environment come together to drive various modes of corrosive attack (Figure 1). Models must be supported through comprehensive materials testing capabilities. Such capabilities are available at LLNL and include: the Long Term Corrosion Test Facility (LTCTF) where large numbers of standard samples can be exposed to realistic test media at several temperature levels; a reverse DC machine that can be used to monitor the propagation of stress corrosion cracking (SCC) in situ; and banks of potentiostats with

  19. Effect of current pulses on fracture morphology in superplastic deformation of 2091 Al-Li alloy

    Institute of Scientific and Technical Information of China (English)

    1999-01-01

    The effect of current pulses on the fracture morphology in the superplastic deformation of 2091 AlLi alloy at two kinds of initial strain rate ((ε)1 = 3.33 × 10 -3 s-1;(ε)2= 3.33 × 10-2 s- 1 ) was investigated. Experimental results show that current pulse turns fracture of superplastic deformation at low strain rate from local interior fracture morphology to typical fracture by growth and interlinkage of cavities, and at high strain rate from rough grain boundary surface to smooth grain boundary surface. It is indicated that the characteristic, that current pulse promotes atomic diffusion, maintains an equiaxial grain microstructure at low strain rate, and accelerates the development of diffusional type of cavity and relaxes stress concentration at triple junction of grain boundaries at high strain rate, and makes the superplastic deformation at two kinds of strain rate show a normal superplastic fracture morphology.

  20. Effect of Alloying Elements in Hot-Rolled Metastable β-Titanium Alloys. Part II: Mechanical Properties

    Science.gov (United States)

    Manda, Premkumar; Chakkingal, Uday; Singh, A. K.

    2016-07-01

    This paper describes the tensile properties, flow and work-hardening behavior of four metastable β-titanium alloys Ti-5Al-5Mo-5V-3Cr (A1), Ti-5Al-3.5Mo-7.2V-3Cr (A2), Ti-5Al-5Mo-8.6V-1.5Cr (A3), and Ti-5Al-3.5Mo-5V-3.94Cr (A4) in α+β hot-rolled condition. The decreasing order of average strength parameters ( σ YS and σ UTS) is A4, A2, A1, and A3. The maximum strength observed in alloy A4 is due to the presence of highest wt. fraction of Cr. The elongation is the maximum and minimum in alloys A3 and A4, respectively. These alloys display moderate to high percent in-plane anisotropy ( A IP) and reasonably low anisotropic index ( δ) values. Both the A IP and δ values are maximum and minimum in alloys A1 and A3, respectively. The yield locus plots also exhibit the presence of anisotropy due to relatively large differences in yield strength values along tension and compression directions. The flow behavior of alloys A1, A2, and A4 follows Swift equation, while the alloy A3 displays best fit with Holloman equation. The presence of prestrain ( ɛ 0) in hot-rolled materials before tensile testing has an important bearing on the flow curves of A1, A2, and A4 alloys. The instantaneous work-hardening rate curves of the alloys A1, A2, and A3 exhibit all the three typical stages (stage I, stage II, and stage III) in RD samples, while the alloy A4 shows the presence of only stage I and stage III. The 45 deg to RD and TD samples of alloys A1, A2, and A4 display only stage I. The stages I and III as well as I and II are present in alloy A3 in 45 deg to RD and TD samples, respectively. Dislocation-controlled strain hardening occurs in all the three stages of these alloys in the absence of stress-induced martensitic transformation (α″) and twinning. Slip is the predominant deformation mechanism during tensile testing. Three types of slip lines, i.e., planar, wavy, and intersecting have been observed close to fracture surfaces of post tensile-tested specimens.

  1. Fatigue Performance of Microalloyed High-strength Rebar and Analysis of Fracture Mechanism

    Institute of Scientific and Technical Information of China (English)

    Peng-yan LU; Yu LIU; Hua-jie WU; Gang LIU; Xiang MENG; Yang XU

    2015-01-01

    Fatigue performance of hot-rolled ribbed-steel bar with the yield strength of 500 MPa (HRB500)was stud-ied with bend-rotating fatigue test at a stress ratio of R=-1 .It is determined by staircase method that its fatigue strength for 107 cycles is 451 MPa,which is higher than that of common carbon structural steel.This should be at-tributed to the fine-grain strengthening resulting from the high content of alloy element V and Thermo-Mechanical Control Process (TMCP).The S-N curve function is also obtained by nonlinear regression with three parameters power function.The fatigue fractures of the specimen were further analyzed with Scanning Electron Microscopy (SEM)and Energy Disperse Spectroscopy (EDS)to study the fracture mechanism.Taking into account microstruc-ture,hardness and cleanliness of the material,it implies that the fatigue fractures of HRB500 rebar all arise from surface substrates in which many brittle inclusions are contained,and that the fatigue crack propagation is principally based on the mechanism of quasi-cleavage fracture,because of the intracrystalline hard spots leading to stress con-centration and thus to the cracks.Moreover,the transient breaking area exhibits microvoid coalescence of ductile fracture due to the existing abundant inclusions.

  2. Microstructure and thermal stability of mechanically alloyed Al3Ti/Al alloy

    Institute of Scientific and Technical Information of China (English)

    林建国; 魏浩岩; 黄正

    2001-01-01

    The microstructure stability of Al3Ti/Al alloy prepared by mechanical alloying (MA) was investigated in the simulating environment in which they may be used. The results show that the MA alloy possesses fine microstructure (the grain size is about 0.5  μm). After cycling loaded followed by heat exposure at 350  ℃ for 24  h, no microstructure coarsening of the alloy occurred, which means that the Al3Ti/Al alloy behaves good microstructure stability at high temperature. The compression yield strength of the alloy reaches up to 247  MPa at 350  ℃.

  3. Effects of minor Si on microstructures and room temperature fracture toughness of niobium solid solution alloys

    International Nuclear Information System (INIS)

    Controlling the elements content in the niobium solid solution (NbSS) is significant for the better comprehensive performance of Nb-silicide-based alloys. In this paper, the effects of minor Si on the microstructures and room temperature fracture toughness of Nb–(0/0.5/1/2)Si–27.63Ti–12.92Cr–2.07Al–1.12Hf (at%, unless stated otherwise) solid solution alloys were investigated. The alloys were processed by vacuum arc-casting (AC), and then heat treated (HT) at 1425 °C for 10 h. In HT alloys, NbSS grains are refined gradually with the increase of Si content. Meanwhile, the volume fraction of Cr2Nb and silicides phases precipitates increases. The fracture toughness of HT alloys decreases at first but then increases in the range of 0 to 2% Si, because it is a combinatorial process of positive and negative effects caused by the addition of Si. The refinement of NbSS grains displays positive effect on fracture toughness, while the increase of solid solubility of Si in NbSS and brittle Cr2Nb and Nb-silicides precipitate phases display negative effect

  4. Fracture mechanics solution of confined water progressive intrusion height of mining fracture floor

    Institute of Scientific and Technical Information of China (English)

    Lu Haifeng; Yao Duoxi; Shen Dan; Cao Jiyang

    2015-01-01

    In order to obtain the value of confined water progressive intrusion height of mining fracture floor, the analysis equation was deduced based on the fracture extension theory of the fracture mechanics. Further-more, the influence of some parameters (e.g., advancing distance of working face, water pressure, initial fracture length and its angle) on confined water progressive intrusion height were analyzed. The results indicate that tension-shearing fracture of floor is extended more easily than compression-shearing frac-ture under the same conditions. When floor fracture dip angle is less than 90?, tension-shearing extension occurs more easily on the left edge of the goaf. If fracture dip angle is larger than 90?, it occurs more easily on the right edge of the goaf. The longer the advancing distance of working face is, the greater initial frac-ture length goes; or the larger water pressure is, the greater possibility of tension-shearing extension occurs. The confined water progressive intrusion height reaches the maximum on the edge of the goaf. Field in situ test is consistent with the theoretical analysis result.

  5. 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.

  6. Microstructure and mechanical properties of Ti-15Zr alloy used as dental implant material.

    Science.gov (United States)

    Medvedev, Alexander E; Molotnikov, Andrey; Lapovok, Rimma; Zeller, Rolf; Berner, Simon; Habersetzer, Philippe; Dalla Torre, Florian

    2016-09-01

    Ti-Zr alloys have recently started to receive a considerable amount of attention as promising materials for dental applications. This work compares mechanical properties of a new Ti-15Zr alloy to those of commercially pure titanium Grade4 in two surface conditions - machined and modified by sand-blasting and etching (SLA). As a result of significantly smaller grain size in the initial condition (1-2µm), the strength of Ti-15Zr alloy was found to be 10-15% higher than that of Grade4 titanium without reduction in the tensile elongation or compromising the fracture toughness. The fatigue endurance limit of the alloy was increased by around 30% (560MPa vs. 435MPa and 500MPa vs. 380MPa for machined and SLA-treated surfaces, respectively). Additional implant fatigue tests showed enhanced fatigue performance of Ti-15Zr over Ti-Grade4. PMID:27258932

  7. Fracture mechanics and statistical mechanics of reinforced elastomeric blends

    CERN Document Server

    Heinrich, Gert; Kaliske, Michael; Klüppel, Manfred; Schneider, Konrad; Vilgis, Thomas

    2013-01-01

    Elastomers are found in many applications ranging from technology to daily life applications for example in tires, drive systems, sealings and print rollers. Dynamical operation conditions put extremely high demands on the performance and stability of these materials and their elastic and flow properties can be easily adjusted by simple manipulations on their elastic and viscous properties. However, the required service life suffers often from material damage as a result of wear processes such as abrasion and wear fatigue, mostly caused by crack formation and propagation. This book covers interdisciplinary research between physics, physical chemistry, material sciences and engineering of elastomers within the range from nanometres to millimetres and connects these aspects with the constitutive material properties. The different chapters describe reliable lifetime and durability predictions based on new fracture mechanical testing concepts and advanced material-theoretical methods which are finally implemented...

  8. Interface characteristics and fracture behavior of brazed polycrystalline CBN grains using Cu-Sn-Ti alloy

    Energy Technology Data Exchange (ETDEWEB)

    Ding, Wen-Feng, E-mail: dingwf2000@vip.163.com [College of Mechanical and Electrical Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 210016 (China); Xu, Jiu-Hua; Chen, Zhen-Zhen; Miao, Qing; Yang, Chang-Yong [College of Mechanical and Electrical Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 210016 (China)

    2013-01-01

    Polycrystalline CBN grains were brazed onto AISI 1045 steel matrix using Cu-Sn-Ti brazing alloy. Brazing temperature was 880 Degree-Sign C, 900 Degree-Sign C, 920 Degree-Sign C respectively, and the holding time was 8 min. Interface characteristics, elemental distribution and fracture behavior were analyzed in detail by means of scanning electron microscopy, energy dispersive spectroscopy and testing machine for grain compressive strength. The maximum value of the mean compressive strength of brazed PCBN grains reached 879.3 MPa when the brazing temperature was 900 Degree-Sign C. The resultants layer composed of TiN, TiB{sub 2}, TiB and TiAl{sub 3} was formed at grain/alloy interface. Elemental distribution showed that Ti mainly concentrated within the interface zone. The intercrystalline fracture along the CBN/CBN particle boundary was the main fracture modes of brazed polycrystalline CBN grains.

  9. Influence of heat treatment regimes on microstructures and fracture characteristics of 7055Al alloy containing Ag

    Institute of Scientific and Technical Information of China (English)

    李海; 郑子樵; 王芝秀

    2004-01-01

    Tensile properties, fracture characteristics and microstructures of 7055 aluminum-based alloy containing Ag after T6, T73 and RRA treatment were investigated. The results show that RRA treatment retains strength of 7055-T6 with higher electrical conductivity close to that of 7055-T73 alloy, but its elongation decreases greatly.SEM fractographs reveal that intergranular cracking and shear-type transgranular cracking are both presented on the fracture appearance of 7055-T6 specimen. After T73 treatment, the fractographs mainly consist of dimple-type transgranular cracking with minor intergranular cracking. For 7055-RRA specimen, intergranular cracking dominates with minor dimples on the fracture surface. The type and size of precipitates, width of grain boundary and the ability of precipitates to impede dislocation motion vary with heat treatment regimes. Three frature models were built on the basis of microstructural analyses.

  10. Identification of modes of fracture in a 2618-T6 aluminum alloy using stereophotogrammetry

    Energy Technology Data Exchange (ETDEWEB)

    Salas Zamarripa, A., E-mail: a.salaszamarripa@gmail.com [Facultad de Ingenieria Mecanica y Electrica, Universidad Autonoma de Nuevo Leon. Av. Universidad S/N, Ciudad Universitaria, C.P. 66451, Apartado Postal 076 Suc. ' F' San Nicolas de los Garza, N.L. (Mexico); Pinna, C.; Brown, M.W. [Department of Mechanical Engineering, University of Sheffield. Sir Frederick Mappin Building, Mappin Street, Sheffield, S1 3JD (United Kingdom); Mata, M.P. Guerrero; Morales, M. Castillo; Beber-Solano, T.P. [Facultad de Ingenieria Mecanica y Electrica, Universidad Autonoma de Nuevo Leon. Av. Universidad S/N, Ciudad Universitaria, C.P. 66451, Apartado Postal 076 Suc. ' F' San Nicolas de los Garza, N.L. (Mexico)

    2011-12-15

    The identification and the development of a quantification technique of the modes of fracture in fatigue fracture surfaces of a 2618-T6 aluminum alloy were developed during this research. Fatigue tests at room and high temperature (230 Degree-Sign C) were carried out to be able to compare the microscopic fractographic features developed by this material under these testing conditions. The overall observations by scanning electron microscopy (SEM) of the fracture surfaces showed a mixture of transgranular and ductile intergranular fracture. The ductile intergranular fracture contribution appears to be more significant at room temperature than at 230 Degree-Sign C. A quantitative methodology was developed to identify and to measure the contribution of these microscopic fractographic features. The technique consisted of a combination of stereophotogrammetry and image analysis. Stereo-pairs were randomly taken along the crack paths and were then analyzed using the profile module of MeX software. The analysis involved the 3-D surface reconstruction, the trace of primary profile lines in both vertical and horizontal directions within the stereo-pair area, the measurements of the contribution of the modes of fracture in each profile, and finally, the calculation of the average contribution in each stereo-pair. The technique results confirmed a higher contribution of ductile intergranular fracture at room temperature than at 230 Degree-Sign C. Moreover, there was no indication of a direct relationship between this contribution and the strain amplitudes range applied during the fatigue testing. - Highlights: Black-Right-Pointing-Pointer Stereophotogrammetry and image analysis as a measuring tool of modes of fracture in fatigue fracture surfaces. Black-Right-Pointing-Pointer A mixture of ductile intergranular and transgranular fracture was identified at room temperature and 230 Degree-Sign C testing. Black-Right-Pointing-Pointer Development of a quantitative methodology to

  11. Fracture mechanical assessment of the quality of piping

    International Nuclear Information System (INIS)

    The function, goals and methods of fracture-mechanical analysis of pipeline systems are described as a function of their safety relevance and defect conditions. A distinction is made between postulated, production-induced and operation-induced defects, and the interdependence between fracture-mechanical and non-destructive testing is pointed out. To maintain the integrity of pipelines and exclude pipeline fracture, it is necessary to know about damage mechanisms so that defects can be excluded already during production. Here, fracture mechanical analysis is a supplementary method for proof of integrity. As there are no real findings, defect sizes must be postulated on the basis of the minimum defect size identified by non-destructive testing

  12. Influence of alloy ingredients on mechanical properties of ternary boride hard alloy clad materials

    Institute of Scientific and Technical Information of China (English)

    LIU Fu-tian; SONG Shi-xue; YANG Jun-ru; HUANG Wei-ling; HUANG Chuan-zhen; CHENG Xin; LI Zhao-qian

    2004-01-01

    Using Mo, B-Fe alloy and Fe powders as raw materials, and adding C, Cr and Ni ingredients, respectively, or C, Cr and Ni mixed powders, ternary boride hard alloy clad materials was prepared on Q235 steel substrate by means of in-situ reaction and vacuum liquid phase sintering technology. The influence of alloy ingredients on the mechanical properties of ternary boride hard alloy clad materials was investigated. The results indicate that a mixture of 0.8% C, 5% Cr and 2% Ni ingredients gives a ternary boride hard alloy clad material with optimal mechanical properties, such as high transverse rupture strength, high hardness and good wear resistance.

  13. Microstructural evolution and mechanical properties of hypereutectic Al–Si alloy processed by liquid die forging

    Indian Academy of Sciences (India)

    F F Wu; S T Li; G A Zhang; F Jiang

    2014-08-01

    The microstructural evolution and mechanical properties of a hypereutectic Al–Si alloy processed by liquid die forging were investigated. It is found that the grain size of the primary Si was significantly reduced by liquid die forging with increased pressure. The volume fraction of eutectic silicon was decreased with increased pressure. By liquid die forging with pressure up to 180 MPa, the average size of the primary Si was reduced to about 18 m, which results in the remarkable increase in the fracture strength and hardness of the hypereutectic Al–Si alloy.

  14. Microstructure and fracture behavior of SiO_2 glass ceramic and TC4 alloy joint brazed with TiZrNiCu alloy

    Institute of Scientific and Technical Information of China (English)

    LIU Duo; ZHANG Li-xia; FENG Ji-cai; LIU Hong-bin; HE Peng

    2009-01-01

    Vacuum brazing of SiO_2 glass ceramic and TC4 alloy using a commercially available TiZrNiCu foil was investigated. The interfaciai microstructure and the fractures were examined with an optical microscope (OM) and an S-4700 scanning electron microscope (SEM) equipped with an energy dispersive spectrometer (EDS) and an electron probe X-ray microanalyzer (EPMA). The structure of joint interface was identified by XRD (JDX-3530M). Meanwhile, the fracture paths of the joints were comprehensively studied. The results show that processing parameters, especially the brazing temperature, have a significant effect on the microstructurc and mechanical properties of joints. The typical interface structure is SiO_2/Ti_2O+Zr_3Si_2+Ti_5Si_3/(Ti,Zr)+Ti_2O+ TiZrNiCu/Ti(s.s)/TiZrNiCu+Ti(s.s)+Ti_2(Cu,Ni)/TC4 from SiO_2 glass ceramic to TC4 alloy side. Based on the mechanical property tests, the joints brazed at 880℃ for 5 min has the maximum shear strength of 23 MPa.

  15. Progress report on the influence of test temperature and grain boundary chemistry on the fracture behavior of ITER copper alloys

    Energy Technology Data Exchange (ETDEWEB)

    Li, M.; Stubbins, J.F. [Univ. of Illinois, Urbana, IL (United States). Dept. of Nuclear Engineering; Edwards, D.J. [Pacific Northwest National Lab., Richland, WA (United States)

    1998-09-01

    This collaborative study was initiated to determine mechanical properties at elevated temperatures of various copper alloys by University of Illinois and Pacific Northwestern National Lab (PNNL) with support of OMG Americas, Inc. and Brush Wellman, Inc. This report includes current experimental results on notch tensile tests and pre-cracked bend bar tests on these materials at room temperature, 200 and 300 C. The elevated temperature tests were performed in vacuum and indicate that a decrease in fracture resistance with increasing temperature, as seen in previous investigations. While the causes for the decreases in fracture resistance are still not clear, the current results indicate that environmental effects are likely less important in the process than formerly assumed.

  16. Phase evolution and alloying mechanism of titanium aluminide nanoparticles

    International Nuclear Information System (INIS)

    Highlights: • An evolution of phase composition of TiAl alloy nanoparticles was investigated. • An alloying mechanism was analyzed according to the variation of phase composition. • The alloying reaction was possible to perform between the small clusters of Ti and Al. • The alloying product is determined by the temperature of Ti and Al small clusters. • The alloying mechanism can be explained based on Gibbs free energy of alloying reaction. - Abstract: The evolution of phase composition of titanium aluminide nanoparticles synthesized by the flow-levitation method was systematically investigated by adjustment of the evaporating temperature of the mixed metallic droplet and the X-ray diffraction spectrum. Their alloying mechanism was analyzed according to the variation of phase composition. ε(h, l)-TiAl3, γ-TiAl and α2-Ti3Al phases are gradually formed in TiAl alloy nanoparticles with the increasing of evaporating temperature of the mixed droplet. The alloying reaction is possible to perform between the small clusters of Ti and Al during the cooling process with high cooling rate. And the alloying mechanism can be explained based on the Gibbs free energy of alloying reaction of Ti and Al small clusters

  17. Phase evolution and alloying mechanism of titanium aluminide nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Luo, J.S.; Li, K.; Li, X.B. [Research Center of Laser Fusion, Science and Technology on Plasma Physics Laboratory, China Academy of Engineering Physics, Mianyang 621900 (China); Shu, Y.J. [Institute of Chemical Materials, China Academy of Engineering Physics, Mianyang 621900 (China); Tang, Y.J., E-mail: tangyongjian2000@sina.com [Research Center of Laser Fusion, Science and Technology on Plasma Physics Laboratory, China Academy of Engineering Physics, Mianyang 621900 (China)

    2014-12-05

    Highlights: • An evolution of phase composition of TiAl alloy nanoparticles was investigated. • An alloying mechanism was analyzed according to the variation of phase composition. • The alloying reaction was possible to perform between the small clusters of Ti and Al. • The alloying product is determined by the temperature of Ti and Al small clusters. • The alloying mechanism can be explained based on Gibbs free energy of alloying reaction. - Abstract: The evolution of phase composition of titanium aluminide nanoparticles synthesized by the flow-levitation method was systematically investigated by adjustment of the evaporating temperature of the mixed metallic droplet and the X-ray diffraction spectrum. Their alloying mechanism was analyzed according to the variation of phase composition. ε(h, l)-TiAl{sub 3,} γ-TiAl and α{sub 2}-Ti{sub 3}Al phases are gradually formed in TiAl alloy nanoparticles with the increasing of evaporating temperature of the mixed droplet. The alloying reaction is possible to perform between the small clusters of Ti and Al during the cooling process with high cooling rate. And the alloying mechanism can be explained based on the Gibbs free energy of alloying reaction of Ti and Al small clusters.

  18. In Vitro Fracture of Human Cortical Bone: Local Fracture Criteria and Toughening Mechanisms

    Energy Technology Data Exchange (ETDEWEB)

    Nalla, R; Stolken, J; Kinney, J; Ritchie, R

    2004-08-18

    A micro-mechanistic understanding of bone fracture that encompasses how cracks interact with the underlying microstructure and defines their local failure mode is lacking, despite extensive research on the response of bone to a variety of factors like aging, loading, and/or disease. Micro-mechanical models for fracture incorporating such local failure criteria have been widely developed for metallic and ceramic materials systems; however, few such deliberations have been undertaken for the fracture of bone. In fact, although the fracture event in mineralized tissues such as bone is commonly believed to be locally strain controlled, until recently there has been little experimental evidence to support this widely held belief. In the present study, a series of in vitro experiments involving a double-notch bend test geometry are performed in order to shed further light on the nature of the local cracking events that precede catastrophic fracture in bone and to define their relationship to the microstructure. Specifically, crack-microstructure interactions are examined to determine the salient toughening mechanisms in human cortical bone and to characterize how these may affect the anisotropy in fracture properties. Based on preliminary micro-mechanical models of these processes, in particular crack deflection and uncracked ligament bridging, the relative importance of these toughening mechanisms is established.

  19. Mechanisms of hydrogen absorption by zirconium alloys

    International Nuclear Information System (INIS)

    This paper summarizes our present understanding of the three primary mechanisms by which hydrogen isotopes can enter zirconium alloys in service. These are: (i) reaction with and adsorption of hydrogen gas from atmospheres containing insufficient oxidant to maintain the protective oxide film, (ii) diffusion into the metal of a fraction of the hydrogen released in the cathodic partial cell during oxidation in water or steam, (iii) diffusion of hydrogen isotopes through a metallurgical bond with a dissimilar metal which provides a window through the normally protective oxide film. It is shown that while all three mechanisms can be specified qualitatively with some certainty, and while supporting circumstantial evidence is often available, the basic rate constants for the various steps in the reactions are largely unknown

  20. Fracture behavior of low-density replicated aluminum alloy foams

    NARCIS (Netherlands)

    Amsterdam, E.; Goodall, R.; Mortensen, A.; Onck, P. R.; De Hosson, J. Th. M.

    2008-01-01

    Tensile tests have been performed on replicated aluminum alloy foams of relative density between 4.5% and 8%. During the test the electrical resistance was measured with a four-point set-up and the displacements along the gage section were measured using a digital image correlation (DIC) technique.

  1. Mechanical alloying in the Fe-Cu system

    DEFF Research Database (Denmark)

    Jiang, Jianzhong; Gente, C.; Bormann, R.

    1998-01-01

    in the Fe-Cu system is; (3) where the positive energy is stored in the alloys; (4) what the decomposition process of the supersaturated alloys is; and (5) what type of magnetic properties the new materials have. The elucidation of these problems will shed light on the understanding of the mechanisms...... for the preparation of materials under highly non-equilibrium conditions in systems with positive heats of mixing by mechanical alloying....

  2. Study of Alpha-Sigma Phase Transformation in Mechanically Alloyed Fe-Cr-Sn Alloys

    OpenAIRE

    Costa, B. F. O.; Caër, G. Le; Campos, N. Ayres de

    2001-01-01

    The solubility of tin is significantly extended by mechanical alloying in near equiatomic Fe-Cr alloys. The influences of Sn concentration and of grain size on the kinetics of formation of the sigma-phase have been studied using different techniques. The sigma-phase formation is much faster for as-milled alloys than it is for conventional alloys. The sigma-phase formation rate decreases with the increase of Sn concentration in alloys with nanometer-sized grains as it does in coarse-grained al...

  3. Decomposition mechanism in supercooled liquid alloys.

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, W. L.; Loffler, J. F.; Thiyagarajan, P.

    1999-07-12

    The authors performed small-angle neutron scattering experiments on the bulk amorphous alloy Zr{sub 41.2}Ti{sub 13.8}Cu{sub 12.5}Ni{sub 10}Be{sub 22.5} (Vit1{reg_sign}) and on further alloys, where the ZrTi and CuBe content have been changed, following the tie-line in the direction of Zr{sub 46.8}Ti{sub 8.2}Cu{sub 7.5}Ni{sub 10}Be{sub 27.5} (Vit4{reg_sign}). The SANS data of the samples, preannealed at temperatures between 330 C and 390 C, show interference peaks giving evidence for spatially correlated arrangements of inhomogeneities. The Q values of the interference peaks, Q{sub max}, decrease with increasing annealing temperature T{sub a} and, at a given annealing temperature, with composition following the tie-line from Vit1 to Vit4. They find that, in two distinguished regimes, the data follow a relation 1/L{sup 2} {proportional_to} T{sub a} as predicted by Cahn's theory (L = 2{pi}/Q{sub max} is the wavelength of the decomposition), with a crossover at the glass transition temperature T{sub g} = 350 C. The authors explain the crossover by different diffusion mechanisms below and above T{sub g}.

  4. Softening and fatigue fracture of Al-Si-X alloy casts

    OpenAIRE

    Oshikiri, Jouji; Umezawa, Osamu; Nakamura, Norio

    2011-01-01

    Ductile manner such as dimple fully covered on fatigue fracture surface of the specimens at 523 K. Softening behavior of eutectic or hyper-eutectic Al-Si-Cu-Mg-(Ni, Fe, Mn) alloy casts has been examined to estimate the influence of heating on their fatigue strength at higher temperature. The hyper-eutectic alloys showed remarkable softening rather than eutectic ones. The softening during heating over 523 K may be related to Al-Cu-Mg-Si precipitation and lowered content of Cu in the matrix.

  5. Mechanical Properties and Fracture Behavior of Directionally Solidified NiAl-V Eutectic Composites

    Science.gov (United States)

    Milenkovic, Srdjan; Caram, Rubens

    2015-02-01

    Directional solidification of eutectic alloys has been recognized as promising technique for producing in situ composite materials exhibiting balance of properties. Therefore, an in situ NiAl-V eutectic composite has been successfully directionally solidified using Bridgman technique. The mechanical behavior of the composite including fracture resistance, microhardness, and compressive properties at room and elevated temperatures was investigated. Damage evolution and fracture characteristics were also discussed. The obtained results indicate that the NiAl-V eutectic retains high yield strength up to 1073 K (800 °C), above which there is a rapid decrease in strength. Its yield strength is higher than that of binary NiAl and most of the NiAl-based eutectics. The exhibited fracture toughness of 28.5 MPa√m is the highest of all other NiAl-based systems investigated so far. The material exhibited brittle fracture behavior of transgranular type and all observations pointed out that the main fracture micromechanism was cleavage.

  6. Coating hydroxyapatite/alpha alumina composites by mechanical alloying

    International Nuclear Information System (INIS)

    The biomaterials field has become a vital area, as these materials can enhance the quality and longevity of human life and science and technology associated with this field has now led to multi-million dollar business. Hydroxyapatite [Ca10(PO4)6(OH)2-HA] and alumina ceramics materials have been clinically applied in many areas of dentistry and orthopaedics. Their widespread use is based on a combination of good strength, modest fracture toughness, high wear resistance, good biocompatibility and excellent corrosion resistance. Alumina has also been used in jaw bone reconstruction. Other clinical applications include knee prostheses, bone segment replacements, bone screws, middle ear bone substitutes, and corneal replacements. Optimization of the surface structure of materials is of great concern at the present time since most failures occur on the surface (fatigue, fretting corrosion, corrosion, wear, etc.). As a result, improving the surface properties would greatly enhance the overall behaviour of materials. It is widely recognized that titanium displays poor wear resistance and that its fatigue performance depends to a large extent on its surface properties. The newly developed process, mechanical alloying MA, is therefore of considerable technological importance since it provides the possibility of dramatically improving the surface properties of titanium. Presented work describes the effect of MA treatment, as a non-conventional solid-state process, on the microstructure of IA/α-Al2O3 composites. Also, the necessary conditions for coating HA/α- Al2O3 composites on Ti-substrate were examined. To make HA and Al2O3 composites, α-Al2O3 powder was used because of its better sinterability than γ-AI2O3. HA/α-Al2O3 was successfully deposited on Ti-substrate by mechanical alloying (MA). From the X-Ray Diffraction (XRD) the as-synthesized and heat treated samples between 300C and 600C have not any phase transition or decomposition. From the scanning electron

  7. The effects of the local fracture stress and carbides on the cleavage fracture characteristics of Mn-Mo-Ni low alloy steels in the transition region

    International Nuclear Information System (INIS)

    In the ductile-brittle transition temperature region of SA508 C1.3 Mn-Mo-Ni low alloy steels, the relationship of the local fracture stress and carbides influencing the cleavage fracture behavior was investigated. Based on the ASTM E1921-97 standard method, the reference transition temperatures were determined by three point bending fracture toughness tests. A local fracture stress σf*, was determined from a theoretical stress distribution in front of crack tip using the cleavage initiation distance measured in each fractured specimen surface. The local fracture stress values showed a strong relationship with toughness characteristics of the materials and those were larger in the materials of smaller carbide size. Quantitative analysis of carbides showed that carbides larger than a certain size are mainly responsible for the cleavage fracture in the ductile-brittle transition temperature region. (author)

  8. Effect of Carburization on the Mechanical Properties of Biomedical Grade Titanium Alloys

    Institute of Scientific and Technical Information of China (English)

    Yong Luo; Haibo Jiang; Gang Cheng; Hongtao Liu

    2011-01-01

    Titanium cermets were successfully synthesized on the surface of biomedical grade titanium alloys by using sequential carburization method. The mechanical properties such as hardness, fracture toughness and plasticity were measured to estimate the potential application of titanium cermets. The results show that after carburization the surface hardness of titanium cermets was 778 HV, with a significant improvement of 128% compared with that of titanium alloys. In addition, the fracture toughness of titanium cermets was 21.5×106 Pa·m1/2, much higher than that of other ceramics. Furthermore, the analysis of the loading-unloading curve in the nanoindentation test also indicates that the plasticity of titanium cermet reached 32.1%, a relatively high value which illustrates the combination of the metal and ceramics properties. The results suggest that sequential carburization should be an efficient way to produce titanium cermets with hard surface, high toughness and plasticity.

  9. Amorphization and magnetic properties of Fe62Nb38 mechanically alloyed powders

    Institute of Scientific and Technical Information of China (English)

    QIN Hongwei; HU Jifan; YANG Fuming

    2004-01-01

    The amorphization and magnetic properties of Fe62Nb38 mechanically alloyed powders were investigated. In the initial mechanical alloying processes, the lattice structure of pure Fe is destroyed due to the cold-welding and fracturing, accompanying the reduction of ferromagnetic properties. The Ms value of Fe62Nb38 powders with ball-milling time t = 6 h is only 48.1 A.m2/kg. With prolongating of mechanical alloying processes, a solid state amorphization reaction (SSAR) takes place and the Fe-Nb ferromagnetic amorphous phase is formed. With the milling time increasing from 6 to 18 h, the satura tion magnetization of Fe62NB38 powders increases with enhancement of the proportion of ferromagnetic amorphous phase in from dilute model. However, the Curie temperature of the Fe62Nb38 amorphous phase is only 206°C, which is much smaller than that of the pure Fe. This implies that the exchange interaction between Fe atoms in amorphous alloyed Fe62Nb38 becomes weak due to the Nb dilution. Investigation shows that the variation of magnetic properties of milled powders is one of important tools for describing the amorphization by mechanical alloying.

  10. Theoretical Analysis of the Mechanism of Fracture Network Propagation with Stimulated Reservoir Volume (SRV Fracturing in Tight Oil Reservoirs.

    Directory of Open Access Journals (Sweden)

    Yuliang Su

    Full Text Available Stimulated reservoir volume (SRV fracturing in tight oil reservoirs often induces complex fracture-network growth, which has a fundamentally different formation mechanism from traditional planar bi-winged fracturing. To reveal the mechanism of fracture network propagation, this paper employs a modified displacement discontinuity method (DDM, mechanical mechanism analysis and initiation and propagation criteria for the theoretical model of fracture network propagation and its derivation. A reasonable solution of the theoretical model for a tight oil reservoir is obtained and verified by a numerical discrete method. Through theoretical calculation and computer programming, the variation rules of formation stress fields, hydraulic fracture propagation patterns (FPP and branch fracture propagation angles and pressures are analyzed. The results show that during the process of fracture propagation, the initial orientation of the principal stress deflects, and the stress fields at the fracture tips change dramatically in the region surrounding the fracture. Whether the ideal fracture network can be produced depends on the geological conditions and on the engineering treatments. This study has both theoretical significance and practical application value by contributing to a better understanding of fracture network propagation mechanisms in unconventional oil/gas reservoirs and to the improvement of the science and design efficiency of reservoir fracturing.

  11. The hydro-mechanical modeling of the fractured media; Modelisation hydromecanique des milieux fractures

    Energy Technology Data Exchange (ETDEWEB)

    Kadiri, I

    2002-10-15

    The hydro-mechanical modeling of the fractured media is quite complex. Simplifications are necessary for the modeling of such media, but, not always justified, Only permeable fractures are often considered. The rest of the network is approximated by an equivalent continuous medium. Even if we suppose that this approach is validated, the hydraulic and mechanical properties of the fractures and of the continuous medium are seldom known. Calibrations are necessary for the determination of these properties. Until now, one does not know very well the nature of measurements which must be carried out in order to carry on a modeling in discontinuous medium, nor elements of enough robust validation for this kind of modeling. For a better understanding of the hydro-mechanical phenomena in fractured media, two different sites have been selected for the work. The first is the site of Grimsel in Switzerland in which an underground laboratory is located at approximately 400 m of depth. The FEBEX experiment aims at the in-situ study of the consecutive phenomena due to the installation of a heat source representative of radioactive waste in the last 17 meters of the FEBEX tunnel in the laboratory of Grimsel. Only, the modeling of the hydro-mechanical of the excavation was model. The modeling of the Febex enabled us to establish a methodology of calibration of the hydraulic properties in the discontinuous media. However, this kind of study on such complex sites does not make possible to answer all the questions which arise on the hydro-mechanical behavior of the fractured media. We thus carried out modeling on an other site, smaller than the fist one and more accessible. The experimental site of Coaraze, in the Maritime Alps, is mainly constituted of limestone and fractures. Then the variation of water pressure along fractures is governed by the opening/closure sequence of a water gate. Normal displacement as well as the pore pressure along these fractures are recorded, and then

  12. A Fracture Mechanical Model and a Cohesive Zone Model of Interface Fracture

    DEFF Research Database (Denmark)

    Jensen, Henrik Myhre

    2006-01-01

    quasi-static conditions. The cohesive zone model has several advantages over the fracture mechanics based model. It is easier to generalise the cohesive zone model to take into account effects such as plastic deformation in the adherends, and to take into account effects of large local curvatures......A comparison between the prediction of crack propagation through an adhesive interface based on a fracture mechanics approach and a cohesive zone approach is presented. Attention is focussed on predicting the shape of the crack front and the critical stress required to propagate the crack under...... of the interface crack front. The comparison shows a convergence of the results based on the cohesive zone model towards the results based on a fracture mechanics approach in the limit where the size of the cohesive zone becomes smaller than other relevant geometrical lengths for the problem....

  13. Microstructures and mechanical properties of Mg–Zn–Zr–Dy wrought magnesium alloys

    Indian Academy of Sciences (India)

    Z H Huang; W J Qi; K H Zheng; X M Zhang; M Liu; Z M Yu; J Xu

    2013-06-01

    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 increases gradually, while MgZn2 phase decreases gradually to disappear. As-cast microstructure is refined gradually; meanwhile extruded one is refined further with decreasing average grain size to 1 m for ZK60–4.32Dy alloy. Second phase, tending to distribute along grain boundary by continuous network in as-cast state, breaks and distributes dispersedly in extrusion state. As-cast tensile mechanical property remains almost unchanged at ambient temperature; however, extruded ones are enhanced significantly at ambient and elevated temperatures, respectively. Tensile strength at 298 and 473 K increases gradually from 355 and 120 MPa for ZK60 alloy to 395 and 171 MPa for ZK60–4.32Dy alloy, respectively. Extruded tensile fractures exhibit a typical character of ductile fracture.

  14. Environment enhanced fatigue crack propagation in metals: Inputs to fracture mechanics life prediction models

    Science.gov (United States)

    Gangloff, Richard P.; Kim, Sang-Shik

    1993-01-01

    This report is a critical review of both environment-enhanced fatigue crack propagation data and the predictive capabilities of crack growth rate models. This information provides the necessary foundation for incorporating environmental effects in NASA FLAGRO and will better enable predictions of aerospace component fatigue lives. The review presents extensive literature data on 'stress corrosion cracking and corrosion fatigue.' The linear elastic fracture mechanics approach, based on stress intensity range (Delta(K)) similitude with microscopic crack propagation threshold and growth rates, provides a basis for these data. Results are presented showing enhanced growth rates for gases (viz., H2 and H2O) and electrolytes (e.g. NaCl and H2O) in aerospace alloys including: C-Mn and heat treated alloy steels, aluminum alloys, nickel-based superalloys, and titanium alloys. Environment causes purely time-dependent accelerated fatigue crack growth above the monotonic load cracking threshold (KIEAC) and promotes cycle-time dependent cracking below (KIEAC). These phenomenon are discussed in terms of hydrogen embrittlement, dissolution, and film rupture crack tip damage mechanisms.

  15. Fracture toughness of welded joints of a high strength low alloy steel

    International Nuclear Information System (INIS)

    The fracture toughness of the different regions of welded joints of a high strength low alloy steel, Niocor 2, was evaluated at different temperatures and compared with the toughness of the base metal. The studied regions were: the weld metal, fusion boundary and heat affected zone. The welding process used was the manual metal arc. It is shown that the weld metal region has the highest toughness values. (Author)

  16. Fracture of an {alpha}/{beta} titanium alloy under stress triaxiality states at 773 K

    Energy Technology Data Exchange (ETDEWEB)

    Bourgeois, M.; Feaugas, X.; Clavel, M. [Univ. de Technologie de Compiegne (France). Division Mecanique

    1996-05-01

    This study has shown that the fracture of titanium alloy 6246 at high temperature is very sensitive to the loading path. In addition, it is demonstrated that the concept of the critical void size, provided by Rice and Tracey`s approach, is only applicable to high triaxialities ({chi} > 0.9). Under low triaxiality ({chi} {le} 0.9) the plastic flow instigates the damage process, favoring shearing instability in prior {beta} grain.

  17. Determination of design allowable properties. Fracture of 2219-T87 aluminum alloy

    Science.gov (United States)

    Engstrom, W. L.

    1972-01-01

    A literature survey was conducted to provide a comprehensive report of available valid data on tensile properties, fracture toughness, fatigue crack propagation, and sustained load behavior of 2219-T87 aluminum alloy base metal and weldments, as applicable to manned spacecraft tankage. Most of the data found were from tests conducted at room temperature, -320 F and -423 F. Data are presented in graphical and tabular form, and areas in which data are lacking are established.

  18. Metallurgical Source of Cryogenic Intergranular Fracture of Fe-38Mn Austenitic Alloy

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    SEM and Field emitting TEM-EDAX were used to investigate the fracture surface of series impact specimens and the grain boundary chemistries of VIM (vacuum-induction-melted) Fe-38Mn austenitic alloy before and after ESR (electroslag remelting,). The quantity and the size of inclusions were also examined. The results show that the VIM Fe-38Mn aust enitinic alloy water-quenched from 1 100 ℃ undergoes an obvious ductile-to-brittle transition, and the impact work at ambient temperature is 242 J, the corresponding fracture surface exhibits adimple character. However, the impact work at 77 K of VIM alloy is only 25 J and the fracture mode is IGF (intergranular f racture). After ESR, the impact work at ambient temperature is 320 J and the fra cture surface exhibits a character of "volcano lava" (meaning excellent toughn ess); The impact work at 77 K is up to 300 J and the fracture mode is microvoid coalescence mixed with quasi-cleavage. The segregation of Mn is not found in all specimens, but the segregation of S is observed, and the S segregation is decreased after ESR. The examined results of inclusions show that ESR reduces the quantity and improves the morphology of inclusions. From the above results it can be seen that the cryogenic IGF of VIM Fe-38Mn austenitic alloy is related to the S segregation at grain boundary. After ESR the decrease in the quantity and size of inclusion results in the increase of the impact work at ambient temperature, while the restriction of IGF is related to the decrease in the total level, and hence in the grain boundary segregation of S.

  19. Metallic Reinforcement of Direct Squeeze Die Casting Aluminum Alloys for Improved Strength and Fracture Resistance

    Energy Technology Data Exchange (ETDEWEB)

    D. Schwam: J.F. Wallace: Y. Zhu: J.W. Ki

    2004-10-01

    The utilization of aluminum die casting as enclosures where internal equipment is rotating inside of the casting and could fracture requires a strong housing to restrain the fractured parts. A typical example would be a supercharger. In case of a failure, unless adequately contained, fractured parts could injure people operating the equipment. A number of potential reinforcement materials were investigated. The initial work was conducted in sand molds to create experimental conditions that promote prolonged contact of the reinforcing material with molten aluminum. Bonding of Aluminum bronze, Cast iron, and Ni-resist inserts with various electroplated coatings and surface treatments were analyzed. Also toughening of A354 aluminum cast alloy by steel and stainless steel wire mesh with various conditions was analyzed. A practical approach to reinforcement of die cast aluminum components is to use a reinforcing steel preform. Such performs can be fabricated from steel wire mesh or perforated metal sheet by stamping or deep drawing. A hemispherical, dome shaped casting was selected in this investigation. A deep drawing die was used to fabricate the reinforcing performs. The tendency of aluminum cast enclosures to fracture could be significantly reduced by installing a wire mesh of austenitic stainless steel or a punched austenitic stainless steel sheet within the casting. The use of reinforcements made of austenitic stainless steel wire mesh or punched austenitic stainless steel sheet provided marked improvement in reducing the fragmentation of the casting. The best strengthening was obtained with austenitic stainless steel wire and with a punched stainless steel sheet without annealing this material. Somewhat lower results were obtained with the annealed punched stainless steel sheet. When the annealed 1020 steel wire mesh was used, the results were only slightly improved because of the lower mechanical properties of this unalloyed steel. The lowest results were

  20. Fracture mechanics life analytical methods verification testing

    Science.gov (United States)

    Favenesi, J. A.; Clemons, T. G.; Riddell, W. T.; Ingraffea, A. R.; Wawrzynek, P. A.

    1994-09-01

    The objective was to evaluate NASCRAC (trademark) version 2.0, a second generation fracture analysis code, for verification and validity. NASCRAC was evaluated using a combination of comparisons to the literature, closed-form solutions, numerical analyses, and tests. Several limitations and minor errors were detected. Additionally, a number of major flaws were discovered. These major flaws were generally due to application of a specific method or theory, not due to programming logic. Results are presented for the following program capabilities: K versus a, J versus a, crack opening area, life calculation due to fatigue crack growth, tolerable crack size, proof test logic, tearing instability, creep crack growth, crack transitioning, crack retardation due to overloads, and elastic-plastic stress redistribution. It is concluded that the code is an acceptable fracture tool for K solutions of simplified geometries, for a limited number of J and crack opening area solutions, and for fatigue crack propagation with the Paris equation and constant amplitude loads when the Paris equation is applicable.

  1. Strength and fracture of uranium, plutonium and several their alloys under shock wave loading

    Science.gov (United States)

    Golubev, V. K.

    2012-08-01

    Results on studying the spall fracture of uranium, plutonium and several their alloys under shock wave loading are presented in the paper. The problems of influence of initial temperature in a range of - 196 - 800∘C and loading time on the spall strength and failure character of uranium and two its alloys with molybdenum and both molybdenum and zirconium were studied. The results for plutonium and its alloy with gallium were obtained at a normal temperature and in a temperature range of 40-315∘C, respectively. The majority of tests were conducted with the samples in the form of disks 4 mm in thickness. They were loaded by the impact of aluminum plates 4 mm thick through a copper screen 12 mm thick serving as the cover or bottom part of a special container. The character of spall failure of materials and the damage degree of samples were observed on the longitudinal metallographic sections of recovered samples. For a concrete test temperature, the impact velocity was sequentially changed and therefore the loading conditions corresponding to the consecutive transition from microdamage nucleation up to complete macroscopic spall fracture were determined. The conditions of shock wave loading were calculated using an elastic-plastic computer program. The comparison of obtained results with the data of other researchers on the spall fracture of examined materials was conducted.

  2. Strength and fracture of uranium, plutonium and several their alloys under shock wave loading

    Directory of Open Access Journals (Sweden)

    Golubev V.K.

    2012-08-01

    Full Text Available Results on studying the spall fracture of uranium, plutonium and several their alloys under shock wave loading are presented in the paper. The problems of influence of initial temperature in a range of − 196 – 800∘C and loading time on the spall strength and failure character of uranium and two its alloys with molybdenum and both molybdenum and zirconium were studied. The results for plutonium and its alloy with gallium were obtained at a normal temperature and in a temperature range of 40–315∘C, respectively. The majority of tests were conducted with the samples in the form of disks 4 mm in thickness. They were loaded by the impact of aluminum plates 4 mm thick through a copper screen 12 mm thick serving as the cover or bottom part of a special container. The character of spall failure of materials and the damage degree of samples were observed on the longitudinal metallographic sections of recovered samples. For a concrete test temperature, the impact velocity was sequentially changed and therefore the loading conditions corresponding to the consecutive transition from microdamage nucleation up to complete macroscopic spall fracture were determined. The conditions of shock wave loading were calculated using an elastic-plastic computer program. The comparison of obtained results with the data of other researchers on the spall fracture of examined materials was conducted.

