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Sample records for alloy superplastic forming

  1. Current assisted superplastic forming of titanium alloy

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    Wang Guofeng

    2015-01-01

    Full Text Available Current assisted superplastic forming combines electric heating technology and superplastic forming technology, and can overcome some shortcomings of traditional superplastic forming effectively, such as slow heating rate, large energy loss, low production efficiency, etc. Since formability of titanium alloy at room temperature is poor, current assisted superplastic forming is suitable for titanium alloy. This paper mainly introduces the application of current assisted superplastic forming in the field of titanium alloy, including forming technology of double-hemisphere structure and bellows.

  2. Superplastic Forming and Diffusion Bonding of Titanium Alloys

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    A. K. Ghosh

    1986-04-01

    Full Text Available New and advanced fabrication methods for titanium components are emerging today to replace age-old fabrication processes and reduce component cost. Superplastic forming and diffusion bonding are two such advanced fabrication technologies which when applied individually or in combination can provide significant cost and weight benefits and a rather broad manufacturing technology base. This paper briefly reviews the state of understanding of the science and technology of super plastic forming of titanium alloys, and their diffusion bonding capability. Emphasis has been placed on the metallurgy of superplastic flow in two phase titanium alloys, the microstructural and external factors which influence this behaviour.

  3. Superplastic forming gas pressure of titanium alloy bellows

    Institute of Scientific and Technical Information of China (English)

    王刚; 张凯锋; 陈军; 阮雪榆

    2004-01-01

    The complex superplastic forming (SPF) technology applying gas pressure and compressive axial load is an advanced forming method for titanium alloy bellows, whose forming process consists of the three main forming phases namely bulging, clamping and calibrating phase. The influence of forming gas pressure in various phases on the forming process was analyzed and the models of forming gas pressure for bellows were derived according to the thin shell theory and the plasticity deformation theory. Using the model values, taking a two-convolution DN250 Ti6Al-4V titanium alloy bellows as an example, a series of superplastic forming tests were performed to evaluate the influence of the variation of forming gas pressure on the forming process. According to the experimental results these models were corrected to make the forming gas pressures prediction more accurate.

  4. A two-step superplastic forging forming of semi-continuously cast AZ70 magnesium alloy

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    Pan Wang

    2015-03-01

    Full Text Available A two-step technology combined forging with superplastic forming has been developed to enhance the forgeability of semi-continuously cast AZ70 magnesium alloy and realize the application of the as-cast magnesium alloy in large deformation bullet shell. In the first step, fine-grained microstructure preforms that are suitable for superplastic forming were obtained by reasonably designing the size of the initial blanks with the specific height-to-diameter ratio, upsetting the blanks and subsequent annealing. In the second step, the heat treated preforms were forged into the end products at the superplastic conditions. The end products exhibit high quality surface and satisfied microstructure. Consequently, this forming technology that not only avoids complicating the material preparation but also utilizes higher strain rate superplastic provides a near net-shaped novel method on magnesium forging forming technology using as-cast billet.

  5. Experimental and FE simulation validation of sheet thickness optimization in superplastic forming of Al alloy

    Energy Technology Data Exchange (ETDEWEB)

    Kumaresan, G.; Jothilingam, A. [Anna University, Chennai (India)

    2016-07-15

    Superplasticity is the ability of a polycrystalline materials to exhibit very large elongations without necking prior to failure. In this paper, the superplastic forming potential of fine grained 7075 aluminium alloy was studied. The process parameters like pressure, forming time and initial sheet thickness were selected, using the design of experiments technique. The same condition of formation process was attempted in the finite element simulation using ABAQUS software. The deviation of the thickness distribution between the simulation and experiment was made and the variation lies within 8%.

  6. Superplastic forming of Al-Li alloys for lightweight, low-cost structures

    Science.gov (United States)

    Hales, Stephen J.; Wagner, John A.

    1991-01-01

    Superplastic forming of advanced aluminum alloys is being evaluated as an approach for fabricating low-cost, light-weight, cryogenic propellant tanks. Built-up structure concepts (with inherent reduced scrap rate) are under investigation to offset the additional raw material expenses incurred by using aluminum lithium alloys. This approach to fabrication offers the potential for significant improvements in both structural efficiency and overall manufacturing costs. Superplasticity is the ability of specially processed material to sustain very large forming strains without failure at elevated temperatures under controlled deformation conditions. It was demonstrated that superplastic forming technology can be used to fabricate complex structural components in a single operation and increase structural efficiency by as much as 60 percent compared to conventional configurations in skin-stiffened structures. Details involved in the application of this technology to commercial grade superplastic aluminum lithium material are presented. Included are identification of optimum forming parameters, development of forming procedures, and assessment of final part quality in terms of cavitation volume and thickness variation.