  3. The hydro-mechanical modeling of the fractured media

    International Nuclear Information System (INIS)

    The hydro-mechanical modeling of the fractured media is quite complex. Simplifications are necessary for the modeling of such media, but, not always justified, Only permeable fractures are often considered. The rest of the network is approximated by an equivalent continuous medium. Even if we suppose that this approach is validated, the hydraulic and mechanical properties of the fractures and of the continuous medium are seldom known. Calibrations are necessary for the determination of these properties. Until now, one does not know very well the nature of measurements which must be carried out in order to carry on a modeling in discontinuous medium, nor elements of enough robust validation for this kind of modeling. For a better understanding of the hydro-mechanical phenomena in fractured media, two different sites have been selected for the work. The first is the site of Grimsel in Switzerland in which an underground laboratory is located at approximately 400 m of depth. The FEBEX experiment aims at the in-situ study of the consecutive phenomena due to the installation of a heat source representative of radioactive waste in the last 17 meters of the FEBEX tunnel in the laboratory of Grimsel. Only, the modeling of the hydro-mechanical of the excavation was model. The modeling of the Febex enabled us to establish a methodology of calibration of the hydraulic properties in the discontinuous media. However, this kind of study on such complex sites does not make possible to answer all the questions which arise on the hydro-mechanical behavior of the fractured media. We thus carried out modeling on an other site, smaller than the fist one and more accessible. The experimental site of Coaraze, in the Maritime Alps, is mainly constituted of limestone and fractures. Then the variation of water pressure along fractures is governed by the opening/closure sequence of a water gate. Normal displacement as well as the pore pressure along these fractures are recorded, and then

  4. FFTF irradiation of fracture mechanics specimens for out-of-core structures

    International Nuclear Information System (INIS)

    The National Program Plan has established data requirements for out-of-core structures for FBRs. Significant FFTF irradiation space with moderate gamma heating levels is required to irradiate relatively large fracture mechanics specimens to total neutron fluences ranging between 5 x 1021 and 5 x 1022 n/cm2 and temperatures which range between 4000C (7500F) and 6500C (12000F). Priority 1 data on stainless steel welds requires a test volume of 7443 cm3 (454 in3). Priority 2 data on 304 and 316 SS and Inconel 718 materials and Inconel 718 welds requires 2760 cm3 (168 in3). Priority 3 data on stainless steels, other nickel-base alloys, and ferritics requires 33,118 cm3 (2021 in3). Priority 4 data at elevated temperatures on stainless steels, other nickel-base alloys and ferritics requires 69,182 cm3

  5. Statistical fracture mechanics approach to the strength of brittle rock

    International Nuclear Information System (INIS)

    Statistical fracture mechanics concepts used in the past for rock are critically reviewed and modifications are proposed which are warranted by (1) increased understanding of fracture provided by modern fracture mechanics and (2) laboratory test data both from the literature and from this research. Over 600 direct and indirect tension tests have been performed on three different rock types; Stripa Granite, Sierra White Granite and Carrara Marble. In several instances assumptions which are common in the literature were found to be invalid. A three parameter statistical fracture mechanics model with Mode I critical strain energy release rate as the variant is presented. Methodologies for evaluating the parameters in this model as well as the more commonly employed two parameter models are discussed. The experimental results and analysis of this research indicate that surfacially distributed flaws, rather than volumetrically distributed flaws are responsible for rupture in many testing situations. For several of the rock types tested, anisotropy (both in apparent tensile strength and size effect) precludes the use of contemporary statistical fracture mechanics models

  6. Fracture toughness of welded joints of a high strenghth low alloy steel

    International Nuclear Information System (INIS)

    The fracture toughness of welded joints of a high strength low alloy atmospheric corrosion resistant steel was investigated. The welded joints were produced using the manual metal arc welding process and fracture toughness was evaluated by the COD method. An effort was made in order to correlate the microstructure of the different regions of the welded joints and their critical COD values. The results appear to indicate that when the structure of the heat affected zone is formed mainly by bainite and ferritic grains the fracture toughness tends to increase. Also, an increase on the amount of acicular ferrite on the weld metal tends to improve its fracture toughness. The fusion boundary showed a structure formed mainly by bainite and ferrite grains and its fracture toughness was higher than that of the parent metal at room temperature whereas it was lower at 00C. Both at 00C and room temperature the fracture toughness of the weld metal was better than those of the other regions of the welded joints. The correlations between critical values of COD and the microstructures of the different regions of the welded joints were very difficult. (Author)

  7. COMPUTER NUMERICAL SIMULATION OF MECHANICAL PROPERTIES OF TUNGSTEN HEAVY ALLOYS

    Institute of Scientific and Technical Information of China (English)

    1999-01-01

    A microstructure model of tungsten heavy alloys has been developed. On the basis of the model and several assumptions, the macro-mechanical properties of 90 W heavy alloy under quasi-static tensile deformation and the effects of microstructural parameters (mechanical properties of the matrix phase and tungsten content) on them have been analyzed by computer numerical simulation. The mechanical properties of the alloy have been found to be dependent on the mechanical parameters of the matrix phase. As the elastic modulus and yield strength of the matrix phase increase, the tensile strength of the alloy increases, while the elongation decreases. If the mechanical parameters except the tensile strength of the matrix phase are constant, both the tensile strength and the elongation of the alloy increase linearly with the increase of tensile strength of the matrix phase. The properties of the alloy are very sensitive to the hardening modulus of the matrix phase. As the hardening modulus increases, both the tensile strength and the elongation of the alloy exponentially decrease. The elongation of the alloys monotonically decreases with the increase of tungsten content, while the decrease of tensile strength is not monotonic. When the tungsten content < 85 %, the strength of tungsten heavy alloys increases with the increase of tungsten content, while decreases when the tungsten content >85 %. The maximum of tensile strength of the alloys appears at the tungsten content of 85 %. The results showed that the binder phase with a higher strength and a lower hardening modulus is advantageous to obtaining an optimum combination of mechanical properties of tungsten heavy alloys.

  8. Fracture Mechanics Prediction of Fatigue Life of Aluminum Highway Bridges

    DEFF Research Database (Denmark)

    Rom, Søren; Agerskov, Henning

    2015-01-01

    Fracture mechanics prediction of the fatigue life of aluminum highway bridges under random loading is studied. The fatigue life of welded joints has been determined from fracture mechanics analyses and the results obtained have been compared with results from experimental investigations....... The fatigue life of welded plate specimens has been investigated. Both the fracture mechanics analyses and the fatigue tests have been carried out using load histories, which correspond to one week's traffic loading, determined by means of strain gauge measurements on the deck structure of the Farø Bridges...... against fatigue in aluminum bridges, may give results which are unconservative. Furthermore, it was in both investigations found that the validity of the results obtained from Miner's rule will depend on the distribution of the load history in tension and compression....

  9. Mechanical properties and corrosion resistance of hot extruded Mg–2.5Zn–1Ca alloy

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Dexue, E-mail: dexeliu@hotmail.com [State Key Laboratory of Advanced Processing and Recycling of Non-Ferrous Metals, Lanzhou University of Technology, Lanzhou 730050 (China); Department of Mechanical and Aerospace Engineering, University of California, San Diego, CA 92093-0411 (United States); Guo, Chenggong; Chai, Liqiang [State Key Laboratory of Advanced Processing and Recycling of Non-Ferrous Metals, Lanzhou University of Technology, Lanzhou 730050 (China); Sherman, Vincent R. [Department of Mechanical and Aerospace Engineering, University of California, San Diego, CA 92093-0411 (United States); Qin, Xiaoqiong; Ding, Yutian [State Key Laboratory of Advanced Processing and Recycling of Non-Ferrous Metals, Lanzhou University of Technology, Lanzhou 730050 (China); Meyers, Marc A. [Department of Mechanical and Aerospace Engineering, University of California, San Diego, CA 92093-0411 (United States)

    2015-05-15

    Highlights: • MgZnCa alloy was extruded into precise microtube for resorbable stent applications. • Interconnection between micro-structure and corrosion properties was revealed. • Both strength and ductility were simultaneously improved by processing sequence. • Better corrosion resistance in PBS solution was achieved after grain refining. - Abstract: It is demonstrated that the mechanical properties and corrosion resistance of Mg–2.5 wt%Zn–1 wt%Ca alloy are enhanced by the microstructural changes imparted by hot extrusion. A processing procedure is developed to form hollow tubes with an outer diameter of ∼2.0 mm and wall thickness of ∼0.1 mm, which is well suited for subsequent stent manufacturing. The influence of thermal and mechanical processing on corrosion and plasticity was found to be associated with grain-size reduction and the redistribution of intermetallic particles within the microstructure, providing significant improvement of performance over the cast alloy. Observation of the fracture surfaces reveals a mode transition from brittle (cast) to ductile (processed). Enhanced mechanical properties and decreased resorption rate represent significantly improved performance of this alloy after the novel processing sequence. Based on the improved properties, the produced Mg alloy is more suitable for practical in vivo applications.

  10. Mechanical transport in two-dimensional networks of fractures

    International Nuclear Information System (INIS)

    The objectives of this research are to evaluate directional mechanical transport parameters for anisotropic fracture systems, and to determine if fracture systems behave like equivalent porous media. The tracer experiments used to measure directional tortuosity, longitudinal geometric dispersivity, and hydraulic effective porosity are conducted with a uniform flow field and measurements are made from the fluid flowing within a test section where linear length of travel is constant. Since fluid flow and mechanical transport are coupled processes, the directional variations of specific discharge and hydraulic effective porosity are measured in regions with constant hydraulic gradients to evaluate porous medium equivalence for the two processes, respectively. If the fracture region behaves like an equivalent porous medium, the system has the following stable properties: (1) specific discharge is uniform in any direction and can be predicted from a permeability tensor; and (2) hydraulic effective porosity is directionally stable. Fracture systems with two parallel sets of continuous fractures satisfy criterion 1. However, in these systems hydraulic effective porosity is directionally dependent, and thus, criterion 2 is violated. Thus, for some fracture systems, fluid flow can be predicted using porous media assumptions, but it may not be possible to predict transport using porous media assumptions. Two discontinuous fracture systems were studied which satisfied both criteria. Hydraulic effective porosity for both systems has a value between rock effective porosity and total porosity. A length-density analysis (LDS) of Canadian fracture data shows that porous media equivalence for fluid flow and transport is likely when systems have narrow aperture distributions. 54 references, 90 figures, 7 tables

  11. Effect of Aging on Fracture Toughness and Stress Corrosion Cracking Resistance of Forged 7475 Aluminum Alloy

    Institute of Scientific and Technical Information of China (English)

    LI Hongying; GENG Jinfeng; DONG Xianjuan; WANG Changjian; ZHENG Feng

    2007-01-01

    The effects of two-stage aging and retrogression and reaging heat treatment on the fracture toughness and stress corrosion cracking resistance of 7475 alloy were studied. The fracture toughness, conductivity and strength of samples of nine groups under duplex aging conditions and three retrogression and reaging heat treatments were also measured. Incorporating the microstructure and property, we found that when the condition of the first order aging kept identical, the fracture toughness and stress corrosion cracking resistance increase with aging time and the second aging temperature. The optimal treatment conditions are (115℃×7h+185℃×13h) among all tested two-stage aging treatments.Although the 7475 alloy treated by RRA method shows the highest strength and its stress corrosion cracking resistance after twenty minutes retrogression can also reach the same level as those by the optimal treatment of (115℃×7h+185℃×13h),the fracture toughness is even low.

  12. Spall fracture and strength of uranium, plutonium and their alloys under shock wave loading

    Science.gov (United States)

    Golubev, Vladimir

    2015-06-01

    Numerous results on studying the spall fracture phenomenon of uranium, two its alloys with molybdenum and zirconium, plutonium and its alloy with gallium under shock wave loading are presented in the paper. The majority of tests were conducted with the samples in the form of disks 4mm in thickness. They were loaded by the impact of aluminum plates 4mm thick through a copper screen serving as the cover or bottom part of a special container. The initial temperature of samples was changed in the range of -196 - 800 C degree for uranium and 40 - 315 C degree for plutonium. The character of spall failure of materials and the degree of damage for all tested samples were observed on the longitudinal metallographic sections of recovered samples. For a concrete test temperature, the impact velocity was sequentially changed and therefore the loading conditions corresponding to the consecutive transition from microdamage nucleation up to complete macroscopic spall fracture were determined. Numerical calculations of the conditions of shock wave loading and spall fracture of samples were performed in the elastoplastic approach. Several two- and three-dimensional effects of loading were taken into account. Some results obtained under conditions of intensive impulse irradiation and intensive explosive loading are presented too. The rather complete analysis and comparison of obtained results with the data of other researchers on the spall fracture of examined materials were conducted.

  13. The influence of internal stresses on the fracture toughness of {alpha}/{beta} titanium alloys

    Energy Technology Data Exchange (ETDEWEB)

    Helbert, A.L.; Feaugas, X.; Clavel, M.

    1999-11-01

    The influence of internal stresses on fracture toughness was investigated in {alpha}/{beta} titanium alloys. It was shown that the direct linkage of K{sub IC} to various microstructural parameters was not so conclusive, since the different parameters act simultaneously on fracture toughness. On the contrary, the metallurgical parameters change the plastic strain incompatibilities inside the material. Thus X, which is a macroscopic measurement of these incompatibilities, is the relevant parameter to account for the different metallurgical influences on toughness. The influence on X of the {alpha}-phase percentage, aspect ratio, and the secondary {alpha}-phase percentage was determined, and it was established that low internal stresses could provide high fracture toughness. The present work also showed the ability of a modified Gurson-Tvergaard (GT) model to calculate the experimental K{sub IC} value.

  14. Computational aspects of nonlinear fracture mechanics

    International Nuclear Information System (INIS)

    The following contribution will essentially restrict to the application of the von Mises theory of incremental plasticity to cracked specimens and components. In particular, the classical parameters of EPFM, J and CTOD, as well as subsequently proposed parameters such as energy dissipation rate and crack-tip opening angle (CTOA) and the related computational aspects will be discussed. Some remarks follow on the 'local approach to fracture' which is based on continuum field quantities, namely stresses and strains, and the damage models of Gurson (1977) and Rousselier (1987), which have now found increasing application, will be briefly addressed in Section 3.03.4. The numerical modeling of decohesion and separation phenomena by 'cohesive elements' will be presented in Section 3.03.5. (orig.)

  15. Oxidation mechanisms for alloys in single-oxidant gases

    Energy Technology Data Exchange (ETDEWEB)

    Whittle, D.P.

    1981-03-01

    Scales formed on alloys invariably contain the alloy constituents in a ratio different from that in the alloy, owing to the differing thermodynamic tendencies of the alloy components to react with the oxidant and to differences in diffusion rates in scale and alloy phases. This complex interrelationship between transport rates and the thermodynamics of the alloy-oxidant system can be analyzed using multicomponent diffusion theory when transport-controlled growth of single or multi-layered scales occurs. In particular, the superimposition of the diffusion data on an isothermal section of the appropriate phase diagram indicates the likely morphologies of the reaction products, including the sequence of phases found in the scale, the occurrence of internal oxidation and the development of an irregular metal/scale interface. The scale morphologies on alloys are also time-dependent: there is an initial transient stage, a steady state period, and a final breakdown, the latter often related to mechanical influences such as scale adherence, spallation, thermal or mechanical stresses and void formation. Mechanical influences have a more devastating effect in alloy oxidation due to the changes in alloy surface composition during the steady state period.

  16. Fracture mechanics based life assessment in petrochemical plants

    International Nuclear Information System (INIS)

    The increasing use of thick walled pressure vessels in petrochemical plants operating at high pressure under severe service conditions could lead to catastrophic failure. In the Malaysian Institute for Nuclear Technology Research (MINT), initial efforts are underway to apply fracture mechanics approach for assessment of significance of defects detected during periodic in service inspection (ISI) of industrial plants. This paper outlines the integrity management strategy based on fracture mechanics and proposes a new procedure for life assessment of petrochemical plants based on ASME Boiler and Pressure Vessel Code, Section XI, BSI PD 6493:1991, BSI 6539:1994, BSI Standard 7910:1999 and API 579:2000. Essential relevant data required for the assessment is listed. Several methods available for determination of fracture toughness are reviewed with limitations in their application to petrochemical plants. A new non destructive method for determination of fracture toughness based on hardness testing and normalized key roughness curve is given. Results of fracture mechanics based life assessment conducted for 100 mm thick ammonia converter of Ni r o steel and 70 mm thick plat forming reactor vessel of ASTM A 38 7 grade B steel in operational fertilizer and petroleum refining plants are presented. (Author)

  17. Fracture mechanics: proceedings of the 12th national symposium on fracture mechanics

    International Nuclear Information System (INIS)

    The conference proceedings contains 30 papers of which five are abstracted separately. The subjects covered include fatigue crack growth in aircraft materials, fractographic measurements, fatigue cracks in nylon 66 blends, cyclic inelastic deformation aspects, prestressing, tensile cracks in creeping solids, creep-crack-growth in 304 stainless steel, high-temperature fatigue, parallel impact loading, numerical fracture dynamic code, J-resistance curves, specimen geometry effects, reactor piping systems, temperature dependence of fracture toughness, small-scale yielding, compact specimens, power hardening materials, semi-empirical fracture analyses, pipeline girth welds, wrought steels, and A36 bridge steels

  18. Fracture mechanics evaluation for at typical PWR primary coolant pipe

    Energy Technology Data Exchange (ETDEWEB)

    Tanaka, T. [Kansai Electric Power Company, Osaka (Japan); Shimizu, S.; Ogata, Y. [Mitsubishi Heavy Industries, Ltd., Kobe (Japan)

    1997-04-01

    For the primary coolant piping of PWRs in Japan, cast duplex stainless steel which is excellent in terms of strength, corrosion resistance, and weldability has conventionally been used. The cast duplex stainless steel contains the ferrite phase in the austenite matrix and thermal aging after long term service is known to change its material characteristics. It is considered appropriate to apply the methodology of elastic plastic fracture mechanics for an evaluation of the integrity of the primary coolant piping after thermal aging. Therefore we evaluated the integrity of the primary coolant piping for an initial PWR plant in Japan by means of elastic plastic fracture mechanics. The evaluation results show that the crack will not grow into an unstable fracture and the integrity of the piping will be secured, even when such through wall crack length is assumed to equal the fatigue crack growth length for a service period of up to 60 years.

  19. Nonlinear Fracture Mechanics and Plasticity of the Split Cylinder Test

    DEFF Research Database (Denmark)

    Olesen, John Forbes; Østergaard, Lennart; Stang, Henrik

    2006-01-01

    The split cylinder testis subjected to an analysis combining nonlinear fracture mechanics and plasticity. The fictitious crack model is applied for the analysis of splitting tensile fracture, and the Mohr-Coulomb yield criterion is adopted for modelling the compressive crushing/sliding failure. Two...... models are presented, a simple semi-analytical model based on analytical solutions for the crack propagation in a rectangular prismatic body, and a finite element model including plasticity in bulk material as well as crack propagation in interface elements. A numerical study applying these models...... demonstrates the influence of varying geometry or constitutive properties. For a split cylinder test in load control it is shown how the ultimate load is either plasticity dominated or fracture mechanics dominated. The transition between the two modes is related to changes in geometry or constitutive...

  20. Finite elements in fracture mechanics theory, numerics, applications

    CERN Document Server

    Kuna, Meinhard

    2013-01-01

    Fracture mechanics has established itself as an important discipline of growing interest to those working to assess the safety, reliability and service life of engineering structures and materials. In order to calculate the loading situation at cracks and defects, nowadays numerical techniques like finite element method (FEM) have become indispensable tools for a broad range of applications. The present monograph provides an introduction to the essential concepts of fracture mechanics, its main goal being to procure the special techniques for FEM analysis of crack problems, which have to date only been mastered by experts. All kinds of static, dynamic and fatigue fracture problems are treated in two- and three-dimensional elastic and plastic structural components. The usage of the various solution techniques is demonstrated by means of sample problems selected from practical engineering case studies. The primary target group includes graduate students, researchers in academia and engineers in practice.

  1. Comparative study of fracture mechanical test methods for concrete

    DEFF Research Database (Denmark)

    Østergaard, Lennart; Olesen, John Forbes

    2004-01-01

    and the interpretation, i.e. the analysis needed to extract the stress-crack opening relationship, the fracture energy etc. Experiments are carried out with each test configuration using mature, high performance concrete. The results show that the UTT is a highly complicated test, which only under very well controlled......This paper describes and compares three different fracture mechanical test methods; the uniaxial tension test (UTT), the three point bending test (TPBT) and the wedge splitting test (WST). Potentials and problems with the test methods will be described with regard to the experiment...... circumstances will yield the true fracture mechanical properties. It is also shown that both the three point bending test and the WST are well-suited substitutes for the uniaxial tension test....

  2. Fracture mechanics behaviour of ductile cast iron and martensitic steel at elevated temperature

    Energy Technology Data Exchange (ETDEWEB)

    Udoh, A.; Klenk, A.; Roos, E. [Stuttgart Univ. (Germany). MPA; Sasikala, G. [Indira Gandhi Centre for Atomic Research (IGCAR), Kalpakkam (India)

    2010-07-01

    Ductile cast iron is employed increasingly due to the advantages regarding foundry practice, design as well as economic advantages in the thermal machinery and power plant construction. It is employed preferably where higher toughness is required, e.g. in valves or thickwalled components of thermal or nuclear power plants. For this reason the safety and availability criteria for fracture mechanics assessment of components are necessary in addition to the conventional strength design. Alloys with silicon and molybdenum are developed for the application at higher temperatures. The increase in the thermal efficiency of fossil fired steam power plant that can be achieved by increasing the steam temperature and pressure has provided the incentive for development of the 9% chromium steels towards improved creep rupture strength. During the last twenty years, three such steels, P91 (9Cr-1Mo-VNb), E911 (9Cr-1Mo-1W-V-Nb) and P92 (9Cr-0,5Mo-1,8W-V-Nb), have been developed for commercial production. For application in piping systems and boiler construction sufficient reliable information concerning the long-term behaviour are necessary as well as knowledge about fracture mechanical behaviour in order to ensure integrity of components. Different methods to characterize fracture behaviour of ductile cast iron and martensitic steel at elevated temperature have been employed. The RBR method is a novel and simple method developed at IGCAR for characterizing the ductile fracture behaviour of materials from tensile tests of cylindrical specimens. Using the data evaluated at both institutes, a fracture mechanics characterisation by determining crack initiation and crack resistance by J{sub R}-curves and RBR parameters is presented. (orig.)

  3. 含腐蚀预损伤铝合金2024-T62的疲劳断裂行为及基于断裂力学的寿命预测%Fatigue and Crack Growth Behavior of Pre-corroded Aluminum Alloy 2024-T62 and Its Life Prediction Based on Fracture Mechanics

    Institute of Scientific and Technical Information of China (English)

    刘建中; 陈勃; 叶序彬; 胡本润; 丁传富

    2011-01-01

    This article reports an experimental study on the effect of pre-corrosive pit damage on the fatigue S-N curve, initiation behavior of small crack, the growth behavior of small and large cracks, and the threshold growth behavior of small physical cracks of an aluminum alloy sheet 2024-T62. The results show that an obvious effect of the pre-corrosive pit damage is found on the fatigue S-N curve and the initiation behavior of small cracks. However, the effect of the pre-corrosive pit damage is not apparent on the growth behavior of both small and large cracks and the threshold growth behavior of small physical cracks. By assuming a pre-corrosive pit as an initiating surface small crack, and based on fracture mechanics, the fatigue S-N curves of the corroded aluminum alloy with different prior corrosions are predicted by using the commercial software FASTRAN3.9. The predictions are found to agree reasonably well with test results. In particular, it is found that the complex small crack effect can be neglected while predicting the aluminum alloy corroded with a big pre-corrosive pit damage.%针对2024-T62铝合金薄板系统地开展了腐蚀预损伤对材料疲劳S-N曲线、小裂纹萌生行为、长短疲劳裂纹扩展及物理小裂纹门槛值扩展行为的影响等试验研究.结果表明:腐蚀预损伤对材料疲劳S-N曲线及材料疲劳小裂纹萌生行为有明显的影响,但时材料长短裂纹扩展及物理小裂纹门槛值扩展行为没有明显的影响.通过假定腐蚀预损伤为初始小裂纹,基于断裂力学理论,利用FASTRAN3.9软件预测了含腐蚀预损伤材料的疲劳S-N曲线.研究发现,预测与试验结果吻合较好.当材料含有较大尺寸的腐蚀预损伤时,对其进行寿命预测可以不考虑小裂纹效应的复杂影响.

  4. Liquid phase separating mechanism and preparation techniques of immiscible alloys

    Institute of Scientific and Technical Information of China (English)

    刘源; 李言祥; 郭景杰; 贾均; 苏彦庆; 丁宏升

    2002-01-01

    Immiscible alloys have attracted growing interest for their valuable physical and mechanical properties. However, their production is difficult because of metallurgical problems in which there is a serious tendency for gravity separation in the region of the miscibility gap. So far the study on the liquid separation mechanism is still one of the important projects in the spatial materials science and the spatial fluid science. The studied results about the liquid phase separating mechanism of immiscible alloys are presented, at the same time the preparation techniques of homogeneous immiscible alloys are summarized, and the existing problems and the related researching areas in the future are also pointed out.

  5. Rheology and Fracture Mechanics of Foods

    NARCIS (Netherlands)

    Vliet, van T.

    2013-01-01

    The mechanical properties of food play an important role during manufacturing, storage, handling, and last but not least, during consumption. For an adequate understanding of the mechanical properties of liquid, liquid-like, soft solid, and solid foods, a basic understanding of relevant aspects of r

  6. A Fracture Probability Competition Mechanism of Stress Corrosion Cracking

    Institute of Scientific and Technical Information of China (English)

    Yanliang HUANG

    2001-01-01

    The stress corrosion cracking (SCC) of austenitic stainless steel was studied via polarization,slow strain rate and scanning electron microscope (SEM) techniques. Many SCC mechanisms have been proposed in which hydrogen embrittlement and passive film rupture-repassivation theories are generally accepted, but they can hardly explain the SCC mechanism of austenitic stainless steel in acidic chloride solution adequately, because the steel is in active dissolution state and cathodic polarization can prevent it from occurring. Our experiment shows that the anodic current increases the creep rate and decreases the plastic strength of the material on single smooth specimen as well as at the SCC crack tip. The fractured surface was characterized as brittle cleavage, while the surface crack of smooth specimen was almost vertical to the tensile strength, which can confirm that the cracks were caused by tensile stresses. A fracture probability competition mechanism of SCC was proposed on the basis of the experimental results combined with the viewpoint of ductile-brittle fracture competition. When the anodic dissolution current is increased to a certain degree, the probability of fracture by tensile stress will exceed that by shear stress, and the brittle fracture will occur. The proposed SCC mechanism can not only explain the propagation of SCC cracks but can explain the crack initiation as well. The strain on the surface distributes unevenly when a smooth specimen is deformed, so does the anodic current distribution. The crack will initiate at a point where the anodic current density is large enough to cause the material at a specific point to fracture in brittle manner.

  7. Microstructural characterisation and mechanical properties of Mg-xSn-Al-Zn Alloys

    Directory of Open Access Journals (Sweden)

    B.H. Kim

    2008-04-01

    Full Text Available Purpose: In this study, the microstructure and mechanical properties of as-cast Mg-xSn-Al-Zn alloys wereinvestigated.Design/methodology/approach: Ingot was fabricated by a squeeze cast. The alloys were induction meltedat 750ºC in a mild steel crucible under CO2+2%SF6 mixed gas atmosphere and cast into a permanent mouldcoated with boron nitride spray held at approximately 350ºC . Tensile tests were carried out at room temperaturein a screw-driven tensile testing machine and crosshead speed was 0.2 mm/min. Microstructural observation wascarried out using a optical microscope (OM and a scanning electron microscope (SEM equipped with energydispersive X-ray spectrometer (EDS.Findings: It is found that the tensile strength and elongation decreased at room temperature increased with Snconcentration. As a consequence, 5wt% Sn addition was the one exhibiting the best tensile properties at roomtemperature. The micro-hardness of the alloy continuously increased with increasing the Sn concentration.Practical implications: The investigations of microstructure of commercially magnesium alloys are importantfor achieving desired mechanical behaviour of the material.Originality/value: The fracture behaviors of magnesium alloys are investigated.

  8. Deformation and fracture behavior of composite structured Ti-Nb-Al-Co(-Ni) alloys

    Energy Technology Data Exchange (ETDEWEB)

    Okulov, I. V., E-mail: i.okulov@ifw-dresden.de; Marr, T.; Schultz, L.; Eckert, J. [IFW Dresden, Helmholtzstr. 20, D-01069 Dresden (Germany); Institut für Werkstoffwissenschaft, Technische Universität Dresden, D-01062 Dresden (Germany); Kühn, U. [IFW Dresden, Helmholtzstr. 20, D-01069 Dresden (Germany); Freudenberger, J. [IFW Dresden, Helmholtzstr. 20, D-01069 Dresden (Germany); Institut für Werkstoffwissenschaft, Technische Universität Bergakademie Freiberg, Gustav-Zeuner-Str. 5, D-09599 Freiberg (Germany); Oertel, C.-G.; Skrotzki, W. [Institut für Strukturphysik, Technische Universität Dresden, D-01062 Dresden (Germany)

    2014-02-17

    Tensile ductility of the Ti-based composites, which consist of a β-Ti phase surrounded by ultrafine structured intermetallics, is tunable through the control of intermetallics. The two Ti-based alloys studied exhibit similar compressive yield strength (about 1000 MPa) and strain (about 35%–40%) but show a distinct difference in their tensile plasticity. The alloy Ti{sub 71.8}Nb{sub 14.1}Ni{sub 7.4}Al{sub 6.7} fractures at the yield stress while the alloy Ti{sub 71.8}Nb{sub 14.1}Co{sub 7.4}Al{sub 6.7} exhibits about 4.5% of tensile plastic deformation. To clarify the effect of microstructure on the deformation behavior of these alloys, tensile tests were carried out in the scanning electron microscope. It is shown that the distribution as well as the type of intermetallics affects the tensile ductility of the alloys.

  9. Fracture mechanics environmental degradation assessment of nuclear pressure vessel and piping materials

    International Nuclear Information System (INIS)

    A new set of fracture mechanics stress corrosion crack growth data is presented for transgranular cracking of low alloy steels used in various nuclear components as well as intergranular cracking of stabilized austenitic stainless steels used primarily for nuclear piping. The essential observations are as follows: In low alloy steels, fast stress corrosion crack growth rates between 10-9 and 10-8 m/s may be observed down to 400 ppb dissolved oxygen at water conductivities of 0.5 μS/cm in refreshed autoclaves. However, there is an indication, substantiated by only few data, that at lower conductivities and/or lower oxygen concentrations the crack growth rates in ferritic steels come down to about 3 x 10-11 m/s. This crack velocity has also been found to be typical for stabilized austenitic stainless steels exposed to faulted simulated BWR water. Crack growth at this rate is observed in mill annealed (fine grained) as well as in sensitized or coarse grained or cold worked stabilized austenitic stainless steels. On average, the crack growth rates measured in the laboratory by using fracture mechanics methods correlate well with stress corrosion service experience of the steels discussed here

  10. Local fracture behavior in an alloy 52M dissimilar metal welded joint in nuclear power plant

    International Nuclear Information System (INIS)

    Background: Dissimilar metal welded joints (DMWJs) were indicated to be vulnerable components in the primary systems, an accurate structural integrity assessment for such DMWJ is needed. Purpose: Understand the fracture performance of the welded joint containing defects, determine if appropriate to assess the defects in the weld joint with the present codes. Methods: The fracture tests of the initial crack located in the different positions of Alloy 52M DMWJ specimens were carried out by using single-edge notched bend (SENB) method. Results: Different crack resistance and crack propagation path were obtained for the SENB specimens, and the cracks always deviate to the materials with lower strength. Conclusions: The crack path deviation is mainly controlled by strength mismatch, rather than toughness mismatch. The J-resistance curves with larger crack path deviation only reflect the apparent fracture resistance along the crack growth region, rather than the intrinsic fracture resistance of the initial crack-tip region material., Without considering the local fracture resistance properties of heat affected zone (HAZ), interface region and internal affected region (IAZ), following present assessment codes will unavoidably produce non-conservative or excessive conservative assessment results. In most cases, the assessment results will be potentially non-conservative. (authors)

  11. Coupled phenomenological and fracture mechanics approach to assess the fracture behaviour of TWC piping component

    Energy Technology Data Exchange (ETDEWEB)

    Saxena, Sanjeev, E-mail: san_bpl@yahoo.co [Advanced Materials and Processes Research Institute (AMPRI), CSIR Concern, Hoshangabad Road, Bhopal 462026 (India); Ramakrishnan, N. [Advanced Materials and Processes Research Institute (AMPRI), CSIR Concern, Hoshangabad Road, Bhopal 462026 (India); Chouhan, J.S. [Civil Engineering Department, Samrat Ashok Technological Institute, Vidisha (India)

    2010-04-15

    The present study demonstrates the numerical prediction of experimental specimen J-R curve using Gurson-Tvergaard-Needleman phenomenologically based material model. The predicted specimen J-R curve is used to determine the geometric independent initiation fracture toughness (J{sub SZWc}) value that compares well with experimental result. Using the experimentally determined and numerically predicted J{sub SZWc} values and specimen J-R curves, the accuracy of predicting the fracture behaviour of the cracked component is judged. Thus the present study proposed a coupled phenomenological and fracture mechanics approach to predict the crack initiation and instability stages in cracked piping components using numerically predicted specimen J-R curve obtained from tensile specimens testing data.

  12. Fracture mechanics applied to the machining of brittle materials

    Energy Technology Data Exchange (ETDEWEB)

    Hiatt, G.D.; Strenkowski, J.S.

    1988-12-01

    Research has begun on incorporating fracture mechanics into a model of the orthogonal cutting of brittle materials. Residual stresses are calculated for the machined material by a combination of Eulerian and Lagrangian finite element models and then used in the calculation of stress intensity factors by the Green`s Function Method.

  13. Hydrogen Embrittlement - Loading Rate Effects in Fracture Mechanics Testing

    NARCIS (Netherlands)

    Koers, R.W.J.; Krom, A.H.M.; Bakker, A.

    2001-01-01

    The fitness for purpose methodology is more and more used in the oil and gas industry to evaluate the significance of pre-existing flaws and material deficiencies with regard to the suitability of continued operation of equipment. In this methodology, traditional fracture mechanics is integrated wit

  14. Draft fracture mechanics code case for American Society of Mechanical Engineers NUPACK rules

    Energy Technology Data Exchange (ETDEWEB)

    McConnell, P.; Sorenson, K. [Sandia National Labs., Albuquerque (United States); Nickell, R. [Applied Science and Technology, Poway (United States); Saegusa, T. [Central Research Inst. for Electric Power Industry, Abiko (Japan)

    2004-07-01

    The containment boundaries of most spent-fuel casks certified for use in the United States by the Nuclear Regulatory Commission are constructed with stainless steel, a material that is ductile in an engineering sense at all temperatures and for which, therefore, fracture mechanics principles are not relevant for the containment application. Ferritic materials may fail in a nonductile manner at sufficiently low temperatures, so fracture mechanics principles may be applied to preclude nonductile fracture. Because of the need to transport and store spent nuclear fuel safely in all types of climatic conditions, these vessels have regulatory lowest service temperatures that range down to -40 C (-40 F) for transport application. Such low service temperatures represent a severe challenge in terms of fracture toughness to many ferritic materials. Linear-elastic and elastic-plastic fracture mechanics principles provide a methodology for evaluating ferritic materials under such conditions.

  15. Effect of DH treatment on microstructure and mechanical properties of an LM28-0.3wt.%Nd hypereutectic aluminum silicon alloy

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    In this article, a novel heat treatment method, deformation heat (DH) treatment (extrusion + aging), was employed on a hypereutectic aluminum silicon alloy (LM28-0.3wt.%Nd), and its effect on microstructure and mechanical properties of this alloy was investigated. It can be concluded that the eutectic microstructure disappears after the DH treatment, in the meantime the morphology of α(Al) solid solution was transformed from fir-tree and cellular to equiaxed, Si was refined with grain sizes of about 1-10 μm and distributed dispersedly, even some of them became globular shape, which can reduce stress accumulation effectively. Mechanical properties test indicated that the DH treatment could significantly improve the room-temperature strength and have little effect on the high-temperature strength of LM28-0.3wt.%Nd alloy. The fracture mechanism is ductile fracture by fracture morphology analysis.

  16. Summary of fracture mechanics problems analysis method in ABAQUS

    Directory of Open Access Journals (Sweden)

    Duan Hongjun

    2015-07-01

    Full Text Available Fracture mechanics is the study of the strength of the materials or structures with crack and crack propagation regularity of a discipline. There are a lot of analysis function of ABAQUS, including fracture analysis. ABAQUS is very easy to use and easy to establish a model of the complicated problem. In order to effectively study of strong discontinuity problems such as crack, provides two methods of simulating the problem of cracks of ABAQUS. This paper describes the two methods respectively, and compare two methods.

  17. Deformation and fracture of low alloy steels at high temperature

    Energy Technology Data Exchange (ETDEWEB)

    Marriott, D.L.; Stubbins, J.F.; Leckie, F.A.; Muddle, B.

    1988-12-01

    This project formed part of the initiative in the AR TD program to characterize high temperature, time-dependent damage processes in low alloy steels, for use in the construction of coal-gasification plant. This project was broadly aimed at adding to the knowledge base for this bainitic form of 2.25Cr 1Mo steel, as it related to time-dependent performance at elevated temperature. Its original intention was to obtain information in specific grades of 2.25Cr 1Mo steel, in particular those containing reduced residual elements and microalloyed modifications, which were being considered as candidate materials at the time. This objective was subsequently modified, in the course of the contract period, to a more generic study of bainitic steel, using the 2.25Cr 1Mo material as a representative of the class. The main thrust of the project was directed initially at the detrimental effect of cyclic loading on creep resistance and manifesting itself in an apparently severe creep-fatigue interaction. Three subtasks were eventually identified. These are: a study of the evolution of microstructural changes in bainitic materials during steady load creep and under constant amplitude cyclic deformation, investigation of the effect of cyclic softening on the fatigue and creep strength of complex geometries, focusing on circumferentially notched bars, and investigation of the influence of environment as a possible cause of observed fatigue/elevated temperature interaction through its effects on crack initiation and propagation, using EDM notched specimens tested in air and vacuum. Results are discussed. 24 refs., 40 figs., 5 tabs.

  18. The effects of Mg addition on the microstructure and mechanical properties of thixoformed Al–5%Si–Cu alloys

    Energy Technology Data Exchange (ETDEWEB)

    Salleh, M.S., E-mail: shukor@utem.edu.my [Department of Mechanical and Materials Engineering, Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia, 43600 Selangor (Malaysia); Department of Manufacturing Process, Faculty of Manufacturing Engineering, Universiti Teknikal Malaysia Melaka, Hang Tuah Jaya, 76100 Durian Tunggal, Melaka (Malaysia); Omar, M.Z., E-mail: zaidi@eng.ukm.my [Department of Mechanical and Materials Engineering, Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia, 43600 Selangor (Malaysia); Syarif, J., E-mail: syarif@eng.ukm.my [Department of Mechanical and Materials Engineering, Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia, 43600 Selangor (Malaysia)

    2015-02-05

    Highlights: • The average globule size of α-Al decreased when Mg amount is increased. • T6 heat treatment has increased the strength of the thixoformed alloys. • The elongation after T6 heat treatment is even significantly improved. • Thixoformed alloy with high Mg content shows a brittle type fracture. • Thixoformed alloy in T6 condition shows a ductile type fracture. - Abstract: In this study, the effects of different amounts of magnesium (Mg) on the microstructures and tensile properties of thixoformed Al–5%Si–Cu alloys were investigated. Three different alloys containing various amounts of Mg (0.5, 0.8 and 1.2 wt%) were prepared through the cooling slope casting technique, before they were thixoformed using a compression press. Several of the thixoformed samples were then treated with a T6 heat treatment, that is, solution treatment at 525 °C for 8 h, quenching in warm water at 60 °C, followed by aging at 155 °C for 4 h. All of the samples were then characterised by optical microscopy (OM), scanning electron microscopy (SEM) energy dispersive X-ray (EDX) spectroscopy and X-ray diffraction (XRD) analysis as well as by tensile tests. The results revealed that magnesium was able to refine the size of α-Al globules and the eutectic silicon in the samples. It was also observed that a compact π-Al{sub 9}FeMg{sub 3}Si{sub 5} phase was formed when the magnesium content was 0.8 wt% and 1.2 wt%. The mechanical properties of the thixoformed alloys improved significantly after the T6 heat treatment. The highest attainment was recorded by the latter alloy (i.e. with 1.2 wt%Mg) with its ultimate tensile strength (UTS) as high as 306 MPa, yield strength (YS), 264 MPa, and elongation to fracture of 1.8%. The fracture of thixoformed alloy with a low Mg content (0.5 wt%) showed a combination of dimple and cleavage fracture, whereas in the alloy that contained the highest Mg content (1.2 wt%), cleavage fracture was observed.

  19. Mechanical properties of tantalum-niobium alloys

    Energy Technology Data Exchange (ETDEWEB)

    Chamdawalla, N; Ettmayer, P.; Femboeck, J.; Aschenbrenner, W.; Bildstein, H.

    1986-02-01

    Young's modulus and shear modulus have been measured on fully dense polycrystalline sintered (swaged and forged and recrystallized) tantalum-niobium alloys. Young's modulus decreases steadily and monotonously from pure tantalum to pure niobium. Ultimate tensile strength values have been measured at 6 different temperatures between 20 and 1500/sup 0/ C. No significant solution hardening effect could be observed. Room temperature and hot hardness of the alloys were evaluated. (orig.).

  20. 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.

  1. Mechanical behavior of a lanthanum-doped magnesium alloy at different strain rates

    Energy Technology Data Exchange (ETDEWEB)

    Shen, J. [Department of Mechanical Engineering, University of North Carolina at Charlotte, Charlotte, NC 28223-0001 (United States); School of Aeronautics, Northwestern Polytechnical University, Xi’an 710072 (China); Yin, W. [Department of Mechanical Engineering, University of North Carolina at Charlotte, Charlotte, NC 28223-0001 (United States); Kondoh, K. [Joining and Welding Research Institute, Osaka University, 11-1 Mihogaoka, Ibaragi, Osaka 567-0047 (Japan); Jones, Tyrone L.; Kecskes, L.J. [WMRD, US Army Research Laboratory, Aberdeen Proving Ground, Deer Creek Loop, Aberdeen Proving Ground, MD 21005-5069 (United States); Yarmolenko, S.N. [NSF-ERC, Department of Mechanical Engineering, NC A& T State University, 1601 E. Market Street, Greensboro, NC 27411 (United States); Wei, Q., E-mail: qwei@uncc.edu [Department of Mechanical Engineering, University of North Carolina at Charlotte, Charlotte, NC 28223-0001 (United States)

    2015-02-25

    The mechanical behavior of a lanthanum doped Mg alloy, AZXE7111, (Mg–7Al–1Zn–1Ca–1La, all in wt%) extruded at different temperatures has been investigated under both quasi-static (strain rate ~1×10{sup −3} s{sup −1}) and dynamic (strain rate ~4×10{sup 3} s{sup −1}) compressive loading. Comparison has been made against the experimental results of two conventional Mg alloys, AZ91E and WE43. It was observed via transmission electron microscopy (TEM) that the nanoscale intermetallic compounds of Al{sub 2}Ca and Al{sub 11}La{sub 3}, have presumably formed during the hot extrusion process. These compounds are believed to contribute significantly to the strength by reducing the grain size and acting as dislocation barriers. Additionally, twinning has been considered as the main mechanism for the higher strain hardening rate at high strain rates than that at low strain rates. It has been found that the ultimate strength of the alloy is only ~10% higher at dynamic loading rate than at quasi-static loading rate. Localized micro-shear fracture was observed and adiabatic shear mode was suggested by further examination of dynamically loaded specimens. The shear localization is further discussed in detail and it is suggested that reduced strain hardening rate is responsible for shear localization and subsequent fracture at both low and high strain rates.

  2. Microstructure and mechanical properties of Ti6321 alloy welded joint by GTAW

    Energy Technology Data Exchange (ETDEWEB)

    Xiong, Jinhui, E-mail: xiongjinhui@126.com; Li, Shikai; Gao, Fuyang; Zhang, Jianxin

    2015-07-29

    Titanium and its alloys have excellent combination of properties, such as low density, high specific strength and corrosion resistance, and they are extensively used in many industrial fields. This work is aiming at investigation on the microstructure and mechanical properties of Ti–6Al–3Nb–2Zr–1Mo (Ti6321) alloy joints by Gas Tungsten Arc Welding (GTAW) with filler materials. The results indicated that the microstructure of the fusion zone (FZ) is composed of acicular α, massive α, and Widmanstatten α+β. The heat affected zone (HAZ) near FZ consists of coarse and acicular α structures of grain boundary α, Widmanstatten α+β. The heat affected zone (HAZ) near base metal consists of primary α phase and transformed β containing acicular α. Microhardness values for HAZ are higher than that of FZ and base metal, and there are the peak values for the HAZ near the weld metal. The tensile strength of joint is almost equal to that of base metal, and the fracture locations of all the tensile specimens are in base metal, and it is well in accordance with the relationship between the content of strengthening and interstitial elements and microstructure and mechanical properties of welded joints. The tensile fracture morphology of joint presents obviously the characteristic of ductile fracture, which is related to the bigger and deeper dimples distributed on the surface of joint. The HAZ impact toughness is lower than that of the BM and FZ.

  3. Probability fracture mechanics analysis of plates with surface cracks

    International Nuclear Information System (INIS)

    Background: The uncertainties of input parameters in an deterministic structural integrity assessment of pressure vessels may affect the assessment results. This can be improved by performing probability fracture mechanics (PFM) analysis. Purpose: This work investigates the effect of uncertainties of load, defect size, fracture toughness and failure criteria on the failure probability of semi-elliptical surface cracks in plates under combined tension and bending. Methods: The correction factor method provided by EPRI is used to estimate the stress intensity factor (SIF). The J-integral values at the deepest point of the surface crack tip are evaluated using the reference stress method and the globe limit load solution developed by Goodall and Webster and Lei. PFM analysis is performed with considering the uncertainty of crack size, yield strength and fracture toughness and Monte-Carlo (MC) simulation is used to calculate the failure probability. Results: Failure probability increases with increase of load level, Lr, for all load ratio values considered in this work for a given failure criterion. However, the failure probability based on the elastic-plastic fracture criterion is higher than that based on the linear elastic fracture criterion for a given load lever, Lr. Conclusions: The load level and the failure criteria have significant effect on the failure probability. However, the load ratio makes a little contribution to the failure probability for a given failure criterion. (authors)

  4. Mechanical alloying nanotechnology, materials science and powder metallurgy

    CERN Document Server

    El-Eskandarany, M Sherif

    2015-01-01

    This book is a detailed introduction to mechanical alloying, offering guidelines on the necessary equipment and facilities needed to carry out the process and giving a fundamental background to the reactions taking place. El-Eskandarany, a leading authority on mechanical alloying, discusses the mechanism of powder consolidations using different powder compaction processes. A new chapter will also be included on thermal, mechanically-induced and electrical discharge-assisted mechanical milling. Fully updated to cover recent developments in the field, this second edition also introduces new a

  5. TEM study of mechanically alloyed ODS steel powder

    Energy Technology Data Exchange (ETDEWEB)

    Hoffmann, Jan, E-mail: j.hoffmann@kit.edu [Karlsruhe Institute of Technology (KIT), Institute for Applied Materials (IAM-AWP), Karlsruhe (Germany); Klimenkov, Michael; Lindau, Rainer; Rieth, Michael [Karlsruhe Institute of Technology (KIT), Institute for Applied Materials (IAM-AWP), Karlsruhe (Germany)

    2012-09-15

    Compared to present reactors, modern nuclear power plant concepts are based on materials which can be operated at higher temperatures and up to higher neutron doses. Oxide dispersion strengthened (ODS) steels - produced by mechanical alloying - with chromium contents of 9 and 14 wt.% (or even more) are typical candidate materials. As the preparation of TEM samples from milled powders is usually very difficult, a new approach has been successfully adopted coming from the TEM sample preparation of biological tissues. Here, the alloyed powder is first embedded and then cut into thin films of 60-90 nm thickness using a microtom. The focal point is to gain a better knowledge of the solution mechanism of Y{sub 2}O{sub 3} in the steel powder during mechanical alloying. Investigations on mechanically alloyed powders containing 13% Cr and Y{sub 2}O{sub 3} were made using a Tecnai Scanning Transmission Electron Microscope (STEM) with EDX detector. Detailed elemental mappings of the powder particles show the presence of Y{sub 2}O{sub 3} particles after different milling times. The non-dissolved Y{sub 2}O{sub 3} phase was detected on the surface of the mechanically alloyed powder particles in the specimen alloyed at times down to 24 h. After mechanically alloying of 80 h, no Y{sub 2}O{sub 3} phase has been detected. Inside the mechanically alloyed powder, no particles were detected. All further results of the elemental mappings after different milling times are analyzed, compared, and discussed in this paper.