  7. Forming of superplastic ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Lesuer, D.R.; Wadsworth, J.; Nieh, T.G.

    1994-05-01

    Superplasticity in ceramics has now advanced to the stage that technologically viable superplastic deformation processing can be performed. In this paper, examples of superplastic forming and diffusion bonding of ceramic components are given. Recent work in biaxial gas-pressure forming of several ceramics is provided. These include yttria-stabilized, tetragonal zirconia (YTZP), a 20% alumina/YTZP composite, and silicon. In addition, the concurrent superplastic forming and diffusion bonding of a hybrid ceramic-metal structure are presented. These forming processes offer technological advantages of greater dimensional control and increased variety and complexity of shapes than is possible with conventional ceramic shaping technology.

  8. Superplastic Forming and Diffusion Bonding for Sandwich Structure of Ti-6Al-4V Alloy

    Institute of Scientific and Technical Information of China (English)

    Wenbo HAN; Kaifeng ZHANG; Guofeng WANG; Xiaojun ZHANG

    2005-01-01

    Superplastic forming and diffusion bonding (SPF/DB) is a well-established process for the manufacture of components almost exclusively from Ti-6Al-4V sheet material. The sandwich structure of Ti-6Al-4V alloy is investigated. The effects of the microstructure on the SPF/DB process were discussed. The microstructure at the interfaces and the distribution of thickness were researched.

  9. Superplasticity and superplastic forming of ceramics

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    Nieh, T.G.; Wadsworth, J.

    1994-05-01

    Recent advances in the basic understanding of superplasticity and superplastic forming of ceramics are reviewed. Deformation mechanisms as well as microstructural requirements for superplastic ceramics are discussed. Microstructural effects, such as grain size, dynamic grain growth, and the presence of grain-boundary liquid phases, on the superplastic properties and deformation behavior of ceramics are addressed. Superplastic forming, and particularly biaxial gas-pressure forming, of several ceramics, including YTZP and Al{sub 2}O{sub 3}/YTZP, is also presented. The forming behavior of these ceramics is correlated with that obtained from conventional uniaxial tests. Examples of concurrent superplastic forming and diffusion bonding (SPF/DB) of metal-ceramic hybrids are given.

  10. Numerical Simulation and Superplastic Forming of Ti-6Al-4V Alloy for a Dental Prosthesis

    Science.gov (United States)

    Li, Xiaomei; Soo, Steven

    2011-04-01

    This article investigates superplastic forming (SPF) technique in conjunction with finite element (FE) simulation applied to dental repair. The superplasticity of Ti-6Al-4V alloys has been studied using a uniquely designed five-hole test with the aim of obtaining the modeled grain size and the flow stress parameters. The data from the five-hole test are subsequently put into the FE program for the simulation of a partial upper denture dental prosthesis (PUD4). The FE simulation of the PUD4 is carried out to set up appropriate input parameters for pressing due to the SPF process being fully automatic controlled. A variety of strain rates ranging from 2.4 × 10-5 to 1 × 10-3 s-1 are selected for the characterization of superplastic properties of the alloy. The Superflag FE program is used to generate an appropriate pressure-time profile and provide information on thickness, grain size, and grain growth rate distribution. Both membrane elements and solid elements have been adopted in the simulation and the results from both types of elements are compared. An evaluation of predicted parameters for the SPF of the prosthesis is presented.

  11. Metallurgical Characterization of Superplastic Forming

    Science.gov (United States)

    1980-09-01

    The trans - formation of constant-crosshead-speed stress-strain curves into constant-strain- rate curves is clearly not satisfactory because it is based...MILL-ANNEALED AND SUPERPLASTICALLY- FORMED CONDITIONS; FORMING TEMPERATURE - 949EPC (17400F). 01"tln Stoi rte yeld grasa Ultimate l to oret~lSri as...1975), p. 163. 7. G. Rai and N. J. Grant, "On the Measurermients of Superplasticity in an Al-Cu Alloy," Met. Trans . 6A, 385 (1975). 8. A. K, Mukherjee

  12. Finite Element Simulation in Superplastic forming of Friction Stir Welded Aluminium Alloy 6061-T6

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    P Ganesh

    2011-09-01

    Full Text Available Superplasticity in materials is the ability of materials to achieve large elongation only under specific conditions of temperature and strain rate. Superplastic Forming (SPF is an important industrial process that has found application in sheet metal forming in the aerospace and automotive industries. Friction Stir Welding (FSW is a solid state joining process that can alter the grain structure of the parent material. FSW process is an effective tool to refine the grain structure of the sheet metal and enhance their Superplasticity. Friction Stir Welding was used to join Superplastic AA 6061-T6 sheets. The Finite Element Simulation was performed for the Superplastic Forming of the Friction Stir Welded joints to evaluate the thinning and formability of AA 6061-T6 for hemispherical shape. The commercially available Finite Element Software ABAQUS was used to execute these simulations.

  13. Development of fine-grain size titanium 6Al–4V alloy sheet material for low temperature superplastic forming

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    Zhang, Tuoyang [State Key Laboratory of Powder Metallurgy, Central South University, Changsha, Hunan (China); Liu, Yong, E-mail: yonliu@csu.edu.cn [State Key Laboratory of Powder Metallurgy, Central South University, Changsha, Hunan (China); Sanders, Daniel G. [Boeing Research and Technology, Seattle, WA (United States); Liu, Bin; Zhang, Weidong; Zhou, Canxu [State Key Laboratory of Powder Metallurgy, Central South University, Changsha, Hunan (China)

    2014-07-01

    Fine-grained titanium 6Al–4V alloy, which typically has a grain size of about 1–2 μm, can be made to superplastic form at around 800 °C with special processing. The normal temperature for superplastic forming (SPF) with conventional titanium 6Al–4V sheet material is 900 °C. The lower temperature performance is of interest to the Boeing Company because it can be exploited to achieve significant cost savings in processing by reducing the high-temperature oxidation of the SPF dies, improving the heater rod life for the hot presses, increasing operator safety and replacing the chemical milling operation to remove alpha case contamination with a less intensive nitric hydrofluoric acid etchant (pickle). In this report, room temperature tensile tests and elevated temperature constant strain rate tensile tests of fine-grained Ti–6Al–4V sheets provided by the Baoti Company of Xi'an, China, were conducted according to the test method standards of ASTM-E8 and ASTM-E2448. The relationships among the processing parameters, microstructure and superplastic behavior have been analyzed. The results show that two of the samples produced met the Boeing minimum requirements for low-temperature superplasticity. The successful material was heat-treated at 800 °C subsequent to hot rolling above the beta transus temperature, T{sub β}-(150–250 °C). It was found that the sheet metal microstructure has a significant influence on superplastic formability of the Ti–6Al–4V alloy. Specifically, fine grains, a narrow grain size distribution, low grain aspect ratio and moderate β phase volume fraction can contribute to higher superplastic elongations.

  14. Superplastic forming of the Cd-17.4Zn alloy; Conformado superplastico de la aleacion Cd-17.4Zn

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    Llanes-Briceno, J. A.; Torres-Villasenor, G. [Universidad Nacional Autonoma de Mexico, Mexico, D.F. (Mexico)

    2000-06-01

    In the present work the necessary steps to carry on the superplastic forming of the Cd-17.4Zn alloy are defined. The use of either atmospheric pressure or gas pressure as forming tools is analyzed. The optimum values of the variable involved (temperature, maximum strain and sensitivity index) are determined while a method for the characterization of futures superplastic alloys is set forth. The experimental characterization of the superplastic forming is achieved with free bulging of circular membranes of 12, 16, 24, 32 and 40 mm in diameter and with three different membrane thicknesses (0.4, 0.6, 0.8 mm). [Spanish] Se definen los pasos necesarios para el conformado superplastico de la aleacion Cd-17.4 Zn. Se comparan la presion atmosferica y el gas a presion como herramientas de conformado. Se determinan los valores optimos de la variables involucradas (temperatura, deformacion maxima e indice de sensibilidad) y se plantea una metodologia para la caracterizacion de futuras aleaciones superplasticas. El conformado superplastico se caracteriza experimentalmente mediante el inflado libre de membranas circulares de 12, 16, 24, 32 y 40 mm de diametro y tres diferentes espesores (0.4, 0.6 y 0.8 mm). Se muestra la estructura perlitica (enfuiada al aive Cd-17.4Zn) y la estructura grano fino. Se muestra la profundidad de deformacion en tres espesores (0.4, 0.6, 0.8 mm) a P=200 Kpa y T = 200 y a T = 230.

  15. Effect of superplastic forming exposure on fatigue crack propagation behavior of Ti-6Al-4V alloy

    Science.gov (United States)

    Jeong, Daeho; Kwon, Yongnam; Goto, Masahiro; Kim, Sangshik

    2016-09-01

    The effect of superplastic forming (SPF) exposure on the ɛ (strain)-N (number of cycles to failure) fatigue and fatigue crack propagation (FCP) behaviors of Ti-6Al-4V (Ti64) alloy was examined at 298 and 473 K. To simulate the thermal exposure during superplastic forming process, the mill-annealed Ti64 alloy sheet was heated in the vacuum chamber with the pre-determined temperature profile. Notable microstructural change during the SPF exposure included the shape of transformed β phase from fine and round particles in the as-received specimen to coarse angular particles in the as-exposed specimen. The effective grain size tended to increase with the exposure, enhancing the slip reversibility and the resistance to FCP. However, the crack hindering effect by fine, particle-like β phase became weak with the exposure, offseting the beneficial effect associated with the increment of effective grain size. The effect of SPF exposure on ɛ-N fatigue and FCP behavior of mill-annealed Ti64 alloy was therefore marginal, excluding the effect of α-case (the oxygen-enriched phase) on the surface.