  6. Hydraulic Fracture Extending into Network in Shale: Reviewing Influence Factors and Their Mechanism

    Directory of Open Access Journals (Sweden)

    Lan Ren

    2014-01-01

    Full Text Available Hydraulic fracture in shale reservoir presents complex network propagation, which has essential difference with traditional plane biwing fracture at forming mechanism. Based on the research results of experiments, field fracturing practice, theory analysis, and numerical simulation, the influence factors and their mechanism of hydraulic fracture extending into network in shale have been systematically analyzed and discussed. Research results show that the fracture propagation in shale reservoir is influenced by the geological and the engineering factors, which includes rock mineral composition, rock mechanical properties, horizontal stress field, natural fractures, treating net pressure, fracturing fluid viscosity, and fracturing scale. This study has important theoretical value and practical significance to understand fracture network propagation mechanism in shale reservoir and contributes to improving the science and efficiency of shale reservoir fracturing design.

  7. Formative mechanism of intracanal fracture fragments in thoracolumbar burst fractures: a finite element study

    Institute of Scientific and Technical Information of China (English)

    ZENG Zhi-li; ZHU Rui; LI Shan-zhu; YU Yan; WANG Jian-jie; JIA Yong-wei; CHEN Bo

    2013-01-01

    Background Thoracolumbar burst fracture is a common clinical injury,and the fracture mechanism is still controversial.The aim of this research was to study the formation of intracanal fracture fragments in thoracolumbar burst fractures and to provide information for the prevention of thoracolumbar bursts fractures and reduction of damage to the nervous system.Methods A nonlinear three-dimensional finite element model of T11-L3 segments was established,and the injury processes of thoracolumbar bursts were simulated.The intact finite element model and the finite element model after the superior articular were impacted by 100 J of energy in different directions.The distribution and variation of stress in the superior posterior region of the L1 vertebral body were analyzed.Abaqus 6.9 explicit dynamic solver was used as finite element software in calculations.Results A three-dimensional nonlinear finite element model of the thoracolumbar spine was created.In the intact model,stress was concentrated in the superior posterior region of the L1 vertebral body.The stress peak was a maximum for the extension impact load and a minimum for the flexion impact load.The stress peak and contact force in the facet joint had close correlation with time.The stress peak disappeared after excision of the superior articular process.Conclusions The three-dimensional nonlinear finite element model was suitable for dynamic analysis.The contact force in the facet joint,which can be transferred to the superior posterior vertebral body,may explain the spinal canal fragment in thoracolumbar burst fractures.

  8. Mechanical behavior of tungsten–vanadium–lanthana alloys as function of temperature

    Energy Technology Data Exchange (ETDEWEB)

    Palacios, T., E-mail: teresa.palacios@mater.upm.es [Departamento de Ciencia de Materiales-CISDEM, Universidad Politécnica de Madrid, E.T.S.I. Caminos, Canales y Puertos, C/Professor Aranguren s/n, 28040 Madrid (Spain); Pastor, J.Y. [Departamento de Ciencia de Materiales-CISDEM, Universidad Politécnica de Madrid, E.T.S.I. Caminos, Canales y Puertos, C/Professor Aranguren s/n, 28040 Madrid (Spain); Aguirre, M.V. [Departamento de Tecnologías Especiales Aplicadas a la Aeronáutica, Universidad Politécnica de Madrid, E.I. Aeronáutica y del Espacio, 28040 Madrid (Spain); Martín, A. [Departamento de Ciencia de Materiales-CISDEM, Universidad Politécnica de Madrid, E.T.S.I. Caminos, Canales y Puertos, C/Professor Aranguren s/n, 28040 Madrid (Spain); Monge, M.A.; Muñóz, A.; Pareja, R. [Departamento de Física, Universidad Carlos III de Madrid, Leganés (Spain)

    2013-11-15

    The mechanical behavior of three tungsten (W) alloys with vanadium (V) and lanthana (La{sub 2}O{sub 3}) additions (W–4%V, W–1%La{sub 2}O{sub 3}, W–4%V–1%La{sub 2}O{sub 3}) processed by hot isostatic pressing (HIP) have been compared with pure-W to analyze the influence of the dopants. Mechanical characterization was performed by three point bending (TPB) tests in an oxidizing air atmosphere and temperature range between 77 (immersion tests in liquid nitrogen) and 1273 K, through which the fracture toughness, flexural strength, and yield strength as function of temperature were obtained. Results show that the V and La{sub 2}O{sub 3} additions improve the mechanical properties and oxidation behavior, respectively. Furthermore, a synergistic effect of both dopants results in an extraordinary increase of the flexure strength, fracture toughness and resistance to oxidation compared to pure-W, especially at higher temperatures. In addition, a new experimental method was developed to obtain a very small notch tip radius (around 5–7 μm) and much more similar to a crack through the use of a new machined notch. The fracture toughness results were lower than those obtained with traditional machining of the notch, which can be explained with electron microscopy, observations of deformation in the rear part of the notch tip. Finally, scanning electron microscopy (SEM) examination of the microstructure and fracture surfaces was used to determine and analyze the relationship between the macroscopic mechanical properties and the micromechanisms of failure involved, depending on the temperature and the dispersion of the alloy.

  9. Effects of nitrogen addition on microstructure and mechanical behavior of biomedical Co-Cr-Mo alloys.

    Science.gov (United States)

    Yamanaka, Kenta; Mori, Manami; Chiba, Akihiko

    2014-01-01

    In the present study, the microstructures and tensile deformation behaviors of biomedical Co-29Cr-6Mo (wt%) alloys containing different concentrations of nitrogen (0-0.24wt%) were systematically investigated. As the nitrogen concentration increased, the volume fraction of athermal ε martensite decreased, because nanoprecipitates hindered the formation of stacking faults (SFs) by acting as obstacles to Shockley partial dislocation formation, and athermal ε martensite usually forms through the regular overlapping of SFs. The formation of the athermal ε martensite was completely suppressed when the nitrogen concentration exceeded 0.10wt%, resulting in a simultaneous improvement in the strength and ductility of the alloys. It was found that the glide of the Shockley partial dislocations and the strain-induced γ (fcc)→ε (hcp) martensitic transformation (SIMT) operated as the primary deformation mechanisms. However, adding nitrogen reduced the work hardening by suppressing the formation of the SFs and preventing the SIMT from taking place. This resulted in an intrinsic decrease in the tensile ductility of the alloys. It is also shown that all the alloys exhibited premature fractures owing to the SIMT. The formation of annealing twins in the γ grains is found to be enhanced by nitrogen addition and to promote the SIMT, resulting in a reduction in the elongation-to-failure due to nitrogen addition. These results should aid in the design of alloys that contain nitrogen.

  10. Mechanisms of defect complex formation and environmental-assisted fracture behavior of iron aluminides

    Energy Technology Data Exchange (ETDEWEB)

    Cooper, B.R.; Muratov, L.S.; Kang, B.S.J.; Li, K.Z. [West Virginia Univ., Morgantown, WV (United States)

    1997-12-01

    Iron aluminide has excellent corrosion resistance in high-temperature oxidizing-sulfidizing environments; however, there are problems at room and medium temperature with hydrogen embrittlement as related to exposure to moisture. In this research, a coordinated computational modeling/experimental study of mechanisms related to environmental-assisted fracture behavior of selected iron aluminides is being undertaken. The modeling and the experimental work will connect at the level of coordinated understanding of the mechanisms for hydrogen penetration and for loss of strength and susceptibility to fracture. The focus of the modeling component at this point is on the challenging question of accurately predicting the iron vacancy formation energy in Fe{sub 3}A{ell} and the subsequent tendency, if present, for vacancy clustering. The authors have successfully performed, on an ab initio basis, the first calculation of the vacancy formation energy in Fe{sub 3}A{ell}. These calculations include lattice relaxation effects which are quite large. This has significant implications for vacancy clustering effects with consequences to be explored for hydrogen diffusion. The experimental work at this stage has focused on the relationship of the choice and concentration of additives to the improvement of resistance to hydrogen embrittlement and hence to the fracture behavior. For this reason, comparative crack growth tests of FA-186, FA-187, and FA-189 iron aluminides (all with basic composition of Fe-28A{ell}-5Cr, at % with micro-alloying additives of Zr, C or B) under, air, oxygen, or water environment have been performed. These tests showed that the alloys are susceptible to room temperature hydrogen embrittlement in both B2 and DO{sub 3} conditions. Test results indicated that FA-187, and FA-189 are intrinsically more brittle than FA-186.

  11. Microstructure and Fractural Morphology of Cobalt-based Alloy Laser Cladding

    Institute of Scientific and Technical Information of China (English)

    CHEN Hao; PAN Chun-xu

    2003-01-01

    The solidification features,micro-segregation,and fracture characteristics of cobalt-based alloy on the substrate of 20CrMo steel by laser cladding were studied by using electron microscopy.Experimental results show that the fine columnar grains and cellular dendrite grains are obtained which are perpendicular to the coating/substrate interface;the primary arms are straight while the side branches are degenerated;the microstructure consists of primary face-centered cubic (fcc) Co dendrites and a network of Cr-enriched eutectic M23C6 (M=Cr,W,Fe) carbides;the micro-segregation is severe for the rapid heating and cooling of laser cladding;the typical brittle intergranular fracture occurs in cobalt-based laser cladding layer.

  12. Hydraulic Fracture Extending into Network in Shale: Reviewing Influence Factors and Their Mechanism

    OpenAIRE

    Lan Ren; Jinzhou Zhao; Yongquan Hu

    2014-01-01

    Hydraulic fracture in shale reservoir presents complex network propagation, which has essential difference with traditional plane biwing fracture at forming mechanism. Based on the research results of experiments, field fracturing practice, theory analysis, and numerical simulation, the influence factors and their mechanism of hydraulic fracture extending into network in shale have been systematically analyzed and discussed. Research results show that the fracture propagation in shale reservo...

  13. Interface Shear Actions and Mechanical Properties of Nanostructured Dissimilar Al Alloy Laminated Metal Composites

    Directory of Open Access Journals (Sweden)

    Zejun Chen

    2015-01-01

    Full Text Available The laminated metal composites (LMCs of dissimilar metals (aluminium alloys: AA1100/AA7075 were fabricated using the accumulative roll bonding technique in conjunction with cold rolling. The LMCs of ultrafine grained AA1100 and nanostructured precipitates of AA7075 achieved metallurgical bonding. The microstructure of the bonding interfaces and constituent metals was investigated using scanning electron microscopy and transmission electron microscopy for the LMCs with different layers. The deformation incompatibility and shear actions were analyzed using the microanalysis of dissimilar bonding interfaces. The mechanism of grain refinement of LMCs was investigated and described based on the microstructure characterization. The mechanical properties, strengthening mechanism, and fracture mechanism of LMCs were also investigated. The research results showed that the strengthening mechanism of LMCs is the recombination action of grain refinement, dislocation, and laminated interfacial strengthening. The coordinated deformation of dissimilar metals and the layer thickness are important in improving the mechanical properties of LMCs consisting of dissimilar metals.

  14. 2219铝合金VPTIG焊接头的低温断裂韧性%Cryogenic Fracture Toughness of 2219 Aluminum Alloy VPTIG Welded Joint

    Institute of Scientific and Technical Information of China (English)

    林一桐; 王东坡; 王颖

    2015-01-01

    采用裂纹尖端张开位移(crack tip opening displacement,CTOD)试验研究了高强2219铝合金变极性钨极氩弧焊(variable polarity tungsten inert gas welding,VPTIG)接头各部位的低温断裂韧性,利用扫描电镜对各部位的CTOD 试验断口特征进行分析,并结合金相组织进一步阐明组织与断裂韧性的关联。研究结果表明,2219铝合金VPTIG 焊接头各部位表现出不同的低温断裂韧性,熔合线最低,热影响区高于焊缝,但均低于母材。扫描电镜断口观察结果表明,母材、焊缝及热影响区的断裂机制为剪切断裂,熔合线的断裂机制为准解理断裂。金相组织分析较好地解释了焊接接头不同部位断裂韧性的差异。%Cryogenic fracture toughness of high strength 2219 aluminum alloy variable polarity tungsten inert gas welding(VPTIG) welded joint was studied in terms of tests of crack tip opening displacement(CTOD). The fracture characters of CTOD tests of different parts were analyzed using scanning electron microscopy(SEM),and the rela-tionship between microstructure and fracture toughness was further clarified according to microstructure. Results showed that the distribution of cryogenic fracture toughness of 2219 aluminum alloy VPTIG welded joint was of no uniformity. The cryogenic fracture toughness of fusion line was the lowest,while in the weld it was lower than that in the heat affected zone. In all the three cases,the cryogenic fracture toughness was lower than that of parent metal. The result of fracture observation of SEM showed that the fracture mechanism of parent metal,weld and heat af-fected zone was shear fracture,while that of fusion line was quasi-cleavage fracture. Microstructure analysis well explained the difference in fracture toughness among various parts of the joint.

  15. Defect generation and analysis in mechanically alloyed stoichiometric Fe–Ni alloys

    Energy Technology Data Exchange (ETDEWEB)

    Geng, Yunlong, E-mail: gengyunlong@gmail.com [Mechanical & Materials Engineering, University of Nebraska-Lincoln, Lincoln, NE 68588 (United States); Nebraska Center for Materials and Nanoscience, University of Nebraska-Lincoln, Lincoln, NE 68588 (United States); Ablekim, Tursunjan [Center for Materials Research, Washington State University, Pullman, WA 99164 (United States); Koten, Mark A. [Mechanical & Materials Engineering, University of Nebraska-Lincoln, Lincoln, NE 68588 (United States); Nebraska Center for Materials and Nanoscience, University of Nebraska-Lincoln, Lincoln, NE 68588 (United States); Weber, Marc; Lynn, Kelvin [Center for Materials Research, Washington State University, Pullman, WA 99164 (United States); Shield, Jeffrey E. [Mechanical & Materials Engineering, University of Nebraska-Lincoln, Lincoln, NE 68588 (United States); Nebraska Center for Materials and Nanoscience, University of Nebraska-Lincoln, Lincoln, NE 68588 (United States)

    2015-06-05

    Highlights: • An initial increase in strain followed by decrease with further alloying was studied. • A decrease of the net concentration with mechanical alloying was revealed by DBPAS. • Decrease of relative permeability μ{sub r} with internal strain was observed. - Abstract: FeNi, with the chemically-ordered L1{sub 0} tetragonal structure, is a promising material for next-generation rare-earth-free permanent magnets. Due to the extremely low atomic Fe and Ni mobility below the critical chemical order/disorder temperature of 320 °C, no conventional metallurgical methods are able to induce its formation. Diffusion rates could be enhanced with the creation of excessive vacancies. High-energy mechanical alloying was employed to produce a nanocrystalline Fe–50 at.%Ni alloy. The high energy mechanical milling is expected to change the defect characteristics that would be used to study the effect that mechanical alloying has on the defect concentrations. X-ray diffraction revealed that over the entirety of the milling period, the Fe and Ni powders formed an fcc solid solution. The Williamson–Hall equation and Scherrer equation revealed that reductions in grain sizes were caused during alloying. The initial increase in internal strain, and by extension dislocations, was followed by a decrease in strain with further alloying, which was due to the combination effect of creation of dislocation from mechanical deformation and annihilation of dislocations at increasing grain boundaries. Doppler broadening positron annihilation spectroscopy (DB-PAS) showed that the overall number of open-volume defects decreased with increased milling time. Finally, changes of relative permeability, for the mechanically alloyed FeNi phase, were explained by the pinning effect of dislocations.

  16. Similarities and Differences in Mechanical Alloying Processes of V-Si-B and Mo-Si-B Powders

    Directory of Open Access Journals (Sweden)

    Manja Krüger

    2016-10-01

    Full Text Available V-Si-B and Mo-Si-B alloys are currently the focus of materials research due to their excellent high temperature capabilities. To optimize the mechanical alloying (MA process for these materials, we compare microstructures, morphology and particles size as well as hardness evolution during the milling process for the model alloys V-9Si-13B and Mo-9Si-8B. A variation of the rotational speed of the planetary ball mill and the type of grinding materials is therefore investigated. These modifications result in different impact energies during ball-powder-wall collisions, which are quantitatively described in this comparative study. Processing with tungsten carbide vials and balls provides slightly improved impact energies compared to vials and balls made of steel. However, contamination of the mechanically alloyed powders with flaked particles of tungsten carbide is unavoidable. In the case of using steel grinding materials, Fe contaminations are also detectable, which are solved in the V and Mo solid solution phases, respectively. Typical mechanisms that occur during the MA process such as fracturing and comminution are analyzed using the comminution rate KP. In both alloys, the welding processes are more pronounced compared to the fracturing processes.

  17. Structure changes and mechanical properties of laser alloyed magnesium cast alloys

    Directory of Open Access Journals (Sweden)

    W. Kwaśny

    2009-02-01

    Full Text Available Purpose: The aim of this work was to investigate structure and mechanical properties of the MCMgAl12Zn1 casting magnesium alloys after laser treatment. The laser treatment was carried out using a high power diode laser (HPDL.Design/methodology/approach: The laser processing of TiC, WC, SiC particles in MCMgAl12Zn1 and the resulted microstructures and properties are discussed in this paper. The resulting microstructure in the modified surface layer was examined. Phase composition was determined by the X-ray diffraction method using XPert device. The measurements of hardness after laser melt injection was also studied.Findings: Structure of the solidyifying material after laser alloying is characteristic with occurrences of areas with the diversified morphology, dependent on solidification rate of the magnesium alloys, is characteristic of structure of the solidified material after laser alloying. The MCMgAl12Zn1 casting magnesium alloys after laser alloying demonstrate similar hardness tests results, in reference to hardness of the alloys before their laser treatment.Research limitations/implications: In this research three powders (titanium carbide, tungsten carbide and silicon carbide were used to reinforcing the surface of the MCMgAl12Zn1 casting magnesium alloys.Practical implications: High power diode laser can be used as an economical substitute for CO2 and Nd:YAG lasers to modify the surface magnesium alloy by feeding the carbide particles.Originality/value: The originality of this work is applying of High Power Diode Laser for laser treatment of cast magnesium alloy consisting in fusion penetration of the hard particles of titanium, tungsten, and silicon carbides into the remelted surface layer of the alloy.

  18. Cyclic Fracture Toughness of Railway Axle and Mechanisms of its Fatigue Fracture

    Directory of Open Access Journals (Sweden)

    Sorochak Andriy

    2015-06-01

    Full Text Available The main regularities in fatigue fracture of the railway axle material - the OSL steel - are found in this paper. Micromechanisms of fatigue crack propagation are described and systematized, and a physical-mechanical interpretation of the relief morphology at different stages of crack propagation is proposed for fatigue cracks in specimens cut out of the surface, internal and central layers of the axle.

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

    OpenAIRE

    B.K.Raghunath; Rao, T H; Jayakumar, J.

    2013-01-01

    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 micro...

  20. The effects of artificial aging on the microstructure and fracture toughness of Al-Cu-Li alloy 2195

    Energy Technology Data Exchange (ETDEWEB)

    Chen, P.S.; Kuruvilla, A.K. [IIT Research Inst., Huntsville, AL (United States). Metallurgy Research Facilities; Malone, T.W.; Stanton, W.P. [National Aeronautics and Space Administration, Huntsville, AL (United States). Marshall Space Flight Center

    1998-10-01

    Aluminum-lithium alloys have shown promise for aerospace applications, and National Aeronautics and Space Administration (NASA) has selected the aluminum-lithium Alloy 2195 for the main structural alloy of the super light weight tank (SLWT) for the space shuttle. This alloy has significantly higher strength than conventional 2xxx alloys (such as 2219) at both ambient and cryogenic temperatures. If properly processed and heat treated, this alloy can display higher fracture toughness at cryogenic temperature than at ambient temperature. However, the properties of production materials have shown greater variation than those of other established alloys, as is the case with any new alloy that is being transitioned to a demanding application. A multistep heating-rate controlled (MSRC) aging treatment has been developed that can improve the cryogenic fracture toughness of aluminum-lithium Alloy 2195. At the same levels of yield strength (YS), this treatment results in considerably higher fracture toughness than that found in Alloy 2195, which has received conventional (isothermal) aging. Transmission electron microscopy revealed that the new treatment greatly reduces the size and density of subgrain-boundary T{sub 1} precipitates. In addition, it promotes T{sub 1} and {theta}{double_prime} nucleation, resulting in a fine and dense distribution of precipitate particles in the matrix. The MSRC aging treatment consists of (a) aging at 127 C (260 F) for 5 h, (b) heating continuously from 127 C (260 F) to 135 C (275 F) at a rate of 0.556 C/h (1 F/h), (c) holding at 135 C (275 F) for 5 h, (d) heating continuously from 135 to 143 C (275 to 290 F) at a rate of 0.556 C/h (1 F/h), and (e) holding at 143 C (290 F) for 25 h to obtain a near peak-aged condition.

  1. Mechanism of Nickel-Aluminium Alloy Electroplating

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    The effect of operating conditions on the aluminium content of Ni-Al alloy deposit and the catalytic function of NaF on electrodeposition in the nonaqueous solution containing aluminium are investigated.The results indicate that the plated aluminuim content will be increased with the rise of current density in a given range.When the current density is 2.5A/dm2,nickle-aluminium alloy containing 13.1 wt% aluminium will be deposited.The plated aluminium content will be increased by 2wt% as 0.1mol/L NaF is added to the bath.

  2. Microstructure and mechanical properties of NZ30K alloy by semi-continuous direct chill and sand mould casting processes

    Directory of Open Access Journals (Sweden)

    Zheng Xingwei

    2011-02-01

    Full Text Available The Mg-3.0Nd-0.2Zn-0.4Zr (NZ30K alloys were prepared by direct-chill casting (DCC and sand mould casting (SMC processes, respectively and their microstructures and mechanical properties were investigated. The results indicate that casting method plays a remarkable influence on the microstructure and mechanical properties of as-cast NZ30K alloy. The grain size increases from 35-40 μm in the billets made by the DCC to about 100-120 μm in the billets by the SMC. The aggregation of Mg12Nd usually found at the triple joints of grain boundaries in the billets prepared by SMC while is not observable from the billets by DCC. The tensile strengths and elongations of the billets are 195.2 MPa and 15.5% by DCC, and 162.5 MPa and 3.2% by SMC, respectively. The tensile strength of the alloy by DCC is remarkably enhanced by T6 heat treatment, which reached 308.5 MPa. Fracture surfaces of NZ30K alloy have been characterized as intergranular fracture by SMC and quasi-cleavage fracture by DCC, respectively.

  3. Effect of hydrogen charging on the mechanical properties of medium strength aluminium alloys 2091 and 2014

    DEFF Research Database (Denmark)

    Bandopadhyay, A.; Ambat, Rajan; Dwarakadasa, E.S.

    1992-01-01

    Cathodic hydrogen charging in 3.5% NaCl solution altered the mechanical properties of 2091-T351 (Al-Cu-Li-Mg-Zr) determined by a slow (10(-3)/s) strain rate tensile testing technique. UTS and YS decreased in the caw of 2091-T351 and 2014-T6(Al-Cu-Mn-Si-Mg) with increase in charging current density....... Elongation showed a decrease with increase in charging current density for both the alloys. However, elongation occurring throughout the gauge length in uncharged specimens changed over to localized deformation, thus increasing the reduction in area in charged specimens. A transition in fracture mode from...

  4. Effect of long-period stacking ordered phase on microstructure, mechanical property and corrosion resistance of Mg alloys:A review

    Institute of Scientific and Technical Information of China (English)

    Daokui Xu; En-hou Han; Yongbo Xu

    2016-01-01

    Magnesium alloys containing long period stacking ordered (LPSO) phase have been received a great deal of attention in the last decade owing to their excellent comprehensive properties of mechanical strength and corrosion resistance. In this paper, some fundamental aspects of LPSO containing Mg alloys have been reviewed, including:(1) microstructural characterization, formation conditions and the associated phase transformation of LPSO phases in Mg alloys;(2) deformation mechanism of LPSO phases and their influence on the deformation mechanism of the Mg matrix; (3) effect of LPSO structure on the me-chanical performance such as tensile strength, creep resistance, fracture toughness and fatigue strength;(4) corrosion behavior of LPSO containing Mg alloys and their possible applications as the biomaterials. Moreover, some remaining unsolved issues of the LPSO containing Mg alloys and the future target about how to further improve their service properties have been also described.

  5. Structure of nanocomposites of Al–Fe alloys prepared by mechanical alloying and rapid solidification processing

    Indian Academy of Sciences (India)

    S S Nayak; B S Murty; S K Pabi

    2008-06-01

    Structures of Al-based nanocomposites of Al–Fe alloys prepared by mechanical alloying (MA) and subsequent annealing are compared with those obtained by rapid solidification processing (RSP). MA produced only supersaturated solid solution of Fe in Al up to 10 at.% Fe, while for higher Fe content up to 20 at.% the nonequilibrium intermetallic Al5Fe2 appeared. Subsequent annealing at 673 K resulted in more Al5Fe2 formation with very little coarsening. The equilibrium intermetallics, Al3Fe (Al13Fe4), was not observed even at this temperature. In contrast, ribbons of similar composition produced by RSP formed fine cellular or dendritic structure with nanosized dispersoids of possibly a nano-quasicrystalline phase and amorphous phase along with -Al depending on the Fe content in the alloys. This difference in the product structure can be attributed to the difference in alloying mechanisms in MA and RSP.

  6. Microstructure and mechanical properties of a new type of austempered boron alloyed high silicon cast steel

    Directory of Open Access Journals (Sweden)

    Chen Xiang

    2013-05-01

    Full Text Available In the present paper, a new type of austempered boron alloyed high silicon cast steel has been developed, and its microstructures and mechanical properties at different temperatures were investigated. The experimental results indicate that the boron alloyed high silicon cast steel comprises a dendritic matrix and interdendritic eutectic borides in as-cast condition. The dendritic matrix is made up of pearlite, ferrite, and the interdendritic eutectic boride is with a chemical formula of M2B (M represents Fe, Cr, Mn or Mo which is much like that of carbide in high chromium white cast iron. Pure ausferrite structure that consists of bainitic ferrite and retained austenite can be obtained in the matrix by austempering treatment to the cast steel. No carbides precipitate in the ausferrite structure and the morphology of borides remains almost unchanged after austempering treatments. Secondary boride particles precipitate during the course of austenitizing. The hardness and tensile strength of the austempered cast steel decrease with the increase of the austempering temperature, from 250 篊 to 400 篊. The impact toughness is 4-11 J昪m-2 at room temperature and the impact fracture fractogragh indicates that the fracture is caused by the brittle fracture of the borides.

  7. Effect of deep cryogenic treatment on mechanical behavior of a Cu-Cr-Zr alloy for electrodes of spot welding

    Institute of Scientific and Technical Information of China (English)

    WANG Xiaofeng; SHAN Ping; HU Shengsun; WU Zhisheng; WANG Xibao

    2005-01-01

    The effects of deep cryogenic treatment on mechanical behavior of a Cu-Cr-Zr alloy for electrodes of spot welding were investigated employing Brinell-hardness testing unit, abrasion examination machine, electronic almighty testing machine and X-ray stress analyzer. Tensile fracture surfaces of the alloy were characterized by scanning electronic microscope (SEM) with energy dispersive X-ray spectroscopy (EDS). The results showed that, after deep cryogenic treatment, σb and σ0.2 increased 23 MPa and 21 MPa respectively, the wear rate of the alloy exhibited the trend of decrease with the decreasing temperature and increasing time of deep cryogenic treatment, and the surface residual stress of the alloy was partially eliminated by deep cryogenic treatment.

  8. Fatigue and fracture mechanics analysis of threaded connections

    OpenAIRE

    Brennan, F. P.

    1992-01-01

    This thesis aims to develop a comprehensive usable engineering design approach to the fatigue analysis of threaded connections. Although primarily concerned with the fatigue-fracture mechanics behaviour of screw threads, a broad review of stress analysis investigations in such connections is reported. Connection types, their functions and standardisation authorities are presented with the purpose of familiarising the reader with the subject and the options available to th...

  9. Virtual examinations of alloying elements influence on alloy structural steels mechanical properties

    OpenAIRE

    L.A. Dobrzański; R. Honysz

    2011-01-01

    Purpose: The paper introduces analysis results of selected alloying elements influence on mechanical properties of alloy structural steels for quenching and tempering.Design/methodology/approach: Investigations were performed in virtual environment with use of materials science virtual laboratory. Virtual investigations results were verified in real investigative laboratory.Findings: Materials researches performed with use of material science virtual laboratory in range of determining the mec...

  10. Effect of mechanical alloying atmosphere on the microstructure and Charpy impact properties of an ODS ferritic steel

    International Nuclear Information System (INIS)

    Two types of oxide dispersion strengthened (ODS) ferritic steels, with the composition of Fe-14Cr-2W-0.3Ti-0.3Y2O3 (in weight percent), have been produced by mechanically alloying elemental powders of Fe, Cr, W, and Ti with Y2O3 particles either in argon atmosphere or in hydrogen atmosphere, degassing at various temperatures, and compacting the mechanically alloyed powders by hot isostatic pressing. It was found in particular that mechanical alloying in hydrogen yields a significant reduction in oxygen content in the materials, a lower dislocation density, and a strong improvement in the fast fracture properties of the ODS ferritic steels, as measured by Charpy impact tests.

  11. Water coning mechanism in Tarim fractured sandstone gas reservoirs

    Institute of Scientific and Technical Information of China (English)

    沈伟军; 刘晓华; 李熙喆; 陆家亮

    2015-01-01

    The problem of water coning into the Tarim fractured sandstone gas reservoirs becomes one of the major concerns in terms of productivity, increased operating costs and environmental effects. Water coning is a phenomenon caused by the imbalance between gravity and viscous forces around the completion interval. There are several controllable and uncontrollable parameters influencing this problem. In order to simulate the key parameters affecting the water coning phenomenon, a model was developed to represent a single well with an underlying aquifer using the fractured sandstone gas reservoir data of the A-Well in Dina gas fields. The parametric study was performed by varying six properties individually over a representative range. The results show that matrix permeability, well penetration (especially fracture permeability), vertical-to-horizontal permeability ratio, aquifer size and gas production rate have considerable effect on water coning in the fractured gas reservoirs. Thus, investigation of the effective parameters is necessary to understand the mechanism of water coning phenomenon. Simulation of the problem helps to optimize the conditions in which the breakthrough of water coning is delayed.

  12. Microstructural and magnetic behavior of an equiatomic NiCoAlFe alloy prepared by mechanical alloying

    Energy Technology Data Exchange (ETDEWEB)

    Gómez-Esparza, C.D.; Baldenebro-López, F.J.; Santillán-Rodríguez, C.R.; Estrada-Guel, I.; Matutes-Aquino, J.A.; Herrera-Ramírez, J.M., E-mail: martin.herrera@cimav.edu.mx; Martínez-Sánchez, R.

    2014-12-05

    Highlights: • Equiatomic NiCoAlFe powder alloys were synthesized by mechanical alloying. • The nanocrystalline alloys were characterized after milled and annealed conditions. • In alloyed and annealed powders, only BCC and FCC structure phases were observed. • Magnetic properties are strongly affected by the phases formed after annealing. - Abstract: Equiatomic NiCoAlFe powder alloys were synthesized by mechanical alloying. The microstructural evolution of the mechanically alloyed powders at different times was followed with X-ray diffraction and scanning electron microscopy. The as-mechanically alloyed powders were subjected to a rapid annealing treatment at 1273 K and 1473 K during 3 min in vacuum. X-ray diffraction studies show the structure of both, the as-mechanically alloyed and annealed powders, consisted in a mixture of nanocrystalline simple phases (FCC + BCC). Crystallite size, after annealing, still remained in nanoscale. Coercivity increased due to the decrease in crystallite size and because of the defects caused by mechanical alloying in the as-mechanically alloyed samples; then coercivity decreased due to the phenomenon of random magnetic anisotropy and tended to stabilize with longer alloying times. A similar behavior was observed in annealed samples at 1273 K. However, random magnetic anisotropy was not observed after annealing at 1473 K because crystals with larger sizes were produced, and a steady increase in coercivity was observed.

  13. On the mechanical properties of TiNb based alloys

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Y. [SIMAP-CNRS, Institut Polytechnique de Grenoble, BP 75, St. Martin d’Hères 38402 (France); Georgarakis, K. [WPI Advanced Institute for Materials Research, Tohoku University, Sendai (Japan); SIMAP-CNRS, Institut Polytechnique de Grenoble, BP 75, St. Martin d’Hères 38402 (France); Yokoyama, Y. [WPI Advanced Institute for Materials Research, Tohoku University, Sendai (Japan); Yavari, A.R., E-mail: euronano@minatec.inpg.fr [SIMAP-CNRS, Institut Polytechnique de Grenoble, BP 75, St. Martin d’Hères 38402 (France)

    2013-09-15

    Highlights: •Systematic study of compressive behaviors of TiNb based alloys in different states. •Comparison between X-ray diffraction results in reflection and transmission mode. •High melting temperature TiNb based alloys were fabricated by copper mold casting. •Textures of studied alloys are analyzed through synchrotron radiation data. -- Abstract: A series of TiNb(Sn) alloys were synthesized by copper mold suction casting and subjected to different heat treatments (furnace cooling or water quenching). The microstructure, thermal and mechanical properties of the as-cast and heat treated samples were investigated. For the Ti–8.34 at.% Nb alloy, the as-cast and water quenched samples possess martensitic α′′ phase at room temperature and compression tests of these samples show occurrence of shape memory effect. For β phase Ti–25.57 at.% Nb alloys, stress-induced martensitic transformation was found during compression in the as-cast and water quenched samples. For the ternary Ti–25.05 at.%Nb–2.04 at.%Sn alloy, conventional linear elastic behavior was observed. It is shown that the addition of Sn increases the stability of the β phase. The Young’s moduli of these alloys were also measured by ultrasonic measurements. Water-quenched Ti–25.57 at.%Nb alloy was found to exhibit the lowest Young’s modulus value. Sn addition has small impact on the Young’s moduli of the TiNb alloys.

  14. State-of-the-art report on piping fracture mechanics

    International Nuclear Information System (INIS)

    This report is an in-depth summary of the state-of-the-art in nuclear piping fracture mechanics. It represents the culmination of 20 years of work done primarily in the US, but also attempts to include important aspects from other international efforts. Although the focus of this work was for the nuclear industry, the technology is also applicable in many cases to fossil plants, petrochemical/refinery plants, and the oil and gas industry. In compiling this detailed summary report, all of the equations and details of the analysis procedure or experimental results are not necessarily included. Rather, the report describes the important aspects and limitations, tells the reader where he can go for further information, and more importantly, describes the accuracy of the models. Nevertheless, the report still contains over 150 equations and over 400 references. The main sections of this report describe: (1) the evolution of piping fracture mechanics history relative to the developments of the nuclear industry, (2) technical developments in stress analyses, material property aspects, and fracture mechanics analyses, (3) unresolved issues and technically evolving areas, and (4) a summary of conclusions of major developments to date

  15. State-of-the-art report on piping fracture mechanics

    Energy Technology Data Exchange (ETDEWEB)

    Wilkowski, G.M.; Olson, R.J.; Scott, P.M. [Battelle, Columbus, OH (United States)

    1998-01-01

    This report is an in-depth summary of the state-of-the-art in nuclear piping fracture mechanics. It represents the culmination of 20 years of work done primarily in the US, but also attempts to include important aspects from other international efforts. Although the focus of this work was for the nuclear industry, the technology is also applicable in many cases to fossil plants, petrochemical/refinery plants, and the oil and gas industry. In compiling this detailed summary report, all of the equations and details of the analysis procedure or experimental results are not necessarily included. Rather, the report describes the important aspects and limitations, tells the reader where he can go for further information, and more importantly, describes the accuracy of the models. Nevertheless, the report still contains over 150 equations and over 400 references. The main sections of this report describe: (1) the evolution of piping fracture mechanics history relative to the developments of the nuclear industry, (2) technical developments in stress analyses, material property aspects, and fracture mechanics analyses, (3) unresolved issues and technically evolving areas, and (4) a summary of conclusions of major developments to date.

  16. Mechanical Properties and Microstructure of Neutron Irradiated Cold-worked Al-1050 and Al-6063 Alloys

    International Nuclear Information System (INIS)

    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 4.5x1025 and 8x1025 thermal neutrons/m2 (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 1x1025 thermal neutrons/m2 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

  17. Effect of constituent-particles distribution on mechanical behavior of an AlMgSi alloy

    International Nuclear Information System (INIS)

    In the present work, the effect of constituent particles distribution on mechanical behavior of a high strength AlMgSi alloy is investigated. The study consists of the tensile and fatigue testing of the material in longitudinal and transverse directions. Monotonic tensile properties, in both the directions showed virtually identical yield and tensile strengths. However, higher values of elongation and reduction in area were observed in the longitudinal direction. SN curves produced after fatigue testing displayed a shorter fatigue life in transverse direction as compared to the longitudinal direction. Microstructural analysis exposed that the material had clusters of constituent particles. Post fracture analysis of tensile and fatigue samples, in SEM, revealed that the topographical features change with the sample orientation. The present study revealed that the distribution of constituent particles in longitudinal and transverse directions has a pronounced effect on the tensile and fatigue behavior of the alloy and also induce anisotropy in the material

  18. Effect of constituent-particles distribution on mechanical behavior of an AIMgSi alloy

    International Nuclear Information System (INIS)

    In the present work, the effect of constituent particles distribution on mechanical behavior of a high strength AlMgSi alloy is investigated. The study consists of the tensile and fatigue testing of the material in longitudinal and transverse directions. Monotonic tensile properties, in both the directions showed virtually identical yield and tensile strengths. However, higher values of elongation and reduction in area were observed in the longitudinal direction. SN curves produced after fatigue testing displayed a shorter fatigue life in transverse direction as compared to the longitudinal direction. Microstructural analysis exposed that the material had clusters of constituent particles. Post fracture analysis of tensile and fatigue samples, in SEM, revealed that the topographical features change with the sample orientation. The present study revealed that the distribution of constituent particles in longitudinal and transverse directions has a pronounced effect on the tensile and fatigue behavior of the alloy and also induce anisotropy in the material. (author)

  19. Master curve characterization of the fracture toughness behavior in SA508 Gr.4N low alloy steels

    Science.gov (United States)

    Lee, Ki-Hyoung; Kim, Min-Chul; Lee, Bong-Sang; Wee, Dang-Moon

    2010-08-01

    The fracture toughness properties of the tempered martensitic SA508 Gr.4N Ni-Mo-Cr low alloy steel for reactor pressure vessels were investigated by using the master curve concept. These results were compared to those of the bainitic SA508 Gr.3 Mn-Mo-Ni low alloy steel, which is a commercial RPV material. The fracture toughness tests were conducted by 3-point bending with pre-cracked charpy (PCVN) specimens according to the ASTM E1921-09c standard method. The temperature dependency of the fracture toughness was steeper than those predicted by the standard master curve, while the bainitic SA508 Gr.3 steel fitted well with the standard prediction. In order to properly evaluate the fracture toughness of the Gr.4N steels, the exponential coefficient of the master curve equation was changed and the modified curve was applied to the fracture toughness test results of model alloys that have various chemical compositions. It was found that the modified curve provided a better description for the overall fracture toughness behavior and adequate T0 determination for the tempered martensitic SA508 Gr.4N steels.

  20. Influence of W-phase on mechanical properties and damping capacity of Mg–Zn–Y–Nd–Zr alloys

    Energy Technology Data Exchange (ETDEWEB)

    Feng, Hao, E-mail: haofeng804@gmail.com [College of Science, Hebei North University, Zhangjiakou 075000, Hebei (China); Yang, Yang [College of Science, Hebei North University, Zhangjiakou 075000, Hebei (China); Chang, Haixia [College of Law and Politics, Hebei North University, Zhangjiakou 075000 (China)

    2014-07-15

    This work mainly investigated the influence of W-phase on the mechanical properties and damping capacities of as-cast Mg–Zn–Y–Nd–Zr alloys with Zn/RE (rare element) ratio about 1.0. Obtained results indicate that the alloys with Zn and RE addition are composed of α-Mg matrix and W-phase. With the contents of Zn and RE increasing, the diffraction peaks of W-phase are gradually intensified and the morphology of W-phase transforms from fine-network microstructure to coarse-network microstructure. The tensile strength and fracture mechanism are strongly dependent on the quality of W-phase and the alloy with W-phase content of 8.0% has the highest strength as a result of strong atomic bonding between the W-phase and the Mg matrix. The damping capacities of Mg–Zn–Y–Nd–Zr alloys decrease gradually with the increasing amount of W-phase and then maintain at high level at high strain amplitude. The decline of damping capacity can be explained by the forming of W-phase, which makes more phases and interfaces form in the alloys. And the mobile dislocation densities in the alloys increase as residual stress at the interface of W-phase/Mg matrix and long dislocations generate in the α-Mg matrix. Therefore, the damping of alloy with high W-phase content improves accordingly with the increasing amount of moving dislocations.

  1. Investigations of mechanically alloyed nanocrystalline materials by microacoustic techniques

    Science.gov (United States)

    Dubief, P.; Hunsinger, J. J.; Gaffet, E.

    1996-09-01

    The purpose of this work is to determine whether yes or no, there is a difference between the physico-chemical properties of the nanocrystalline and the microcrystalline materials. This paper deals with the acoustical behavior of nanocrystalline materials which were prepared by ball- milling and mechanical alloying. Based on two specific techniques (acoustic microinterferometry and acoustic microechography), some of the mechanical properties (elastic ones) may be determined, related to a materials volume of about a few micrometers 3 (for the high frequency 600 MHz apparatus). Thus the mechanically alloyed powders (typically 200 micrometers in diameter), behave as massive materials in this range of frequency. The measurements are directly obtained on the grains and do not take into account the voids induced by further sinthering process. The result of such a micromechanical approach will be given for pure ball-milled elements (Fe) and for the supersaturated solid phase Fe(Si) obtained by mechanical alloying.

  2. Microstructure, mechanical behavior and low temperature superplasticity of ECAP processed ZM21 Mg alloy

    Energy Technology Data Exchange (ETDEWEB)

    Mostaed, Ehsan, E-mail: ehsan.mostaed@polimi.it [Department of Mechanical Engineering, Politecnico di Milano, Milan (Italy); Fabrizi, Alberto [Department of Management and Engineering, Università di Padova, Stradella S. Nicola 3, 36100 Vicenza (Italy); Dellasega, David [Department of Energy, Politecnico di Milano, Milan (Italy); Bonollo, Franco [Department of Management and Engineering, Università di Padova, Stradella S. Nicola 3, 36100 Vicenza (Italy); Vedani, Maurizio [Department of Mechanical Engineering, Politecnico di Milano, Milan (Italy)

    2015-07-25

    Highlights: • We studied the effects of texture and grain size on ZM21 alloy mechanical behavior. • Yielding asymmetry was alleviated by either texture weakening or grain refining. • At room temperature and 150 °C fracture elongation was strongly texture dependent. • Superplasticity at 200 °C was influenced by grain size, appearing only in UFG alloy. - Abstract: In this study, ultra-fine grained ZM21 Mg alloy was obtained through two-stage equal channel angular pressing process (ECAP) at temperatures of 200 and 150 °C. For each stage four passes were used. Plastic behavior, mechanical asymmetry and low temperature superplasticity of ultra-fine grained ZM21 alloy were investigated as a function of processing condition with particular attention to microstructural and texture evolution. Microstructural observations showed that after the first stage of ECAP an equiaxed ultra-fine grain (UFG) structure with average size of 700 nm was obtained. Additional stage did not cause any further grain refinement. However, Electron Backscattered Diffraction analysis showed that the original extrusion fiber texture evolved into a new one featuring a favorable alignment of the basal planes along ECAP shear planes. Such a preferential alignment provided a considerably higher Schmid factor value of 0.32, resulting in a remarkable loss in tensile yield stress, from 212 to 110 MPa and an improvement of the tensile fracture elongation, from 24% to 40%. Tensile and compression tests at room temperature revealed that yielding asymmetry could be alleviated by either weakening of basal plane fiber texture or by grain refinement. Tensile tests at 150 °C showed that texture supplies a significant contribution to plastic flow and elongation, making dislocation slip the dominant mechanism for deformation, while grain boundary sliding was not actively operated at this temperature. However, at 200 °C the effect of texture on fracture elongation of UFG alloys was subtle and the impact

  3. Thermal-mechanical coupled effect on fracture mechanism and plastic characteristics of sandstone

    Institute of Scientific and Technical Information of China (English)

    ZUO; JianPing; XIE; HePing; ZHOU; HongWei; PENG; SuPing

    2007-01-01

    Scanning electronic microscopy (SEM) was employed to investigate fractographs of sandstone in mine roof strata under thermal-mechanical coupled effect. Based on the evolution of sandstone surface morphology in the failure process and fractography, the fracture mechanism was studied and classified under meso and micro scales, respectively. The differences between fractographs under different temperatures were examined in detail. Under high temperature, fatigue fracture and plastic deformation occurred in the fracture surface. Therefore, the temperature was manifested by these phenomena to influence strongly on micro failure mechanism of sandstone. In addition, the failure mechanism would transit from brittle failure mechanism at low temperature to coupled brittle-ductile failure mechanism at high temperature. The variation of sandstone strength under different temperature can be attributed to the occurrence of plastic deformation, fatigue fracture, and microcracking. The fatigue striations in the fracture surfaces under high temperature may be interpreted as micro fold. And the coupled effect of temperature and tensile stress may be another formation mechanism of micro fold in geology.

  4. Comparison of fracture properties in SA508 Gr.3 and Gr.4N high strength low alloy steels for advanced pressure vessel materials

    International Nuclear Information System (INIS)

    Nuclear power systems are moving to a larger capacity or smaller modular type. In any either case, advanced pressure vessel materials with high strength and toughness are definitely needed for an optimization of the design and construction, as well as the long-term operation. In this paper, two candidate materials, both of which are within the current ASME specifications of SA508 steel forging, are compared from the view point of fracture resistance properties for a nuclear pressure vessel steel. The microstructure and mechanical properties of SA508 Gr.3 Cl.1, Cl.2, and Gr.4N steels were also characterized. The predominant microstructure of SA508 Gr.4N model alloy is tempered martensite, while SA508 Gr.3 Cl.1 and Cl.2 steels show a tempered upper bainitic structure. SA508 Gr. 4N model alloy showed the best strength and transition behavior among the three types of SA508 steel. SA508 Gr.3 Cl.2 steel has good strength and fracture toughness, but there is a decrease in the upper-self energy. The fracture resistance and fatigue crack growth rate of SA508 Gr.3 Cl.2 and Gr.4N steels were comparable to those of SA508 Gr.3 Cl.1 steel. In terms of mechanical properties, SA508 Gr.4N steel is a fascinating material for the pressure vessel application although it still needs verification on the aging behavior such as the irradiation embrittlement resistance

  5. The physical metallurgy of mechanically-alloyed, dispersion-strengthened Al-Li-Mg and Al-Li-Cu alloys

    Science.gov (United States)

    Gilman, P. S.

    1984-01-01

    Powder processing of Al-Li-Mg and Al-Li-Cu alloys by mechanical alloying (MA) is described, with a discussion of physical and mechanical properties of early experimental alloys of these compositions. The experimental samples were mechanically alloyed in a Szegvari attritor, extruded at 343 and 427 C, and some were solution-treated at 520 and 566 C and naturally, as well as artificially, aged at 170, 190, and 210 C for times of up to 1000 hours. All alloys exhibited maximum hardness after being aged at 170 C; lower hardness corresponds to the solution treatment at 566 C than to that at 520 C. A comparison with ingot metallurgy alloys of the same composition shows the MA material to be stronger and more ductile. It is also noted that properly aged MA alloys can develop a better combination of yield strength and notched toughness at lower alloying levels.

  6. [Bone fracture and the healing mechanisms. Fragility fracture and bone quality].

    Science.gov (United States)

    Mawatari, Taro; Iwamoto, Yukihide

    2009-05-01

    Fracture occurs in bone having less than normal elastic resistance without any violence. Numerous terms have been used to classify various types of fractures from low trauma events; "fragility fracture", "stress fracture", "insufficiency fracture", "fatigue fracture", "pathologic fracture", etc. The definitions of these terms and clinical characteristics of these fractures are discussed. Also state-of-the-art bone quality assessments; Finite element analysis of clinical CT scans, assessments of the Microdamage, and the Cross-links of Collagen are introduced in this review.

  7. The Shear Mechanisms of Natural Fractures during the Hydraulic Stimulation of Shale Gas Reservoirs

    Directory of Open Access Journals (Sweden)

    Zhaobin Zhang

    2016-08-01

    Full Text Available The shearing of natural fractures is important in the permeability enhancement of shale gas reservoirs during hydraulic fracturing treatment. In this work, the shearing mechanisms of natural fractures are analyzed using a newly proposed numerical model based on the displacement discontinuities method. The fluid-rock coupling system of the model is carefully designed to calculate the shearing of fractures. Both a single fracture and a complex fracture network are used to investigate the shear mechanisms. The investigation based on a single fracture shows that the non-ignorable shearing length of a natural fracture could be formed before the natural fracture is filled by pressurized fluid. Therefore, for the hydraulic fracturing treatment of the naturally fractured shale gas reservoirs, the shear strength of shale is generally more important than the tensile strength. The fluid-rock coupling propagation processes of a complex fracture network are simulated under different crustal stress conditions and the results agree well with those of the single fracture. The propagation processes of complex fracture network show that a smaller crustal stress difference is unfavorable to the shearing of natural fractures, but is favorable to the formation of complex fracture network.

  8. Mechanical properties of neutron irradiated vanadium alloys under liquid sodium environment

    International Nuclear Information System (INIS)

    Full text of publication follows: Vanadium alloys are candidate materials for fusion reactor blanket structural materials, but its knowledge about the mechanical properties at high temperatures during neutron irradiation is limited and there are uncertainties that may have influenced the results such as the interstitial impurity content of specimens. The objective of this study is to investigate the mechanical properties and microstructural changes of the high-purified V-4Cr-4Ti alloys, NIFS-HEAT2 during neutron irradiation. In this study, tensile test, Charpy impact test and microstructural observation were done for V-4Cr-4Ti alloys and vanadium binary alloys. Small sized tensile specimens, 1.5 Charpy V-notched specimens and TEM specimens of highly purified V-4Cr-4Ti alloys, NIFS-Heat and vanadium binary alloys were irradiated in Joyo in the temperature range from 450 deg. C to 650 deg. C with a damage level from 1 to 5 dpa. In the irradiation experiment, we have developed Na-enclosed irradiation rig in Joyo in order to equalize the irradiation temperature of large scale specimens and prevent the invasion of interstitial impurities from the circumstance in irradiation rig during irradiation for irradiation specimens. After dismantling the Na-enclosed capsule and cleaning the surface of specimens, tensile tests at room temperature, Charpy impact tests and TEM observation were performed. Irradiation hardening and reduction of ductility for NIFS-Heat alloys could be seen at 450 deg. C irradiation in tensile tests, but the destructive loss of plasticity could not be in any vanadium specimens even at 450 deg. C irradiation. Results of Charpy impact test showed that the amounts of upper shelf energy of NIFS-heat specimens irradiated at 450 deg. C and 600 deg. C were about 0.1-0.2 J at room temperature and brittle behavior could not be seen from load displacement relationship and SEM observation of fracture surface. From the TEM observation of NIFS-Heat alloys

  9. Microstructure and Mechanical Properties of Solution Heat-Treated Alloy 617 ODS Alloy

    International Nuclear Information System (INIS)

    Alloy 617 is a solution hardened Ni-based Superalloy containing Cr, Co, Mo, and Fe, and is among the best candidate materials for the key components of VHTR (Very High Temperature Reactor) system. As an alternative, Oxide Dispersion Strengthened (ODS) Ni-based superalloys, are known to possess superior high temperature mechanical properties and long-term high temperature microstructural stability due to the nano sized oxide dispersoids, which effectively hinder the dislocation motion at high temperature. This study is focused on the fabrication and characterization of nanosized oxide dispersion strengthened alloy 617. The influences of alloy composition and processing variables such as the content of Y2O3, hot extrusion ratio, and hydrogen reduction on the microstructure and mechanical properties were studied. From the analyses of microstructure of solution heat treated Alloy 617 ODS alloy specimens, a proper solid solution heat treatment temperature to reduce carbides is 1250 .deg. C. The major phases present in the alloy 617 ODS were found to be M23C6 and Al-O

  10. Development of Numerical Analysis Techniques Based on Damage Mechanics and Fracture Mechanics

    Energy Technology Data Exchange (ETDEWEB)

    Chang, Yoon Suk; Lee, Dock Jin; Choi, Shin Beom; Kim, Sun Hye; Cho, Doo Ho; Lee, Hyun Boo [Sungkyunkwan University, Seoul (Korea, Republic of)

    2010-04-15

    The scatter of measured fracture toughness data and transferability problems among different crack configurations as well as geometry and loading conditions are major obstacles for application of fracture mechanics. To address these issues, recently, concerns on the local approach employing reliable micro-mechanical damage models are being increased again in connection with a progress of computational technology. In the present research, as part of development of fracture mechanical evaluation model for material degradation of reactor pressure boundary, several investigations on fracture behaviors were carried out. Especially, a numerical scheme to determine key parameters consisting both cleavage and ductile fracture estimate models was changed efficiently by incorporating a genetic algorithm. Also, with regard to the well-known master curve, newly reported methods such as bimodal master curve, randomly inhomogeneous master curve and single point estimation were reviewed to deal with homogeneous and inhomogeneous material characteristics. A series of preliminary finite element analyses was conducted to examine the element size effect on micro-mechanical models. Then, a new thickness correction equation was derived from parametric three-dimensional numerical simulations, which was founded on the current test standard, ASTM E1921, but could lead to get more realistic fracture toughness values. As a result, promising modified master curves as well as fracture toughness diagrams to convert data between pre-cracked V-notched and compact tension specimens were generated. Moreover, a user-subroutine in relation to GTN(Gurson-Tvergaard-Needleman) model was made by adopting Hill's 48 yield potential theory. By applying GTN model combined with the subroutine to small punch specimens, the effect of inhomogeneous properties on fracture behaviors of miniature specimens was confirmed. Therefore, it is anticipated that the aforementioned enhanced research results can be

  11. Principles of fracture mechanics applications in nuclear power plants

    International Nuclear Information System (INIS)

    Fracture mechanics is widely used in nuclear plants safety assessment and remaining life evaluation. Methods of flow assessment in nuclear components are at an advanced stage of development and are suitable for general application in light water reactors and liquid metal cooled reactors. Following the first Saclay International Seminar on Structural Integrity (SISSI), hold in October 1991 and devoted to fracture in austenitic steels components, the second SISSI convened in April 1994 the European specialists to review the flaw assessment guides in application or in development in their countries, to discuss supporting research and development validation programs, application experience on the nuclear power plants and consequences on the components design. The seminar is sponsored by the CEA, Electricite de France, Framatome and the European Union D.G. XI. (J.S.)

  12. FRACTURAL PROCESS AND TOUGHENING MECHANISM OF LAMINATED CERAMIC COMPOSITES

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Based on the model of multi-layer beam and the assumption of micro-inhomogeneity of material, the 3D fractural characteristics of laminated ceramic composites have been studied with numerical simulation. Under three-point bending load, crack initiation, coalescence, propagation, tuning off in the weak interface and final rupture have been simulated. The spatial distribution and evolution process of acoustic emission are also presented in the paper. The simulation verifies the primary mechanism of the weak interface inducing the crack to expand along there and absorbing the fractural energy. The disciplinary significance of the effect of strength and properties of material on the toughness and strength of laminated ceramic composites is, therefore,discussed in this paper.

  13. OCA-P, PWR Vessel Probabilistic Fracture Mechanics

    International Nuclear Information System (INIS)

    1 - Description of program or function: OCA-P is a probabilistic fracture-mechanics code prepared specifically for evaluating the integrity of pressurized-water reactor vessels subjected to overcooling-accident loading conditions. Based on linear-elastic fracture mechanics, it has two- and limited three-dimensional flaw capability, and can treat cladding as a discrete region. Both deterministic and probabilistic analyses can be performed. For deterministic analysis, it is possible to conduct a search for critical values of the fluence and the nil-ductility reference temperature corresponding to incipient initiation of the initial flaw. The probabilistic portion of OCA-P is based on Monte Carlo techniques, and simulated parameters include fluence, flaw depth, fracture toughness, nil-ductility reference temperature, and concentrations of copper, nickel, and phosphorous. Plotting capabilities include the construction of critical-crack-depth diagrams (deterministic analysis) and a variety of histograms (probabilistic analysis). 2 - Method of solution: OAC-P accepts as input the reactor primary- system pressure and the reactor pressure-vessel downcomer coolant temperature, as functions of time in the specified transient. Then, the wall temperatures and stresses are calculated as a function of time and radial position in the wall, and the fracture-mechanics analysis is performed to obtain the stress intensity factors as a function of crack depth and time in the transient. In a deterministic analysis, values of the static crack initiation toughness and the crack arrest toughness are also calculated for all crack depths and times in the transient. A comparison of these values permits an evaluation of flaw behavior. For a probabilistic analysis, OCA-P generates a large number of reactor pressure vessels, each with a different combination of the various values of the parameters involved in the analysis of flaw behavior. For each of these vessels, a deterministic fracture

  14. Manufacturing of self-passivating W-Cr-Si alloys by mechanical alloying and HIP

    Energy Technology Data Exchange (ETDEWEB)

    Lopez-Ruiz, P. [CEIT and Tecnun (University of Navarra), E-20018 San Sebastian (Spain); Koch, F. [Max-Planck-Institut fuer Plasmaphysik, EURATOM Association, D-85748 Garching (Germany); Ordas, N. [CEIT and Tecnun (University of Navarra), E-20018 San Sebastian (Spain); Lindig, S. [Max-Planck-Institut fuer Plasmaphysik, EURATOM Association, D-85748 Garching (Germany); Garcia-Rosales, C., E-mail: cgrosales@ceit.es [CEIT and Tecnun (University of Navarra), E-20018 San Sebastian (Spain)

    2011-10-15

    Self-passivating tungsten-based alloys may provide a major safety advantage in comparison with pure tungsten, which is presently the main candidate material for the plasma-facing protection of future fusion power reactors. WCrSi alloys were manufactured by mechanical alloying (MA) and HIP at 1300 deg. C and 200 MPa for 1 h. Different MA conditions were investigated to obtain powders with lowest possible amount of contaminants and small and homogeneous particle and crystallite size. Milling in WC vials under Ar without process control agent provided best results. After HIP densities close to 100% were obtained. First oxidation tests on preliminary alloys showed self-passivating behavior with rates comparable to WCrSi thin films at 800 deg. C but worse performance at 1000 deg. C. In all cases a Cr{sub 2}WO{sub 6} protective layer is formed at the surface.

  15. Tensile properties and mechanical heterogeneity of friction stir welded joints of 2014 aluminum alloy

    Institute of Scientific and Technical Information of China (English)

    ZHAO Yan-hua; LIN San-bao; WU Lin; QU Fu-xing

    2005-01-01

    2014 Al alloy of 8mm in thickness was successfully welded by friction stir welding method. The experimental results show that the tensile properties of the joints are significantly affected by the welding parameters. When the weld pitch is 0.25mm/r corresponding to the rotation speed of 400r/min and the welding speed of 100mm/min, the maximum ultimate strength of the joints is 78% that of the base material. For a certain weld joint, different parts possess different mechanical properties. In the three parts of the joint, the upper part is strongest and the middle part is poorest in mechanical properties. The mechanical properties and fracture locations of the joints are dependent on the microstructure variation and micro-hardness distributions of the joints, which attributes to the different thermo-mechanical actions on the different parts of the joints.

  16. Role of Alloying Elements in the Mechanical Behaviors of An Mg-Zn-Zr-Er Alloy

    Science.gov (United States)

    Zhang, Jing; Liu, Min; Dou, Yuchen; Liu, Guobao

    2014-11-01

    The mechanical behavior of the as-extruded and heat-treated Mg-1.5Zn-0.6Zr and Mg-1.5Zn-0.6Zr-2Er alloys was investigated and correlated with microstructure evolution. Deformation mechanisms are detailed. No evidence of twinning was observed under compression in the Er-bearing alloy throughout the grain size range of ~5 to 27 μm at a strain rate of 0.001 or 1/s. The compressive yield strength followed a Hall-Petch relation with a slope of ~10.3 MPa/mm1/2. Er played a major role in the pyramidal slip that was identified as a dominant plastic deformation mechanism. The CRSS for slip system was greatly reduced and was 98 MPa in the as-extruded alloy. While it did not change the mechanical response of the Mg-1.5Zn-0.6Zr-2Er alloy, annealing was found to promote dissolution of Zn in the Mg matrix, leading to an increase in CRSS for extension twinning in the heat-treated Mg-1.5Zn-0.6Zr alloy. As a result, twinning was only observed under a higher strain rate of 1/s in compression. The CRSS for extension twinning for the heat-treated alloy with a grain size of ~28 μm was estimated to be 40 MPa, a bit lower than that for the Er-bearing alloy of the same grain size, which was 42 MPa.

  17. Analysis of fracture toughness in transition temperature region of a Mn-Mo-Ni low-alloy steel

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Sang Ho; Hwang, Byoung Chul; Lee, Sung Hak [Pohang Univ. of Science and Technology, Pohang (Korea, Republic of)

    2002-08-01

    This study is concerned with the analysis of fracture toughness in the transition region of a Mn-Mo-Ni low-alloy steel according to ASTM E1921 standard test method. Elastic-plastic cleavage fracture toughness, K{sub Jc} was determined by 3-point bend tests, using precracked Charpy V-notch (PCVN) specimens, and then the measured K{sub Jc} values were interpreted by the 3-parameter Weibull distribution with a theoretical slope of 4. fractographic observation indicated that the critical distance from a precrack tip to a cleavage initiation site linearly increased with increasing the critical J(J{sub c}) value, and that the stretch zone width had a good correlation with K{sub Jc} value, irrespective of testing temperature. Relationship between J{sub c} and critical distance, local fracture stress, and plane strain fracture toughness were discussed on the basis of the cleavage fracture behavior in the transition temperature region.

  18. Fracturing Behavior of Direct Bonded Ti with Mg Alloys by Solid State Bonding

    OpenAIRE

    Pripanapong, Patchara; Takahashi, Makoto; Umeda, Junko; Kondoh, Katsuyoshi

    2014-01-01

    Ti and Mg alloys (AZ61, AZ80 and AZ91) were directly bonded together by state bonding method in vacuum. These two materials appeared to be bonded well together although there was no intermetallic compound between Ti and Mg. Al element existing in Mg alloys seems to be an important factor involved in the bonding mechanism. The high bonding efficiency as 86% obtained from Ti bonded with AZ91 at 400 ℃ for 1 hr by applying 40 MPa was guaranteed in the successful bonding.

  19. Influence of sub-rapid solidification on microstructure and mechanical properties of AZ61A magnesium alloy

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The microstructure of sub-rapid solidification processed AZ61A magnesium alloy was presented and discussed. The results show that the grain size of the foil is significantly refined, and the grain morphology is cellular or globular. The eutectic transformation L→α-Mg+β-Mg17Al12 and microsegregation in conventionally solidified AZ61A alloy are suppressed to a great extent.The β-Mg17Al12 phases located in the α-Mg grain boundaries are largely decreased due to high solidification cooling rate. As a consequence, the alloying elements Al, Zn, Mn show much higher solid solubility and the sub-rapid solidification microstructure dominantly consists of supersaturated α-Mg solid solution. The mechanical properties and fractographic analysis reveal that the fracture mechanism and corresponding morphology of the rapture surface of tensile bars are linked to the microstructure obtained and depend on the sub-solidification processes.

  20. Phase stability, deformation mechanisms, and mechanical properties of Nb-Al-Ti alloys

    International Nuclear Information System (INIS)

    The phase stability, deformation mechanisms and mechanical properties of two alloys based on Nb3Al containing additions of Ti have been studied. These two alloys, with nominal compositions (in at.%) of Nb-15Al-10Ti (alloy 1) and Nb-15Al-40Ti (alloy 2), have the B2 crystal structure in as cast form. The ALCHEMI technique has been employed to assess qualitatively the distribution of atom types over the two sublattices of the B2 compounds. It is found that Ti and Al occupy different sublattices in alloy 2. Heat-treatment of alloy 1 at 1,100 C results in the precipitation of an A15 phase in the B2 matrix. Annealing at 900 C for short time introduces an w-phase. Prolonged annealing of alloy 1 at 700 C reveals the presence of an orthorhombic phase. The same orthorhombic phase is also found to exist between 800 and 1,000 C in alloy 2. Specific orientation relationships exist between the matrix phase and precipitates. The yield strength in compression of Alloy 1 and 2 were determined at various temperatures. Alloy 1 is strong compared to superalloy IN 718 over a range of temperatures up to 950 C. Both alloys with the B2 crystal structure are deformed by one or more of the following slip systems, namely (110), (112) and (123). Dislocations with Burgers vector, b, given by b= are present in the form of dissociated superpartial pairs, each with b=1/2. The inherent ductility of both alloys is indicated by the active slip systems and illustrated by 20% elongation to failure obtained in alloy 2 under room temperature tensile test. A trend of increasing tensile yield stress with increasing antiphase domain size was found. No evidence of interaction between dislocations and antiphase boundaries has been found to account for this increase of strength

  1. Effect of hydrogen on mechanical properties of -titanium alloys

    Indian Academy of Sciences (India)

    H-J Christ; A Senemmar; M Decker; K Prüßner

    2003-06-01

    Conflicting opinions exist in the literature on the manner in which hydrogen influences the mechanical properties of -titanium alloys. This can be attributed to the -stabilizing effect of hydrogen in these materials leading to major changes in the microstructure as a result of hydrogen charging. The resulting (extrinsic) effect of hydrogen on the mechanical properties can possibly cover up the direct (intrinsic) influences. On the basis of experimentally determined thermodynamic and kinetic data regarding the interaction of hydrogen with -titanium alloys, hydrogen concentrations of up to 8 at.% were established in three commercial alloys by means of hydrogen charging from the gas phase. In order to separate intrinsic and extrinsic effects the charging was carried out during one step of the two-step heat treatment typical of metastable -titanium alloys, while the other step was performed in vacuum. The results on the single-phase condition represent the intrinsic hydrogen effect. Monotonic and cyclic strength increase at the expense of ductility with increasing hydrogen concentration. The brittle to ductile transition temperature shifts to higher values and the fatigue crack propagation threshold value decreases. The microstructure of the metastable, usually two-phase -titanium alloys is strongly affected by hydrogen, although the extent of this effect depends not only on the hydrogen concentration but also on the temperature of charging. This microstructural influence (extrinsic effect) changes the mechanical properties in the opposite direction as compared to the intrinsic hydrogen effect.

  2. Dynamic Fracture Initiation Toughness at Elevated Temperatures With Application to the New Generation of Titanium Aluminide Alloys. Chapter 8

    Science.gov (United States)

    Shazly, Mostafa; Prakash, Vikas; Draper, Susan; Shukla, Arun (Editor)

    2006-01-01

    Recently, a new generation of titanium aluminide alloy, named Gamma-Met PX, has been developed with better rolling and post-rolling characteristics. I'revious work on this alloy has shown the material to have higher strengths at room and elevated temperatures when compared with other gamma titanium aluminides. In particular, this new alloy has shown increased ductility at elevated temperatures under both quasi-static and high strain rate uniaxial compressive loading. However, its high strain rate tensile ductility at room and elevated temperatures is limited to approx. 1%. In the present chapter, results of a study to investigate the effects of loading rate and test temperature on the dynamic fracture initiation toughness in Gamma-Met PX are presented. Modified split Hopkinson pressure bar was used along with high-speed photography to determine the crack initiation time. Three-point bend dynamic fracture experiments were conducted at impact speeds of approx. 1 m/s and tests temperatures of up-to 1200 C. The results show that thc dynamic fracture initiation toughness decreases with increasing test temperatures beyond 600 C. Furthermore, thc effect of long time high temperature air exposure on the fracture toughness was investigated. The dynamic fracture initiation toughness was found to decrease with increasing exposure time. The reasons behind this drop are analyzed and discussed.

  3. Mechanical Properties of DS NiAl/Cr(Mo) Alloys with Low Addition of Hf for High-temperature Applications

    Institute of Scientific and Technical Information of China (English)

    Xinghao DU; Jianting GUO

    2005-01-01

    A multiphase NiAl-28Cr-5.85Mo-0.15Hf alloy, which was directionally solidified (DS) in an Al2O3-SiO2 mold by standard Bridgman method and then underwent prolonged solution and aging treatment was prepared. The microstructure, tensile properties as well as tensile creep of the heat-treated alloy at different temperatures were studied. The alloy was composed of NiAl, Cr(Mo) and Hf-rich phase and small amount of fine Heusler phase (Ni2AlHf). Although the present alloy exhibited high tensile strength at Iow temperature, it was weaker than that of system with high content Hf but still stronger than that of many NiAl-based alloys at high temperatures. The fracture toughness is lower than that of DS NiAl-28Cr-6Mo alloy. Nevertheless, advantageous effects on the mechanical properties, i.e.the decrease in brittle-to-ductile transition temperature (BDTT) were obtained for the Iow content of Hf. The obtained creep curves exhibit conventional shape: a short primary creep and long accelerated creep stages. The rupture properties of the heat-treated alloy follow the Monkman-Grant relationship, which exhibits similar creep behavior to that of NiAl/Cr(Mo) system with high Hf content.

  4. Role of Chloride in the Corrosion and Fracture Behavior of Micro-Alloyed Steel in E80 Simulated Fuel Grade Ethanol Environment

    OpenAIRE

    Olufunmilayo O. Joseph; Cleophas A. Loto; Seetharaman Sivaprasad; John A. Ajayi; Soumitra Tarafder

    2016-01-01

    In this study, micro-alloyed steel (MAS) material normally used in the production of auto parts has been immersed in an E80 simulated fuel grade ethanol (SFGE) environment and its degradation mechanism in the presence of sodium chloride (NaCl) was evaluated. Corrosion behavior was determined through mass loss tests and electrochemical measurements with respect to a reference test in the absence of NaCl. Fracture behavior was determined via J-integral tests with three-point bend specimens at a...

  5. Mechanism for Corrosion Prevention by a Mechanical Plating of Uniform Zinc-Iron Alloy

    Science.gov (United States)

    Kasai, Naoya; Kaku, Yoshihiko; Okazaki, Shinji; Hirai, Kuninori

    2016-09-01

    In situ electrochemical monitoring with a three-electrode cell was applied to investigate the anti-corrosion properties of a mechanical zinc-iron alloy plating. Several electron probe microanalyses were also conducted to identify the chemical elements in the plating. The results indicated the formation of a Zn-Fe intermetallic compound, which allowed a mechanism for corrosion prevention to be proposed. In the proposed mechanism, Zn(OH)2 plays a significant role in the corrosion prevention of steel alloys.

  6. Analysis Of Transport Properties of Mechanically Alloyed Lead Tin Telluride

    Science.gov (United States)

    Krishna, Rajalakshmi

    The work described in this thesis had two objectives. The first objective was to develop a physically based computational model that could be used to predict the electronic conductivity, Seebeck coefficient, and thermal conductivity of Pb1-xSnxTe alloys over the 400 K to 700 K temperature as a function of Sn content and doping level. The second objective was to determine how the secondary phase inclusions observed in Pb1-xSn xTe alloys made by consolidating mechanically alloyed elemental powders impact the ability of the material to harvest waste heat and generate electricity in the 400 K to 700 K temperature range. The motivation for this work was that though the promise of this alloy as an unusually efficient thermoelectric power generator material in the 400 K to 700 K range had been demonstrated in the literature, methods to reproducibly control and subsequently optimize the materials thermoelectric figure of merit remain elusive. Mechanical alloying, though not typically used to fabricate these alloys, is a potential method for cost-effectively engineering these properties. Given that there are deviations from crystalline perfection in mechanically alloyed material such as secondary phase inclusions, the question arises as to whether these defects are detrimental to thermoelectric function or alternatively, whether they enhance thermoelectric function of the alloy. The hypothesis formed at the onset of this work was that the small secondary phase SnO2inclusions observed to be present in the mechanically alloyed Pb1-xSnxTe would increase the thermoelectric figure of merit of the material over the temperature range of interest. It was proposed that the increase in the figure of merit would arise because the inclusions in the material would not reduce the electrical conductivity to as great an extent as the thermal conductivity. If this were to be true, then the experimentally measured electronic conductivity in mechanically alloyed Pb1-xSnxTe alloys that have

  7. Mechanical properties of hot rolled 2519 aluminum alloy plate

    Institute of Scientific and Technical Information of China (English)

    彭大暑; 陈险峰; 林启权; 张辉

    2003-01-01

    The effects of differences of temper on mechanical properties of T6, T7 and T8 plates of aluminum alloy 2519 were studied. The stress corrosion cracking(SCC) sensitivity was evaluated with parameters such as Kσ and Kδ.Tensile tests were divided into two groups: one was performed on tensile specimens without pre-corrosion, the other was performed on tensile specimens which were pre-corroded in 3.5%NaCl+1%H2O2 solution at 25 ℃.The results show that SCC resistance of alloy 2519 ranks in the order of T8>T7>T6 and the mechanical properties rank in the order of T6>T8>T7. SEM fractographs of the failed specimen show that the SCC sensitivity can be determined by the distribution of the second phase particles and size and the shape of grains in the alloy.

  8. Probabilistic/Fracture-Mechanics Model For Service Life

    Science.gov (United States)

    Watkins, T., Jr.; Annis, C. G., Jr.

    1991-01-01

    Computer program makes probabilistic estimates of lifetime of engine and components thereof. Developed to fill need for more accurate life-assessment technique that avoids errors in estimated lives and provides for statistical assessment of levels of risk created by engineering decisions in designing system. Implements mathematical model combining techniques of statistics, fatigue, fracture mechanics, nondestructive analysis, life-cycle cost analysis, and management of engine parts. Used to investigate effects of such engine-component life-controlling parameters as return-to-service intervals, stresses, capabilities for nondestructive evaluation, and qualities of materials.

  9. (Environmental and geophysical modeling, fracture mechanics, and boundary element methods)

    Energy Technology Data Exchange (ETDEWEB)

    Gray, L.J.

    1990-11-09

    Technical discussions at the various sites visited centered on application of boundary integral methods for environmental modeling, seismic analysis, and computational fracture mechanics in composite and smart'' materials. The traveler also attended the International Association for Boundary Element Methods Conference at Rome, Italy. While many aspects of boundary element theory and applications were discussed in the papers, the dominant topic was the analysis and application of hypersingular equations. This has been the focus of recent work by the author, and thus the conference was highly relevant to research at ORNL.

  10. Elastic, plastic, and fracture mechanisms in graphene materials.

    Science.gov (United States)

    Daniels, Colin; Horning, Andrew; Phillips, Anthony; Massote, Daniel V P; Liang, Liangbo; Bullard, Zachary; Sumpter, Bobby G; Meunier, Vincent

    2015-09-23

    In both research and industry, materials will be exposed to stresses, be it during fabrication, normal use, or mechanical failure. The response to external stress will have an important impact on properties, especially when atomic details govern the functionalities of the materials. This review aims at summarizing current research involving the responses of graphene and graphene materials to applied stress at the nanoscale, and to categorize them by stress-strain behavior. In particular, we consider the reversible functionalization of graphene and graphene materials by way of elastic deformation and strain engineering, the plastic deformation of graphene oxide and the emergence of such in normally brittle graphene, the formation of defects as a response to stress under high temperature annealing or irradiation conditions, and the properties that affect how, and mechanisms by which, pristine, defective, and polycrystalline graphene fail catastrophically during fracture. Overall we find that there is significant potential for the use of existing knowledge, especially that of strain engineering, as well as potential for additional research into the fracture mechanics of polycrystalline graphene and device functionalization by way of controllable plastic deformation of graphene.

  11. Elastic, plastic, and fracture mechanisms in graphene materials

    International Nuclear Information System (INIS)

    In both research and industry, materials will be exposed to stresses, be it during fabrication, normal use, or mechanical failure. The response to external stress will have an important impact on properties, especially when atomic details govern the functionalities of the materials. This review aims at summarizing current research involving the responses of graphene and graphene materials to applied stress at the nanoscale, and to categorize them by stress–strain behavior. In particular, we consider the reversible functionalization of graphene and graphene materials by way of elastic deformation and strain engineering, the plastic deformation of graphene oxide and the emergence of such in normally brittle graphene, the formation of defects as a response to stress under high temperature annealing or irradiation conditions, and the properties that affect how, and mechanisms by which, pristine, defective, and polycrystalline graphene fail catastrophically during fracture. Overall we find that there is significant potential for the use of existing knowledge, especially that of strain engineering, as well as potential for additional research into the fracture mechanics of polycrystalline graphene and device functionalization by way of controllable plastic deformation of graphene. (topical review)

  12. Elastic, plastic, and fracture mechanisms in graphene materials

    Science.gov (United States)

    Daniels, Colin; Horning, Andrew; Phillips, Anthony; Massote, Daniel V. P.; Liang, Liangbo; Bullard, Zachary; Sumpter, Bobby G.; Meunier, Vincent

    2015-09-01

    In both research and industry, materials will be exposed to stresses, be it during fabrication, normal use, or mechanical failure. The response to external stress will have an important impact on properties, especially when atomic details govern the functionalities of the materials. This review aims at summarizing current research involving the responses of graphene and graphene materials to applied stress at the nanoscale, and to categorize them by stress-strain behavior. In particular, we consider the reversible functionalization of graphene and graphene materials by way of elastic deformation and strain engineering, the plastic deformation of graphene oxide and the emergence of such in normally brittle graphene, the formation of defects as a response to stress under high temperature annealing or irradiation conditions, and the properties that affect how, and mechanisms by which, pristine, defective, and polycrystalline graphene fail catastrophically during fracture. Overall we find that there is significant potential for the use of existing knowledge, especially that of strain engineering, as well as potential for additional research into the fracture mechanics of polycrystalline graphene and device functionalization by way of controllable plastic deformation of graphene.

  13. Fatigue and fracture mechanics analysis of high pressure vessels

    International Nuclear Information System (INIS)

    A companion document to the ASME Boiler and Pressure Code, section VIII, Division 3 Alternative rules for Construction of High Pressure Vessels, emphasizes that Division 3 is 'intended for vessels in the design pressure range of about 10,000 to 165,000 psi: but no upper or lower limits are given nor are any upper limits implied for Divisions 1 and 2'. Although Division 3 includes much information on welded vessels, attention herein will be focused on the design of vessels that operate above 10,000 psi and are of monobloc or compound construction, using two or more cylindrical shells, that are forged from low- alloy high strength steel ingots. Threaded, pinned, or clamped closures are often used at one or both ends of such vessels; in some cases one end may be forged integrally with the cylindrical body, so-called 'blind end' closure. High pressure piping is connected to such vessels at holes in the end closures or at holes through the cylindrical part of the vessel, usually referred to as cross-bores. These vessels or components thereof may be overstrained (autofrettaged) to enhance static and/or fatigue performance. Division 3 was first published in 1997. In the interim there have been advances in the static, fatigue, and fracture analysis of such vessels and their closures and connections. The aim of this paper is to review some of these advances. (author)

  14. Mechanical Characterization and Corrosion Testing of X608 Al Alloy

    Energy Technology Data Exchange (ETDEWEB)

    Prabhakaran, Ramprashad; Choi, Jung-Pyung; Stephens, Elizabeth V.; Catalini, David; Lavender, Curt A.; Rohatgi, Aashish

    2016-02-07

    This paper describes the mechanical characterization and corrosion testing of X608 Al alloy that is being considered for A-pillar covers for heavy-duty truck applications. Recently, PNNL developed a thermo-mechanical process to stamp A-pillar covers at room temperature using this alloy, and the full-size prototype was successfully stamped by a tier-1 supplier. This study was conducted to obtain additional important information related to the newly developed forming process, and to further improve its mechanical properties. The solutionization temperature, pre-strain and paint-bake heat-treatment were found to influence the alloy’s fabricability and mechanical properties. Natural aging effect on the formability was investigated by limiting dome height (LDH) tests. Preliminary corrosion experiments showed that the employed thermo-mechanical treatments did not significantly affect the corrosion behavior of Al X608.

  15. A comparison of the stress corrosion cracking susceptibility of commercially pure titanium grade 4 in Ringer's solution and in distilled water: a fracture mechanics approach.

    Science.gov (United States)

    Roach, Michael D; Williamson, R Scott; Thomas, Joseph A; Griggs, Jason A; Zardiackas, Lyle D

    2014-01-01

    From the results of laboratory investigations reported in the literature, it has been suggested that stress corrosion cracking (SCC) mechanisms may contribute to early failures in titanium alloys that have elevated oxygen concentrations. However, the susceptibility of titanium alloys to SCC in physiological environments remains unclear. In this study, a fracture mechanics approach was used to examine the SCC susceptibility of CP titanium grade 4 in Ringer's solution and distilled de-ionized (DI) water, at 37°C. The study duration was 26 weeks, simulating the non-union declaration of a plated fracture. Four wedge loads were used corresponding to 86-95% of the alloy's ligament yield load. The longest cracks were measured to be 0.18 mm and 0.10 mm in Ringer's solution and DI water, respectively. SEM analysis revealed no evidence of extensive fluting and quasi-cleavage fracture features which, in literature reports, were attributed to SCC. We thus postulate that the Ringer's solution accelerated the wedge-loaded crack growth without producing the critical stresses needed to change the fracture mechanism. Regression analysis of the crack length results led to a significant best-fit relationship between crack growth velocity (independent variable) and test electrolyte, initial wedge load, and time of immersion of specimen in electrolyte (dependent variables).

  16. A fracture criterion for widespread cracking in thin-sheet aluminum alloys

    Science.gov (United States)

    Newman, J. C., Jr.; Dawicke, D. S.; Sutton, M. A.; Bigelow, C. A.

    1993-01-01

    An elastic-plastic finite-element analysis was used with a critical crack-tip-opening angle (CTOA) fracture criterion to model stable crack growth in thin-sheet 2024-T3 aluminum alloy panels with single and multiple-site damage (MSD) cracks. Comparisons were made between critical angles determined from the analyses and those measured with photographic methods. Calculated load against crack extension and load against crack-tip displacement on single crack specimens agreed well with test data even for large-scale plastic deformations. The analyses were also able to predict the stable tearing behavior of large lead cracks in the presence of stably tearing MSD cracks. Small MSD cracks significantly reduced the residual strength for large lead cracks.

  17. An investigation of the fatigue and fracture behavior of a Nb-12Al-44Ti-1.5Mo intermetallic alloy

    Energy Technology Data Exchange (ETDEWEB)

    Soboyejo, W.O.; Dipasquale, J.; Ye, F.; Mercer, C. [Ohio State Univ., Columbus, OH (United States). Dept. of Materials Science and Engineering; Srivatsan, T.S. [Univ. of Akron, OH (United States). Dept. of Mechanical Engineering; Konitzer, D.G. [General Electric Aircraft Engines, Cincinnati, OH (United States)

    1999-04-01

    This article presents the results of a study of the fatigue and fracture behavior of a damage-tolerant Nb-12Al-44Ti-1.5Mo alloy. This partially ordered B2 + orthorhombic intermetallic alloy is shown to have attractive combinations of room-temperature ductility (11 to 14 pct), fracture toughness (60 to 92 MPa{radical}m), and comparable fatigue crack growth resistance to IN718, Ti-6Al-4V, and pure Nb at room temperature. The studies show that tensile deformation in the Nb-12Al-44Ti-1.5Mo alloy involves localized plastic deformation (microplasticity via slip-band formation) which initiates at stress levels that are significantly below the uniaxial yield stress ({approximately}9.6 pct of the 0.2 pct offset yield strength (YS)). The onset of bulk yielding is shown to correspond to the spread of microplasticity completely across the gage sections of the tensile specimen. Fatigue crack initiation is also postulated to occur by the accumulation of microplasticity (coarsening of slip bands). Subsequent fatigue crack growth then occurs by the unzipping of cracks along slip bands that form ahead of the dominant crack tip. The proposed mechanism of fatigue crack growth is analogous to the unzipping crack growth mechanism that was suggested originally by Neumann for crack growth in single-crystal copper. Slower near-threshold fatigue crack growth rates at 750 C are attributed to the shielding effects of oxide-induced crack closure. The fatigue and fracture behavior are also compared to those of pure Nb and emerging high-temperature niobium-based intermetallics.

  18. Tensile and fracture toughness properties of the nanostructured oxide dispersion strengthened ferritic alloy 13Cr-1W-0.3Ti-0.3Y 2O 3

    Science.gov (United States)

    Eiselt, Ch. Ch.; Klimenkov, M.; Lindau, R.; Möslang, A.; Odette, G. R.; Yamamoto, T.; Gragg, D.

    2011-10-01

    The realization of fusion power as an attractive energy source requires advanced structural materials that can cope with ultra-severe thermo-mechanical loads and high neutron fluxes experienced by fusion power plant components, such as the first wall, divertor and blanket structures. Towards this end, two variants of a 13Cr-1W-0.3Ti-0.3Y 2O 3 reduced activation ferritic (RAF-) ODS steel were produced by ball milling phase blended Fe-13Cr-1W, 0.3Y 20 3 and 0.3Ti powders in both argon and hydrogen atmospheres. The milled powders were consolidated by hot isostatic pressing (HIP). The as-HIPed alloys were then hot rolled into 6 mm plates. Microstructural, tensile and fracture toughness characterization of the hot rolled alloys are summarized here and compared to results previously reported for the as-HIPed condition.

  19. Kinetic process of mechanical alloying in Fe50Cu50

    DEFF Research Database (Denmark)

    Huang, J.Y.; Jiang, Jianzhong; Yasuda, H.;

    1998-01-01

    It is shown that mechanical alloying in the immiscible Fe-Cu system is governed by the atomic shear event and shear-induced diffusion process. We found that an alpha-to-gamma phase transformation, as evidenced by the Nishiyama-Wasserman orientation relationship, occurs by simultaneous shearing...

  20. Mechanical properties of titanium alloys with strengthened surface layers

    Directory of Open Access Journals (Sweden)

    I.M. Pohreliuk

    2011-12-01

    Full Text Available Influence of oxinitriding and boriding on the mechanical properties (ultimate strength to destruction at uniaxial tension, plasticity, tendency to delayed destruction, fatigue resistance at bending with rotation, fatigue life at lowcycle pure bending of titanium alloys is studied.

  1. CT for diagnosing fractures of the undersurface of the talus and mechanism of injury

    Energy Technology Data Exchange (ETDEWEB)

    Okamoto, Hideaki; Shibata, Yoshimori; Nishi, Genzaburo; Tago, Kyoji; Tsuchiya, Daiji; Chiba, Takehiro; Okumura, Hisashi [Aichiken Koseiren Kainan Hospital, Yatomi (Japan); Ikeda, Takeshi; Wada, Ikuo

    2000-02-01

    Talus fractures whose fracture lines extend to the subtalar joint, except fractures of the neck and the body of the talus, are defined as fractures of the lower portion of the talus. It is difficult to make a correctly diagnosis of inferior fractures of the talus by plain radiography or tomography alone. The author encountered 12 cases of inferior fractures of the talus between 1989 and 1997, and CT imaging in 2 directions, in the horizontal and frontal plane, was useful in making the diagnosis. The correct diagnosis rate was 100%, and differentiation of the site and extent of the fractures was possible. Based on the CT findings, the fractures were classified into 8 types (fractures of the lateral process of the talus, fractures of the medial tubercle, fractures of the posterior process, and combinations of the above, and comminuted fractures). The mechanism of the injuries was also investigated, and the fractures of the lateral process of the talus seemed to have been caused by excessive eversion force on the ankle joint, with the lateral process becoming trapped between the fibula and the calcaneus. Medial tubercle fractures also seemed to be caused by forcible inversion of the ankle, with the tip of the medial malleous impacting and the medial tubercle being trapped between it and the sustentaculum tali. The comminuted fractures seem to have been caused by axial compression added to various of external forces. (K.H.)

  2. CT for diagnosing fractures of the undersurface of the talus and mechanism of injury

    International Nuclear Information System (INIS)

    Talus fractures whose fracture lines extend to the subtalar joint, except fractures of the neck and the body of the talus, are defined as fractures of the lower portion of the talus. It is difficult to make a correctly diagnosis of inferior fractures of the talus by plain radiography or tomography alone. The author encountered 12 cases of inferior fractures of the talus between 1989 and 1997, and CT imaging in 2 directions, in the horizontal and frontal plane, was useful in making the diagnosis. The correct diagnosis rate was 100%, and differentiation of the site and extent of the fractures was possible. Based on the CT findings, the fractures were classified into 8 types (fractures of the lateral process of the talus, fractures of the medial tubercle, fractures of the posterior process, and combinations of the above, and comminuted fractures). The mechanism of the injuries was also investigated, and the fractures of the lateral process of the talus seemed to have been caused by excessive eversion force on the ankle joint, with the lateral process becoming trapped between the fibula and the calcaneus. Medial tubercle fractures also seemed to be caused by forcible inversion of the ankle, with the tip of the medial malleous impacting and the medial tubercle being trapped between it and the sustentaculum tali. The comminuted fractures seem to have been caused by axial compression added to various of external forces. (K.H.)

  3. Fabrication of nanocrystalline alloys Cu–Cr–Mo super satured solid solution by mechanical alloying

    Energy Technology Data Exchange (ETDEWEB)

    Aguilar, C., E-mail: claudio.aguilar@usm.cl [Departamento de Ingeniería Metalúrgica y Materiales, Universidad Técnica Federico Santa María, Av. España 1680, Valparaíso (Chile); Guzmán, D. [Departamento de Ingeniería en Metalurgia, Facultad de Ingeniería, Universidad de Atacama y Centro Regional de Investigación y Desarrollo Sustentable de Atacama (CRIDESAT), Av. Copayapu 485, Copiapó (Chile); Castro, F.; Martínez, V.; Cuevas, F. de las [Centro de Estudios e Investigaciones Técnicas de Gipuzkoa, Paseo de Manuel Lardizábal, N° 15, 20018 San Sebastián (Spain); Lascano, S. [Departamento de Ingeniería Mecánica, Universidad Técnica Federico Santa María, Av. España 1680, Valparaíso (Chile); Muthiah, T. [Departamento de Ingeniería Metalúrgica y Materiales, Universidad Técnica Federico Santa María, Av. España 1680, Valparaíso (Chile)

    2014-08-01

    This work discusses the extension of solid solubility of Cr and Mo in Cu processed by mechanical alloying. Three alloys processed, Cu–5Cr–5Mo, Cu–10Cr–10Mo and Cu–15Cr–15Mo (weight%) using a SPEX mill. Gibbs free energy of mixing values 10, 15 and 20 kJ mol{sup −1} were calculated for these three alloys respectively by using the Miedema's model. The crystallite size decreases and dislocation density increases when the milling time increases, so Gibbs free energy storage in powders increases by the presence of crystalline defects. The energy produced by crystallite boundaries and strain dislocations were estimated and compared with Gibbs free energy of mixing values. The energy storage values by the presence of crystalline defects were higher than Gibbs free energy of mixing at 120 h for Cu–5Cr–5Mo, 130 h for Cu–10Cr–10Mo and 150 h for Cu–15Cr–15Mo. During milling, crystalline defects are produced that increases the Gibbs free energy storage and thus the Gibbs free energy curves are moved upwards and hence the solubility limit changes. Therefore, the three alloys form solid solutions after these milling time, which are supported with the XRD results. - Highlights: • Extension of solid solution Cr and Mo in Cu achieved by mechanical alloying. • X-ray characterization of Cu–Cr–Mo system processed by mechanical alloying. • Thermodynamics analysis of formation of solid solution of the Cu–Cr–Mo system.

  4. 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.