  16. Method of producing superplastic alloys and superplastic alloys produced by the method

    Science.gov (United States)

    Troeger, Lillianne P. (Inventor); Starke, Jr., Edgar A. (Inventor); Crooks, Roy (Inventor)

    2002-01-01

    A method for producing new superplastic alloys by inducing in an alloy the formation of precipitates having a sufficient size and homogeneous distribution that a sufficiently refined grain structure to produce superplasticity is obtained after subsequent PSN processing. An age-hardenable alloy having at least one dispersoid phase is selected for processing. The alloy is solution heat-treated and cooled to form a supersaturated solid solution. The alloy is plastically deformed sufficiently to form a high-energy defect structure useful for the subsequent heterogeneous nucleation of precipitates. The alloy is then aged, preferably by a multi-stage low and high temperature process, and precipitates are formed at the defect sites. The alloy then is subjected to a PSN process comprising plastically deforming the alloy to provide sufficient strain energy in the alloy to ensure recrystallization, and statically recrystallizing the alloy. A grain structure exhibiting new, fine, equiaxed and uniform grains is produced in the alloy. An exemplary 6xxx alloy of the type capable of being produced by the present invention, and which is useful for aerospace, automotive and other applications, is disclosed and claimed. The process is also suitable for processing any age-hardenable aluminum or other alloy.

  17. Superplastic Forming of Aluminum (Task C)

    Science.gov (United States)

    1989-03-01

    purchase order number 9-342779-01 was modified to incorporate integral hinge attachment features to drawing number 160K136160. The material used to form a...0.805 7. Trans. Drill 8 his. from 136153-3 & 136152-1 Hinges C/T Straps and 136161-11 & -13 Fittings .016 0.053 8. Disassemble 0.182 9. DBR 0.008 0.158 10...door utilizes a conventional aluminum alloy skin stiffened by a weld bonded monolithic superplastically formed element fabricated trom Supral 220

  18. Dental implant superstructures by superplastic forming

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    Curtis, R.V.; Garriga-Majo, D.; Soo, S.; Pagliaria, D. [Kings Coll., London (United Kingdom). Dept. of Dental Biomaterials Science; Juszczyk, A.S.; Walter, J.D. [Kings Coll., London (United Kingdom). Dept. of Prosthetic Dentistry

    2001-07-01

    A novel application of superplastic forming is described for the production of fixed-bridge dental implant superstructures. Finite element analysis (FEA) has shown that Ti-6Al-4V sheet would be a suitable candidate material for the design of a fixed-bridge dental implant superstructure. Traditionally superstructures are cast in gold alloy onto pre-machined gold alloy cylinders but castings are often quite bulky and 25% of castings do not fit accurately (1) which means that sectioning and soldering is required to obtain a fit that is clinically acceptable and will not prejudice the integrity of the commercially pure cp-titanium implants osseointegrated with the bone. Superplastic forming is shown to be a forming technique that would allow the production of strong, light-weight components of thin section with low residual stress that could be suitable for such applications. Considerable cost savings over traditional dental techniques can be achieved using a low-cost ceramic die material. The properties of these die materials are optimised so that suitable components can be produced. Satisfactory hot strength is demonstrated and thermal properties are matched to those of the titanium alloy for accurate fit of the prosthesis. (orig.)

  19. Superplastic Deformation of TC6 Alloy

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    DING Ling

    2016-12-01

    Full Text Available The superplastic tensile tests of TC6 alloy were conducted in the temperature range of 800-900℃ by using the maximum m value superplasticity deformation (Max m SPD method and the constant strain rate deformation method at the strain rate range of 0.0001-0.1 s-1. The stress-strain curve of the tensile tests was obtained and the microstructure near the fracture were analyzed by metallographic microscope. The result shows that the superplasticity of TC6 alloy is excellent, and the elongation increases first and then decreases with the increase of strain rate or temperature. When the temperature is 850℃ and strain rate is 0.001 s-1 at constant stain rate tensile tests, the elongation reaches up to 993%. However, the elongation using Max m SPD method at 850℃ is 1353%. It is shown that the material can achieve better superplasticity by using Max m SPD tensile compared to constant stain rate tensile under the same temperature. The superplastic deformation of TC6 alloy can enhance the dynamic recrystallization behavior significantly, the dynamic recrystallization behavior is promoted when strain rate and temperature are increased.