  5. Understanding Plasticity and Fracture in Aluminum Alloys and their Composites by 3D X-ray Synchrotron Tomography and Microdiffraction

    Science.gov (United States)

    Hruby, Peter

    Aluminum alloys and their composites are attractive materials for applications requiring high strength-to-weight ratios and reasonable cost. Many of these applications, such as those in the aerospace industry, undergo fatigue loading. An understanding of the microstructural damage that occurs in these materials is critical in assessing their fatigue resistance. Two distinct experimental studies were performed to further the understanding of fatigue damage mechanisms in aluminum alloys and their composites, specifically fracture and plasticity. Fatigue resistance of metal matrix composites (MMCs) depends on many aspects of composite microstructure. Fatigue crack growth behavior is particularly dependent on the reinforcement characteristics and matrix microstructure. The goal of this work was to obtain a fundamental understanding of fatigue crack growth behavior in SiC particle-reinforced 2080 Al alloy composites. In situ X-ray synchrotron tomography was performed on two samples at low (R=0.1) and at high (R=0.6) R-ratios. The resulting reconstructed images were used to obtain three-dimensional (3D) rendering of the particles and fatigue crack. Behaviors of the particles and crack, as well as their interaction, were analyzed and quantified. Four-dimensional (4D) visual representations were constructed to aid in the overall understanding of damage evolution. During fatigue crack growth in ductile materials, a plastic zone is created in the region surrounding the crack tip. Knowledge of the plastic zone is important for the understanding of fatigue crack formation as well as subsequent growth behavior. The goal of this work was to quantify the 3D size and shape of the plastic zone in 7075 Al alloys. X-ray synchrotron tomography and Laue microdiffraction were used to non-destructively characterize the volume surrounding a fatigue crack tip. The precise 3D crack profile was segmented from the reconstructed tomography data. Depth-resolved Laue patterns were obtained using

  6. Application of probabilistic fracture mechanics to the PTS issue

    International Nuclear Information System (INIS)

    As a part of the NRC effort to obtain a resolution to the PWR PTS issue, a probabilistic approach has been applied that includes a probabilistic fracture-mechanics (PFM) analysis. The PFM analysis is performed with OCA-P, a computer code that performs thermal, stress and fracture-mechanics analyses and estimates the conditional probability of vessel failure, P(F/E), using Monte Carlo techniques. The stress intensity factor (K/sub I/) is calculated for two- and three-dimensional surface flaws using superposition techniques and influence coefficients. Importance-sampling techniques are used, as necessary, to limit to a reasonable value the number of vessels actually calculated. Analyses of three PWR plants indicate that (1) the critical initial flaw depth is very small (5 to 15 mm), (2) the benefit of warm prestressing and the role of crack arrest are transient dependent, (3) crack arrest does not occur for the dominant transients, and (4) the single largest uncertainty in the overall probabilistic analysis is the number of surface flaws per vessel. 30 refs., 6 figs., 4 tabs

  7. A fracture mechanics analysis of the DCDC specimen

    International Nuclear Information System (INIS)

    The ''double cleavage drilled compression'' (DCDC) specimen is a rectangular bar with a circular hole in its centre that is loaded by compressive stresses. Due to the hole, positive stresses are generated in the vicinity that cause positive mode-I stress intensity factors. This specimen is used for the determination of crack growth under mode-I and in a modified version under mixed-mode loading conditions. A fracture mechanics analysis is presented on the basis of finite element computations. After compilation of literature results on mixed-mode stress intensity factors and T-stresses, weight functions for mode I and mode II are derived. The consequences of load misalignment and crack kinking are shown. Since stress intensity factor results from literature are available for long cracks compared with the hole radius only, also short-crack solutions are derived by use of the weight function technique. These results al-low to discuss the generation of the initial cracks necessary for fracture mechanics tests. In several papers, the side surface displacements were reported and discussed with respect to the occurrence of plasticity effects in glass. In order to decide whether deviations from the pure linear-elastic material behaviour are measured, it is necessary to know the elastic response. Therefore, a 3-dimensional finite element study is performed. It exhibits depression and uplifting of the free surface very similar to the re-sults found in literature

  8. Application of fracture mechanics to weldments; Bruchmechanische Bewertung von Schweissverbindungen

    Energy Technology Data Exchange (ETDEWEB)

    Zerbst, U.; Kocak, M. [GKSS-Forschungszentrum Geesthacht GmbH (Germany). Inst. fuer Werkstofforschung; Huebner, P. [Technische Univ. Bergakademie Freiberg (Germany)

    2002-07-01

    Weldments have been a major topic of engineering fracture mechanics research for many years as it shows up in the immense number of scientific papers published recently. Part of this generated knowledge has already been implemented in some industrial codes and standards. The focussing on weldments has its own reason in the utmost importance of this class of components in many industrial fields, but also in its susceptibility to the formation of defects during manufacturing and cracks in service, which promotes the danger of component failure. The present report is addressed to designers and material testers to provide updated information on the present state-of-the-art of fracture mechanics application to weldments. (orig.) [German] Schweissverbindungen bilden seit vielen Jahren einen Schwerpunkt der anwendungsnahen bruchmechanischen Forschung, was seinen Niederschlag in einer nahezu unuebersehbaren Fuelle an wissenschaftlichen Publikationen findet. Ein Teil der Ergebnisse hat bereits Eingang in industrienahe bruchmechanische Bewertungsvorschriften gefunden. Die Konzentration auf Schweissverbindungen hat ihre Ursache in der immensen Bedeutung dieser Bauteilklasse fuer viele Gebiete der Volkswirtschaft, aber auch in ihrer besonderen Anfaelligkeit zur Rissbildung in der Fertigung und im Betrieb und damit hinsichtlich der Gefahr von Bauteilversagen. Der vorliegende Beitrag wendet sich an Konstrukteure und Werkstoffpruefer, die einen Einblick in den gegenwaertigen Stand der Ingenieurbruchmechanik an Schweissverbindungen gewinnen wollen. (orig.)

  9. Mechanisms of diffusional phase transformations in metals and alloys

    CERN Document Server

    Aaronson, Hubert I; Lee, Jong K

    2010-01-01

    Developed by the late metallurgy professor and master experimentalist Hubert I. Aaronson, this collection of lecture notes details the fundamental principles of phase transformations in metals and alloys upon which steel and other metals industries are based. Mechanisms of Diffusional Phase Transformations in Metals and Alloys is devoted to solid-solid phase transformations in which elementary atomic processes are diffusional jumps, and these processes occur in a series of so-called nucleation and growth through interface migration. Instead of relying strictly on a pedagogical approach, it doc

  10. Microstructure and mechanical properties of eutectic nickel alloy coatings

    Science.gov (United States)

    Bezborodov, V. P.; Saraev, Yu N.

    2016-04-01

    The paper discusses the peculiarities of a structure and a coating composition after reflow. It was established that the structure of coatings from nickel alloy is a solid solution based on nickel, the eutectic of γ-Ni+Ni3B composition and dispersed reinforcing particles. The content of alloying elements in the initial powder material determines the type of the coating structure and the formation of hypoeutectic or hypereutectic structures. The influence of formation conditions on the structure and physical-mechanical properties of the coatings is considered in this paper.

  11. Mechanical biocompatibilities of titanium alloys for biomedical applications.

    Science.gov (United States)

    Niinomi, Mitsuo

    2008-01-01

    Young's modulus as well as tensile strength, ductility, fatigue life, fretting fatigue life, wear properties, functionalities, etc., should be adjusted to levels that are suitable for structural biomaterials used in implants that replace hard tissue. These factors may be collectively referred to as mechanical biocompatibilities. In this paper, the following are described with regard to biomedical applications of titanium alloys: the Young's modulus, wear properties, notch fatigue strength, fatigue behaviour on relation to ageing treatment, improvement of fatigue strength, fatigue crack propagation resistance and ductility by the deformation-induced martensitic transformation of the unstable beta phase, and multifunctional deformation behaviours of titanium alloys.

  12. Mechanical alloying of Cu-xCr (x = 3, 5 and 8 wt.%) alloys

    Energy Technology Data Exchange (ETDEWEB)

    Aguilar, C., E-mail: ceaguilar@uach.c [Instituto de Materiales y Procesos Termomecanicos, Facultad de Ciencias de la Ingenieria, Universidad Austral de Chile, General Lagos 2086, Valdivia (Chile); Ordonez, S. [Departamento de Ingenieria Metalurgica, Facultad de Ingenieria, Universidad de Santiago de Chile, Av. L. Bernardo O' Higgins 3363, Santiago (Chile); Guzman, D. [Departamento de Metalurgia, Facultad de Ingenieria, Universidad de Atacama, Av. Copayapu 485, Copiapo (Chile); Rojas, P.A. [Escuela de Ingenieria Mecanica, Facultad de Ingenieria, Pontificia Universidad Catolica de Valparaiso, Av. Los Carrera 01567, Quilpue (Chile)

    2010-08-13

    This work studies the structural evolution of Cu-xCr (x = 3, 5 and 8 wt.%) alloys processed by mechanical alloying using X-ray diffraction profiles, scanning microscopy and microhardness analysis. X-ray diffraction analysis using the modified Williamson-Hall and Warren-Averbach methods were used to determine structural properties, such as crystallite size, stacking fault probability and energy, dislocation density, lattice parameters and crystallite size distribution of metallic powder as a function of Cr amount and milling time. Lattice defects increase the Gibbs free energy and the Gibbs free energy curves shift upward, therefore the solubility limit change.

  13. Fracture Behavior of TiNi Based Shape Memory Alloy Cold-rolled Tube

    Institute of Scientific and Technical Information of China (English)

    LI Yan-wu; LIU Fu-shun

    2006-01-01

    The microstructures and interfacial characteristics of matrices at the inwalls and the out-walls of the cold-rolled tube with different amounts of deformation were investigated by the scanning electronic microscope (SEM), the optical microscope (OM), and the transmission electronic microscope (TEM) techniques. It was observed that as the amount of deformation increases, the flaws nucleate at the out-walls of the cold rolled tube, the stress-induced martensites change from (11) type Ⅰ twins to (011) type Ⅱ twins and then to (100) compound twins, nanocrystals and bulk amorphisation happen, the high density dislocation causes stress concentration at the out-walls of the Ti50Ni50 cold-rolled tube, and then precipitates its fracture, and the Ti2Ni particles strengthen the grain boundaries and curb the dislocation movements during plastic deformation. The inhomogeneity level of the grains in the Ti50Ni50 alloy plays an important role on the fracture of the Ti50Ni50 cold rolled tube.

  14. Ti-25Ta alloy with the best mechanical compatibility in Ti-Ta alloys for biomedical applications

    International Nuclear Information System (INIS)

    The microstructures, dynamic elastic modulus, and mechanical properties of the Ti-25Ta (mass%) alloy are investigated in this study in order to assess its mechanical compatibility for biomedical applications. The microstructures are examined by X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The dynamic elastic modulus is measured by the resonance vibration method and the mechanical properties are determined from uniaxial tensile tests. The experimental results indicate that the Ti-25Ta alloy exhibits an orthorhombic martensite (α'') twinned structure after solution treatment. The Ti-25Ta alloy has the lowest elastic modulus and the highest ratio of strength to modulus among Ti-Ta alloys. Thus, the Ti-25Ta alloy exhibits the best mechanical compatibility among Ti-Ta alloys and is a promising candidate for novel metallic biomaterials.

  15. Aluminum alloys for ALS cryogenic tanks: Comparative measurements of cryogenic mechanical properties of Al-Li alloys and alloy 2219, February 1993

    International Nuclear Information System (INIS)

    Tensile and fracture toughness were obtained at cryogenic temperatures to compare the Al-Li alloys 8090, 2090, and WL049, and alloy 2219 in various tempers and specimen orientations. The strongest alloy at very low temperatures is WL049-T851, which is about 10 percent stronger than 2090-T81. Both alloys are considerably stronger than 2219-T87. Alloy 2090-T81 is tougher (about 50 percent) than WL049-T851 at low temperatures; the higher toughness is attributed to the presence of fewer constituent particles and the tendency to delaminate at low temperatures. The delamination divides the moving crack, thus separating it into smaller regions where plane stress (rather than plane strain) conditions are conducive to increased toughness

  16. Design of experiment (DOE) study of biodegradable magnesium alloy synthesized by mechanical alloying using fractional factorial design

    Science.gov (United States)

    Salleh, Emee Marina; Ramakrishnan, Sivakumar; Hussain, Zuhailawati

    2014-06-01

    The biodegradable nature of magnesium (Mg) makes it a most highlighted and attractive to be used as implant materials. However, rapid corrosion rate of Mg alloys especially in electrolytic aqueous environment limits its performance. In this study, Mg alloy was mechanically milled by incorporating manganese (Mn) as alloying element. An attempt was made to study both effect of mechanical alloying and subsequent consolidation processes on the bulk properties of Mg-Mn alloys. 2k-2 factorial design was employed to determine the significant factors in producing Mg alloy which has properties closes to that of human bones. The design considered six factors (i.e. milling time, milling speed, weight percentage of Mn, compaction pressure, sintering temperature and sintering time). Density and hardness were chosen as the responses for assessing the most significant parameters that affected the bulk properties of Mg-Mn alloys. The experimental variables were evaluated using ANOVA and regression model. The main parameter investigated was compaction pressure.

  17. Superior Mechanical Properties of AlCoCrFeNiTi x High-Entropy Alloys upon Dynamic Loading

    Science.gov (United States)

    Jiao, Z. M.; Ma, S. G.; Chu, M. Y.; Yang, H. J.; Wang, Z. H.; Zhang, Y.; Qiao, J. W.

    2016-02-01

    High-entropy alloys with composition of AlCoCrFeNiTi x ( x: molar ratio; x = 0, 0.2, 0.4) under quasi-static and dynamic compression exhibit excellent mechanical properties. A positive strain-rate sensitivity of yield strength and the strong work-hardening behavior during plastic flows dominate upon dynamic loading in the present alloy system. The constitutive relationships are extracted to model flow behaviors by employing the Johnson-Cook constitutive model. Upon dynamic loading, the ultimate strength and fracture strain of AlCoCrFeNiTi x alloys are superior to most of bulk metallic glasses and in situ metallic glass matrix composites.

  18. Formation of nano quasicrystalline and crystalline phases by mechanical alloying

    Energy Technology Data Exchange (ETDEWEB)

    Shamah, A.M.; Ibrahim, S. [Faculty of Petroleum and Mining Engineering, Suez Canal University, Suez (Egypt); Hanna, F.F., E-mail: fariedhanna@yahoo.com [Faculty of Petroleum and Mining Engineering, Suez Canal University, Suez (Egypt)

    2011-02-03

    Research highlights: > Mechanical alloying (MA) is an important method to investigate the formation of nano sized quasicrystalline phases in Al{sub 86}Cr{sub 14}, Al{sub 84}Fe{sub 16} and Al{sub 62.5}Cu{sub 25}Fe{sub 12.5} compounds. The second part of the present work is an attempt to examine the possibility of formation of the i-phase of the Al{sub 62.5}Cu{sub 25}Fe{sub 12.5}, which lies in the region of the perfect i-phase in the ternary phase diagram, by rapid solidification method. To perform the obtained quasi phase mechanical alloying and heat treatment at the rapid solidified sample were done. - Abstract: In the present work, the formation of nano quasicrystalline icosahedral phase in Al{sub 86}Cr{sub 14}, Al{sub 84}Fe{sub 16} and Al{sub 62.5}Cu{sub 25}Fe{sub 12.5} alloys has been investigated by mechanical alloying. Mixtures of quasicrystalline and related crystalline phases have been observed under various milling conditions. The X-ray diffraction, differential thermal analysis and electrical resistivity techniques have been used for characterization and physical property measurements. The particle size was calculated by X-ray profile using Williamson-Hall plot method and it was found to be 25-50 nm size.

  19. Effects and mechanisms of grain refinement in aluminium alloys

    Indian Academy of Sciences (India)

    K T Kashyap; T Chandrashekar

    2001-08-01

    Grain refinement plays a crucial role in improving characteristics and properties of cast and wrought aluminium alloys. Generally Al–Ti and Al–Ti–B master alloys are added to the aluminium alloys to grain refine the solidified product. The mechanism of grain refinement is of considerable controversy in the scientific literature. The nucleant effects i.e. which particle and its characteristics nucleate -Al, has been the subject of intensive research. Lately the solute effect i.e. the effect of dissolved titanium on grain refinement, has come into forefront of grain refinement research. The present paper attempts to review the literature on the nucleant effects and solute effects on grain refinement and addresses the importance of dissolved titanium in promoting nucleation of -Al on nucleant particles.

  20. Nickel-Titanium Alloys: Corrosion "Proof" Alloys for Space Bearing, Components and Mechanism Applications

    Science.gov (United States)

    DellaCorte, Christopher

    2010-01-01

    An intermetallic nickel-titanium alloy, 60NiTi (60 wt% Ni, 40 wt% Ti), is shown to be a promising candidate tribological material for space mechanisms. 60NiTi offers a broad combination of physical properties that make it unique among bearing materials. 60NiTi is hard, electrically conductive, highly corrosion resistant, readily machined prior to final heat treatment, and is non-magnetic. Despite its high Ti content, 60NiTi is non-galling even under dry sliding. No other bearing alloy, metallic or ceramic, encompasses all of these attributes. Since 60NiTi contains such a high proportion of Ti and possesses many metallic properties, it was expected to exhibit poor tribological performance typical of Ti alloys, namely galling type behavior and rapid lubricant degradation. In this poster-paper, the oil-lubricated behavior of 60NiTi is presented.

  1. Mechanical Behavior and Microstructural Analysis of Extruded AZ31B Magnesium Alloy Processed by Backward Extrusion

    Science.gov (United States)

    Zhou, Ping; Beeh, Elmar; Friedrich, Horst E.; Grünheid, Thomas

    2016-07-01

    This study investigates the mechanical behavior of an extruded AZ31B magnesium alloy profile at various strain rates from 0.001 to 375/s. The electron backscatter diffraction analysis revealed that the profile has \\{ { 0 0 0 1} \\}extrusion direction (ED), the profile shows the highest yield strength (YS) but the lowest total elongation at fracture (TE) due to a hard activation of non-basal slip and \\{ { 1 0overline{1} 1} \\}< { 1 0overline{1} overline{2} } rangle twinning; in the diagonal direction (DD), it shows the lowest ultimate tensile strength (UTS) but the highest TE due to an easy activation of basal slip; in the transverse direction (TD), it shows the lowest YS due to an easy activation of \\{ {10overline{1} 2} \\}< {10overline{1} overline{1} } rangle twinning. Moreover, the number of twins increases with the increasing strain rate. This indicates that deformation twinning becomes prevalent to accommodate high-rate deformation. Due to the different deformation mechanisms, the profile exhibits an orientation-dependent effect of strain rate on the mechanical properties. A positive effect of strain rate on the YS and UTS was found in the ED, while the effect of strain rate on the YS is negligible in the DD and TD. The TE in the ED, DD, and TD decreases in general as the strain rate increases. Fractographic analysis under a scanning electron microscope revealed that the fracture is a mixed mode of ductile and brittle fracture, and the magnesium oxide inclusions could be the origins of the fracture.

  2. Evaluation of mechanical properties of the alloy NiCr22Co12Mo (Alloy 617) for heat exchanging components of HTGRs

    International Nuclear Information System (INIS)

    The HTR-materials program in Germany has been directed towards the qualification of high temperature alloys for heat exchanging components of advanced nuclear process heat plants. From the available conventional alloys, the nickel-base alloy NiCr22Co12Mo (Alloy 617) has been selected for the highest working temperatures. With respect to the design of intermediate heat exchanger and methane reformer tubes long term properties for different semifinished products and weldments of this material have been determined. The experimental work included creep and creep rupture tests, fatigue and creep/fatigue tests and short term mechanical tests after thermal ageing. With regard to the development of fracture mechanics criteria for leak before break argumentations, additional creep and fatigue crack growth experiments have been carried out. Typical examples of the data obtained will be presented. The implementation of the data in the derivation of design curves and the formulation of design rules will be shown. (author). 17 figs, 1 tab

  3. Mechanical Properties and Microstructural Evolution in Al 2014 Alloy Processed Through Multidirectional Cryoforging

    Science.gov (United States)

    Joshi, Amit; Kumar, Nikhil; Yogesha, K. K.; Jayaganthan, R.; Nath, S. K.

    2016-07-01

    Mechanical properties and microstructure evolution of Al 2014 alloy subjected to cryoforging (MDF) to a cumulative strain of 1.2, 1.8, and 2.4 were investigated in the present work. The deformed samples after 4 cycles at a cumulative strain of 2.4 shows the formation of ultrafine grain sizes in the range of 100-450 nm with high-angle grain boundaries as observed from TEM analysis. The tensile and hardness of the deformed sample were measured by Universal Testing machine and Vickers hardness Tester, respectively. The tests were also conducted for sample deformed at room temperature to compare with cryo-forged samples. The sample deformed at cryogenic temperature up to a cumulative strain 2.4 shows an improvement of tensile strength, hardness, and apparent fracture toughness (KQ) from 318 MPa to 470 MPa, 103HV to 171 HV, and 23.93 MPa √ m to 37.7 MPa √ m, respectively, with decrease in ductility from 18% to 6% as compared with solution-treated alloy. The cryo-forged Al 2014 alloy exhibits an increment of 7% in tensile strength, 3% in yield strength, and 3% in hardness up to cumulative true strain of 2.4 as compared to the samples forged at room temperature. The improvement in tensile properties of MDFed alloy is attributed to dislocation strengthening and grain boundary strengthening effect at both temperatures. The effective suppression of cross slip and climb at liquid nitrogen temperature improves the strength of cryo-forged sample better than that of room temperature-forged alloy.

  4. Characterization and corrosion behaviour of CoNi alloys obtained by mechanical alloying

    Energy Technology Data Exchange (ETDEWEB)

    Olvera, S. [Instituto Politécnico Nacional, ESIQIE, Departamento de Ingeniería en Metalurgia y Materiales, México, D. F. (Mexico); Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Química-Física Aplicada, 28049 Madrid (Spain); Sánchez-Marcos, J. [Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Química-Física Aplicada, 28049 Madrid (Spain); Palomares, F.J. [Instituto de Ciencia de Materiales de Madrid, ICMM-CSIC, Cantoblanco, 28049 Madrid (Spain); Salas, E. [Spline Spanish CRG Beamline at the European Synchrotron Radiation Facilities, ESRF, BP 220-38043, Grenoble Cedex (France); Arce, E.M. [Instituto Politécnico Nacional, ESIQIE, Departamento de Ingeniería en Metalurgia y Materiales, México, D. F. (Mexico); Herrasti, P., E-mail: pilar.herrasti@uam.es [Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Química-Física Aplicada, 28049 Madrid (Spain)

    2014-07-01

    CoNi alloys including Co{sub 30}Ni{sub 70}, Co{sub 50}Ni{sub 50} and Co{sub 70}Ni{sub 30} were prepared via mechanical alloying using Co and Ni powders. The crystallinity and short-range order were studied using X-ray diffraction and X-ray absorption spectroscopy. The results show that the milling process increases the number of vacancies, especially around the Co atoms, while the milling time decreases the crystalline size and enhances the crystallinity. X-ray photoelectron spectroscopy was used to characterise the chemical composition of the samples surface. The magnetic properties were analysed using zero-field cooling, field cooling and a magnetic hysteresis loops. The magnetic saturation moment is approximately 1.05 μ{sub B}/atom; this value decreases with the mechanical alloying time, and it is proportional to the cobalt concentration. The polarization and impedance curves in different media (NaCl, H{sub 2}SO{sub 4} and NaOH) showed similar corrosion resistance values. The corrosion resistance increased in the order NaCl, H{sub 2}SO{sub 4} and NaOH. A good passivation layer was formed in NaOH due to the cobalt and nickel oxides on the particle surfaces. - Highlights: • Ni{sub x}Co{sub 100-x} alloys were synthesized by mechanical alloying • Milling time decrease size and enhances crystallinity. • Oxygen is not present in a significant percentage in bulk but is detected on the surface. • Magnetic saturation moment is 1.05 mB/atom and decrease with mechanical allowing time • Corrosion resistance is higher in NaOH than in NaCl or HCl solutions.

  5. THE APPLICATION OF SHAPE MEMORY ALLOY ENCIRCLED FIXER TO BONE FRACTURE%形状记忆合金环抱器在骨折中的应用

    Institute of Scientific and Technical Information of China (English)

    刘宝荣; 康亦锋

    2002-01-01

    Objective:To evaluate the effect of encircled fixer of shape memory alloy on bone fracture. Methods:A total of twenty patients with eighteen males and two females was studied. There were three patients with fractares in the upper one third of thighbone, five with fractures in the middle part of thighbone, six with humeral fractures, three with collarbone fractures,one with ulna fracture and two with thighbone fractures as complication of artificial hipbone arthroplasty. After exposure and fixation of fracture ends, prepared encircled fixer was inserted into 0~4℃ normal reline(NS) to lower its temperature, then pulled out with a clamp. Encircled fixer was put on the tersile side of the fractured bone(center pointed to fracture line), restored and stabilized after raising temperature in 40℃ NS. Results: Encircled fixers of shape memory alloy were used to treat twenty patients with bone fracture.Clinical concrescence was obtained in 1.5 to 3 months after operation,and the joint gained its normal function without complication. Conclusion:Encircled fixer of shape memory alloy has features as exerting vertical pressure continoulsy, little stress shield effect and convenient manipulation, especially adapt to stem fracture after artificial arthroplasty.

  6. Structural and magnetic properties of nanocrystalline Fe–Co–Si alloy powders produced by mechanical alloying

    Energy Technology Data Exchange (ETDEWEB)

    Shyni, P.C.; Perumal, Alagarsamy, E-mail: perumal@iitg.ernet.in

    2015-11-05

    We report the structural and magnetic properties of nanocrystalline Fe{sub 100−x−y}Co{sub y}Si{sub x} (x = 10, 15, y = 0–20) alloy powders prepared by mechanical alloying process in a planetary ball mill. All the as-milled powders exhibit non-equilibrium α-Fe(Co,Si) solid solution with average crystallite size of 7–11 nm. The lattice constant increases initially up to 10 at.% Co and then decreases with further increase in Co content due to delay in dissolution of Co into Fe lattice by the introduction of more Si. The variations of structural parameters such as average crystallite size, dislocation density and fraction of grain boundary as a function of Co content show good correlations among them. The substitution of Co in Fe{sub 100−x−y}Co{sub y}Si{sub x} alloy powder increases both saturation magnetization and coercivity due to atomic ordering which induce additional magnetic anisotropy. Thermomagnetization studies reveal that Curie temperature (T{sub C}) increases at a rate of 4 K per at.% Co for Co content up to 10 at.% and the rate of increase in T{sub C} reduces to 1.4 K per at.% Co for higher Co addition. The variation of structural and magnetic parameters reveals a strong dependence on the composition of Fe–Co–Si alloy. The observed results show the improvement in soft magnetic properties of nanocrystalline Fe–Co–Si alloy powders by proper substitution of Co and Si for Fe. - Graphical abstract: Structural and magnetic properties of nanocrystalline Fe{sub 100−x−y}Co{sub y}Si{sub x} alloy powders prepared by mechanical alloying process in a planetary ball mill are reported. The non-equilibrium solid solution with nanosized crystallites could be obtained for all the alloy powders. The substitution of Co in Fe{sub 100−x−y}Co{sub y}Si{sub x} alloy powder increases both saturation magnetization and coercivity. The Curie temperature also increases with increasing Co content. The observed results show the improvement in soft magnetic

  7. Mechanics, hydraulic and coupled hydromechanics of fractured rock mass investigated by numerical experiment

    International Nuclear Information System (INIS)

    The Discrete Fracture Network-Discrete Element Method (DFN-DEM) approach uses DFN as the geometry of fractured rock and DEM for the solution technique to simulate the hydraulic and mechanical behaviour of fractured rock. This overview paper intends to summarize the applications on fractured rock using the DFN-DEM approach with the focus upon the determination of mechanical and hydraulic properties of fractured rock and their stress dependencies. The establishment of methodologies and actual applications in a site considered for geological repository of nuclear waste are introduced. (author)

  8. Effect of high-temperature water and hydrogen on the fracture behavior of a low-alloy reactor pressure vessel steel

    Science.gov (United States)

    Roychowdhury, S.; Seifert, H.-P.; Spätig, P.; Que, Z.

    2016-09-01

    Structural integrity of reactor pressure vessels (RPV) is critical for safety and lifetime. Possible degradation of fracture resistance of RPV steel due to exposure to coolant and hydrogen is a concern. In this study tensile and elastic-plastic fracture mechanics (EPFM) tests in air (hydrogen pre-charged) and EFPM tests in hydrogenated/oxygenated high-temperature water (HTW) was done, using a low-alloy RPV steel. 2-5 wppm hydrogen caused embrittlement in air tensile tests at room temperature (25 °C) and at 288 °C, effects being more significant at 25 °C and in simulated weld coarse grain heat affected zone material. Embrittlement at 288 °C is strain rate dependent and is due to localized plastic deformation. Hydrogen pre-charging/HTW exposure did not deteriorate the fracture resistance at 288 °C in base metal, for investigated loading rate range. Clear change in fracture morphology and deformation structures was observed, similar to that after air tests with hydrogen.

  9. Influence of Route-R on wrought magnesium AZ61 alloy mechanical properties through equal channel angular pressing

    Directory of Open Access Journals (Sweden)

    Muralidhar Avvari

    2014-06-01

    Full Text Available A new fundamental route entitled ‘Route-R’ is introduced to refine the grains in the material through Equal Channel Angular Pressing (ECAP process. In route R, specimen is inverted to the original position in each ECAP pass. In the present work, AZ61 alloy is processed using ECAP process for three different fundamental routes mainly route A, route Bc, and route R. ECAP experiment is carried out on AZ61 alloy at lower temperature of 483 K up to two passes. Microstructural characterization is evaluated on unECAPed and ECAPed specimens for three routes. Average grain size of the alloy is to be reduced from 66 μm to 16 μm, 14.1 μm and 10 μm for route A routes Bc, and route R respectively. Vickers microhardness of the alloy is found to be 60 HV for as received material. This microhardness of the alloy is increased to 71 HV, 72 HV, and 74 HV for route A, route Bc, and route R respectively. Mechanical properties of the AZ61 alloy are observed to be route R is providing maximum YS, UTS, and percentage elongation than other route A and route Bc. Tensile fracture topography of the specimen is analyzed using three different routes for two passes.

  10. Effects of Silicon on Mechanical Properties and Fracture Toughness of Heavy-Section Ductile Cast Iron

    Directory of Open Access Journals (Sweden)

    Liang Song

    2015-01-01

    Full Text Available The effects of silicon (Si on the mechanical properties and fracture toughness of heavy-section ductile cast iron were investigated to develop material for spent-nuclear-fuel containers. Two castings with different Si contents of 1.78 wt.% and 2.74 wt.% were prepared. Four positions in the castings from the edge to the center, with different solidification cooling rates, were chosen for microstructure observation and mechanical properties’ testing. Results show that the tensile strength, elongation, impact toughness and fracture toughness at different positions of the two castings decrease with the decrease in cooling rate. With an increase in Si content, the graphite morphology and the mechanical properties at the same position deteriorate. Decreasing cooling rate changes the impact fracture morphology from a mixed ductile-brittle fracture to a brittle fracture. The fracture morphology of fracture toughness is changed from ductile to brittle fracture. When the Si content exceeds 1.78 wt.%, the impact and fracture toughness fracture morphology transforms from ductile to brittle fracture. The in-situ scanning electronic microscope (SEM tensile experiments were first used to observe the dynamic tensile process. The influence of the vermicular and temper graphite on fracture formation of heavy section ductile iron was investigated.

  11. Analysis of fracture toughness in the transition-temperature region of an Mn-Mo-Ni low-alloy steel

    Science.gov (United States)

    Kim, Sangho; Hwang, Byoungchul; Lee, Sunghak; Lee, Sunghak

    2003-06-01

    This study is concerned with the analysis of fracture toughness in the transition region of an Mn-Mo-Ni low-alloy steel, in accordance with the ASTM E1921 standard test method. Elastic-plastic cleavage fracture toughness ( K Jc ) was determined by three-point bend tests, using precracked Charpy V-notch (PCVN) specimens, and relationships between K Jc , the critical component of J ( J c ), critical distance ( X c ), stretch-zone width (SZW), local fracture stress, and plane-strain fracture toughness ( K Ic were discussed on the basis of the cleavage fracture behavior in the transition region. The master curve and the 95 pct confidence curves well explained the variation in the measured K Jc , and the Weibull slope measured on the Weibull plots was consistent with the theoretical slope of 4. Fractographic observation indicated that X c linearly increased with increasing J c , and that the SZW had a good correlation with K Jc , irrespective of the test temperature. In addition, the local fracture stress was independent of the test temperature, because the tempered bainitic steel used in this study showed a propagation-controlled cleavage fracture behavior.

  12. Glass forming ability, mechanical and magnetic properties in Fe-W-Y-B alloys

    International Nuclear Information System (INIS)

    Glass forming ability (GFA), mechanical and magnetic properties of Fe72WxY6-xB22 (x = 0, 1, 2 and 3 at.%) and Fe72-xWxY6B22 (x 1, 2, 3, 4, 5 and 6 at.%) alloys have been experimentally investigated. It is found that fully amorphous Fe69W3Y6B22 and Fe68W4Y6B22 cylindrical rods with 4 mm in diameter can be prepared by using copper mold casting. The newly developed Fe-based quaternary alloys exhibit excellent combination properties: good GFA, high onset crystallization temperature of 970 K, high fracture strength of about 4 GPa, Vickers hardness of about 1000 kg/mm2, and good soft magnetic properties at ambient temperature (saturation magnetization of about 0.8 T and coercive force of below 2 A/m), which show potential applications in electronic industries. The effect of W addition on GFA in the Fe-Y-B alloy system is discussed.

  13. Wear resistance and fracture mechanics of WC-Co composites

    International Nuclear Information System (INIS)

    Manufacturing of WC-Co composites using the electroless precipitation method at different sintering temperatures of 1 100, 1 250, 1 350 and 1 500 C was successfully achieved. The chemical composition of the investigated materials was 90 wt.% WC with 10 wt.% Co, and 80 wt.% WC with 20 wt.% Co. The specific density, densification, and Vickers microhardness measurements were found to increase with increased sintering temperature for both the WC-Co compositions. The composites of tungsten carbide with 10 wt.% Co had a higher specific density and Vickers microhardness measurements than those for the composites of tungsten carbide with 20 wt.% Co. Composites with WC-10 wt.% Co had better wear resistance. The stress-strain and transverse rupture strength increased monotonically with the increase in sintering temperatures, agreeing with the material hardness and wear resistance behavior. Fractographical scanning electron microscopy analysis of the fracture surface demonstrated a rough characteristic conical shape failure in the direction of the maximum shear stress. A proposed mechanism for the formation of the conical fracture surface under compression testing is presented. (orig.)

  14. Wear resistance and fracture mechanics of WC-Co composites

    Energy Technology Data Exchange (ETDEWEB)

    Kaytbay, Saleh [Benha Univ. (Egypt). Dept. of Mechanical Engineering; El-Hadek, Medhat [Port-Said Univ. (Egypt). Dept. of Production and Mechanical Design

    2014-06-15

    Manufacturing of WC-Co composites using the electroless precipitation method at different sintering temperatures of 1 100, 1 250, 1 350 and 1 500 C was successfully achieved. The chemical composition of the investigated materials was 90 wt.% WC with 10 wt.% Co, and 80 wt.% WC with 20 wt.% Co. The specific density, densification, and Vickers microhardness measurements were found to increase with increased sintering temperature for both the WC-Co compositions. The composites of tungsten carbide with 10 wt.% Co had a higher specific density and Vickers microhardness measurements than those for the composites of tungsten carbide with 20 wt.% Co. Composites with WC-10 wt.% Co had better wear resistance. The stress-strain and transverse rupture strength increased monotonically with the increase in sintering temperatures, agreeing with the material hardness and wear resistance behavior. Fractographical scanning electron microscopy analysis of the fracture surface demonstrated a rough characteristic conical shape failure in the direction of the maximum shear stress. A proposed mechanism for the formation of the conical fracture surface under compression testing is presented. (orig.)

  15. Hydro-thermo-mechanical response of a fractured rock block

    International Nuclear Information System (INIS)

    Hydro-thermo-mechanical effects in fractured rocks are important in many engineering applications and geophysical processes. Modeling these effects is made difficult by the fact that the governing equations are nonlinear and coupled, and the problems to be solved are three dimensional. In this paper we describe a numerical code developed for this purpose. The code is finite element based to allow for complicated geometries, and the time differencing is implicit, allowing for large time steps. The use of state-of-the-art equation solvers has resulted in a practical code. The code is capable of fully three dimensional simulations, however, in this paper we consider only the case of two dimensional heat and mass flow coupled to one dimensional deformation. Partial verification of the code is obtained by comparison with published semianalytical results. Several examples are presented to demonstrate the effects of matrix expansion, due to pore pressure and heating, on fracture opening due to fluid injection. 16 refs., 11 figs

  16. Microstructures and fatigue fracture behavior of an Al-Cu-Mg-Ag alloy with addition of rare earth Er

    International Nuclear Information System (INIS)

    The effects of rare earth erbium (Er) on microstructures and fatigue fracture behavior of an Al-Cu-Mg-Ag alloy were investigated. Microstructural examinations first revealed that the precipitation kinetics of Ω phase was distinctly retarded by promoting the formation of θ' phase with the Er addition during the initial aging. The fatigue crack propagation resistance of Er-containing microstructure was significantly enhanced arising from the presence of the crystallographic secondary cracks, which was directly relative to the large grain size. Results also suggested that the dendritic substructure of as-cast Al-Cu-Mg-Ag alloy was refined remarkably by Er addition.

  17. Deformation and damage mechanism of aluminum alloy under different stress states

    Institute of Scientific and Technical Information of China (English)

    ZHU Hao; ZHU Liang; CHEN Jian-hong; CHE Hong-yan

    2006-01-01

    The deformation and damage mechanism of aluminum alloy (6063) were investigated by 0°, 30°, 45°, 60° and 90° tensile tests and tensile-unload tests with the modified Arcan fixture on the butterfly specimens. The results show: the curves of engineering stress-engineering strain under different stress states are obviously different. There were microvoids in the specimen when 0°direction loading was preformed. The microcracks were produced in the root of notch as the result of the microvoids shearing fracture and then they led to specimen fracture with microcracks being coalesced. With tensile angle increasing, the shear stress in the center of butterfly specimen increases gradually, while the deformation bands become more and more concentrative. In these concentrative deformation bands, the microcracks are produced and then microcracks propagation and coalescence result in specimen fracture. When 90° direction loading is preformed, the shear bands are obviously formed. The G-T-N damage model and the Johnson-cook model were used to simulate 0° tensile test and 90° tensile test respectively. The simulated engineering stress-engineering strain curves fit the measured ones very well.

  18. Mechanical and fracture mechanical properties of fine grained concrete for textile reinforced composites

    OpenAIRE

    Brockmann, Tanja

    2006-01-01

    The development of textile reinforced concrete (TRC), where multi-axial fabrics are used in combination with fine grained concrete, allows the design of very thin-structured concrete elements with a high strength in compression as well as tension. It is the main objective of this study to determine the mechanical and fracture mechanical characteristics of the newly developed fine grained binder systems as a main component of the composite to allow for a reliable dimensioning of TRC structures...

  19. The mechanical behaviour of hydraulic fractured, possibly saturated materials

    NARCIS (Netherlands)

    Visser, J.H.M.; Mier, J.G.M. van

    1998-01-01

    The influence of a fluid pressure load on the extensile fracturing of mortar and sandstone has been investigated. A fluid pressure in the (initiating) fracture stimulates both fracture initiation and propagation and may be as effective as a directly applied uniaxial tensile stress. The efficiency of

  20. The influence of initial powder properties on the mechanical alloying process and the final powders structure

    OpenAIRE

    Szymczak, M.; R. Nowosielski; W. Pilarczyk

    2011-01-01

    Purpose: The main aim of this work is to study the influence of initial powder properties on the mechanical alloying process and final powders structure and the production of chosen powder alloy by mechanical alloying method.Design/methodology/approach: The test material was the pure niobium, tin and copper powders. The powders were ground for 2 and 10 hrs. The mechanical alloying process was conducted in a high energy SPEX mill under inert argon atmosphere. The chemical constitution and conc...

  1. Mechanical properties and structure of magnesium alloy AS31

    Directory of Open Access Journals (Sweden)

    A. Hanus

    2008-07-01

    Full Text Available Contemporary materials should possess high mechanical properties, physical and chemical, as well as technological ones, to ensure long and reliable use. The non-ferrous metals alloys used nowadays, including the magnesium alloys, meet the above-mentioned requirements and expectations regarding the contemporary materials.Magnesium alloys are primarily used in aeronautical and automobile industry in wide variety of structural characteristics because of their favorable combination of tensile strength (160 to 365 MPa, elastic modulus (45 GPa, and low density (1 740 kg/m3, which is two-thirds that of aluminum. Magnesium alloys have high strength-to-weight ratio (tensile strength/density, comparable to those of other structural metals. [1-6]Knowledge of the relaxation properties of metal materials at high temperatures is necessary for the verification of susceptibility of castings to the creation of defects during the production process. Temperature limits of materials where highest tension values are generated may be detected with tensile tests under high temperatures. The generated tensions in the casting are a cause of the creation and development of defects. At acoustic emission (hereinafter called the "AE" use, tensile tests at high temperatures may, among other things, be used for analysis of the AE signal sources and set, in more detail, the temperature limit of elastic-plastic deformations existence in the material under examination. The results of the temperature drop where tension at casting cooling is generated or its release at heating are basic data for controlled cooling mode (and temperature of casting knocking out of the form as well as necessary for the thermal mode for the casting tension reduction. [7-9]Knowledge of elastic-plastic properties at elevated temperatures is often important for complex evaluation of magnesium alloys. Objective of the work was focused on determination of changes of elastic-plastic properties of magnesium

  2. The importance of metallurgical variables in environment sensitive fracture of austenitic alloys

    International Nuclear Information System (INIS)

    The effects of metallurgical variables on environment sensitive cracking of austenitic Fe-Cr-Ni alloys, in particular austenitic stainless steels, have been examined. It is demonstrated by reviewing available literature data and by new, unpublished results that the nature and extent of susceptibility are sensitive such metallurgical variables as composition, grain size, microstructure, thermal treatment and radiation damage. Environment sensitive cracking has been classified as hydrogen-induced cracking or selective dissolution of an active path (Cr-depleted zone, segregations or deformation structures). The common factors between stress corrosion cracking and hydrogen embrittlement of these alloys are identified. Finally, possible aspects of the role and mechanism of hydrogen-induced cracking in environment sensitive cracking are discussed. (author)

  3. Tensile Fracture Mechanism of Claviform Hybrid Composite Rebar

    Institute of Scientific and Technical Information of China (English)

    CAI Lurong; ZENG Qingdun; WANG Ronghui

    2012-01-01

    Based on the shear-lag theory,a hexagonal model of fiber bundles was established to study the tensile fracture mechanism of a claviform hybrid composite rebar.Firstly,the stress redistributions are investigated on two conditions:one condition is that interfacial damage is taken into accotmt and the other is not.Then,a micro-statistical analysis of the multiple tensile failures of the rebar was performed by using the random critical-core theory.The results indicate that the predictions of the tensile failure strains of the rebar,in which the interracial damage is taken into account,are in better agreement with the existing experimental results than those when only elastic case is considered.Through the comparison between the theoretical and experimental results,the shear-lag theory and the model are verified feasibly in studying the claviform hybrid composite rebar.

  4. Fracture propagation in sandstone and slate e Laboratory experiments, acoustic emissions and fracture mechanics

    Institute of Scientific and Technical Information of China (English)

    Ferdinand Stoeckhert; Michael Molenda; Sebastian Brenne; Michael Alber

    2015-01-01

    abstract Fracturing of highly anisotropic rocks is a problem often encountered in the stimulation of unconven-tional hydrocarbon or geothermal reservoirs by hydraulic fracturing. Fracture propagation in isotropic material is well understood but strictly isotropic rocks are rarely found in nature. This study aims at the examination of fracture initiation and propagation processes in a highly anisotropic rock, specifically slate. We performed a series of tensile fracturing laboratory experiments under uniaxial as well as triaxial loading. Cubic specimens with edge lengths of 150 mm and a central borehole with a diameter of 13 mm were prepared from Fredeburg slate. An experiment using the rather isotropic Bebertal sandstone as a rather isotropic rock was also performed for comparison. Tensile fractures were generated using the sleeve fracturing technique, in which a polymer tube placed inside the borehole is pressurized to generate tensile fractures emanating from the borehole. In the uniaxial test series, the loading was varied in order to observe the transition from strength-dominated fracture propagation at low loading mag-nitudes to stress-dominated fracture propagation at high loading magnitudes.

  5. Fracture propagation in sandstone and slate – Laboratory experiments, acoustic emissions and fracture mechanics

    Directory of Open Access Journals (Sweden)

    Ferdinand Stoeckhert

    2015-06-01

    Full Text Available Fracturing of highly anisotropic rocks is a problem often encountered in the stimulation of unconventional hydrocarbon or geothermal reservoirs by hydraulic fracturing. Fracture propagation in isotropic material is well understood but strictly isotropic rocks are rarely found in nature. This study aims at the examination of fracture initiation and propagation processes in a highly anisotropic rock, specifically slate. We performed a series of tensile fracturing laboratory experiments under uniaxial as well as triaxial loading. Cubic specimens with edge lengths of 150 mm and a central borehole with a diameter of 13 mm were prepared from Fredeburg slate. An experiment using the rather isotropic Bebertal sandstone as a rather isotropic rock was also performed for comparison. Tensile fractures were generated using the sleeve fracturing technique, in which a polymer tube placed inside the borehole is pressurized to generate tensile fractures emanating from the borehole. In the uniaxial test series, the loading was varied in order to observe the transition from strength-dominated fracture propagation at low loading magnitudes to stress-dominated fracture propagation at high loading magnitudes.

  6. Structure and mechanical properties of as-cast (ZrTi){sub 100−x}B{sub x} alloys

    Energy Technology Data Exchange (ETDEWEB)

    Xia, C.Q.; Jiang, X.J.; Wang, X.Y.; Zhou, Y.K.; Feng, Z.H. [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China); Tan, C.L. [Beijing Institute of Spacecraft System Engineering, Beijing 100094 (China); Ma, M.Z. [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China); Liu, R.P., E-mail: riping@ysu.edu.cn [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China)

    2015-07-15

    Highlights: • Trace boron additions result in significant grain refinement. • Large numbers of stacking faults are observed in ZrB{sub 2} and TiB intermetallics. • The tensile strength is enhanced by increasing the amount of B. • Intermetallics microcracking causes the failure of the alloys. - Abstract: The microstructure, mechanical properties, and fracture characteristics of (Zr{sub 50}Ti{sub 50}){sub 100−x}B{sub x} alloys (x = 0, 0.5, 1, 2 at.%) obtained by casting were investigated. Trace additions of boron (B) to the Zr{sub 50}Ti{sub 50} alloys induced significant microstructural changes. Changes included the promotion of dendritic growth and refinement in prior-β grain and α′-lath size. Large numbers of stacking faults were also observed in ZrB{sub 2} and TiB intermetallics. The location of B atoms and the lattice mismatch energy between intermetallics and matrix were responsible for the stacking faults. (ZrTi)B alloys demonstrated higher tensile strength than matrix material. Both the intermetallics with high strength and modulus and the grain refinement played important roles in improving the mechanical properties of alloys. This result could be explained in terms of a shear-lag model based on the load transfer concept and Hall–Petch mechanism. The elongation-to-failure of (ZrTi)B alloys decreased with increased B concentration. The reduction in elongation-to-failure of (ZrTi)B alloys could be attributed to the presence of ZrB{sub 2} and TiB intermetallics and refinement of α′-laths.

  7. About the Transformation Phase Zones of Shape Memory Alloys' Fracture Tests on Single Edge-Cracked Specimen

    Science.gov (United States)

    Taillebot, V.; Lexcellent, C.; Vacher, P.

    2012-03-01

    The thermomechanical behavior of shape memory alloys is now well mastered. However, a hindrance to their sustainable use is the lack of knowledge of their fracture behavior. With the aim of filling this partial gap, fracture tests on edge-cracked specimens in NiTi have been made. Particular attention was paid to determine the phase transformation zones in the vicinity of the crack tip. In one hand, experimental kinematic fields are observed using digital image correlation showing strain localization around the crack tip. In the other hand, an analytical prediction, based on a modified equivalent stress criterion and taking into account the asymmetric behavior of shape memory alloys in tension-compression, provides shape and size of transformation outset zones. Experimental results are relatively in agreement with our analytical modeling.