  20. Biomedical Titanium alloy prostheses manufacturing by means of Superplastic and Incremental Forming processes

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    Piccininni Antonio

    2016-01-01

    Full Text Available The present work collects some results of the three-years Research Program “BioForming“, funded by the Italian Ministry of Education (MIUR and aimed to investigate the possibility of using flexible sheet forming processes, i.e. Super Plastic Forming (SPF and Single Point Incremental Forming (SPIF, for the manufacturing of patient-oriented titanium prostheses. The prosthetic implants used as case studies were from the skull; in particular, two different Ti alloys and geometries were considered: one to be produced in Ti-Gr23 by SPF and one to be produced in Ti-Gr2 by SPIF. Numerical simulations implementing material behaviours evaluated by characterization tests were conducted in order to design both the manufacturing processes. Subsequently, experimental tests were carried out implementing numerical results in terms of: (i gas pressure profile able to determine a constant (and optimal strain rate during the SPF process; (ii tool path able to avoid rupture during the SPIF process. Post forming characteristics of the prostheses in terms of thickness distributions were measured and compared to data from simulations for validation purposes. A good correlation between numerical and experimental thickness distributions has been obtained; in addition, the possibility of successfully adopting both the SPF and the SPIF processes for the manufacturing of prostheses has been demonstrated.

  1. Grain size control and superplasticity in 6013-type aluminum alloys

    Science.gov (United States)

    Troeger, Lillianne Plaster Whitelock

    Aluminum alloys have been the material of choice for aircraft construction since the 1930's. Currently, the automotive industry is also showing an increasing interest in aluminum alloys as structural materials. 6xxx aluminum alloys possess a combination of strength and formability which makes them attractive to both industries. In addition, 6xxx alloys are highly weldable, corrosion resistant, and low in cost as compared with the 2xxx and 7xxx aluminum alloys. Superplastic forming (SPF) is a manufacturing process which exploits the phenomenon of superplasticity in which gas pressure is used to form complex-shaped parts in a single forming operation. This reduces part counts and the need for fasteners and connectors, resulting in reduced product weight. Reduced product/vehicle weight improves fuel economy. Most alloys must be specially processed for superplasticity. Much research effort has been directed at the development of thermomechanical processes for the grain refinement of aluminum alloys by static or dynamic recrystallization. to induce superplasticity. While large numbers of studies have been conducted on 2xxx, 5xxx, 7xxx, and 8xxx aluminum alloys, very few studies have been focused on the grain refinement of 6xxx aluminum alloys for superplasticity. The current research describes a new thermomechanical process for application to 6xxx aluminum alloys for grain refinement and superplasticity. The process is shown to successfully refine and induce superplasticity in an Al-Mg-Si-Cu alloy which falls within the compositional limits of both 6013 and 6111. The grain refinement is by particle-stimulated nucleation of recrystallization. The microstructural evolution during the thermomechanical processing is characterized in terms of precipitate size, shape, distribution and composition; texture; recrystallization; and grain size, shape, and thermal stability. The new process produces a statically-stable, weakly-textured, equiaxed grain structure with an average

  2. Integrated Manufacturing of Aerospace Components by Superplastic Forming Technology

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    Ju Min Kyung

    2015-01-01

    Full Text Available Aerospace vehicle requires lightweight structures to obtain weight saving and fuel efficiency. It is known that superplastic characteristics of some materials provide significant opportunity for forming complicated, lightweight components of aerospace structure. One of the most important advantages of using superplastic forming process is its simplicity to form integral parts and economy in tooling[1]. For instance, it can be applied to blow-forming, in which a metal sheet is deformed due to the pressure difference of hydrostatic gas on both sides of the sheet. Since the loading medium is gas pressure difference, this forming is different from conventional sheet metal forming technique in that this is stress-controlled rather than strain and strain rate controlled. This method is especially advantageous when several sheet metals are formed into complex shapes. In this study, it is demonstrated that superplastic forming process with titanium and steel alloy can be applied to manufacturing lightweight integral structures of aerospace structural parts and rocket propulsion components. The result shows that the technology to design and develop the forming process of superplastic forming can be applied for near net shape forming of a complex contour of a thrust chamber and a toroidal fuel tank.

  3. Research on the diffusion bonding of superplastic magnesium alloy

    Institute of Scientific and Technical Information of China (English)

    于彦东; 张凯锋; 蒋大鸣; 郑海荣; 王刚

    2002-01-01

    The elevated temperature tensile experiments have been carried out on the magnesium alloy and results indicate that the magnesium alloy has excellent superplastic property. Gleebe-1500 testing machine was used in the diffusion bonding experiment on the superplastic magnesium alloy. Then, the shear strength of the joints under different conditions is obtained through shear testing and the optimum processing parameters for the diffusion bonding are achieved. By metallurgical microscope and scanning electron microscope (SEM), it is revealed that the micromechanism of diffusion bonding is the slide of grain boundaries caused by the growth of grains and atom diffusion of the superplastic magnesium alloy.

  4. Effect of thermal processing practices on the properties of superplastic Al-Li alloys

    Science.gov (United States)

    Hales, Stephen J.; Lippard, Henry E.

    1993-01-01

    The effect of thermal processing on the mechanical properties of superplastically formed structural components fabricated from three aluminum-lithium alloys was evaluated. The starting materials consisted of 8090, 2090, and X2095 (Weldalite(TM) 049), in the form of commercial-grade superplastic sheet. The experimental test matrix was designed to assess the impact on mechanical properties of eliminating solution heat treatment and/or cold water quenching from post-forming thermal processing. The extensive hardness and tensile property data compiled are presented as a function of aging temperature, superplastic strain and temper/quench rate for each alloy. The tensile properties of the materials following superplastic forming in two T5-type tempers are compared with the baseline T6 temper. The implications for simplifying thermal processing without degradation in properties are discussed on the basis of the results.

  5. Superplasticity in Aeroengine Titanium Alloy VT-9 and its Modified Compositions

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    Abhijit Dutta

    1986-04-01

    Full Text Available The alloy (Ti-6.5AL-3.3 Mo-1.6Zr-O.3Si is a Soviet composition designated VT-9. Excellent superplastic characteristics found by us in this alloy prompted us to explore the possibility of use of Si-free VT-9 in sheet form for superplastic forming. An optimum thermomechanical processing produced a microstructure that resulted in an elongation of 1700 per cent at a fairly high deformation rate (2 X 10-3 set-1. Thus, the same aeroengine alloy (VT-9 can be used for superplastically formed airframe parts in the Si-free condition. The present study also shows that for making the forming process commercially viable, deformation temperature could be lowered by temporarily alloying with hydrogen in a particular concentration range (0.1 to 0.2 wt per cent.

  6. Superplasticity

    Science.gov (United States)

    Rouxel, T.

    Permanent deformation of a material through flow, e.g., creep, viscosity, viscoplasticity, gets easier as the grain size in the material gets smaller. In the most spectacular cases, relative extensions greater than 100% (nominal strain > 1) can be obtained at relatively low temperatures compared with the temperatures usually required to observe creep in materials: this is the effect known as superplasticity. Typically, superplasticity only occurs in fine-grained dense materials (grains 0.5Tmelting, when such a temperature has any meaning (materials sometimes decomposing before melting). Even in ancient times, smiths made good use of this remarkable property to forge tough, hard steel blades. The steel used by the Persians at the time of the crusades, and by Saladin's armies, or Damascus steel, is one of the greatest achievements of metallurgy and the forge, where the choice of alloy at the outset (in this case a steel with a high carbon content, known as wootz, from India) and the masterly control of a judicious forging cycle (the thickness of the initial ingot was first reduced by a factor of about 10 by hammering) produced a material with ideal fine microstructure for making sharp cutting blades that could also resist mechanical shocks. Figure 9.1 illustrates the phenomenon of superplastic behaviour for a steel containing 1.6% carbon (ultrahigh carbon steel), with a fine microstructure, close to Damascus steel, which seems to have been produced first in India in the fourth century BC.

  7. Numerical simulation of industrial superplastic forming. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Haberman, K.S.; Bennett, J.G.; Piltch, M.S.

    1996-11-01

    Superplastic forming (SPF) is a metal forming process that allows a variety of components with very complex geometries to be produced at a fraction of the cost of conventional machining. The industrial superplastic forming process can be optimized with the application of the finite element method to predict the optimal pressure schedules, overall forming time, and the final thickness distribution. This paper discusses the verification and applications of NIKE3D in 4 optimizing the industrial superplastic forming process.

  8. Superplasticity and cavitation in an aluminum-magnesium alloy

    Science.gov (United States)

    Bae, Donghyun

    2000-10-01

    Fundamental issues related to the forming performance of superplastic metals include the mechanisms of flow and cavitation occurring during the forming process. Cavitation beyond a critical amount is damaging to the mechanical behavior of fabricated parts. Therefore, the role of process parameters which influence cavitation must be precisely documented and understood. In this study, (1) the mechanism of deformation, (2) cavity formation and growth, and (3) the effect of forming parameters on cavitation are systematically investigated in a fine grain Al-4.7%Mg-0.8%Mn-0.4%Cu alloy. The mechanical flow response of the alloy is characterized by a new type of step strain-rate test which preserves the initial microstructure of the alloy. Under isostructural condition, sigmoidal log s vs. log 3˙ relationship is determined and then analyzed by using a grain-mantle based quantitative model1 for superplastic flow. The activation energies in both grain-mantle creep and core creep are analyzed, and the overall controlling mechanism is found to be dislocation glide and climb. Grain-mantle creep rate in the low strain-rate region is found to be enhanced many times due to a high concentration of vacancies near grain boundaries. Cavitation caused by superplastic straining under uniaxial tension is evaluated by the SEM (for frame associated with superplastic deformation. In the model, faster cavity growth is predicted for lower m and for smaller cavity density when cavity stress fields are not overlapping. Observed cavitation quantitatively agrees with the present model, but diffusional growth is found to be too slow, which cannot explain the observed nanoscale void growth behavior. Another parameter affecting the degree of cavitation is the imposed stress-state. Cavity growth rate as well as cavity nucleation rate increase with the level of mean hydrostatic tension. For a fixed cavitation volume fraction, V, the principal surface strains, 31 and 32 , for the various stress