  8. ORNL probabilistic fracture-mechanics code OCA-P

    International Nuclear Information System (INIS)

    The computer code OCA-P was developed at the request of the USNRC for the purpose of helping to evaluate the integrity of PWR pressure vessels during overcooling accidents (OCA's). The code can be used for both deterministic and probabilistic fracture-mechanics calculations, and consists essentially of OCA-II and a Monte Carlo routine similar to that developed by Strosnider et al. In the probabilistic mode OCA-P generates a large number of vessels (106 more or less), each with a different combination of the various values of the different parameters involved in the analysis of flaw behavior. For each of these vessels a deterministic fracture-mechanics analysis is performed (calculation of K/sub I/, K/sub Ic/, K/sub Ia/) to determine whether vessel failure takes place. The conditional probability of failure is simply the number of vessels that fail divided by the number of vessels generated. OCA-II is used for the deterministic analysis. Basic input to OCA-II includes, among other things, the primry-system pressure transient and the temperature transient for the coolant in the reactor-vessel downcomer. With this and additional information available OCA-II performs a one-dimensional thermal analysis to obtain the temperature distribution in the wall as a function of time and then a one-dimensional linear-elastic stress analysis. OCA-P has been checked against similar codes and is presently being used in the Integrated Pressurized Thermal Shock Program for specific PWR plants

  9. Fracture mechanics analysis on VVER1000 RPV with different methodologies

    International Nuclear Information System (INIS)

    The main component that limits the operational life of the (Nuclear Power Plant) NPP is the Reactor pressure Vessel (RPV) because of the property of carbon steel material change during the operational life due to the different causes: high neutron flux in the welding region, thermal aging etc. This results in an increase of RPV embrittlement level that decreases the safety margin for the crack propagation in case of transients with fast cooling rate due to the emergency systems injection, or increase of secondary side heat exchange. This problem is known as Pressurized Thermal Shock (PTS) and constitutes a relevant problem for the safety of the NPP that are in operation from several years. Nowadays, the scientific community is trying to change the approach to the PTS analysis toward a “Best Estimate” (BE) scheme with the aim to remove the excess of conservatism in each step of the analysis coming from the limited knowledge of the phenomena in the eighties when the problem has been considered in the safety analysis. This change has been pushed from the possibility to extend the operational life of some plants and this has been possible due to the availability of always more powerful computer and sophisticated computer codes that allows to the analyst to perform very detailed analysis with very high degree of precision of the mixing phenomena occurring at small scale in the down-comer and to calculate the stress intensity factor at crack tip with very refined mesh of millions of nodes. This paper describes the main steps of a PTS analysis: system thermal-hydraulic calculation, CFD analysis, stress analysis and the Fracture Mechanics analysis for the RPV of a generic VVER1000. In particular the paper shows the comparison of the results of the fracture mechanics analysis performed with different methodology for the calculation of the stress intensity factor at crack tip (KI). (author)

  10. A mechanism-based approach to modeling ductile fracture.

    Energy Technology Data Exchange (ETDEWEB)

    Bammann, Douglas J.; Hammi, Youssef; Antoun, Bonnie R.; Klein, Patrick A.; Foulk, James W., III; McFadden, Sam X.

    2004-01-01

    Ductile fracture in metals has been observed to result from the nucleation, growth, and coalescence of voids. The evolution of this damage is inherently history dependent, affected by how time-varying stresses drive the formation of defect structures in the material. At some critically damaged state, the softening response of the material leads to strain localization across a surface that, under continued loading, becomes the faces of a crack in the material. Modeling localization of strain requires introduction of a length scale to make the energy dissipated in the localized zone well-defined. In this work, a cohesive zone approach is used to describe the post-bifurcation evolution of material within the localized zone. The relations are developed within a thermodynamically consistent framework that incorporates temperature and rate-dependent evolution relationships motivated by dislocation mechanics. As such, we do not prescribe the evolution of tractions with opening displacements across the localized zone a priori. The evolution of tractions is itself an outcome of the solution of particular, initial boundary value problems. The stress and internal state of the material at the point of bifurcation provides the initial conditions for the subsequent evolution of the cohesive zone. The models we develop are motivated by in-situ scanning electron microscopy of three-point bending experiments using 6061-T6 aluminum and 304L stainless steel, The in situ observations of the initiation and evolution of fracture zones reveal the scale over which the failure mechanisms act. In addition, these observations are essential for motivating the micromechanically-based models of the decohesion process that incorporate the effects of loading mode mixity, temperature, and loading rate. The response of these new cohesive zone relations is demonstrated by modeling the three-point bending configuration used for the experiments. In addition, we survey other methods with the potential

  11. Mechanical strength of laser-welded cobalt-chromium alloy.

    Science.gov (United States)

    Baba, N; Watanabe, I; Liu, J; Atsuta, M

    2004-05-15

    The purpose of this study was to investigate the effect of the output energy of laser welding and welding methods on the joint strength of cobalt-chromium (Co-Cr) alloy. Two types of cast Co-Cr plates were prepared, and transverse sections were made at the center of the plate. The cut surfaces were butted against one another, and the joints welded with a laser-welding machine at several levels of output energy with the use of two methods. The fracture force required to break specimens was determined by means of tensile testing. For the 0.5-mm-thick specimens, the force required to break the 0.5-mm laser-welded specimens at currents of 270 and 300 A was not statistically different (p > 0.05) from the results for the nonwelded control specimens. The force required to break the 1.0-mm specimens double-welded at a current of 270 A was the highest value among the 1.0-mm laser-welded specimens. The results suggested that laser welding under the appropriate conditions improved the joint strength of cobalt- chromium alloy. PMID:15116400

  12. The effect of multiaxial stress state on creep behavior and fracture mechanism of P92 steel

    International Nuclear Information System (INIS)

    The creep experiments on plain and double U-typed notched specimens were conducted on P92 steel at 650 °C. The notch strengthening effect was found in the notched specimens. Fracture appearance observed by scanning electron microscopy revealed that dimpled fracture for relatively blunt notched specimen, and dimpled fracture doubled with intergranular brittle fracture for relatively sharp notched specimen, which meant that fracture mechanism of P92 steel altered due to the presence of the notch. Meanwhile, based on Norton–Bailey and Kachanov–Robotnov constitutive models, a modified model was proposed. Finite element simulations were carried out to investigate the effect of multiaxial stress state on the creep behavior, fracture mechanism and damage evolvement of P92 steel. The simulation results agreed well with the fracture behaviors observed experimentally

  13. Mechanical rock properties, fracture propagation and permeability development in deep geothermal reservoirs

    Science.gov (United States)

    Leonie Philipp, Sonja; Reyer, Dorothea

    2010-05-01

    Deep geothermal reservoirs are rock units at depths greater than 400 m from which the internal heat can be extracted using water as a transport means in an economically efficient manner. In many geothermal reservoirs, fluid flow is largely, and may be almost entirely, controlled by the permeability of the fracture network. No flow, however, takes place along a particular fracture network unless the fractures are interconnected. For fluid flow to occur from one site to another there must be at least one interconnected cluster of fractures that links these sites, that is, the percolation threshold must be reached. In "hydrothermal systems", only the natural fracture system (extension and shear fractures) creates the rock or reservoir permeability that commonly exceeds the matrix permeability by far; in "petrothermal systems", by contrast, interconnected fracture systems are formed by creating hydraulic fractures and massive hydraulic stimulation of the existing fracture system in the host rock. Propagation (or termination, that is, arrest) of both natural extension and shear fractures as well as man-made hydraulic fractures is mainly controlled by the mechanical rock properties, particularly rock toughness, stiffness and strengths, of the host rock. Most reservoir rocks are heterogeneous and anisotropic, in particular they are layered. For many layered rocks, the mechanical properties, particularly their Young's moduli (stiffnesses), change between layers, that is, the rocks are mechanically layered. Mechanical layering may coincide with changes in grain size, mineral content, fracture frequencies, or facies. For example, in sedimentary rocks, stiff limestone or sandstone layers commonly alternate with soft shale layers. In geothermal reservoirs fracture termination is important because non-stratabound fractures, that is, fractures not affected by layering, are more likely to form an interconnected fracture network than stratabound fractures, confined to single rock

  14. Effective Hydro-Mechanical Properties of Fluid-Saturated Fracture Networks

    Science.gov (United States)

    Pollmann, N.; Vinci, C.; Renner, J.; Steeb, H.

    2015-12-01

    Consideration of hydro-mechanical processes is essential for the characterization of liquid-resources as well as for many engineering applications. Furthermore, the modeling of seismic waves in fractured porous media finds application not only in geophysical exploration but also reservoir management. Fractures exhibit high-aspect-ratio geometries, i.e. they constitute thin and long hydraulic conduits. Motivated by this peculiar geometry, the investigation of the hydro-mechanically coupled processes is performed by means of a hybrid-dimensional modeling approach. The effective material behavior of domains including complex fracture patterns in a porous rock is assessed by investigating the fluid pressure and the solid displacement of the skeleton saturated by compressible fluids. Classical balance equations are combined with a Poiseuille-type flow in the dimensionally reduced fracture. In the porous surrounding rock, the classical Biot-theory is applied. For simple geometries, our findings show that two main fluid-flow processes occur, leak-off from fractures to the surrounding rock and fracture flow within and between the connected fractures. The separation of critical frequencies of the two flow processes is not straightforward, in particular for systems containing a large number of fractures. Our aim is to model three dimensional hydro-mechanically coupled processes within complex fracture patterns and in particular determine the frequency-dependent attenuation characteristics. Furthermore, the effect of asperities of the fracture surfaces on the fracture stiffness and on the hydraulic conductivity will be added to the approach.

  15. Thermal-Hydrologic-Mechanical Behavior of Single Fractures in EGS Reservoirs

    Science.gov (United States)

    Zyvoloski, G.; Kelkar, S.; Yoshioka, K.; Rapaka, S.

    2010-12-01

    Enhanced Geothermal Systems (EGS) rely on the creation a connected fracture system or the enhancement of existing (natural) fractures by hydraulic and chemical treatments. EGS studies at Fenton Hill (New Mexico, USA) and Hijiori (Japan) have revealed that only a limited number of fractures contribute to the effective heat transfer surface area. Thus, the economic viability of EGS depends strongly on the creation and spacing of single fractures in order to efficiently mine heat from given volume of rock. Though there are many similarities between EGS and natural geothermal reservoirs, a major difference between the reservoir types is the (typically) high pumping pressures and induced thermal stresses at the injection wells of an EGS reservoir. These factors can be responsible for fracture dilation/extension and thermal short circuiting and depend strongly on the surrounding state of stress in the reservoir and mechanical properties. We will present results from our study of the thermal-hydrologic-mechanical (THM) behavior of a single fracture in a realistic subsurface stress field. We will show that fracture orientation, the stress environment, fracture permeability structure, and the relationship between permeability changes in a fracture resulting from mechanical displacement are all important when designing and managing an EGS reservoir. Lastly, we present a sensitivity analysis of the important parameters that govern fracture behavior with respect to field measurements. Temperature in high permeability fracture in an EGS reservoir

  16. High-coercivity ferrite magnets prepared by mechanical alloying

    International Nuclear Information System (INIS)

    Nanocrystalline hexaferrite (BaFe12O19 or SrFe12O19) and mixed Fe,Co-ferrite ((FexCo1-x)Fe2O4 with x=0-1) materials have been prepared by mechanical alloying and subsequent annealing. High coercivities were obtained in these nanocrystalline materials, 6-7 kOe for hexaferrite and ∝3 kOe for Co-ferrite. Hexaferrite powders prepared by mechanical alloying have been used as the starting material for high-coercivity bonded magnets. Hot-pressed anisotropic hexaferrite magnets have been produced with high values of coercivity and remanence. High magnetic performance was also achieved in some mixed Fe,Co-ferrites after magnetic annealing. (orig.)

  17. Determination of parameters of the Johnson-Cook model for the description of deformation and fracture of titanium alloys

    Science.gov (United States)

    Buzyurkin, A. E.; Gladky, I. L.; Kraus, E. I.

    2015-03-01

    Stress-strain curves of dynamic loading of VT6, OT4, and OT4-0 titanium-based alloys are constructed on the basis of experimental data, and the Johnson-Cook model parameters are determined. Results of LS-DYNA simulations of the processes of deformation and fracture of the fan casing after its high-velocity impact with a fan blade simulator are presented.

  18. Modeling and simulation of deformation and fracture behavior of components made of fully lamellar {gamma}TiAl alloy

    Energy Technology Data Exchange (ETDEWEB)

    Kabir, Mohammad Rizviul [GKSS-Forschungszentrum Geesthacht GmbH (Germany). Inst. fuer Materialforschung

    2008-07-01

    The present work deals with the modeling and simulation of deformation and fracture behavior of fully lamellar {gamma}TiAl alloy; focusing on understanding the variability of local material properties and their influences on translamellar fracture. Afracture model has been presented that takes the inhomogeneity of the local deformation behavior of the lamellar colonies as well as the variability in fracture strength and toughness into consideration. To obtain the necessary model parameters, a hybrid methodology of experiments and simulations has been adopted. The experiments were performed at room temperature that demonstrates quasi-brittle response of the TiAl polycrystal. Aremarkable variation in stress-strain curves has been found in the tensile tests. Additional fracture tests showed significant variations in crack initiation and propagation during translamellar fracture. Analyzing the fracture surfaces, the micromechanical causes of these macroscopic scatter have been explained. The investigation shows that the global scatter in deformation and fracture response is highly influenced by the colony orientation and tilting angle with respect to the loading axis. The deformation and fracture behavior have been simulated by a finite element model including the material decohesion process described by a cohesive model. In order to capture the scatter of the macroscopic behavior, a stochastic approach is chosen. The local variability of stressstrain in the polycrystal and the variability of fracture parameters of the colonies are implemented in the stochastic approach of the cohesive model. It has been shown that the proposed approach is able to predict the stochastic nature of crack initiation and propagation as observed from the experiments. The global specimen failure with stable or unstable crack propagation can be explained in terms of the local variation of material properties. (orig.)

  19. Intergranular brittle fracture of a low alloy steel induced by grain boundary segregation of impurities: influence of the microstructure

    International Nuclear Information System (INIS)

    The study contributes to improve the comprehension of intergranular embrittlement induced by the phosphorus segregation along prior austenitic grain boundaries of low alloy steels used in pressurized power reactor vessel. A part of this study was performed using a A533 steel which contains chemical fluctuations (ghost lines) with two intensities. Axi-symmetrically notched specimens were tested and intergranular brittle de-cohesions were observed in the ghost lines. The fracture initiation sites observed on fracture surfaces were identified as MnS inclusions. A bimodal statistic obtained in a probabilistic model of the fracture is explained by the double population of ghost lines' intensities. A metallurgical study was performed on the same class of steel by studying the influence of the microstructure on the susceptibility to temper embrittlement. Brittle fracture properties of such microstructures obtained by dilatometric experiments were tested on sub-sized specimens to measure the V-notched fracture toughness. Fraction areas of brittle fracture modes were determined on surface fractures. A transition of the fracture mode with the microstructure is observed. It is shown that tempered microstructures of martensite and lower bainite are more susceptible to intergranular embrittlement than tempered upper bainitic microstructure. The intergranular fracture is the most brittle mode. The analysis of crystalline mis-orientations shows a grain boundary structure appreciably more coherent for tempered microstructures of martensite and lower bainite. The higher density of random grain boundaries is susceptible to drag the phosphorus in the upper bainitic matrix and to make the quantity of free phosphorus decreasing. Microstructure observations show a difference in the size and the spatial distribution of carbides, essentially cementite, between tempered martensite and upper bainite. It can explain the bigger susceptibility of this last microstructure to cleavage mode

  20. Synthesis of MoSi2 by Mechanical Alloying

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The microstructure evolution of mechanical alloyed Mo-66.7%Si powder using the high-energy ball mill has been studied by X-ray diffraction and scanning electron microscopy. The results showed that MoSi2 can be synthesized by MA of Mo-66.7%Si powder mixtures. Cold welding behavior between Mo and Si powders plays an important role in the preparation of MoSi2 by the MA.

  1. Corrosion of Mechanically Alloyed Nanostructured FeAl Intermetallic Powders

    OpenAIRE

    Torres-Islas, A.; C. Carachure; Serna, S.; B. Campillo; G. Rosas

    2012-01-01

    The corrosion behavior of the Fe40Al60 nanostructured intermetallic composition was studied using electrochemical impedance spectroscopy (EIS) and linear polarization resistance (LPR) techniques with an innovative electrochemical cell arrangement. The Fe40Al60 (% at) intermetallic composition was obtained by mechanical alloying using elemental powders of Fe (99.99%) and Al (99.99%). All electrochemical testing was carried out in Fe40Al60 particles that were in water with different pH values. ...

  2. Failure mechanisms in DP600 steel: Initiation, evolution and fracture

    Energy Technology Data Exchange (ETDEWEB)

    Ghadbeigi, H., E-mail: h.ghadbeigi@sheffield.ac.uk [The University of Sheffield, Department of Mechanical Engineering, Mappin Street, Sheffield S1 3JD (United Kingdom); Pinna, C. [The University of Sheffield, Department of Mechanical Engineering, Mappin Street, Sheffield S1 3JD (United Kingdom); Celotto, S. [Tata Steel R and D, IJmuiden, 1970 CA (Netherlands)

    2013-12-20

    Local deformation and damage mechanisms have been studied for a commercial DP600 steel using in-situ tensile testing inside a scanning electron microscope (SEM) in combination with Digital Image Correlation (DIC). Different gauge geometries have been used to study damage evolution processes during tensile testing up to final failure. Strain distributions have been measured within the ferrite and martensite phases, together with the corresponding strain values for identified damage initiation mechanisms. According to the strain maps, large plastic deformation with strain values as large as 4.5 have been measured within the ferrite phase. Severe deformation localization and slip band formation were observed within the ferrite grains. The DIC results show that martensite in the studied material is plastically deformable with a heterogeneous strain distribution within the islands with values of up to 0.9 close to the phase boundaries. Failure of the martensite islands occurs mostly due to micro-crack initiation at the boundaries with the ferrite followed by crack propagation towards the centre of the islands. As for the ferrite matrix, it is found that its interface with the martensite is strong and cohesive. Localized damage in the matrix occurs by sub-micron void formation within the ferrite adjacent to the interface as opposed to the separation along the phase boundary itself or in the central regions of the ferrite grains A mechanism has been proposed to explain the deformation and damage evolution in the microstructure of the studied DP600 steel up to the final fracture.

  3. Deformation and fracture of a composite material based on a high-strength maraging steel covered with a melt-quenched Co69Fe4Cr4Si12B11 alloy layer

    Science.gov (United States)

    Sevost'yanov, M. A.; Kolmakov, A. G.; Molokanov, V. V.; Zabolotnyi, V. T.; Umnov, P. P.; Umnova, N. V.

    2011-04-01

    Multifractal analysis is used to study the deformation and fracture of a promising composite material consisting of a wire base made of K17N9M14 maraging steel covered with a surface layer made from a Co69Fe4Cr4Si12B11 amorphous alloy. As compared to its components, this material has a substantially better set of the mechanical properties.

  4. Phase evolution and thermal stability of 2 Mg–Cu alloys processed by mechanical alloying

    Energy Technology Data Exchange (ETDEWEB)

    Martínez, C., E-mail: carola.martinezu@usach.cl [Departamento de Ingeniería Metalúrgica, Facultad de Ingeniería, Universidad de Santiago de Chile, Av. Lib. Bernardo O’Higgins 3363, Casilla de correo 10233, Santiago (Chile); Ordoñez, S., E-mail: stella.ordonez@usach.cl [Departamento de Ingeniería Metalúrgica, Facultad de Ingeniería, Universidad de Santiago de Chile, Av. Lib. Bernardo O’Higgins 3363, Casilla de correo 10233, Santiago (Chile); Guzmán, D. [Departamento de Ingeniería en Metalurgia, Facultad de Ingeniería, Universidad de Atacama y CRIDESAT, Av. Copayapu 485, Casilla de Correo 240, Copiapó (Chile); Serafini, D. [Departamento de Física, Facultad de Ciencia, Universidad de Santiago de Chile, Av. Lib. Bernardo O’Higgins 3363, Casilla de correo 307, Santiago (Chile); Iturriza, I. [CEIT, Manuel de Lardizábal 15, 20018 San Sebastián, España (Spain); Bustos, O. [Departamento de Ingeniería Metalúrgica, Facultad de Ingeniería, Universidad de Santiago de Chile, Av. Lib. Bernardo O’Higgins 3363, Casilla de correo 10233, Santiago (Chile)

    2013-12-25

    Highlights: •Study of phase evolution of elemental powders Mg and Cu by mechanical alloying. •The presence of an amorphous precursor which crystallizes to Mg{sub 2}Cu can be observed. •Establishing the sequence of phase transformations leading to the formation of Mg{sub 2}Cu. •The feasibility to obtain Mg{sub 2}Cu by means two possible routes has been established. -- Abstract: Phase evolution during mechanical alloying (MA) of elemental Mg and Cu powders and their subsequent heat treatment is studied. Elemental Mg and Cu powders in a 2:1 atomic ratio were mechanically alloyed in a SPEX 8000D mill using a 10:1 ball-to-powder ratio. X-ray diffraction (XRD) shows that the formation of the intermetallic Mg{sub 2}Cu takes place between 3 and 4 h of milling, although traces of elemental Cu are still present after 10 h of milling. The thermal behavior of different powder mixtures was evaluated by differential scanning calorimetry (DSC). The combination of DSC, heat treatment and XRD has shown a sequence of phase transformations that results in the intermetallic Mg{sub 2}Cu from an amorphous precursor. This amorphous phase is converted into Mg{sub 2}Cu by heating at low temperature (407 K). Short MA times and the formation of the amorphous precursor, together with its subsequent transformation into Mg{sub 2}Cu at low temperatures; represent an advantageous alternative route for its preparation.

  5. Mechanical properties and microstructures of dental cast Ti-6Nb-4Cu, Ti-18Nb-2Cu, and Ti-24Nb-1Cu alloys.

    Science.gov (United States)

    Takahashi, Masatoshi; Kikuchi, Masafumi; Takada, Yukyo

    2016-01-01

    The mechanical properties -tensile strength, yield strength, elongation after fracture, and Vickers hardness- and alloy phases of the dental cast alloys Ti-6%Nb-4%Cu, Ti-18%Nb-2%Cu, and Ti-24%Nb-1%Cu were investigated. Ti-6%Nb-4%Cu consisted of a single α-phase, while Ti-18%Nb-2%Cu and Ti-24%Nb-1%Cu consisted of α- and β-phases. The tensile strengths, yield strengths, and hardnesses of these alloys were higher than those of Ti-5%Cu and Ti-30%Nb; however, their breaking elongations were smaller. These differences in the mechanical properties are attributable to solid-solution strengthening or to precipitation strengthening by the dual-phase (α+β) structure. Thus, Ti-Nb-Cu alloys are suitable for use in high-strength dental prostheses, such as implantretained superstructures and narrow-diameter implants. PMID:27477221

  6. Strain heterogeneity and the production of coarse grains in mechanically alloyed iron-based PM2000 alloy

    OpenAIRE

    Capdevila, Carlos; Miller, U; Jelenak, H; Bhadeshia, H. K. D. H.

    2001-01-01

    Mechanically alloyed iron-based ODS alloys have the potential for application in heat exchangers for biomass processing, with gas operating temperatures and pressures of approximately 1100°C and 15–30 bar. The yttria dispersion in such alloys improves the high-temperature creep and stress rupture life. The elevated temperature strength is enhanced by the development of a coarse-grained microstructure during recrystallisation. Factors controlling the evolution of this desirable micros...

  7. The effect of minor additions of titanium on the fracture toughness of Fe-12Ni alloys at 77K

    Science.gov (United States)

    Conrad, H.; Yin, C.; Sargent, G.

    1978-01-01

    Titanium additions ranging from 0.18 to 0.99 atomic percent and heat treatments of 2 hours at 550, 685 and 820 C respectively followed by a water quench were considered. Cubic and rectangular shaped inclusions were noted in the SEM fractographs of the alloys with the Ti additions. A fine precipitate was observed by TEM for the Fe-12Ni-0.18Ti alloys heat treated at 550 C; this precipitate was not observed for the 685 and 820 C heat treatments of the same alloy. Auger mappings of the fracture surfaces indicated a weak to moderate association of the interstitials C, N and O with Ti, the degree of which depended on the particular interstitial and the heat treatment temperature.

  8. Tribological property and wear mechanism of undercooled Ni-Pb monotectic alloys

    Institute of Scientific and Technical Information of China (English)

    谢辉; 杨根仓; 郝维新; 喇培清; 刘维民; 许丽君

    2004-01-01

    The tribological properties of Ni-31.440% Pb monotectic alloys were measured by using a SRV reciprocating tribo-tester. The effects of load, sliding speed and melt undercooling on wear rate of the sample were investigated. The worn surface of Ni-31.44%Pb was examined using scanning electron microscope (SEM) and X-ray photoelectron spectroscope (XPS). The results show that the wear properties of the samples undercooled by 80 K and 310 K are obviously superior, which is attributed to more efficient transfer of Pb from the bulk material to the worn surface. The lubricating film is identified as a mixture of Ni2 O3 and PbO by XPS analysis. At the same load and sliding speed, the predominant wear mechanisms can be identified as oxidative wear for the lower and larger undercooling,and plastic deformation and fracture for the medium undercooling.

  9. Texture evolution and mechanical anisotropy of biomedical hot-rolled Co-Cr-Mo alloy.

    Science.gov (United States)

    Mori, Manami; Yamanaka, Kenta; Sato, Shigeo; Chiba, Akihiko

    2015-11-01

    Crystallographic textures and their effect on the mechanical anisotropy of a hot-rolled biomedical Co-Cr-Mo alloy were investigated. The hot-rolled Co-28Cr-6Mo-0.13N (mass%) alloy examined here exhibited a monotonic strength increment following hot-rolling reduction, eventually reaching a 0.2% proof stress of 1400 MPa while maintaining acceptable ductility (>10%). The dominant hot-rolling texture was a brass-type component, which is characterized by the alloy's peculiarly low stacking fault energy (SFE) even at hot rolling temperatures, although the minor peaks of the near copper component were also identified. However, because of the onset of dynamic recrystallization (DRX) during the hot rolling process, the texture intensity was relatively weak even after 90% hot rolling, although the grain refinement originating from the DRX was not significant (the "less active DRX" condition increased the strain accumulation during the process, resulting in high-strength samples). The weakened texture development resulted in negligible in-plane anisotropy for the hot-rolled specimen strength, when the specimens were tensile strained in the rolling direction (RD) and transverse direction (TD). The elongation-to-failure, however, exhibited a difference with respect to the tensile loading axis. It is suggested that the ductility anisotropy is closely related to a strain-induced γ (fcc) → ε (hcp) martensitic transformation during tensile loading, resulting in a difference in the proportion of quasi-cleavage fracture surfaces. The obtained results will be helpful in the development of high-strength Co-Cr-Mo alloy plates and sheets, and have implications regarding plastic deformation and texture evolution during the hot rolling of non-conventional metallic materials with low SFE at elevated temperatures, where planar dislocation slips of Shockley partial dislocations and thermally activated process interplay.

  10. Microstructure and mechanical properties of the pressure die cast magnesium alloy AZ91D after long-term thermal exposure

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    The thermal resistance of the pressure die cast magnesium alloy AZ91D is yet not investigated sufficiently. In order to assess the effect of a thermal exposure on the microstructural stability and the mechanical properties, the alloy AZ91D is subjected to a long-term annealing for 1 000 h at 80 ℃, 100 ℃, 120 ℃, 150 ℃, 180 ℃ and 200 ℃. After the annealing, the microstructural appearance of the material is investigated by light and scanning electron microscopy and compared with the as-cast condition. Furthermore, tensile tests, hardness measurements and fracture toughness tests are carried out and the measured values are discussed on the basis of the microstructural changes. The results reveal the distinct correlation between the microstructural changes, especially the precipitation of discontinuous and continuous β-particles (Mg17Al12), and the mechanical properties.

  11. Comparison of mechanical and corrosion behaviour of Alloy 800 H and the new alloy AC 66

    International Nuclear Information System (INIS)

    In coal gasification plants based on nuclear process heat, materials are subjected to high temperature corrosion in process gas atmosphere at 750 to 900 deg. C. The process gas consists of steam, CO, CH4, CO2 and, depending on the gasified coal, low or high H2S-concentrations. The service problems can be divided as follows: 1. Gas-metal interaction: (a) high temperature corrosion; (b) sulphidation; (c) carburization; (d) internal oxidation or internal sulphidation. 2. Ash (slag)-metal interaction: (a) corrosion in molten salts; (b) erosion. 3. Mechanical loading: (a) embrittlement; (b) thermal fluctuations/strain fluctuations; (c) low cycle fatigue; (d) high temperature creep. Therefore materials for heat exchangers must be resistant to these types of high temperature corrosion and they should also have adequate creep rupture strength. Some commercial alloys and various model alloys were exposed to a process gas atmosphere to determine the corrosion behaviour and also stressed mechanically to investigate the interaction of high temperature creep behaviour and corrosion. The tests were carried out for a total period of 10,000 h and specimens were taken out after periods of 1000, 3000, 5000 and 10,000 h. A programme for the development of alloys was started with the aim of optimizing the chemical composition resulting in a good high temperature corrosion resistance and adequate mechanical properties, particularly high creep strength. However, the material must be such that it can be deformed to tubes. Compared with Incoloy 800, one of the new and optimized model alloys (30-32% Ni, 25-27% Cr, and Ce, Fe-balance) exhibits a very good corrosion resistance even when sulphur rich coal is gasified. The creep rupture strength at 900 deg. C is in the range of the creep strength for Incoloy 800. 29 figs

  12. Constraint corrected fracture mechanics in structural integrity assessment

    Energy Technology Data Exchange (ETDEWEB)

    Laukkanen, A.; Wallin, K. [VTT Industrial Systems, Espoo (Finland)

    2004-07-01

    Specimen size, crack depth and loading conditions may affect the materials fracture toughness. In order to safeguard against these geometry effects, fracture toughness testing standards prescribe the use of highly constrained deep cracked bend specimens having a sufficient size to guarantee conservative fracture toughness values. One of the more advanced testing standards, for brittle fracture, is the Master Curve standard ASTM E1921, which is based on technology developed at VTT Industrial Systems. When applied to a structure with low constraint geometry, the standard fracture toughness estimates may lead to strongly over-conservative estimate of structural performance. In some cases this may lead to unnecessary repairs or even to an early 'retirement' of the structure. In the case of brittle fracture, essentially three different methods to quantify constraint have been proposed, J-small scale yielding correction (SSYC), Q-parameter and the T{sub stress}. (orig.)

  13. Structural Analysis and Magnetic Properties of FeCo Alloys Obtained by Mechanical Alloying

    Directory of Open Access Journals (Sweden)

    F. Sánchez-De Jesús

    2016-01-01

    Full Text Available A systematic study on the structural and magnetic properties of Fe100-xCox alloys (10mechanical alloying is presented. Elemental powders of Fe and Co mixed in an adequate weight ratio were milled at room temperature in a shaker mixer mill using vials and balls of hardened steel as milling media with a ball : powder weight ratio of 12 : 1. The mixtures were milled for 3 h. The results show that, after milling, for almost all the composition (up to x=60, solid solutions based on bcc structures were obtained. For Co-rich alloys (x≥70, different phases were found, revealing the formation of a metastable intermetallic phase (FeCo, wairauite together with fcc-Co and hcp-Co phases. The specific saturation magnetization increases by increasing Co content, reaching a maximum value of 225 emu/g for hcp-Fe70Co30, and then it shows a diminution up to 154 emu/g for bcc-Fe30Co70. All studied alloys (Fe100-xCox present low coercivity, in the range from 0 to 65 Oe, which is lower than reported. The coercivity increases with the increment in Co, reaching a maximum of 64.1 Oe for Fe40Co60. After that, the coercivity falls up to 24.5 Oe for Co-rich alloys, which make them a very low coercive material.

  14. Isolated posterior malleolus fracture: a rare injury mechanism

    OpenAIRE

    Serbest, Sancar; Tiftikçi, Uğur; Tosun, Haci Bayram; Kesgin, Engin; KARATAŞ, Metin

    2015-01-01

    Sprain of the ankle is undoubtedly a common injury during athletic activity, and the sprain can be also associated with fracture of the ankle. Isolated posterior malleolus fracture is a very rare condition, which is usually missed. Here, we are presenting a 37 years old female patient, who suffered injury secondary pressing on brake pedal during collision in a traffic accident. Clinical evaluation is based on Ottawa Ankle Rules and a fracture is diagnosed; patient is started on daily activiti...

  15. Flow and Fracture of Bulk Metallic Glass Alloys and their Composites

    Energy Technology Data Exchange (ETDEWEB)

    Flores, K M; Suh, D; Howell, R; Asoka-Kumar, P; Dauskardt, R H

    2001-06-20

    The fracture and plastic deformation mechanisms of a Zr-Ti-Ni-Cu-Be bulk metallic glass and a composite utilizing a crystalline reinforcement phase are reviewed. The relationship between stress state, free volume and shear band formation are discussed. Positron annihilation techniques were used to confirm the predicted increase in free volume after plastic straining. Strain localization and failure were examined for a wide range of stress states. Finally, methods for toughening metallic glasses are considered. Significant increases in toughness are demonstrated for a composite bulk metallic glass containing a ductile second phase which stabilizes shear band formation and distributes plastic deformation.

  16. Evolution of microstructures and mechanical properties during dissimilar electron beam welding of titanium alloy to stainless steel via copper interlayer

    Energy Technology Data Exchange (ETDEWEB)

    Tomashchuk, I., E-mail: iryna.tomashchuk@u-bourgogne.fr [Laboratoire Interdisciplinaire Carnot de Bourgogne, UMR 6303 CNRS-Université de Bourgogne, 12 rue de la Fonderie, F-71200 Le Creusot (France); Sallamand, P. [Laboratoire Interdisciplinaire Carnot de Bourgogne, UMR 6303 CNRS-Université de Bourgogne, 12 rue de la Fonderie, F-71200 Le Creusot (France); Belyavina, N. [Department of Physics, Taras Shevchenko University, 2, Glushkov Avenue, 03022 Kiev (Ukraine); Pilloz, M. [Laboratoire Interdisciplinaire Carnot de Bourgogne, UMR 6303 CNRS-Université de Bourgogne, 12 rue de la Fonderie, F-71200 Le Creusot (France)

    2013-11-15

    The influence of operational parameters on the local phase composition and mechanical stability of the electron beam welds between titanium alloy and AISI 316L austenitic stainless steel with a copper foil as an intermediate layer has been studied. It was shown that two types of weld morphologies could be obtained depending on beam offset from the center line. Beam shift toward the titanium alloy side results in formation of a large amount of the brittle TiFe{sub 2} phase, which is located at the steel/melted zone interface and leads to reducing the mechanical resistance of the weld. Beam shift toward the steel side inhibits the melting of titanium alloy and, so, the formation of brittle intermetallics at the titanium alloy/melted zone interface. Mechanical stability of the obtained junctions was shown to depend on the thickness of this intermetallic layer. The fracture zone of the weld was found to be a mixture of TiCu (3–42 wt%), TiCu{sub 1−x}Fe{sub x} (x=0.72–0.84) (22–68 wt%) and TiCu{sub 1−x}Fe{sub x} (x=0.09–0.034) (0–22 wt%). In order to achieve the maximal ultimate tensile strength (350 MPa), the diffusion path length of Ti in the melted zone should be equal to 40–80 µm.

  17. Isolated posterior malleolus fracture: a rare injury mechanism.

    Science.gov (United States)

    Serbest, Sancar; Tiftikçi, Uğur; Tosun, Haci Bayram; Kesgin, Engin; Karataş, Metin

    2015-01-01

    Sprain of the ankle is undoubtedly a common injury during athletic activity, and the sprain can be also associated with fracture of the ankle. Isolated posterior malleolus fracture is a very rare condition, which is usually missed. Here, we are presenting a 37 years old female patient, who suffered injury secondary pressing on brake pedal during collision in a traffic accident. Clinical evaluation is based on Ottawa Ankle Rules and a fracture is diagnosed; patient is started on daily activities at postoperative Week 8. This study aims to emphasize that Ottawa Ankle Rules are usually efficient for evaluating fractures of ankle, but clinicians should always make a detailed physical examination. PMID:26097627

  18. Study on mechanical parameters of fractured rock masses

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    The equivalent strength parameters of fractured rock masses are prerequisite for stability analysis of geotechnical engineering projects constructed in fractured rock masses which are encountered frequently in western china.Based on generated mesh of fractured rock masses,combined with statistic damage constitutive model of intact rock and damage model of structural plane,progressive failure of fractured rock masses is studied using finite element method(FEM) .Furthermore,Scale effect and anisotropy of compressive strength of fractured rock masses are studied.Study results show that the strength decreases and tend towards stability rapidly from intact rock to fractured rock masses,and the anisotropy of strength of fractured rock masses is not significant.At last,based on numerical simulation conducted on 10 m scale rock masses under different confining pressures,the equivalent strength parameters of fractured rock masses are gained and the results are compared with Hoek-Brown criteria.The method developed is helpful for determination of strength parameters of fractured rock masses.

  19. Strengthening mechanism of steels treated by barium-bearing alloys

    Institute of Scientific and Technical Information of China (English)

    Zhouhua Jiang; Yang Liu

    2008-01-01

    The deoxidation, desulfurization, dephosphorization, microstructure, and mechanical properties of steels treated by barium-bearing alloys were investigated in laboratory and by industrial tests. The results show that barium takes part in the deoxidation reaction at the beginning of the experiments, generating oxide and sulfide compound inclusions, which easily float up from the molten steel, leading to the rapid reduction of total oxygen content to a very low level. The desulfurization and dephosphorization capabilities of calcium-bearing alloys increase with the addition of barium. The results of OM and SEM observations and mechanical property tests show that the structure of the steel treated by barium-bearing alloys is refined remarkably, the iamellar thickness of pearlitic structure decreases, and the pearlitic morphology shows clustering distribution. Less barium exists in steel substrate and the enrichment of barium-bearing precipitated phase mostly occurs in grain boundary and phase boundary, which can prevent the movement of grain boundary and dislocation during the heat treatment and the deformation processes. Therefore, the strength and toughness of barium-treated steels are improved by the effect of grain-boundary strengthening and nail-prick dislocation.

  20. Effect of heat treatment on Fe-B-Si-Nb alloy powder prepared by mechanical alloying

    Directory of Open Access Journals (Sweden)

    Rodrigo Estevam Coelho

    2005-06-01

    Full Text Available The effect of heat treatment on crystallization behavior of Fe73.5B15Si10Nb1.5 alloy powder prepared by mechanical alloying was studied. The powder samples were prepared by mechanical alloying (MA and for different milling times (1, 5, 25, 70 and 100 hours. Crystalline powders of iron, boron, silicon and niobium were sealed with tungsten carbide balls in a cylindrical vial under nitrogen atmosphere. The ball-to-powder weight ratio was 20 to 1. A Fritsch Pulverizette 5 planetary ball mill was used for MA the powders at room temperature and at 250 rpm. To study the microstructural evolution, a small amount of powder was collected after different milling times and examined by X-ray diffraction, using CuKalpha radiation (lambda = 0.15418 nm. The crystallization behavior was studied by differential thermal analysis, from 25 up to 1000 °C at a heating rate of 25 °C min-1.

  1. Effect of Yttrium and Cerium Addition on Microstructure and Mechanical Properties of AM50 Magnesium Alloy

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    To develop magnesium alloy with low cost, high strength and excellent elevated temperature properties, effect of Y and Ce addition on microstructure and mechanical properties of AM50 magnesium alloy was studied. Result showed that addition of small amount of Y and Ce to AM50 alloys resulted in refinement of microstructure. Owing to the improvement of microstructure, the mechanical properties of alloys at both ambient and elevated temperature were increased. AM50 alloy containing 0.6%Ce-0.3%Y (mass fraction) had good refinement effect and relatively ideal mechanical properties.

  2. Fracture toughness of shape memory alloy actuators: effect of transformation-induced plasticity

    Science.gov (United States)

    Jape, Sameer; Solomou, Alexandros; Baxevanis, Theocharis; Lagoudas, Dimitris C.

    2016-04-01

    Numerical analysis of static cracks in a plane strain center-cracked infinite medium shape memory alloy (SMA) panel subjected to cyclic thermal variations and a constant mechanical load is conducted using the finite element method. In solid-state SMA actuators, permanent changes in the material's microstructure in the form of dislocations are caused during cyclic thermomechanical loading, leading to macroscopic irreversible strains, known as transformation induced plastic (TRIP) strains. The influence of these accumulated TRIP strains on mechanical fields close to the crack tip is investigated in the present paper. Virtual crack growth technique (VCCT) in ABAQUS FEA suite is employed to calculate the crack tip energy release rate and crack is assumed to be stationary (or static) so that the crack tip energy release rate never reaches the material specific critical value. Increase in the crack tip energy release rate is observed during cooling and its relationship with accumulation of TRIP due to cyclic transformation is studied.

  3. EFFECTS OF ALTERNATIVE RAW MATERIALS AND VARYING RESIN CONTENT ON MECHANICAL AND FRACTURE MECHANICAL PROPERTIES OF PARTICLE BOARD

    Directory of Open Access Journals (Sweden)

    Jörn Rathke,

    2012-05-01

    Full Text Available Particle boards were produced from different types of wood particles, i.e. spruce, recovered particles, willow, poplar, and locust. Effects of raw material, as well as varying resin content on mechanical and fracture mechanical properties were investigated. For the analysis of mechanical properties, specific fracture energy, stress intensity factors, and the industrial European standard methods internal bond strength according to EN 319 and bending strength according to EN 310 were used. The total fracture energy was measured, and the stress intensity factor was calculated by means of data achieved through finite element simulations. Results of the fracture energy analysis were compared to internal bond strength (IB and bending strength. While IB and the modulus of elasticity (MOE showed a high variability, data scattering for fracture energy tests and modulus of rupture (MOR were smaller, which are due to significant differences between the resin contents of the various board types.

  4. Effects of high-energy electro-pulsing treatment on microstructure, mechanical properties and corrosion behavior of Ti–6Al–4V alloy

    International Nuclear Information System (INIS)

    The effect of electro-pulsing treatment (EPT) on the microstructure, mechanical properties and corrosion behavior of cold-rolled Ti–6Al–4V alloy strips was investigated in this paper. It was found that the elongation to failure of materials obtains a noticeable enhancement with increased EPT processing time while slightly sacrificing strength. Fine recrystallized grains and the relative highest elongation to failure (32.5%) appear in the 11 second-EPT samples. Grain coarsening and decreased ductility were brought in with longer EPT duration time. Fracture surface analysis shows that transition from intergranular brittle facture to transgranular dimple fracture takes place with an increase in processing time of EPT. Meanwhile, corrosion behavior of titanium alloys is greatly improved with increased EPT processing time, which is presented by polarization test and surface observation with the beneficial effect of forming a protective anatase-TiO2 film on the surface of alloys. The rapid recrystallization behavior and oxide formation of the titanium alloy strip under EPTs are attributed to the enhancement of nucleation rate, atomic diffusion and oxygen migration resulting from the coupling of the thermal and athermal effects. - Highlights: • Rapid recrystallization of Ti alloy occurred under electro-pulsing treatment (EPT). • Heterogeneous effect was found in agreement with selective effect of EPT. • Ductility of the materials was greatly improved to 32.5% by EPT. • Anti-corrosion performance was improved by forming moderate oxidation layer. • EPT oxidation kinetics of Ti alloy strips was put forward

  5. Effects of high-energy electro-pulsing treatment on microstructure, mechanical properties and corrosion behavior of Ti–6Al–4V alloy

    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); Wang, Lingsheng [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@sz.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); Song, Guolin [Advanced Materials Institute, Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055 (China)

    2015-04-01

    The effect of electro-pulsing treatment (EPT) on the microstructure, mechanical properties and corrosion behavior of cold-rolled Ti–6Al–4V alloy strips was investigated in this paper. It was found that the elongation to failure of materials obtains a noticeable enhancement with increased EPT processing time while slightly sacrificing strength. Fine recrystallized grains and the relative highest elongation to failure (32.5%) appear in the 11 second-EPT samples. Grain coarsening and decreased ductility were brought in with longer EPT duration time. Fracture surface analysis shows that transition from intergranular brittle facture to transgranular dimple fracture takes place with an increase in processing time of EPT. Meanwhile, corrosion behavior of titanium alloys is greatly improved with increased EPT processing time, which is presented by polarization test and surface observation with the beneficial effect of forming a protective anatase-TiO{sub 2} film on the surface of alloys. The rapid recrystallization behavior and oxide formation of the titanium alloy strip under EPTs are attributed to the enhancement of nucleation rate, atomic diffusion and oxygen migration resulting from the coupling of the thermal and athermal effects. - Highlights: • Rapid recrystallization of Ti alloy occurred under electro-pulsing treatment (EPT). • Heterogeneous effect was found in agreement with selective effect of EPT. • Ductility of the materials was greatly improved to 32.5% by EPT. • Anti-corrosion performance was improved by forming moderate oxidation layer. • EPT oxidation kinetics of Ti alloy strips was put forward.

  6. Fracture mechanics parameters for cracks on a slightly undulating interface

    Science.gov (United States)

    Yang, Lin; Qu, Jianmin

    1993-11-01

    Typical bimaterial interfaces are nonplanar due to surface facets or roughness. Crack-tip stress fields of an interface crack must be influenced by nonplanarity of the interface. Consequently, interface toughness is affected. The crack-tip fields of a finite crack on an elastic/rigid interface with periodic undulation are studied. Particular emphasis is given to the fracture mechanics parameters, such as the stress intensity factors, crack-tip energy release rate, and crack-tip mode mixity. When the amplitude of interface undulation is very small relative to the crack length (which is the case for rough interfaces), asymptotic analysis is used to convert the nonplanarity effects into distributed dislocations located on the planar interface. Then, the resulting stress fields near the crack tip are obtained by using the Fourier integral transform method. It is found that the stress fields at the crack tip are strongly influenced by nonplanarity of the interface. Generally speaking, nonplanarity of the interface tends to shield the crack tip by reducing the crack-tip stress concentration.

  7. Comparison of GTN Model and XFEM for Fracture Mechanics Analysis

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Sung Jun; Chang, Yoon Suk [Kyung Hee University, Youngin (Korea, Republic of)

    2014-10-15

    The simulation of discontinuities such as stationary and growing cracks by conventional finite element(FE) method is limited for bulk materials due to the necessity of computationally expensive remeshing process and high mesh densities. Accordingly, several advanced finite element techniques have been introduced to model crack propagation without remeshing. However, there are still many modeling uncertainties relating to arbitrary discontinuities in respect of accuracy and efficiency. In order to overcome this problem, eXtended Finite Element Method(XFEM) which allows the presence of discontinuities in elements by enriching degrees of freedom(DOF) with special displacement function was developed by Belytschko and Black. In this paper, the XFEM was applied to tensile tests for API X65 steel to implement crack simulation based on fracture mechanics analyses and verify through the comparison with the preceding study using Gurson-Tvergaard-Needleman (GTN) model. In this paper, a comprehensive numerical analyses were carried out to verify an adequacy of the XFEM by comparing its results with those obtained from experiments and GTN model. The XFEM has an efficiency due to the accessibility to the corresponding parameters such as cohesive strength, cohesive energy and critical separation. Also, visualization of crack simulation has an advantage compared to the GTN model. In these respects, the XFEM can be widely used in industrial fields and further analyses for bulk materials are needed.

  8. Effects of Strain Rates on Mechanical Properties and Fracture Mechanism of DP780 Dual Phase Steel

    Science.gov (United States)

    Li, Shengci; Kang, Yonglin; Zhu, Guoming; Kuang, Shuang

    2015-06-01

    The mechanical properties of DP780 dual phase steel were measured by quasi-static and high-speed tensile tests at strain rates between 0.001 and 1000 s-1 at room temperature. The deformation and fracture mechanisms were analyzed by observation of the tensile fracture and microstructure near the fracture. Dynamic factor and feret ratio quantitative methods were applied to study the effect of strain rate on the microstructure and properties of DP780 steel. The constitutive relation was described by a modified Johnson-Cook and Zerilli-Armstrong model. The results showed that the strain rate sensitivity of yield strength is bigger than that of ultimate tensile strength; as strain rate increased, the formation of microcracks and voids at the ferrite/martensite interface can be alleviated; the strain rate effect is unevenly distributed in the plastic deformation region. Moreover, both models can effectively describe the experimental results, while the modified Zerilli-Armstrong model is more accurate because the strain-hardening rate of this model is independent of strain rate.