  9. Effect of Rare Earth on Superplasticity of Zn-5Al Eutectic Alloy

    Institute of Scientific and Technical Information of China (English)

    石志强; 叶以富; 李世春; 王焕荣; 滕新营

    2002-01-01

    The superplastic deformation curves of Zn-5Al eutectic alloy containing small amount of rare earth were measured, and the influence of rare earth on structure and superplasticity characteristics of the alloy was examined with optical microscope, XDF and TEM. The results show that the elongation of Zn-5Al eutectic alloy can be increased if less than 0.2 %(mass fraction) misch-metal was added. Rare earth which exists in the form of compounds Al2CeZn2 and CeZn3 can refrain the dissolution and diffusion of Zn to Al and postpone the saturation of the diffusion-dissolution zone(DDZ) above 350 ℃, and in such a way boost up α/β interface sliding which benefits the superplasticity.

  10. Effect of grain boundary microstructure on superplastic deformation of Al-Li-Cu-Mg-Zr alloy

    Energy Technology Data Exchange (ETDEWEB)

    Kobayashi, S.; Yoshimura, T.; Tsurekawa, S.; Watanabe, T. [Tohoku Univ., Sendai (Japan). Dept. of Machine Intelligence and Syst. Eng.

    1999-07-01

    It is common knowledge that grain boundary sliding (GBS) is the most important deformation mechanism for superplastic deformation. In this investigation, Al-Li-Cu-Mg-Zr alloys having two distinct microstructures were produced to examine the effect of grain boundary (GB) microstructure on superplastic deformation. The effective GB microstructure to develop the superplastic deformation is discussed. Specimens with homogeneous and {l_brace}011{r_brace} textured grains, including high frequency of low-angle GBs showed superplastic behavior. The texture was weakened and most of low-angle GBs were changed into random GBs during deformation. Mean grain size increased slightly with deformation. On the other hand, specimens with heterogeneous and randomly oriented grains, with a high frequency of random GBs resulted in nonsuperplastic behavior. This microstructure was essentially unchanged by deformation. Extensive cavitation at GB triple junctions was also observed after superplastic deformation. In particular, cavities were most likely to form at the triple junctions composed of two or more random GBs. We will discuss the development of superplasticity through the optimization of GB microstructures in polycrystalline materials. (orig.)

  11. Superplastic forming of Ti6Al4V alloy using ZrO_2-TiO_2 ceramic die with adjustable linear thermal expansion coefficient

    Institute of Scientific and Technical Information of China (English)

    JIANG Shao-song; ZHANG Kai-feng

    2009-01-01

    Firstly, the relation between the coefficient of thermal expansion(CTE) and the volume fraction of TiO_2 was investigated, and also the influence of relative density of ceramic on the CTE was studied. The results show that the volume fraction, of TiO_2 and the relative density both make influence on the CTE of ZrO_2-TiO_2 ceramic. According to the results, the ZrO_2-TiO_2(volume fraction of TiO_2 is 27%) ceramic die with the similar CTE (8.92×10~(-6)℃~(-1)) to Ti6Al4V was fabricated. Secondly, to evaluate the dimensional accuracy of the workpiece superplastically formed, the Ti6Al4V impression experiment was performed. The result shows that the dimensional inaccuracy of workpieee is 0.003. Thirdly, in order to evaluate the practicability, the experiment of superplastic forming Ti6Al4V using ZrO_2-TiO_2 cylinder ceramic die was carried out. The Ti6Al4V cylinder shows good shape retention and surface quality, and high dimensional accuracy. The ceramic dies seem to be adequate for superplastic forming the high accuracy Ti6Al4V,and the trials have confirmed the potential of the ZrO2-TiO2 ceramic die.