  9. Chemically- and mechanically-mediated influences on the transport and mechanical characteristics of rock fractures

    Energy Technology Data Exchange (ETDEWEB)

    Min, K.-B.; Rutqvist, J.; Elsworth, D.

    2009-02-01

    A model is presented to represent changes in the mechanical and transport characteristics of fractured rock that result from coupled mechanical and chemical effects. The specific influence is the elevation of dissolution rates on contacting asperities, which results in a stress- and temperature-dependent permanent closure. A model representing this pressure-dissolution-like behavior is adapted to define the threshold and resulting response in terms of fundamental thermodynamic properties of a contacting fracture. These relations are incorporated in a stress-stiffening model of fracture closure to define the stress- and temperature-dependency of aperture loss and behavior during stress and temperature cycling. These models compare well with laboratory and field experiments, representing both decoupled isobaric and isothermal responses. The model was applied to explore the impact of these responses on heated structures in rock. The result showed a reduction in ultimate induced stresses over the case where chemical effects were not incorporated, with permanent reduction in final stresses after cooling to ambient conditions. Similarly, permeabilities may be lower than they were in the case where chemical effects were not considered, with a net reduction apparent even after cooling to ambient temperature. These heretofore-neglected effects may have a correspondingly significant impact on the performance of heated structures in rock, such as repositories for the containment of radioactive wastes.

  10. Solid state amorphisation in binary systems prepared by mechanical alloying

    Energy Technology Data Exchange (ETDEWEB)

    Gonzalez, G., E-mail: gemagonz@ivic.v [Lab. Ciencia e Ing. de Materiales, Instituto Venezolano de Investigaciones Cientificas, IVIC, Caracas (Venezuela, Bolivarian Republic of); Sagarzazu, A. [Lab. Ciencia e Ing. de Materiales, Instituto Venezolano de Investigaciones Cientificas, IVIC, Caracas (Venezuela, Bolivarian Republic of); Bonyuet, D. [Instituto de Investigacion en Biomedicina y Ciencias Aplicadas, Universidad de Oriente, Cumana (Venezuela, Bolivarian Republic of); D' Angelo, L. [UNEXPO, Universidad Experimental Politecnica Luis Caballero Mejias, Dpto. Ing. Mecanica (Venezuela, Bolivarian Republic of); Villalba, R. [Lab. Ciencia e Ing. de Materiales, Instituto Venezolano de Investigaciones Cientificas, IVIC, Caracas (Venezuela, Bolivarian Republic of)

    2009-08-26

    In the present work a detailed study of amorphisation in different systems prepared by mechanical alloying under the same experimental conditions was carried out, milling up to 50 and 100 h in some cases. The systems studied were: AlTi, AlNi, AlFe, FeNi, FeCo, NiMo, NiW, NiCo, MoW, CoMo. These systems were chosen to study the effect of Al-transition metal, transition metal-transition metal and also systems with large and small negative heat of mixing, different and similar crystal structures, atomic sizes and diffusion coefficients. Calculations based on the Miedema model for alloy formation and amorphisation on all the alloys studied were performed. The experimental results from X-ray diffraction and transmission electron microscopy showed that the systems based on Fe (FeNi, FeCo and FeAl) did not amorphised, even after milling for 100 h, and formed a stable solid solution with a nanometric grain size of 7 nm. The systems NiMo, NiW, MoW and CoMo (systems with small negative heat of mixing), showed amorphisation after 50 h of milling. NiAl and TiAl form an intermediate amorphous phase after around 20 h of milling and with further milling they recrystallize into a fcc solid solution. Agreement between the theoretical calculations based on the Miedema model and the experimental results was found in most of the systems.

  11. Mechanism of Bainite Nucleation in Steel, Iron and Copper Alloys

    Institute of Scientific and Technical Information of China (English)

    Mokuang KANG; Ming ZHU; Mingxing ZHANG

    2005-01-01

    During the incubation period of isothermal treatment(or aging) within the bainitic transformation temperature range in a salt bath (or quenching in water) immediately after solution treatment, not only are the defects formed at high temperatures maintained, but new defects can also be generated in alloys, iron alloys and steels. Due to the segregation of the solute atoms near defects through diffusion, this leads to non-uniform distributions of solute atoms in the parent phase with distinct regions of both solute enrichment and solute depletion. It is proposed that when the Ms temperature at the solute depleted regions is equal to or higher than the isothermal (or aged) temperature,nucleation of bainite occurs within these solute depleted regions in the manner of martensitic shear. Therefore it is considered that, at least in steel, iron and copper alloy systems, bainite is formed through a shear mechanism within solute depleted regions, which is controlled and formed by the solute atoms diffusion in the parent phase.

  12. Microstructure and highly enhanced mechanical properties of fine-grained tungsten heavy alloy after one-pass rapid hot extrusion

    International Nuclear Information System (INIS)

    Research highlights: → The strength of fine-grained WHAs is as high as 1570 MPa after rapid hot extrusion. → Plastic deformation of fine-grained WHAs during rapid hot extrusion is uniform. → Slight dynamic recovery-recrystallization process occurred during hot extrusion. → Fine grains and reserved numerous dislocations contribute to the high strength. - Abstract: One-pass rapid hot extrusion of fine-grained 93W-4.9Ni-2.1Fe-0.03Y (wt.%) alloy with an average grain size of ∼10 μm was performed at 1150 deg. C with an extrusion speed of ∼100 mm/s and an extrusion ratio of ∼3.33:1. Microstructure and mechanical properties of the as-extruded alloy were investigated. The results show that the tungsten particles of the as-extruded alloy are severely elongated along the extrusion direction and the aspect ratios of these elongated particles are 5-8. Three crystallographic textures {0 0 1}, {1 1 1} and {1 1 0} arose after rapid hot extrusion and the total volume fraction of these texture components was approximately 30%. Many lath-shaped subgrains with a small misorientation and low density dislocations could be observed in tungsten phase and γ-(Ni, Fe) phase respectively. These microstructure characteristics indicate that slight dynamic recovery-recrystallization process occurred during rapid hot extrusion. In contrast to as-sintered alloy, the as-extruded alloy possessed much higher ultimate tensile strength and hardness (HRC) but a relatively lower ductility (1570 MPa vs. 995 MPa; HRC48 vs. HRC29 and 6.5% vs. 24%). In addition, the fracture morphology shows that the predominant failure mode for the as-extruded alloy is cleavage failure of the tungsten particles, while the ductile rupture of the γ-(Ni, Fe) phase that can be frequently observed in the as-sintered alloy nearly disappeared after rapid hot extrusion.

  13. Deformation and Failure Mechanisms of Shape Memory Alloys

    Energy Technology Data Exchange (ETDEWEB)

    Daly, Samantha Hayes [Univ. of Michigan, Ann Arbor, MI (United States)

    2015-04-15

    The goal of this research was to understand the fundamental mechanics that drive the deformation and failure of shape memory alloys (SMAs). SMAs are difficult materials to characterize because of the complex phase transformations that give rise to their unique properties, including shape memory and superelasticity. These phase transformations occur across multiple length scales (one example being the martensite-austenite twinning that underlies macroscopic strain localization) and result in a large hysteresis. In order to optimize the use of this hysteretic behavior in energy storage and damping applications, we must first have a quantitative understanding of this transformation behavior. Prior results on shape memory alloys have been largely qualitative (i.e., mapping phase transformations through cracked oxide coatings or surface morphology). The PI developed and utilized new approaches to provide a quantitative, full-field characterization of phase transformation, conducting a comprehensive suite of experiments across multiple length scales and tying these results to theoretical and computational analysis. The research funded by this award utilized new combinations of scanning electron microscopy, diffraction, digital image correlation, and custom testing equipment and procedures to study phase transformation processes at a wide range of length scales, with a focus at small length scales with spatial resolution on the order of 1 nanometer. These experiments probe the basic connections between length scales during phase transformation. In addition to the insights gained on the fundamental mechanisms driving transformations in shape memory alloys, the unique experimental methodologies developed under this award are applicable to a wide range of solid-to-solid phase transformations and other strain localization mechanisms.

  14. Formation of nano sized ODS clusters in mechanically alloyed NiAl-(Y,Ti,O) alloys

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Yong Deog; Bae Seong Man [KHNP Central Research Institute, Daejeon (Korea, Republic of); Wirth, Brian D. [Department of Nuclear Engineering, Univ. of California, Berkeley (United States)

    2012-10-15

    The Reactor Pressure Vessel (RPV) is the key component in determining the lifetime of nuclear power plants because it is subject to the significant aging degradation by irradiation and thermal aging, and there is no practical method for replacing that component. Advanced reactors with much larger capacity than current reactor require the usage of higher strength materials inevitably. The SA508 Gr.4N Ni-Cr-Mo low alloy steel, in which Ni and Cr contents are larger than in conventional RPV steels, could be a promising RPV material offering improved strength and toughness from its tempered martensitic microstructure. For a structural integrity of RPV, the effect of neutron irradiation on the material property is one of the key issues. The RPV materials suffer from the significant degradation of transition properties by the irradiation embrittlement when its strength is increased by a hardening mechanism. Therefore, the potential for application of SA508 Gr.4N steel as the structural components for nuclear power reactors depends on its ability to maintain adequate transition properties against the operating neutron does. However, it is not easy to fine the data on the irradiation effect on the mechanical properties of SA508 Gr.4N steel. In this study, the irradiation embrittlement of SA508 Gr.4N Ni-Cr-Mo low alloy steel was evaluated by using specimens irradiated in research reactor. For comparison, the variations of mechanical properties by neutron irradiation for commercial SA508 Gr.3 Mn-Mo-Ni low alloy steel were also evaluated.

  15. Research advances in fracturing mechanism of amorphous materials

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    @@ The fracture behavior of brittle materials is a timehonored problem. Archeologists discover that prehistoric people created their primitive tools using this behavior. During the Stone Age, for example, they made simple wooden butchery implements by taking advantage of a sharp edge caused by the brittle fracture on flint. According to archeologists, the application of brittle fracture to the tool-making was one of monumental inventions to mark the very beginning of human civilization.Afterwards, ancient potters succeeded in decorating their works by having the surface of pottery inlaid with cracks and fissures.

  16. Effect of strain rate on shear properties and fracture characteristics of DP600 and AA5182-O sheet metal alloys

    Science.gov (United States)

    Rahmaan, Taamjeed; Butcher, Cliff; Abedini, Armin; Worswick, Michael

    2015-09-01

    Shear tests were performed at strain rates ranging from quasi-static (.01 s-1) to 600 s-1 for DP600 steel and AA5182-O sheet metal alloys at room temperature. A miniature sized shear specimen was modified and validated in this work to perform high strain rate shear testing. Digital image correlation (DIC) techniques were employed to measure the strains in the experiments, and a criterion to detect the onset of fracture based on the hardening rate of the materials is proposed. At equivalent strains greater than 20%, the DP600 and AA5182 alloys demonstrated a reduced work hardening rate at elevated strain rates. At lower strains, the DP600 shows positive rate sensitivity while the AA5182 was not sensitive to strain rate. For both alloys, the equivalent fracture strain and elongation to failure decreased with strain rate. A conversion of the shear stress to an equivalent stress using the von Mises yield criterion provided excellent agreement with the results from tensile tests at elevated strain rates. Unlike the tensile test, the shear test is not limited by the onset of necking so the equivalent stress can be determined over a larger range of strain.

  17. Effect of strain rate on shear properties and fracture characteristics of DP600 and AA5182-O sheet metal alloys

    Directory of Open Access Journals (Sweden)

    Rahmaan Taamjeed

    2015-01-01

    Full Text Available Shear tests were performed at strain rates ranging from quasi-static (.01 s−1 to 600 s−1 for DP600 steel and AA5182-O sheet metal alloys at room temperature. A miniature sized shear specimen was modified and validated in this work to perform high strain rate shear testing. Digital image correlation (DIC techniques were employed to measure the strains in the experiments, and a criterion to detect the onset of fracture based on the hardening rate of the materials is proposed. At equivalent strains greater than 20%, the DP600 and AA5182 alloys demonstrated a reduced work hardening rate at elevated strain rates. At lower strains, the DP600 shows positive rate sensitivity while the AA5182 was not sensitive to strain rate. For both alloys, the equivalent fracture strain and elongation to failure decreased with strain rate. A conversion of the shear stress to an equivalent stress using the von Mises yield criterion provided excellent agreement with the results from tensile tests at elevated strain rates. Unlike the tensile test, the shear test is not limited by the onset of necking so the equivalent stress can be determined over a larger range of strain.

  18. Microstructure and Mechanical Tensile Properties of a VT6 Alloy Manufactured by Selective Laser Melting

    Science.gov (United States)

    Nazarova, T. I.; Imayev, V. M.; Imayev, R. M.; Pavlinich, S. P.

    2015-10-01

    The microstructure and tensile properties of a material manufactured from the VT6 titanium alloy by the method of selective laser melting (SLM) are investigated. In the initial state, the microstructure of the SLMmaterial consists of columnar β-grains elongated in the direction of heat sink, which were transformed during cooling into the acicular martensite α'-phase. A heat treatment, including two-stage annealing at 900 and 700°C, transfers the microstructure into equilibrium, two-phase state, with the elongation of β-grains being retained. Mechanical tensile tests were performed in the direction normal to the layer packing formed during SLM. It is found that strength properties of the workpiece manufactured by the SLM process are similar to those of the VT6 alloy manufactured by conventional casting, while its room-temperature ductility is noticeably higher. Deformation-relief studies of the specimen surface demonstrated that the layers formed during SLM affect neither the development of deformation nor fracture of the material.

  19. PECULARITIES OF COMPOSITE POWDERS PLASMA SPRAYING PREPARED BY MECHANICAL ALLOYING

    OpenAIRE

    Kudinov, V.; Pekshev, P.; Tcherniakov, S.; Kondratenko, L.

    1990-01-01

    In the present paper the main advantages of mechanical alloying compared to the other methods of composite powders preparing are discussed from the point of view both of powder quality and structure and properties of sprayed coatings. As an example on the base of NiCr-ZrO2-, NiCr-Cr2C3-, W-Cu- compositions it is shown, that prepared powders are characterized by high particles composition homogeneity, fine disperse components distribution in particles volume, high values of bound strength and ...

  20. Structure changes and mechanical properties of laser alloyed magnesium cast alloys

    OpenAIRE

    W. Kwaśny; T. Tański,; Sz. Malara; J. Domagała; L.A. Dobrzański

    2009-01-01

    Purpose: The aim of this work was to investigate structure and mechanical properties of the MCMgAl12Zn1 casting magnesium alloys after laser treatment. The laser treatment was carried out using a high power diode laser (HPDL).Design/methodology/approach: The laser processing of TiC, WC, SiC particles in MCMgAl12Zn1 and the resulted microstructures and properties are discussed in this paper. The resulting microstructure in the modified surface layer was examined. Phase composition was...

  1. The effect of mechanical alloying on microstructure and mechanical properties of MoSi2 prepared by spark plasma sintering

    International Nuclear Information System (INIS)

    Highlights: • Powders of Mo and Si according to MoSi2 stoichiometry were mechanically alloyed. • The as milled powder mixture was sintered using spark plasma sintering. • We investigated the microstructure and mechanical properties of samples. - Abstract: In this research the effect of mechanical alloying on the in situ synthesis–sintering behavior and mechanical properties of MoSi2 has been investigated. The Mo and Si powders according to MoSi2 stoichiometric composition were mechanically alloyed at different times. Then, the powders were subjected to spark plasma sintering process for preparing monolithic MoSi2. X-ray diffraction pattern of the sintered samples showed that by increasing the mechanical alloying time, Mo5Si3 has been formed. It seems that the formation of Mo5Si3 is due to the effect of mechanical alloying on microstructure and thermodynamic condition of the reaction

  2. Effect of aging on the fracture mechanics of unsaturated polyester based on recycled PET polymer concrete

    International Nuclear Information System (INIS)

    This research investigates, the fracture mechanics (toughness and energy), at early ages, of polymer concrete made with unsaturated polyester resin as binder. The results indicate that the fracture parameters (toughness and energy) decrease and the brittleness increases with the age of the polymer concrete.

  3. Effect of aging on the fracture mechanics of unsaturated polyester based on recycled PET polymer concrete

    Energy Technology Data Exchange (ETDEWEB)

    Reis, J.M.L., E-mail: jreis@mec.uff.br [Theoretical and Applied Mechanics Laboratory - LMTA, Mechanical Engineering Post Graduate Program - PGMEC, Universidade Federal Fluminense - UFF, Rua Passo da Patria, 156 Bl. E Sala 216, Niteroi, RJ (Brazil)

    2011-03-15

    This research investigates, the fracture mechanics (toughness and energy), at early ages, of polymer concrete made with unsaturated polyester resin as binder. The results indicate that the fracture parameters (toughness and energy) decrease and the brittleness increases with the age of the polymer concrete.

  4. Research progress in mechanism of traumatic brain injury affecting speed of fracture healing

    Institute of Scientific and Technical Information of China (English)

    ZHAO Xiao-gang; ZHAO Guang-feng; MA Yue-feng; JIANG Guan-yu

    2007-01-01

    @@ In patients who have sustained traumatic brain injury with associated extremity fracture, there is often a clinical perception that the rate of new bone formation around the fracture site increases. 1 An overgrowth of callus is observed and ectopic ossification even occurs in the muscle,2 but the mechanism remains unclear.

  5. The improvement of cryogenic mechanical properties of Fe-12 Mn and Fe-8 Mn alloy steels through thermal/mechanical treatments

    Science.gov (United States)

    Hwang, S. K.; Morris, J. W., Jr.

    1979-01-01

    An investigation has been made to improve the low temperature mechanical properties of Fe-8Mn and Fe-12Mn-0.2 Ti alloy steels. A reversion annealing heat treatment in the two-phase (alpha + gamma) region following cold working has been identified as an effective treatment. In an Fe-12Mn-0.2Ti alloy a promising combination of low temperature (-196 C) fracture toughness and yield strength was obtained by this method. The improvement of properties was attributed to the refinement of grain size and to the introduction of a uniform distribution of retained austenite (gamma). It was also shown that an Fe-8Mn steel could be grain-refined by a purely thermal treatment because of its dislocated alpha-prime martensitic structure and absence of epsilon martensite. As a result, a significant reduction of ductile to brittle transition temperature was obtained.

  6. The WST method, a fracture mechanics test method for FRC

    DEFF Research Database (Denmark)

    Lofgren, I.; Stang, Henrik; Olesen, John Forbes

    2008-01-01

    -crack opening (sigma-w) relationships have been determined for each mix and test method. For the two WST specimen sizes, there is no apparent difference either in the number of fibres (per cm(2)) crossing the fracture plane or in the fracture properties. The major factor contributing to the scatter in the test......The applicability of the wedge-splitting test method (WST), for determining fracture properties of fibre-reinforced concrete, is discussed. Experimental results, using the WST method, are compared with results from uniaxial tension tests (UTT) and three-point bending tests (3PBT) for five different...... results is believed to be related to the variation in the number of fibres across the fracture plane. Furthermore, the inverse analyses indicate no systematic differences in the determined parameters between two WST specimens or between the WST and the 3PBT....

  7. Verification of a fracture mechanics concept for the cleavage fracture behaviour of RAFM steels using local fracture criteria. Final report for task TW2-TTMS-005/D3

    International Nuclear Information System (INIS)

    An effort is made within the European Fusion Technology Programme framework to obtain a fracture mechanics description of the material behaviour in the ductile to brittle transition-regime using local fracture criteria. In a companion report, the necessary procedural steps towards the development of an according design code scheme were described. The present report contains application examples and verification results of the different procedural steps and identifies limitations of the approach for the two reference RAFM steels F82Hmod and EUROFER97. (orig.)

  8. Mechanical Responses of Superlight β-Based Mg-Li-Al-Zn Wrought Alloys under Resonance

    Science.gov (United States)

    Song, Jenn-Ming; Lin, Yi-Hua; Su, Chien-Wei; Wang, Jian-Yih

    2009-05-01

    To extend the application of lightweight Mg alloys in the automotive industry, this study suggests a β-based Mg-Li alloy (LAZ1110) with superior vibration fracture resistance by means of material design. In the cold-rolled state, a strengthened β matrix by the additions of Al and Zn, as well as intergranular platelike α precipitates, which are able to stunt the crack growth, contributes to a comparable vibration life with commercial Mg-Al-Zn alloys under a similar strain condition.

  9. A numerical model of hydro-thermo-mechanical coupling in a fractured rock mass

    Energy Technology Data Exchange (ETDEWEB)

    Bower, K.M.

    1996-06-01

    Coupled hydro-thermo-mechanical codes with the ability to model fractured materials are used for predicting groundwater flow behavior in fractured aquifers containing thermal sources. The potential applications of such a code include the analysis of groundwater behavior within a geothermal reservoir. The capability of modeling hydro-thermo systems with a dual porosity, fracture flow model has been previously developed in the finite element code, FEHM. FEHM has been modified to include stress coupling with the dual porosity feature. FEHM has been further developed to implicitly couple the dependence of fracture hydraulic conductivity on effective stress within two dimensional, saturated aquifers containing fracture systems. The cubic law for flow between parallel plates was used to model fracture permeability. The Bartin-Bandis relationship was used to determine the fracture aperture within the cubic law. The code used a Newton Raphson iteration to implicitly solve for six unknowns at each node. Results from a model of heat flow from a reservoir to the moving fluid in a single fracture compared well with analytic results. Results of a model showing the increase in fracture flow due to a single fracture opening under fluid pressure compared well with analytic results. A hot dry rock, geothermal reservoir was modeled with realistic time steps indicating that the modified FEHM code does successfully model coupled flow problems with no convergence problems.

  10. Radiology of Fractures in Intoxicated Emergency Department Patients: Locations, Mechanisms, Presentation, and Initial Interpretation Accuracy.

    Science.gov (United States)

    Morita, Yuka; Nozaki, Taiki; Starkey, Jay; Okajima, Yuka; Ohde, Sachiko; Matsusako, Masaki; Yoshioka, Hiroshi; Saida, Yukihisa; Kurihara, Yasuyuki

    2015-06-01

    The purpose of this study was to investigate the relationship of alcohol intoxication to time-to-presentation following injury, fracture type, mechanism of injury leading to fracture, and initial diagnostic radiology interpretation performance of emergency physicians versus diagnostic radiologists in patients who present to the emergency department (ED) and are subsequently diagnosed with fracture. Medical records of 1286 patients who presented to the ED and were diagnosed with fracture who also underwent plain film or computed tomography (CT) imaging were retrospectively reviewed. The subjects were divided into intoxicated and sober groups. Patient characteristics, injury-to-presentation time, fracture location, and discrepancies between initial clinical and radiological evaluations were compared. Of 1286 subjects, 181 patients were included in the intoxicated group. Only intoxicated patients presented with head/neck fractures more than 24 hours after injury. The intoxicated group showed a higher rate of head/neck fractures (skull 23.2% vs 5.8%, face and orbit 30.4% vs 9.5%; P spinal fractures during this period. Alcohol-related injuries are more often associated with head/neck fractures but less extremity injuries. The rate of fractures missed by emergency physicians but later diagnosed by radiologists was the same in intoxicated and sober patients. PMID:26091471

  11. Micro-mechanical analysis and modelling of the behavior and brittle fracture of a french 16MND5 steel: role of microstructural heterogeneities

    International Nuclear Information System (INIS)

    Reactor Pressure Vessel is the second containment barrier between nuclear fuel and the environment. Electricite de France's reactors are made with french 16MND5 low-alloyed steel (equ. ASTM A508 Cl.3). Various experimental techniques (scanning electron microscopy, X-ray diffraction...) are set up in order to characterize mechanical heterogeneities inside material microstructure during tensile testing at different low temperatures [-150 C;-60 C]. Heterogeneities can be seen as the effect of both 'polycrystalline' and 'composite' microstructural features. Interphase (until 150 MPa in average between ferritic and bainitic macroscopic stress state) and intra-phase (until 100 MPa in average between ferritic orientations) stress variations are highlighted. Modelling involves micro-mechanical description of plastic glide, mean fields models and realistic three-dimensional aggregates, all put together inside a multi-scale approach. Calibration is done on macroscopic stress-strain curves at different low temperatures, and modelling reproduces experimental stress heterogeneities. This modelling allows to apply a local micro-mechanical fracture criterion for crystallographic cleavage. Deterministic computations of time to fracture for different carbides random selection provide a way to express probability of fracture for the elementary volume. Results are in good agreement with hypothesis made by local approach to fracture. Hence, the main difference is that no dependence to loading nor microstructure features is supposed for probability of fracture on the representative volume: this dependence is naturally introduced by modelling. (author)

  12. Analysis of seismic sources for different mechanisms of fracture growth for microseismic monitoring applications

    International Nuclear Information System (INIS)

    We have developed and illustrated an approach for geomechanic modeling of elastic wave generation (microsiesmic event occurrence) during incremental fracture growth. We then derived properties of effective point seismic sources (radiation patterns) approximating obtained wavefields. These results establish connection between geomechanic models of hydraulic fracturing and microseismic monitoring. Thus, the results of the moment tensor inversion of microseismic data can be related to different geomechanic scenarios of hydraulic fracture growth. In future, the results can be used for calibrating hydrofrac models. We carried out a series of numerical simulations and made some observations about wave generation during fracture growth. In particular when the growing fracture hits pre-existing crack then it generates much stronger microseismic event compared to fracture growth in homogeneous medium (radiation pattern is very close to the theoretical dipole-type source mechanism)

  13. Analysis of seismic sources for different mechanisms of fracture growth for microseismic monitoring applications

    Energy Technology Data Exchange (ETDEWEB)

    Duchkov, A. A., E-mail: DuchkovAA@ipgg.sbras.ru [Trofimuk Institute of Petroleum Geology and Geophysics SB RAS, Novosibirsk, 630090 (Russian Federation); Novosibirsk State University, Novosibirsk, 630090 (Russian Federation); Stefanov, Yu. P., E-mail: stefanov@ispms.tsc.ru [Trofimuk Institute of Petroleum Geology and Geophysics SB RAS, Novosibirsk, 630090 (Russian Federation)

    2015-10-27

    We have developed and illustrated an approach for geomechanic modeling of elastic wave generation (microsiesmic event occurrence) during incremental fracture growth. We then derived properties of effective point seismic sources (radiation patterns) approximating obtained wavefields. These results establish connection between geomechanic models of hydraulic fracturing and microseismic monitoring. Thus, the results of the moment tensor inversion of microseismic data can be related to different geomechanic scenarios of hydraulic fracture growth. In future, the results can be used for calibrating hydrofrac models. We carried out a series of numerical simulations and made some observations about wave generation during fracture growth. In particular when the growing fracture hits pre-existing crack then it generates much stronger microseismic event compared to fracture growth in homogeneous medium (radiation pattern is very close to the theoretical dipole-type source mechanism)

  14. Mechanical properties and the electronic structure of transition of metal alloys

    Science.gov (United States)

    Arsenault, R. J.; Drew, H. D.

    1977-01-01

    This interdiscipline research program was undertaken in an effort to investigate the relationship between the mechanical strength of Mo based alloys with their electronic structure. Electronic properties of these alloys were examined through optical studies, and the classical solid solution strengthening mechanisms were considered, based on size and molecular differences to determine if these mechanisms could explain the hardness data.

  15. Elements of a fracture mechanics concept for the cleavage fracture behaviour of RAFM steels using local fracture criteria. Final report for task TW1-TTMS-005/D3

    International Nuclear Information System (INIS)

    An effort is made within the European Fusion Technology Programme framework to obtain a fracture mechanics description of the material behaviour in the ductile to brittle transition-regime using local fracture criteria. This report summarizes the necessary procedural steps towards the development of an according design code scheme. It makes heavy use of available code schemes such as the British Energy R6-Code or the ESIS P6 procedure and specializes in application to the class of low activation materials that are envisaged for ITER. Through an integrated approach using a numerical stress analysis at experimentally observed fracture loads of notched tensile specimens, a statistical evaluation of cleavage fracture parameters can be performed. The report contains a description of the necessary steps for the experimental characterization and the numerical analysis as well as results for the two RAFM steel variants F82Hmod and EUROFER 97 which serve as basis for the verification of the method. Statistical inference methods are addressed as well as fractographic investigations that are essential for the verification of the approach via numerical prediction of the fracture origin distribution. Limits of the current methodology are given and topics of future research are indicated. (orig.)

  16. Moessbauer and XRD study of the Fe{sub 65}Si{sub 35} alloy obtained by mechanical alloying

    Energy Technology Data Exchange (ETDEWEB)

    Velez, G. Y., E-mail: giovelez29@gmail.com [Universidad del Valle, Departamento de Fisica (Colombia); Rodriguez, R. R. [Corporacion Universidad Autonoma de Occidente (Colombia); Melo, C. A.; Perez Alcazar, G. A.; Zamora, Ligia E.; Tabares, J. A. [Universidad del Valle, Departamento de Fisica (Colombia)

    2011-11-15

    A study was made on the alloy Fe{sub 65}Si{sub 35} using x-ray diffraction and Moessbauer spectrometry. The alloy was obtained by mechanical alloying in a high energy planetary mill, with milling times of 15, 30, 50, 75 and 100 h. The results show that in the alloys two structural phases are present, a Fe-Si BCC disordered phase and ferromagnetic, and a Fe-Si SC phase, whose nature is paramagnetic and which decreases with milling time. In the temporal evolution of the milling two stages are differentiated: one between 15 and 75 h of milling, in which silicon atoms diffuse into the bcc matrix of iron and its effect is to reduce the hyperfine magnetic field; the other, after 75 h of milling, where the alloy is consolidated, the effect of the milling is only to increase the disorder of the system, increasing the magnetic order.

  17. Mechanics and mechano-biology of fracture healing in normal and osteoporotic bone.

    Science.gov (United States)

    Augat, Peter; Simon, Ulrich; Liedert, Astrid; Claes, Lutz

    2005-03-01

    Fracture repair, which aims at regaining the functional competence of a bone, is a complex and multifactorial process. For the success of fracture repair biology and mechanics are of immense importance. The biological and mechanical environments must be compatible with the processes of cell and tissue proliferation and differentiation. The biological environment is characterized by the vascular supply and by many biochemical components, the biochemical milieu. A good vascular supply is a prerequisite for the initiation of the fracture repair process. The biochemical milieu involves complex interactions among local and systemic regulatory factors such as growth factors or cytokines. The mechanical environment is determined by the local stress and strain within the fracture. However, the local stress and strain is not accessible, and the mechanical environment, therefore, is described by global mechanical factors, e.g., gap size or interfragmentary movement. The relationship between local stress and strain and the global mechanical factors can be obtained by numerical models (Finite Element Model). Moreover, there is considerable interaction between biological factors and mechanical factors, creating a biomechanical environment for the fracture healing process. The biomechanical environment is characterized by osteoblasts and osteocytes that sense the mechanical signal and express biological markers, which effect the repair process. This review will focus on the effects of biomechanical factors on fracture repair as well as the effects of age and osteoporosis.

  18. Influence of UFG structure formation on mechanical and fatigue properties in Ti-6Al-7Nb alloy

    Science.gov (United States)

    Polyakova, V. V.; Anumalasetty, V. N.; Semenova, I. P.; Valiev, R. Z.

    2014-08-01

    Ultrafine-grained (UFG) Ti alloys have potential applications in osteosynthesis and orthopedics due to high bio-compatibility and increased weight-to- strength ratio. In current study, Ti6Al7Nb ELI alloy is processed through equal channel angular pressing-conform (ECAP-Conform) and subsequent thermomechanical processing to generate a UFG microstructure. The fatigue properties of UFG alloys are compared to coarse grained (CG) alloys. Our study demonstrates that the UFG alloys with an average grain size of ~180 nm showed 35% enhancement of fatigue endurance limit as compared to coarse-grained alloys. On the fracture surfaces of the UFG and CG samples fatigue striations and dimpled relief were observed. However, the fracture surface of the UFG sample looks smoother; fewer amounts of secondary micro-cracks and more ductile rupture were also observed, which testifies to the good crack resistance in the UFG alloy after high-cyclic fatigue tests.

  19. Fabrication and characterization of fluoridated hydroxyapatite nanopowders via mechanical alloying

    Energy Technology Data Exchange (ETDEWEB)

    Fathi, M.H. [Department of Materials Engineering, Isfahan University of Technology, Isfahan, 8415683111 (Iran, Islamic Republic of); Zahrani, E. Mohammadi [Department of Materials Engineering, Isfahan University of Technology, Isfahan, 8415683111 (Iran, Islamic Republic of)], E-mail: emohamadizahrani@gmail.com

    2009-05-05

    The aim of this work was preparation and characterization of fluoridated hydroxyapatite (FHA) nanopowders with different degrees of fluoridation via mechanical alloying (MA) method. FHA nanopowders with a chemical composition of Ca{sub 10}(PO{sub 4}){sub 6}OH{sub 2-x}F{sub x} (where x values were selected equal to 0.0, 0.5, 1.0, 1.5, and 2.0) were synthesized using a mixture of appropriate amounts of calcium hydroxide, phosphorous pentoxide, and calcium fluoride powders by 6 h of mechanical alloying at 300 rpm, using eight balls with a diameter of 20 mm, and the ball-to-powder weight ratio equal to 35:1. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, and ICP-OES analysis techniques were utilized in order to evaluate phase composition, agglomerates size distribution, morphology and particle size, functional groups, and purity of synthesized FHA nanopowders. The FTIR result combined with the X-ray diffraction indicated that single phase of homogeneous FHA with the carbonate peaks in the FTIR spectrum could be prepared after 6 h MA. TEM photomicrograph revealed that obtained powder after 6 h of MA was composed of FHA nanoparticles (35-65 nm). The results of ICP-OES analysis illustrated that synthesized nanopowder could fulfill the requirement of ASTM F1185-88 to be used as a biomaterial.

  20. Structural and magnetic relaxations of mechanically alloyed Fe-Mo

    Science.gov (United States)

    Jiraskova, Y.; Bursik, J.; Turek, I.; Cizek, J.; Prochazka, I.

    2014-10-01

    The Fe-Mo sample mechanically alloyed for 250 h under air atmosphere was exposed to a series of isothermal and isochronal treatments with the aim to follow changes in the structure and magnetic properties regarding relaxations of strains and defects and stability of chemical composition. For this purpose x-ray diffraction, positron annihilation, scanning and transmission electron microscopy, and Mössbauer spectrometry were applied and supplemented by magnetic measurements. The temperatures for the magnetic studies were selected from the thermomagnetic curve of the as-prepared sample. The time interval of isothermal treatments was chosen from 0-300 min. The Mo content in the bcc-Fe(Mo) phase has substantially exceeded the equilibrium solubility limit but it has been found to decrease under the thermal treatment which was reflected by decreasing lattice parameters. The small crystallite size of approximately 10 nm in the initial state starts to grow only after a certain amount of strains induced by severe deformation, due to mechanical alloying being released. This was also reflected in the magnetic parameters. From their time dependences at selected temperatures the characteristic relaxation times were obtained and used for a calculation of the activation enthalpy of relaxation processes.

  1. Cyclic Fatigue Fracture of Zr55Al10Ni5Cu30 Bulk Amorphous Alloy with Quenched-in Crystallites

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    The effects of quenched-in crystallites on the fracture of bulk amorphous alloys under cyclic loading condition wereinvestigated in this paper. For the fully amorphous alloy and specimen with fine crystallites the fatigue crack initiationoccurred on the surface. For the specimen with larger crystallites the crack originated from a big broken crystallitenear the surface. The average striation spacing on amorphous area is much larger than that on the crystallite.Crack initiation occurred at the crystallites is due to that the brittle crystallites broke easily under cyclic deformationcondition. The fine crystallites seemed to be protruded from the amorphous matrix and some bulges appeared onthe surface of specimen with fine crystallites under cyclic loading.

  2. Subcritical fracture propagation in rocks: An examination using the methods of fracture mechanics and non-destructive testing. Ph.D. Thesis

    Science.gov (United States)

    Swanson, P. L.

    1984-01-01

    An experimental investigation of tensile rock fracture is presented with an emphasis on characterizing time dependent crack growth using the methods of fracture mechanics. Subcritical fracture experiments were performed in moist air on glass and five different rock types at crack velocities using the double torsion technique. The experimental results suggest that subcritical fracture resistance in polycrystals is dominated by microstructural effects. Evidence for gross violations of the assumptions of linear elastic fracture mechanics and double torsion theory was found in the tests on rocks. In an effort to obtain a better understanding of the physical breakdown processes associated with rock fracture, a series of nondestructive evaluation tests were performed during subcritical fracture experiments on glass and granite. Comparison of the observed process zone shape with that expected on the basis of a critical normal principal tensile stress criterion shows that the zone is much more elongated in the crack propagation direction than predicted by the continuum based microcracking model alone.

  3. Fracture Toughness (K1C evaluation for dual phase medium carbon low alloy steels using circumferential notched tensile (CNT specimens

    Directory of Open Access Journals (Sweden)

    Kenneth Kanayo Alaneme

    2011-01-01

    Full Text Available The fracture behavior of dual phase medium carbon low alloy steels produced using two different chemical compositions (A - 0.34C, 0.75Mn, 0.12Cr, 0.13Ni steel and B - 0.3C, 0.97Mn, 0.15Cr steel was investigated using circumferential notched tensile (CNT specimens. Intercritical treatments were performed on samples with composition A by 1 austenitizing at 860 °C for 1 hour cooling in air, then treating at 770 °C for 30 minutes before oil quenching; 2 austenitizing at 860 °C for 1 hour quenching in oil, then treating at 770 °C for 30 minutes before quenching in oil; and 3 austenitizing at 860 °C for 1 hour, super-cooling to 770 °C and then quenching in oil. Samples of composition B were subjected to intercritical treatment at temperatures of 740, 760, and 780 °C for 30 minutes, followed by quenching rapidly in oil. Tensile testing was then performed on specimens without notches and the CNT specimens. It was observed that the dual phase steel produced from procedure (2 yielded a fine distribution of ferrite and martensite which gave the best combination of tensile properties and fracture toughness for composition A while the dual phase structure produced by treating at 760 °C yielded the best combination of tensile properties and fracture toughness for composition B. The fracture toughness results evaluated from the test were found to be valid (in plain strain condition and a high correlation between the fracture toughness and notch tensile strength was observed. The fracture toughness values were also found to be in close agreement with data available in literature.

  4. Thermo-hydro-mechanical processes in fractured rock formations during glacial advance

    Science.gov (United States)

    Selvadurai, A. P. S.; Suvorov, A. P.; Selvadurai, P. A.

    2014-11-01

    The paper examines the coupled thermo-hydro-mechanical (THM) processes that develop in a fractured rock region within a fluid-saturated rock mass due to loads imposed by an advancing glacier. This scenario needs to be examined in order to assess the suitability of potential sites for the location of deep geologic repositories for the storage of high-level nuclear waste. The THM processes are examined using a computational multiphysics approach that takes into account thermo-poroelasticity of the intact geological formation and the presence of a system of sessile but hydraulically interacting fractures (fracture zones). The modeling considers coupled thermo-hydro-mechanical effects in both the intact rock and the fracture zones due to contact normal stresses and fluid pressure at the base of the advancing glacier. Computational modelling provides an assessment of the role of fractures that can modify the pore pressure generation within the entire rock mass.

  5. Thermo-hydro-mechanical processes in fractured rock formations during a glacial advance

    Science.gov (United States)

    Selvadurai, A. P. S.; Suvorov, A. P.; Selvadurai, P. A.

    2015-07-01

    The paper examines the coupled thermo-hydro-mechanical (THM) processes that develop in a fractured rock region within a fluid-saturated rock mass due to loads imposed by an advancing glacier. This scenario needs to be examined in order to assess the suitability of potential sites for the location of deep geologic repositories for the storage of high-level nuclear waste. The THM processes are examined using a computational multiphysics approach that takes into account thermo-poroelasticity of the intact geological formation and the presence of a system of sessile but hydraulically interacting fractures (fracture zones). The modelling considers coupled thermo-hydro-mechanical effects in both the intact rock and the fracture zones due to contact normal stresses and fluid pressure at the base of the advancing glacier. Computational modelling provides an assessment of the role of fractures in modifying the pore pressure generation within the entire rock mass.

  6. Fracture Toughness (K1C) evaluation for dual phase medium carbon low alloy steels using circumferential notched tensile (CNT) specimens

    OpenAIRE

    Kenneth Kanayo Alaneme

    2011-01-01

    The fracture behavior of dual phase medium carbon low alloy steels produced using two different chemical compositions (A - 0.34C, 0.75Mn, 0.12Cr, 0.13Ni steel and B - 0.3C, 0.97Mn, 0.15Cr steel) was investigated using circumferential notched tensile (CNT) specimens. Intercritical treatments were performed on samples with composition A by 1) austenitizing at 860 °C for 1 hour cooling in air, then treating at 770 °C for 30 minutes before oil quenching; 2) austenitizing at 860 °C for 1 hour quen...

  7. Effect of strain rate on shear properties and fracture characteristics of DP600 and AA5182-O sheet metal alloys

    OpenAIRE

    Rahmaan Taamjeed; Butcher Cliff; Abedini Armin; Worswick and Michael

    2015-01-01

    Shear tests were performed at strain rates ranging from quasi-static (.01 s−1) to 600 s−1 for DP600 steel and AA5182-O sheet metal alloys at room temperature. A miniature sized shear specimen was modified and validated in this work to perform high strain rate shear testing. Digital image correlation (DIC) techniques were employed to measure the strains in the experiments, and a criterion to detect the onset of fracture based on the hardening rate of the materials is proposed. At equivalent st...

  8. Hardening and fracture of wedge-shaped specimens of uranium and its alloys with molybdenum and zirconium under explosive loading

    International Nuclear Information System (INIS)

    The results of studies of explosion effect on properties of uranium and its alloys, namely U-1,4Mo and U-1,4Mo-0,7Zr, are presented. The specimens in the form of a wedge were loaded with explosion of a plastic explosive layer 1,5-3,0 mm thick. The character of attenuation of shock waves caused by explosion was determined. The data on critical conditions of spall fracture initiation and on degree of shock-wave hardening of the materials were obtained

  9. Method of making quasicrystal alloy powder, protective coatings and articles

    Science.gov (United States)

    Shield, J.E.; Goldman, A.I.; Anderson, I.E.; Ellis, T.W.; McCallum, R.W.; Sordelet, D.J.

    1995-07-18

    A method of making quasicrystalline alloy particulates is disclosed wherein an alloy is superheated and the melt is atomized to form generally spherical alloy particulates free of mechanical fracture and exhibiting a predominantly quasicrystalline in the atomized condition structure. The particulates can be plasma sprayed to form a coating or consolidated to form an article of manufacture. 3 figs.

  10. Nanocrystalline Hydroxyapatite/Si Coating by Mechanical Alloying Technique

    Science.gov (United States)

    Hannora, Ahmed E.; Mukasyan, Alexander S.; Mansurov, Zulkhair A.

    2012-01-01

    A novel approach for depositing hydroxyapatite (HA) films on titanium substrates by using mechanical alloying (MA) technique has been developed. However, it was shown that one-hour heat treatment at 800°C of such mechanically coated HA layer leads to partial transformation of desired HA phase to beta-tri-calcium phosphate (β-TCP) phase. It appears that the grain boundary and interface defects formed during MA promote this transformation. It was discovered that doping HA by silicon results in hindering this phase transformation process. The Si-doped HA does not show phase transition to β-TCP or decomposition after heat treatment even at 900°C. PMID:22312324

  11. Mechanical and corrosion resistance of a new nanostructured Ti-Zr-Ta-Nb alloy.

    Science.gov (United States)

    Raducanu, D; Vasilescu, E; Cojocaru, V D; Cinca, I; Drob, P; Vasilescu, C; Drob, S I

    2011-10-01

    In this work, a multi-elementary Ti-10Zr-5Nb-5Ta alloy, with non-toxic alloying elements, was used to develop an accumulative roll bonding, ARB-type procedure in order to improve its structural and mechanical properties. The alloy was obtained by cold crucible semi-levitation melting technique and then was ARB deformed following a special route. After three ARB cycles, the total deformation degree per layer is about 86%; the calculated medium layer thickness is about 13 μm. The ARB processed alloy has a low Young's modulus of 46 GPa, a value very close to the value of the natural cortical bone (about 20 GPa). Data concerning ultimate tensile strength obtained for ARB processed alloy is rather high, suitable to be used as a material for bone substitute. Hardness of the ARB processed alloy is higher than that of the as-cast alloy, ensuring a better behaviour as a implant material. The tensile curve for the as-cast alloy shows an elastoplastic behaviour with a quite linear elastic behaviour and the tensile curve for the ARB processed alloy is quite similar with a strain-hardening elastoplastic body. Corrosion behaviour of the studied alloy revealed the improvement of the main electrochemical parameters, as a result of the positive influence of ARB processing. Lower corrosion and ion release rates for the ARB processed alloy than for the as-cast alloy, due to the favourable effect of ARB thermo-mechanical processing were obtained. PMID:21783152

  12. Effect of hot plastic deformation on microstructure and mechanical property of Mg-Mn-Ce magnesium alloy

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Hot plastic deformation was conducted using a new solid die on a Mg-Mn-Ce magnesium alloy. The results of microstructural examination through OM and TEM show that the grain size is greatly refined from 45 μm to 1.1 μm with uniform distribution due to the occurrence of dynamic recrystallization. The grain refinement and high angle grain boundary formation improve the mechanical properties through tensile testing with the strain rate of 1.0× 10-4 s-1 at room temperature and Vickers microhardness testing. The maximum values of tensile strength, elongation and Vickers microhardness are increased to 256.37 MPa,17.69% and HV57.60, which are 21.36%, 133.80% and 20.50% more than those of the as-received Mg-Mn-Ce magnesium alloy,respectively. The SEM morphologies of tensile fractured surface indicate that the density and size of ductile dimples rise with accumulative strain increasing. The mechanism of microstructural evolution and the relationship between microstructure and mechanical property of Mg-Mn-Ce magnesium alloy processed by this solid die were also analyzed.

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

    Science.gov (United States)

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

    2014-08-01

    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.

  14. Influence of niobium addition on the high temperature mechanical properties of a centrifugally cast HP alloy

    International Nuclear Information System (INIS)

    The influence of niobium addition on the mechanical properties at high temperature of HP alloy has been investigated. Two HP alloys were centrifugally cast with a similar chemical composition differing only in the niobium content. Low strain rate high temperature tensile tests and creep-rupture tests were performed in the range of 900–1100 °C, and the results compared between the alloys. According to the results, the high temperature mechanical behavior of both alloys is controlled by several factors like solid solution, network of eutectic carbides, intradendritic precipitation and dendrite spacing. A significant increase in the mechanical properties for the HP alloy with niobium addition was found within the temperature range of 900–1050 °C. Beyond this temperature the mechanical behavior of both alloys is basically the same

  15. Influence of niobium addition on the high temperature mechanical properties of a centrifugally cast HP alloy

    Energy Technology Data Exchange (ETDEWEB)

    Andrade, A.R., E-mail: arandrade@gmail.com [Department of Materials Engineering, Federal University of São Carlos, Rod. Washington Luiz, km 235, São Carlos, SP (Brazil); Department of Research and Development, ENGEMASA – Engineering and Materials Ltda., Rua Ernesto Cadinalli, 303, São Carlos, SP (Brazil); Bolfarini, C. [Department of Materials Engineering, Federal University of São Carlos, Rod. Washington Luiz, km 235, São Carlos, SP (Brazil); Ferreira, L.A.M.; Vilar, A.A.A. [Department of Research and Development, ENGEMASA – Engineering and Materials Ltda., Rua Ernesto Cadinalli, 303, São Carlos, SP (Brazil); Souza Filho, C.D.; Bonazzi, L.H.C. [Department of Research and Development, ENGEMASA – Engineering and Materials Ltda., Rua Ernesto Cadinalli, 303, São Carlos, SP (Brazil); Department of Materials, Aeronautical and Automotive Engineering, University of São Paulo, Av. Trabalhador Sancarlense, 400, São Carlos, SP (Brazil)

    2015-03-25

    The influence of niobium addition on the mechanical properties at high temperature of HP alloy has been investigated. Two HP alloys were centrifugally cast with a similar chemical composition differing only in the niobium content. Low strain rate high temperature tensile tests and creep-rupture tests were performed in the range of 900–1100 °C, and the results compared between the alloys. According to the results, the high temperature mechanical behavior of both alloys is controlled by several factors like solid solution, network of eutectic carbides, intradendritic precipitation and dendrite spacing. A significant increase in the mechanical properties for the HP alloy with niobium addition was found within the temperature range of 900–1050 °C. Beyond this temperature the mechanical behavior of both alloys is basically the same.

  16. Control of bcc and fcc phase formation during mechanical alloying of Ti-Al-Nb

    International Nuclear Information System (INIS)

    A Ti-Al-Nb alloy was processed by ball milling or mechanical alloying in a high energy shaker mill in an attempt to produce a fine grained BCC alloy. Previous studies of this alloy resulted in the formation of an amorphous phase followed by a 100% FCC alloy (probably a nitride phase). In the present study, ball milling was conducted in two different laboratories with nitride- and oxide-free starting powders in each location. Two types of starting powders were used: pre-alloyed powders and mixed elemental powders of the same composition. The production of a 90% BCC/10% FCC alloy was accomplished indicating that the production of 100% BCC alloy may be possible. The methods used to prevent the formation of nitrides and oxides of these very reactive constituents during mechanical alloying are discussed and x-ray diffraction results of the mechanically alloyed powders milled by various techniques are presented. The most important factor leading to amorphization and FCC phase formation appears to be contamination associated with periodic sampling of the alloy during ball milling even when dry, inert gas gloveboxes are used for powder transfer

  17. The effect of Si additions on the sintering and sintered microstructure and mechanical properties of Ti-3Ni alloy

    International Nuclear Information System (INIS)

    Highlights: → Silicon is a potent sintering aid for Ti-Ni alloys revealed by predictions and confirmed by experiments. → The addition of Si should be limited to ≤1% to avoid coarse Ti5Si3 phase and ensure good ductility. → Liquid forms during heating at ∼988 deg. C due to reactions between Si and Ni and Ni and Ti. → Silicon can be a unique addition to PM Ti alloys for significantly improved mechanical properties. - Abstract: Thermodynamic predictions suggest that silicon has the potential to be a potent sintering aid for Ti-Ni alloys because small additions of Si lower the solidus of Ti-Ni alloys appreciably (>200 deg. C by 1 wt.% Si). A systematic study has been made of the effect of Si on the sintering of a Ti-3Ni alloy at 1300 deg. C. The sintered density increased from 91.8% theoretical density (TD) to 99.2%TD with increasing Si from 0% to 2%. Microstructural examination reveals that coarse particles and/or continuous networks of Ti5Si3 form along grain boundaries when the addition of Si exceeds 1%. The grain boundary Ti5Si3 phase leads to predominantly intergranular fracture and therefore a sharp decrease in ductility concomitant with increased tensile strengths. The optimum addition of Si is proposed to be ≤1%. Dilatometry experiments reveal different shrinkage behaviours with respect to different Si contents. Interrupted differential scanning calorimetry (DSC) experiments and corresponding X-ray diffraction (XRD) analyses clarify the sequence of phase formation during heating. The results provide a useful basis for powder metallurgy (PM) Ti alloy design with Si.

  18. Effects of low-dose microwave on healing of fractures with titanium alloy internal fixation: an experimental study in a rabbit model.

    Directory of Open Access Journals (Sweden)

    Dongmei Ye

    Full Text Available BACKGROUND: Microwave is a method for improving fracture repair. However, one of the contraindications for microwave treatment listed in the literature is surgically implanted metal plates in the treatment field. The reason is that the reflection of electromagnetic waves and the eddy current stimulated by microwave would increase the temperature of magnetic implants and cause heat damage in tissues. Comparing with traditional medical stainless steel, titanium alloy is a kind of medical implants with low magnetic permeability and electric conductivity. But the effects of microwave treatment on fracture with titanium alloy internal fixation in vivo were not reported. The aim of this article was to evaluate the security and effects of microwave on healing of a fracture with titanium alloy internal fixation. METHODS: Titanium alloy internal fixation systems were implanted in New Zealand rabbits with a 3.0 mm bone defect in the middle of femur. We applied a 30-day microwave treatment (2,450MHz, 25W, 10 min per day to the fracture 3 days after operation. Temperature changes of muscle tissues around implants were measured during the irradiation. Normalized radiographic density of the fracture gap was measured on the 10th day and 30th day of the microwave treatment. All of the animals were killed after 10 and 30 days microwave treatment with histologic and histomorphometric examinations performed on the harvested tissues. FINDINGS: The temperatures did not increase significantly in animals with titanium alloy implants. The security of microwave treatment was also supported by histology of muscles, nerve and bone around the implants. Radiographic assessment, histologic and histomorphometric examinations revealed significant improvement in the healing bone. CONCLUSION: Our results suggest that, in the healing of fracture with titanium alloy internal fixation, a low dose of microwave treatment may be a promising method.

  19. Fracture Mechanics Analyses of the Slip-Side Joggle Regions of Wing-Leading-Edge Panels

    Science.gov (United States)

    Raju, Ivatury S.; Knight, Norman F., Jr.; Song, Kyongchan; Phillips, Dawn R.

    2011-01-01

    The Space Shuttle wing-leading edge consists of panels that are made of reinforced carbon-carbon. Coating spallation was observed near the slip-side region of the panels that experience extreme heating. To understand this phenomenon, a root-cause investigation was conducted. As part of that investigation, fracture mechanics analyses of the slip-side joggle regions of the hot panels were conducted. This paper presents an overview of the fracture mechanics analyses.

  20. Fracture mechanics analyses of the slip-side joggle regions of wing-leading-edge panels

    Directory of Open Access Journals (Sweden)

    Kyongchan Song

    2011-01-01

    Full Text Available The Space Shuttle wing-leading edge consists of panels that are made of reinforced carbon-carbon. Coating spallation was observed near the slip-side region of the panels that experience extreme heating. To understand this phenomenon, a root-cause investigation was conducted. As part of that investigation, fracture mechanics analyses of the slip-side joggle regions of the hot panels were conducted. This paper presents an overview of the fracture mechanics analyses.

  1. Electrochemical hydrogen storage properties of La0.95Mg2.05Ni9 alloy prepared by mechanical alloying

    Institute of Scientific and Technical Information of China (English)

    蒙冕武; 刘心宇; 成钧; 周怀营

    2004-01-01

    The structure, microstructure, thermal stability and hydriding characteristics of amorphous La0.95-Mg2.05 Ni9 have been investigated with differential thermal analysis, X-ray diffraction, scanning electron microscopy and battery test. It is found that the increase in mechanical alloying time leads to enhancement in thermal stabilities of amorphous La0. 95 Mg2.05 Ni9 alloy. The amorphous alloy has good charge/discharge ability at room temperature (430 mA · h · g-1 ), but the discharge capacity decreases seriously during cycling tests due to the crystallization of amorphous and oxidization of magnesium on the particle surface in alkaline aqueous solution.

  2. MICROSTRUCTURAL AND MECHANICAL STUDY OF ALUMINIUM ALLOYS SUBMITTED TO DISTINCT SOAKING TIMES DURING SOLUTION HEAT TREATMENT

    Directory of Open Access Journals (Sweden)

    Valmir Martins Monteiro

    2014-12-01

    Full Text Available This work studies the microstructural characteristics and mechanical properties for different aluminium alloys (1100, 3104 and 8011 hot rolled sheets that were subjected to a solution heat treatment with distinct soaking times, in order to promote microstructural and mechanical changes on these alloys with solute fractions slightly above the maximum solubility limit. Scanning Electronic Microscopy (SEM / Energy Dispersive Spectroscopy X-Ray (EDS, X-Ray Diffraction (XRD and Hardness Tests were employed to observe the microstructural / compositional and mechanical evaluation. For the 1100 and 8011 alloys the more suitable soaking time occur between 1 and 2 hours, and for the 3104 alloy occurs between 2 and 3 hours.

  3. Mechanical Properties and Microstructures of As Printed and Heat Treated Samples of Selective Laser Melted IN625 Alloy Powder

    Directory of Open Access Journals (Sweden)

    Srinivasan Raghavan

    2015-01-01

    Full Text Available The current study focusses in evaluating the mechanical properties (yield strength, ultimate tensile strength and elongation % and microstructures of as printed and heat treated tensile samples produced by Selective Laser Melting (SLM which is an Additive Manufacturing (AM technique. The as printed IN625 alloy exhibited good mechanical properties as compared to cast and wrought alloy, owing to fast cooling rates that give very fine dendritic/cellular structures during the SLM process. Standard solutionizing and precipitation hardening treatment was given to the SLM as printed samples. The as printed sample’s ductility increased from 30% elongation to 47% elongation with small drop in tensile strength from 878MPa to 836MPa. The increase of ductility after heat treatment was evident in the change of fracture morphology from long straight striations with dimple shape ductile like features in the as printed sample to mainly dimple shaped ductile-like fracture surface in the heat treated sample as observed in the FESEM.

  4. Preparation of Plate Fe60Co8Zr10Mo5W2B15 Bulk Amorphous Alloy and Its Fracture Toughness

    Institute of Scientific and Technical Information of China (English)

    XIAO Huaxing; CHEN Guang

    2005-01-01

    With processes of arc melting, inductive melting and copper mold suction casting, a plate Fe-based bulk amorphous alloy Fe60Co8Zr10Mo5W2B15 with a thickness of 1mm was prepared. The surfaces and fractures of the cast bulk amorphous alloy were agleam and with typical metallic luster. The glass transition temperature(Tg), supercooled liquid region(△Tx)and reduced glass transition temperature(T rg)of the prepared Fe-based amorphous alloy are 884 K,63 K, and 0.611 respectively. The fracture toughness of the cast bulk amorphous alloy is at the level of 1.6 MPa·m1/2.

  5. Modelling of the Mechanical Behaviour of Ultra-Fine Grained Titanium Alloys at High Strain Rates

    OpenAIRE

    Halle, T.; Herzig, N.; Krüger, L; Meyer, L.W.; Musch, D.; Razorenov, S. V.; Skripnyak, E. G.; Skripnyak, V. A.

    2008-01-01

    Results of numerical simulations of the mechanical behaviour of coarse grained and UFG titanium alloys under quasi-static uniaxial compression and plane shock wave loading are presented in this paper. Constitutive equations predict the strain hardening behaviour, the strain rate sensitivity of the flow stress and the temperature softening of titanium alloys with a range of grain sizes from 20 µm to 100 nm. Characteristics of the mechanical behaviour of UFG a and a+ß titanium alloys in wide ra...

  6. Influence of boron addition on the grain refinement and mechanical properties of AZ91 Mg alloy

    International Nuclear Information System (INIS)

    This article reports the effect of boron addition on the grain refinement efficiency and mechanical properties of AZ91 magnesium alloy. The results show that the addition of boron in the form of Al-4B master alloy, significantly refines the grain size of AZ91 alloy. This refinement is due to the presence of AlB2 particles, which act as potential nucleants for Mg grains. Improved mechanical properties are obtained with the addition of boron due to the finer grains.

  7. The microstructure and mechanical properties of the alloy CuZn30 after recrystallizion annealing

    Directory of Open Access Journals (Sweden)

    W. Ozgowicz

    2010-05-01

    Full Text Available Purpose: The aim of the investigations is to determine the influence of the recrystallization temperature on the microstructure and mechanical properties of the brass CuZn30 subjected to cold deformation in the process of rolling at various degrees of strain.Design/methodology/approach: The brass CuZn30 was recrystallization annealed within the temperature range of 300-650°C after cold rolling with the strain of 15.8-70.2%. The tensile test was carried out by the use of universal testing machine. Metallographic observations were performed on an optical microscope and fractographic tests on a scanning electron microscope. The hardness was also measured.Findings: The analysis of the results of investigations concerning the mechanical properties permitted to determine the effect of the temperature of recrystallization annealing on the strength and plastic properties of the investigated brass, subjected to cold deformation with a varying strain in the course of rolling. The character of fracture after decohesion in the tension test was determined basing on fractographic investigations.Practical implications: An increase of the recrystallization temperature within the range of 400-650°C results in a deterioration of the mechanical properties of the brass CuZn30 and an increase of its plastic properties.Originality/value: The results of the investigation revealed the occurrence of the phenomenon of heterogeneous plastic deformation in the recrystallized alloy.

  8. Mechanical properties and fracture behavior of single-layer phosphorene at finite temperatures

    Science.gov (United States)

    Sha, Zhen-Dong; Pei, Qing-Xiang; Ding, Zhiwei; Jiang, Jin-Wu; Zhang, Yong-Wei

    2015-10-01

    Phosphorene, a new two-dimensional (2D) material beyond graphene, has attracted great attention in recent years due to its superior physical and electrical properties. However, compared to graphene and other 2D materials, phosphorene has a relatively low Young’s modulus and fracture strength, which may limit its applications due to possible structure failures. For the mechanical reliability of future phosphorene-based nanodevices, it is necessary to have a deep understanding of the mechanical properties and fracture behaviors of phosphorene. Previous studies on the mechanical properties of phosphorene were based on first principles calculations at 0 K. In this work, we employ molecular dynamics simulations to explore the mechanical properties and fracture behaviors of phosphorene at finite temperatures. It is found that temperature has a significant effect on the mechanical properties of phosphorene. The fracture strength and strain reduce by more than 65% when the temperature increases from 0 K to 450 K. Moreover, the fracture strength and strain in the zigzag direction is more sensitive to the temperature rise than that in the armchair direction. More interestingly, the failure crack propagates preferably along the groove in the puckered structure when uniaxial tension is applied in the armchair direction. In contrast, when the uniaxial tension is applied in the zigzag direction, multiple cracks are observed with rough fracture surfaces. Our present work provides useful information about the mechanical properties and failure behaviors of phosphorene at finite temperatures.

  9. Advanced ordered intermetallic alloy deployment

    Energy Technology Data Exchange (ETDEWEB)

    Liu, C.T.; Maziasz, P.J.; Easton, D.S. [Oak Ridge National Lab., TN (United States)

    1997-04-01

    The need for high-strength, high-temperature, and light-weight materials for structural applications has generated a great deal of interest in ordered intermetallic alloys, particularly in {gamma}-based titanium aluminides {gamma}-based TiAl alloys offer an attractive mix of low density ({approximately}4g/cm{sup 3}), good creep resistance, and high-temperature strength and oxidation resistance. For rotating or high-speed components. TiAl also has a high damping coefficient which minimizes vibrations and noise. These alloys generally contain two phases. {alpha}{sub 2} (DO{sub 19} structure) and {gamma} (L 1{sub 0}), at temperatures below 1120{degrees}C, the euticoid temperature. The mechanical properties of TiAl-based alloys are sensitive to both alloy compositions and microstructure. Depending on heat-treatment and thermomechanical processing, microstructures with near equiaxed {gamma}, a duplex structure (a mix of the {gamma} and {alpha}{sub 2} phases) can be developed in TiAl alloys containing 45 to 50 at. % Al. The major concern for structural use of TiAl alloys is their low ductility and poor fracture resistance at ambient temperatures. The purpose of this project is to improve the fracture toughness of TiAl-based alloys by controlling alloy composition, microstructure and thermomechanical treatment. This work is expected to lead to the development of TiAl alloys with significantly improved fracture toughness and tensile ductility for structural use.

  10. Synthesis and Characteristics of WC-Co Alloy Fabricated by Mechanical Alloying and Pressure Sintering

    Science.gov (United States)

    Isonishi, Kazuo

    In this paper, the synthesis of WC-Co alloy was investigated. Especially the formation of WC phase during the solid-phase sintering was discussed. The chemical composition of WC-Co was chosen to be WC-20vol%Co. The powder mixture of stoichiometric quantities of elemental powders was mechanical alloyed by using low-energy ball mill under an Ar atmosphere. After 1800ks milling, the X-ray diffraction profile showed only elemental W phase. At DTA runs, W2C and Co6W6C phase formed about 1140K and then transformed to WC and W3Co3C with increasing temperature. Therefore, it is considered that the WC phase synthesized at the sintering process, not milling stage like other investigations. 1800ks milled powder was consolidated by using pulse current sintering method at the temperature of 1373K. The compact consisted mainly of WC with Co and W3Co3C phases. The hardness of the compact was 1648HV and 91.8HRA. The 3-point bending strength was about 2GPa.

  11. Possibilities of mechanical properties and microstructure improvement of magnesium alloys

    OpenAIRE

    I. Juřička; L.A. Dobrzański; L. Čižek; Kocich, R.; M. Greger

    2007-01-01

    Purpose: Magnesium alloys are the very progressive materials whereon is due to improve their end-useproperties, which . Especially, wrought Mg alloys attract attention since they have more advantageous mechanicalproperties than cast Mg alloys.Design/methodology/approach: The presented article shows some specific physical-metallurgicalcharacteristics of magnesium alloys of the AZ91 kind after hot forming. Special attention has been focused onthe analysis of mutual relations existing between th...

  12. Fracture Mechanics Analysis of a Modified TSD Specimen

    DEFF Research Database (Denmark)

    Berggreen, Christian; Carlsson, Leif A.

    2008-01-01

    The Tilted Sandwich Debond (TSD) specimen has been recognized as a viable candidate for characterization of the face/core fracture resistance. Analysis, however, shows that the range of phase angles that can be realized by altering the tilt angle is quite limited. A parametric study however shows...

  13. Simulation of crack propagation in fiber-reinforced concrete by fracture mechanics

    International Nuclear Information System (INIS)

    Mode I crack propagation in fiber-reinforced concrete (FRC) is simulated by a fracture mechanics approach. A superposition method is applied to calculate the crack tip stress intensity factor. The model relies on the fracture toughness of hardened cement paste (KIC) and the crack bridging law, so-called stress-crack width (σ-δ) relationship of the material, as the fundamental material parameters for model input. As two examples, experimental data from steel FRC beams under three-point bending load are analyzed with the present fracture mechanics model. A good agreement has been found between model predictions and experimental results in terms of flexural stress-crack mouth opening displacement (CMOD) diagrams. These analyses and comparisons confirm that the structural performance of concrete and FRC elements, such as beams in bending, can be predicted by the simple fracture mechanics model as long as the related material properties, KIC and (σ-δ) relationship, are known

  14. Correlating laboratory observations of fracture mechanical properties to hydraulically-induced microseismicity in geothermal reservoirs.

    Energy Technology Data Exchange (ETDEWEB)

    Stephen L. Karner, Ph.D

    2006-02-01

    To date, microseismicity has provided an invaluable tool for delineating the fracture network produced by hydraulic stimulation of geothermal reservoirs. While the locations of microseismic events are of fundamental importance, there is a wealth of information that can be gleaned from the induced seismicity (e.g. fault plane solutions, seismic moment tensors, source characteristics). Closer scrutiny of the spatial and temporal evolution of seismic moment tensors can shed light on systematic characteristics of fractures in the geothermal reservoir. When related to observations from laboratory experiments, these systematic trends can be interpreted in terms of mechanical processes that most likely operate in the fracture network. This paper reports on mechanical properties that can be inferred from observations of microseismicity in geothermal systems. These properties lead to interpretations about fracture initiation, seismicity induced after hydraulic shut-in, spatial evolution of linked fractures, and temporal evolution of fracture strength. The correlations highlight the fact that a combination of temperature, stressing rate, time, and fluid-rock interactions can alter the mechanical and fluid transport properties of fractures in geothermal systems.

  15. Relationship between silver concentration with microstructural and mechanical properties of rolled AlZn alloy

    International Nuclear Information System (INIS)

    The relationship of Ag addition on microstructural and mechanical properties of rolled AlZn alloy was investigated. AlZn alloys were prepared by metal mould casting method and the Ag addition was done by Vortex technique. Microstructural characterization of AlZnAg specimens was analyzed by means of X-ray diffraction, scanning electron microscopy and transmission electron microscopy. Results show that the phases of the as-cast state alloy are solid solution zinc-rich hexagonal close-packed (hcp) crystal structure, named η-phase and α-Al solid solution with Zn dissolved into the matrix. The silver concentration in AlZn alloy influences the volume of AgZn3 precipitates. The mechanical properties, especially the flow stress and elongation of the alloy were improved by the Ag addition. The Vortex method was used in order to diminish the process cost, generating an alloy with homogenous microstructure, less casting porosity and better mechanical properties.

  16. Microstructures and mechanical properties of AZ80 alloy treated by pulsed ultrasonic vibration

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Pulsed ultrasonic field was employed in the melt of the AZ80 magnesium alloy. The effects of pulsed ultrasonic field on mierostructure and mechanical properties of AZ80 magnesium alloy were investigated. The results show that the as-cast mierostructure of the AZ80 alloy with pulsed ultrasonic treatment is significantly changed. Pulsed ultrasonic field significantly decreases the grain size, changes the morphologies of the β-Mg17Al12 phases and reduces their area fraction. It is found that pulse width of ultrasonic plays an important role on the microstrueture formation of AZ80 alloy. With increasing pulse width, grains beeome finer and more uniform. In the range of experimental parameters, the optimum pulse width for melt treatment process is found to be 210 μs. The mechanical tests show that the mechanical properties of the as-cast AZ80 magnesium alloy with pulsed ultrasonic treatment are much higher than those of AZ80 alloy without ultrasonic field.

  17. Physical and Mechanical Properties of Composites and Light Alloys Reinforced with Detonation Nanodiamonds

    Science.gov (United States)

    Sakovich, G. V.; Vorozhtsov, S. A.; Vorozhtsov, A. B.; Potekaev, A. I.; Kulkov, S. N.

    2016-07-01

    The influence of introduction of particles of detonation-synthesized nanodiamonds into composites and aluminum-base light alloys on their physical and mechanical properties is analyzed. The data on microstructure and physical and mechanical properties of composites and cast aluminum alloys reinforced with diamond nanoparticles are presented. The introduction of nanoparticles is shown to result in a significant improvement of the material properties.

  18. Influence of helium and other impurities on mechanical properties of irradiated vanadium alloys

    Energy Technology Data Exchange (ETDEWEB)

    Manichev, V.M. [Rossijskij Nauchnyj Tsentr, Moscow (Russian Federation). Kurchatovskij Inst.; Ryazonov, A.I. [Rossijskij Nauchnyj Tsentr, Moscow (Russian Federation). Kurchatovskij Inst.; Witzenburg, W. van [Netherlands Energy Research Foundation (ECN), Petten (Netherlands)

    1994-09-01

    Helium preimplantation and neutron irradiation influence on the tensile properties of the vanadium alloys in the irradiation/test temperature range of 500-800 C was investigated and principal physical mechanisms of mechanical behaviour of irradiated alloys were considered. (orig.).

  19. Prediction of selected mechanical properties of ferrous alloys through computational modeling of solidification

    Science.gov (United States)

    Guo, Xinqing

    During the last decade, the casting solidification simulation that includes the evolution of microstructure has gained significant attention. A more recent goal is the development of a predictive tool which quantitatively links the processing parameters to the microstructure and finally to the properties of castings. With the continuous improvements in the computational abilities of computers, as well as because of the rapid development of numerical methods, the prediction of microstructure of ferrous casting has become feasible. Consequently, the problem of predicting the mechanical properties of the ferrous castings becomes a problem of establishing the quantitative relationships between the mechanical properties and the microstructures of the castings. The purpose of this study is to provide a fundamental understanding of the mechanical behavior of Fe-C alloys for a rather broad range of compositions and microstructures. Microstructure-properties relationships have been developed and implemented into a computer solidification model to improve the design and production of castings. In the mechanical properties model of gray iron presented in this dissertation, the main factors controlling the tensile strength and hardness are addressed. They include graphite flake length, pearlite content and interlamellar spacing. The influence of the microstructural features of ductile iron, including graphite nodule count, nodularity, fraction of graphite, fraction of ferrite, and fraction of pearlite, on the fracture mechanism and the mechanical properties are discussed in the model for ductile iron. In the case of carbon steel, the ferrite grain size, the fraction of ferrite, and the fraction of pearlite have been found to be the significant factors controlling the properties. It is noted that the formulae used in all of the models are based on physical metallurgical principles and the coefficients for the models are obtained through multiple regression on commercial

  20. The effect of ductile phase reinforcements on dynamic fracture toughness of discontinuously reinforced aluminum (D.R.A.) alloys

    International Nuclear Information System (INIS)

    Discontinuously Reinforced Aluminum Alloys were tested under impact loading using the modified fracture bar apparatus. The apparatus is a modified version of split Hopkinson pressure bar and uses stress wave theory to give an experimental reading of Force-time history during crack initiation and propagation. Specimens of composite 840-854 materials under investigation were made of 7093 Al/SiC/15p toughened with different ductile phase -3 reinforcements. The ductile phase reinforcements were made with different Aluminum Alloys and commercially) sites, Journal of pure aluminum. The purpose of ductile phase reinforcements was to introduce impediments in the crack path thus increasing the crack propagation energy. The crack propagation velocity was measured using crack propagation gages. Stress intensity factor as a function of time was calculated to find out the peak values of K/sub dyn/(t) at crack initiation. Investigations were also made to find out the Crack Arrest Fracture Toughness. It was found out that the commercial purity aluminum reinforcements could act as crack arrestors by blunting the crack tip. (author)

  1. Mode Ⅱ fracture mechanism of direct shearing specimen with guiding grooves of rock

    Institute of Scientific and Technical Information of China (English)

    饶秋华; 孙宗颀; 王桂尧; 徐纪成; 张静宜

    2001-01-01

    Fracture mechanism of direct shear specimen with guiding grooves of rock was investigated experimentally and numerically in order to explore a favorable stress condition for creating Mode Ⅱ fracture and guide design of specimen configuration for determining Mode Ⅱ fracture toughness of rock, KⅡC. The experimental and numerical results demonstrate that Mode Ⅱ fracture can be successfully achieved in the direct shearing specimen with guiding groove because the guiding grooves added in the notch plane can generate a favorable stress condition for Mode Ⅱ fracture, i.e. tensile stress at the notch tip is completely depressed and shear stress at the notch tip is very high in the notch plane. The optimum design of the specimen configuration for KⅡC testing should aim to reduce tensile stress to be compressive stress or be lower than tensile strength and greatly increase shear stress at crack tip.

  2. A macro-mechanical constitutive model of shape memory alloys

    Institute of Scientific and Technical Information of China (English)

    ZHOU Bo; LIU YanJu; LENG JinSong; ZOU GuangPing

    2009-01-01

    It is of practical interest to establish a precise constitutive model which includes the equations de-scribing the phase transformation behaviors and thermo-mechanical processes of shape memory alloy (SMA).The microscopic mechanism of super elasticity and shape memory effect of SMA is explained based on the concept of shape memory factor defined by the author of this paper.The conventional super elasticity and shape memory effect of SMA are further unified as shape memory effect.Shape memory factor is redefined in order to make clear its physical meaning.A new shape memory evolution equation is developed to predict the phase transformation behaviors of SMA based on the differential relationship between martensitic volume fraction and phase transformation free energy and the results of DSC test.It overcomes the limitations that the previous shape memory evolution equations or phase transformation equations fail to express the influences of the phase transformation peak temperatures on the phase transformation behaviors and the transformation from twinned martensite to detwinned martensite occurring in SMA.A new macro-mechanical constitutive equation is established to predict the thermo-mechanical processes realizing the shape memory effect of SMA from the expression of Gibbs free energy.It is expanded from one-dimension to three-dimension with assuming SMA as iso-tropic material.All material constants in the new constitutive equation can be determined from mac-roscopic experiments,which makes it more easily used in practical applications.

  3. A macro-mechanical constitutive model of shape memory alloys

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    It is of practical interest to establish a precise constitutive model which includes the equations describing the phase transformation behaviors and thermo-mechanical processes of shape memory alloy (SMA). The microscopic mechanism of super elasticity and shape memory effect of SMA is explained based on the concept of shape memory factor defined by the author of this paper. The conventional super elasticity and shape memory effect of SMA are further unified as shape memory effect. Shape memory factor is redefined in order to make clear its physical meaning. A new shape memory evolution equation is developed to predict the phase transformation behaviors of SMA based on the differential relationship between martensitic volume fraction and phase transformation free energy and the results of DSC test. It overcomes the limitations that the previous shape memory evolution equations or phase transformation equations fail to express the influences of the phase transformation peak temperatures on the phase transformation behaviors and the transformation from twinned martensite to detwinned martensite occurring in SMA. A new macro-mechanical constitutive equation is established to predict the thermo-mechanical processes realizing the shape memory effect of SMA from the expression of Gibbs free energy. It is expanded from one-dimension to three-dimension with assuming SMA as isotropic material. All material constants in the new constitutive equation can be determined from macroscopic experiments, which makes it more easily used in practical applications.

  4. Microstructure and mechanical properties of vanadium alloys after thermomechanical treatments

    Energy Technology Data Exchange (ETDEWEB)

    Grinyaev, Konstantin V., E-mail: kvgrinyaev@inbox.ru; Ditenberg, Ivan A.; Smirnov, Ivan V.; Tyumentsev, Alexander N. [National Research Tomsk State University, Tomsk, 634050 (Russian Federation); Institute of Strength Physics and Materials Science SB RAS, Tomsk, 634055 (Russian Federation); Siberian Physical-Technical Institute, Tomsk, 634050 (Russian Federation); Tsverova, Anastasiya S. [National Research Tomsk State University, Tomsk, 634050 (Russian Federation); Chernov, Vyacheslav M.; Potapenko, Mikhail M. [A.A. Bochvar High Technology Research Institute of Inorganic Materials, Moscow, 123098 (Russian Federation)

    2015-10-27

    The results of investigation of dispersion strengthening effect on parameters of structural-phase states and characteristics of short-term strength and ductility of vanadium alloys of V–4Ti–4Cr, V–2.4Zr–0.25C, V–1.2Zr–8.8Cr and V–1.7Zr–4.2Cr–7.6W systems with different concentration of interstitial elements after optimized thermomechanical treatment mode were summarized. It was shown that for effective realization of dispersion strengthening by Orowan-type mechanism at least 25–50% of the initial volume fraction of coarse particles should be transformed into fine-disperse state and redistributed over the volume of material.

  5. Modification mechanism of cerium on the Al-18Si alloy

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The effect of the rare earth cerium (Ce) on the hypereutectic Al-Si alloy under different casting states have been studied by optical microscope and quantitative image analysis. It is found that the size and the quantity of primary silicon in castings decrease with the increase of added Ce in the melt. Meanwhile primary silicon changes from branched shape to fine facetted shape. Although the modification on eutectic silicon in castings also improves with the increase of added Ce in the melt, the effect of modification on eutectic silicon away from primary silicon is more obvious than that on eutectic silicon close to primary silicon. The modification mechanism was analyzed in detail by means of scanning electron microscope equipped with energy dispersive analysis of X-ray and thermodynamics analysis, which included the analysis on the change in standard Gibbs energy of reaction and reaction equilibrium.

  6. Mechanical and physical properties of refractory metals and alloys

    International Nuclear Information System (INIS)

    This paper provides some discussion of the technology of refractory metals and alloys for application to space nuclear power. This paper was designed to focus on the mechanical and physical properties of this group of materials with the intent of identifying the status of existing information. Another objective of this paper was to make some assessment of the existing property information and then to determine those measurements that must be made in order to serve the needs of the space nuclear power programs. The review portion of this paper focuses on the following properties: thermal expansion; thermal conductivity; enthalpy and heat capacity; tensile strength; stress rupture and creep strength; and fatigue strength. 62 references, 25 figures

  7. Synthesis of amorphous Ti-Al alloys by mechanical alloying of elemental powders

    Institute of Scientific and Technical Information of China (English)

    张俊红; 黄伯云; 贺跃辉; 周科朝; 刘咏

    2002-01-01

    Blended elemental powders with the nominal compositions (mole fraction, %) of Ti54Al46, Ti52Al48 and Ti50Al50 were mechanically alloyed in a planetary ball milling system for up to 100h.The structure evolution in these powders was characterized by scanning electron microscope, X-ray diffraction and differential thermal a nalysis techniques. It was found that elemental powders were progressively trans formed into nanocrystalline Ti(Al) supersaturated solid solution, then into amor phous phase. With increasing Al content, the formation of a fully Ti(Al) supersa turated solid solution and amorphous phase were accelerated, which are attributed to the fine grain size. And the grain size condition for formation of amorpho us phase in this system is ≤16 nm.

  8. Plastic Instabilities Induced by the Portevin - Le Châtelier Effect and Fracture Character of Deformed Mg-Li Alloys Investigated Using the Acoustic Emission Method

    Directory of Open Access Journals (Sweden)

    Pawełek A.

    2016-06-01

    Full Text Available The results of the investigation of both mechanical and acoustic emission (AE behaviors of Mg4Li5Al and Mg4Li4Zn alloys subjected to compression and tensile tests at room temperature are compared with the test results obtained using the same alloys and loading scheme but at elevated temperatures. The main aim of the paper is to investigate, to determine and to explain the relation between plastic flow instabilities and the fracture characteristics. There are discussed the possible influence of the factors related with enhanced internal stresses such as: segregation of precipitates along grain boundaries, interaction of solute atoms with mobile dislocations (Cottrell atmospheres as well as dislocation pile-ups which may lead to the microcracks formation due to the creation of very high stress concentration at grain boundaries. The results show that the plastic flow discontinuities are related to the Portevin-Le Châtelier phenomenon (PL effect and they are correlated with the generation of characteristic AE pulse trains. The fractography of broken samples was analyzed on the basis of light (optical, TEM and SEM images.

  9. Potential impact of enhanced fracture-toughness data on fracture mechanics assessment of PWR vessel integrity for pressurized thermal shock

    Energy Technology Data Exchange (ETDEWEB)

    Dickson, T.L.; Theiss, T.J.

    1991-01-01

    The Heavy Section Steel Technology (HSST) Program is involved with the generation of enhanced fracture-initiation toughness and fracture-arrest toughness data of prototypic nuclear reactor vessel steels. These two sets of data are enhanced because they have distinguishing characteristics that could potentially impact PWR pressure vessel integrity assessments for the pressurized-thermal shock (PTS) loading condition which is a major plant-life extension issue to be confronted in the 1990's. A series of large-scale fracture-mechanics experiments have produced crack-arrest (K{sub Ia}) data with the distinguishing characteristic that the values are considerably above 220 MPA {center dot} {radical}m. The implicit limit of the ASME Code and the limit used in the Integrated Pressurized Thermal Shock (IPTS) studies. Currently, the HSST Program is planning experiments to verify and quantify for A533B steel the distinguishing characteristic of elevated the distinguishing characteristic of elevated initiation-fracture toughness for shallow flaws which has been observed for other steels. The results of the analyses indicated that application of the enhanced K{sub Ia} data does reduce the conditional probability of failure P(F{vert bar}E); however, it does not appear to have the potential to significantly impact the results of PTS analyses. The application of enhanced fracture-initiation-toughness data for shallow flaws also reduces P(F{vert bar}E), and does appear to have a potential for significantly affecting the results of PTS analyses. 19 refs., 11 figs., 1 tab.

  10. Fracto-mechanoluminescence and mechanics of fracture of solids

    International Nuclear Information System (INIS)

    The present paper explores the correlation between fracto-mechanoluminescence and fracture of solids and thereby provides a clear understanding of the physics of fracto-mechanoluminescence. When a fluorescent or non-photoluminescent crystal is fractured impulsively by dropping a load on it, then initially the mechanoluminescence (ML) intensity increases linearly with time, attains a maximum value Im at a particular time tm and later on it decreases exponentially with time. However, when a phosphorescent crystal is fractured impulsively by dropping a load on it, then initially the ML intensity increases linearly with time, attains a maximum value Im at a particular time tm and later on it decreases initially at a fast rate and then at a slow rate. For low impact velocity the value of tm is constant, however, for higher impact velocity tm decreases logarithmally with the increasing impact velocity. Whereas the peak ML intensity Im increases linearly with the impact velocity, the total ML intensity IT, initially increases linearly with the impact velocity and then it tends to attain a saturation value for higher values of the impact velocity. The value of tm increases logarithmally with the thickness of crystals, Im increases linearly with the area of cross-section of crystals and IT increases linearly with the volume of crystals. Generally, the ML of non-irradiated crystals decreases with increasing temperature of crystals. Depending on the prevailing conditions the ML spectra consist of either gas discharge spectra or solid state luminescence spectra or combination of the both. On the basis of the rate of generation of cracks and the rate of creation of new surface area of crystals, expressions are derived for the ML intensity and they are found to explain satisfactorily the temporal, spectral, thermal, crystal-size, impact velocity, surface area, and other characteristics of ML. The present investigation may be useful in designing of damage sensors, fracture

  11. Microstructural Characteristics and Mechanical Properties of Friction Stir Spot Welded 2A12-T4 Aluminum Alloy

    Directory of Open Access Journals (Sweden)

    Huijie Liu

    2013-01-01

    Full Text Available 2A12-T4 aluminum alloy was friction stir spot welded, and the microstructural characteristics and mechanical properties of the joints were investigated. A softened microstructural region existed in the joint, and it consisted of stir zone (SZ, thermal mechanically affected zone (TMAZ, and heat affected zone (HAZ. The minimum hardness was located in TMAZ, and the average hardness value in SZ can be improved by appropriately increasing welding heat input. The area of complete bonding region at the interface increased with increasing welding heat input because more interface metals were mixed. In a certain range of FSSW parameters, the tensile shear failure load of the joint increased with increasing rotation speed, but it decreased with increasing plunge rate or decreasing shoulder plunging depth. Two kinds of failure modes, that is, shear fracture mode and tensile-shear mixed fracture mode, can be observed in the tensile shear tests, and the joint that failed in the tensile-shear mixed fracture mode possessed a high carrying capability.

  12. Positive effect of hydrogen-induced vacancies on mechanical alloying of Fe and Al

    Energy Technology Data Exchange (ETDEWEB)

    Čížek, J., E-mail: jakub.cizek@mff.cuni.cz [Faculty of Mathematics and Physics, Charles University in Prague, V Holešovičkách 2, Prague 8 CZ-18000 (Czech Republic); Lukáč, F.; Procházka, I.; Vlček, M. [Faculty of Mathematics and Physics, Charles University in Prague, V Holešovičkách 2, Prague 8 CZ-18000 (Czech Republic); Jirásková, Y. [Institute of Physics of Materials, AS CR, Žižkova 22, CZ-616 62 Brno (Czech Republic); Švec, P.; Janičkovič, D. [Institute of Physics, Slovak Academy of Science, Dúbravská cesta 9, 84511 Bratislava (Slovakia)

    2015-04-25

    Highlights: • Fe{sub 82}Al{sub 18} nano-powders were prepared by ball milling and mechanical alloying. • Full mechanical alloying of Fe–Al was achieved using hydrogen atmosphere. • Hydrogen segregating at vacancies enhances vacancy concentration in Fe–Al. • Hydrogen-induced vacancies facilitate diffusion of Al atoms into Fe grains. • Nitrogen inhibits Fe–Al alloying by formation of a nitride layer on Fe grains. - Abstract: Nanocrystalline Fe{sub 82}Al{sub 18} powders were prepared by high energy ball milling in various atmospheres. Two preparation techniques were compared: (i) mechanical milling of pre-alloyed Fe{sub 82}Al{sub 18} pieces and (ii) mechanical alloying of pure Fe and Al powders. Single phase Fe{sub 82}Al{sub 18} nano-powder was formed by mechanical alloying in H{sub 2} atmosphere while milling in N{sub 2} or air environment suppressed mechanical alloying due to passivation of Fe surfaces. Positron annihilation spectroscopy revealed that mechanical alloying of Fe and Al in H{sub 2} atmosphere is mediated by hydrogen-induced vacancies.

  13. Mechanical properties and fracture toughness of rail steels and thermite welds at low temperature

    Science.gov (United States)

    Wang, Yuan-qing; Zhou, Hui; Shi, Yong-jiu; Feng, Bao-rui

    2012-05-01

    Brittle fracture occurs frequently in rails and thermite welded joints, which intimidates the security and reliability of railway service. Railways in cold regions, such as Qinghai-Tibet Railway, make the problem of brittle fracture in rails even worse. A series of tests such as uniaxial tensile tests, Charpy impact tests, and three-point bending tests were carried out at low temperature to investigate the mechanical properties and fracture toughness of U71Mn and U75V rail steels and their thermite welds. Fracture micromechanisms were analyzed by scanning electron microscopy (SEM) on the fracture surfaces of the tested specimens. The ductility indices (percentage elongation after fracture and percentage reduction of area) and the toughness indices (Charpy impact energy A k and plane-strain fracture toughness K IC) of the two kinds of rail steels and the corresponding thermite welds all decrease as the temperature decreases. The thermite welds are more critical to fracture than the rail steel base metals, as indicated by a higher yield-to-ultimate ratio and a much lower Charpy impact energy. U71Mn rail steel is relatively higher in toughness than U75V, as demonstrated by larger A k and K IC values. Therefore, U71Mn rail steel and the corresponding thermite weld are recommended in railway construction and maintenance in cold regions.

  14. Effect of Zn addition on microstructure and mechanical properties of an Al-Mg-Si alloy

    Institute of Scientific and Technical Information of China (English)

    Lizhen Yan; Yongan Zhang; Xiwu Li; Zhihui Li; Feng Wang; Hongwei Liu; Baiqing Xiong

    2014-01-01

    In the present work, an Al-0.66Mg-0.85Si-0.2Cu alloy with Zn addition was investigated by electron back scattering diffraction (EBSD), high resolution electron microscopy (HREM), tensile and Erichsen tests. The mechanical properties of the alloy after pre-aging met the standards of sheet forming. After paint baking, the yield strength of the alloy was improved apparently. GP(II) zones andηʹphases were formed during aging process due to Zn addition. With the precipitation of GP zones,β″phases, GP(II) zones andηʹphases, the alloys displayed excellent mechanical properties.

  15. Effect of hot extrusion process on microstructure and mechanical properties of hypereutectic Al-Si alloys

    OpenAIRE

    Li Runxia; Yu Fuxiao; Zuo Liang

    2011-01-01

    The hypereutectic Al-Si alloy was fabricated by hot extrusion process after solidified under electromagnetic stirring, and the microstructure and mechanical properties of the alloy were studied. The results show that the ultimate tensile strength and elongation of the alloy reached 229.5 MPa and 4.6%, respectively with the extrusion ratio of 10, and 263.2 MPa and 5.4%, respectively with extrusion ratio of 20. This indicates that the mechanical properties of the alloy are obviously improved w...

  16. Effect of Zn addition on microstructure and mechanical properties of an Al–Mg–Si alloy

    Directory of Open Access Journals (Sweden)

    Lizhen Yan

    2014-04-01

    Full Text Available In the present work, an Al–0.66Mg–0.85Si–0.2Cu alloy with Zn addition was investigated by electron back scattering diffraction (EBSD, high resolution electron microscopy (HREM, tensile and Erichsen tests. The mechanical properties of the alloy after pre-aging met the standards of sheet forming. After paint baking, the yield strength of the alloy was improved apparently. GP(II zones and ηʹ phases were formed during aging process due to Zn addition. With the precipitation of GP zones, β″ phases, GP(II zones and ηʹ phases, the alloys displayed excellent mechanical properties.

  17. Evaluation of Aluminum Alloy 2050-T84 Microstructure and Mechanical Properties at Ambient and Cryogenic Temperatures

    Science.gov (United States)

    Hafley, Robert A.; Domack, Marcia S.; Hales, Stephen J.; Shenoy, Ravi N.

    2011-01-01

    Aluminum alloy 2050 is being considered for the fabrication of cryogenic propellant tanks to reduce the mass of future heavy-lift launch vehicles. The alloy is available in section thicknesses greater than that of the incumbent aluminum alloy, 2195, which will enable designs with greater structural efficiency. While ambient temperature design allowable properties are available for alloy 2050, cryogenic properties are not available. To determine its suitability for use in cryogenic propellant tanks, tensile, compression and fracture tests were conducted on 4 inch thick 2050-T84 plate at ambient temperature and at -320degF. Various metallurgical analyses were also performed in order to provide an understanding of the compositional homogeneity and microstructure of 2050.

  18. Evaluation of Aluminum Alloy 2050-T84 Microstructure Mechanical Properties at Ambient and Cryogenic Temperatures

    Science.gov (United States)

    Hafley, Robert A.; Domack, Marcia S.; Hales, Stephen J.; Shenoy, Ravi N.

    2011-01-01

    Aluminum alloy 2050 is being considered for the fabrication of cryogenic propellant tanks to reduce the mass of future heavy-lift launch vehicles. The alloy is available in section thicknesses greater than that of the incumbent aluminum alloy, 2195, which will enable the designs with greater structural efficiency. While ambient temperature design allowable properties are available for alloy 2050, cryogenic properties are not available. To determine its suitability for use in cryogenic propellant tanks, tensile, compression and fracture tests were conducted on 4 inch thick 2050-T84 plate at ambient temperature and at -320 F. Various metallurgical analyses were also performed in order to provide an understanding of the compositional homogeneity and microstructure of 2050.

  19. Mechanical Properties and Fracture Behaviour of Multilayer Alumina Composites

    Institute of Scientific and Technical Information of China (English)

    ZHENG Xinguo; ZHAO Fei; ZHANG Jinyong

    2015-01-01

    Adopting a ceramic/polymer multilayer structure design to simulate the structure of nacre is usually believed to be an effective way to increase the toughness of ceramic composites at the expense of the material's bending strength. However, in this study, we found that both the bending strength and the toughness could be improved simultaneously when using a certain Al2O3/Kevlar multilayer composite design compared to pure alumina samples with the same dimensions. The fracture behaviour of the Al2O3/Kevlar multilayer composite was studied to ifnd a reason for this improvement. The results showed that the complex and asymmetrical stresses occurring in the Kevlar-reinforced layers were the main reason for the differences in fracture behaviour. We expect our results to open up new ways for the design of future high performance ceramic composites.

  20. SYNTHESIS AND CHARECTERIZATION OF AlFeCrNi FOUR COMPONENT HIGH ENTROPY ALLOY BY MECHANICAL ALLOYING

    Directory of Open Access Journals (Sweden)

    P.B.C RAO

    2011-05-01

    Full Text Available The elemental powders of Al,Fe,Ni and Cr are taken with high purity and are mechanically alloyed(MA to produce the High-Entropy Alloy. The samples are taken at regular intervals of 5,10,15,20 hr. These samples are characterized by X-Ray Diffraction (XRD technique. The further analysis of X-Ray Diffraction (XRD patterns for crystallite size and strain is done. The series of transformations were studied by plotting intensity versus 2Ө.The high entropy alloy was synthesized successfully having a single-phase solid solution. The alloy has a Body Centered Cubic (BCC crystal structure and a lattice parameter of 2.8952Ao with a residual strain of 0.772%.