  12. Materials issues in some advanced forming techniques, including superplasticity

    Energy Technology Data Exchange (ETDEWEB)

    Wadsworth, J.; Henshall, G.A.; Nieh, T.G. [and others

    1995-08-22

    From mechanics and macroscopic viewpoints, the sensitivity of the flow stress of a material to the strain rate, i.e. the strain rate sensitivity (m), governs the development of neck formation and therefore has a strong influence on the tensile ductility and hence formability of materials. Values of strain rate sensitivity range from unity, for the case of Newtonian viscous materials, to less than 0.1 for some dispersion strengthened alloys. Intermediate values of m = 0.5 are associated with classical superplastic materials which contain very fine grain sizes following specialized processing. An overview is given of the influence of strain rate sensitivity on tensile ductility and of the various materials groups that can exhibit high values of strain rate sensitivity. Recent examples of enhanced formability (or extended tensile ductility) in specific regimes between m = 1 and m = 0.3 are described, and potential areas for commercial exploitation are noted. These examples include: internal stress superplasticity, superplastic ceramics, superplastic intermetallics, superplastic laminated composites, superplastic behavior over six orders of magnitude of strain rate in a range of aluminum-based alloys and composites, and enhanced ductility in Al-Mg alloys that require no special processing for microstructural development.

  13. Dynamic reverse phase transformation induced high-strain-rate superplasticity in low carbon low alloy steels with commercial potential.

    Science.gov (United States)

    Cao, Wenquan; Huang, Chongxiang; Wang, Chang; Dong, Han; Weng, Yuqing

    2017-08-23

    Superplastic materials are capable of exhibiting large tensile elongation at elevated temperature, which is of great industrial significance because it forms the basis of a fabrication method to produce complex shapes. Superplasticity with elongation larger than 500% has been widely realized in many metals and alloys, but seldomly been succeeded in low carbon low alloy steel, even though it is commercially applied in the largest quantity. Here we report ultrahigh superplastic elongation of 900-1200% in the FeMnAl low carbon steels at high strain rate of 10(-2)-10(-3) s(-1). Such high-strain-rate superplasticity was attributed to dynamic austenite reverse phase transformation from a heavily cold rolled ferrite to fine-grained ferrite/austenite duplex microstructure and subsequent limited dynamic grain coarsening, under which a large fraction of high angle boundaries can be resulted for superplastic deformation. It is believed that this finding of the low carbon low alloy steel with ultrahigh superplasticity and relative low cost would remarkably promote the application of superplastic forming technique in automobile, aeronautical, astronautical and other fields.

  14. Gas-pressure forming of superplastic ceramic sheet

    Energy Technology Data Exchange (ETDEWEB)

    Nieh, T.G.; Wadsworth, J.

    1993-06-24

    Superplasticity in ceramics has now advanced to the stage that technologically viable superplastic deformation processing can be performed. In this paper, examples of biaxial gas-pressure forming of several ceramics are given. These include yttria stabilized, tetragonal zirconia (YTZP) a 20% alumina/YTZP composite, and silicon. In addition, the concurrent superplastic forming and diffusion bonding of a hybrid YTZP/C103 (ceramic-metal) structure are presented. These forming processes offer technological advantages of greater dimensional control and increased variety and complexity of shapes than is possible with conventional ceramic shaping technology.

  15. Numerical simulation and experimental study on cavity growth in uniaxial tension of superplastic magnesium alloy

    Institute of Scientific and Technical Information of China (English)

    于彦东; 张凯锋; 郑海荣; 蒋大鸣

    2003-01-01

    The cavity growth was studied in uniaxial tension of superplastic magnesium alloy. An exponentially increasing cavity growth model was introduced into the numerical simulation effectively. A three-dimensional rigid visco-plastic finite element method (FEM) program was developed to predict the variation of radius and volume fraction of cavity. Experimental radius and volume fraction of cavity were determined based on the optical microscope observation and analyses. The values obtained by numerical simulation are perfectly in agreement with experimental results. The results are potentially helpful to designing the optimal processing parameters for superplastic forming of materials and to enhance their subsequent mechanical properties.

  16. Deformation of superplastic alloys at relatively low strain rates

    Energy Technology Data Exchange (ETDEWEB)

    Grivas, D.

    1978-02-01

    The superplastic and sub-superplastic creep properties of Pb-Sn eutectic and Al-Zn eutectoid alloys were studied. Various thermomechanical treatments we tested to check the possibilities of whether the subsuperplastic deformation mechanism is affected by these treatments. All thermomechanical histories were found to reveal the same stress exponent, which is believed to be indicative of the predominant mechanism. The mechanical data in the low stress region lead us to suggest that dislocation glide is the predominant mechanism in this region. At higher stresses extensive grain boundary sliding takes place and the dislocation movement is directed to relieve the stress concentration developed by the grain movement.

  17. Thinning Behavior Simulations in Superplastic Forming of Friction Stir Processed Titanium 6Al-4V

    Science.gov (United States)

    Edwards, Paul D.; Sanders, Daniel G.; Ramulu, M.; Grant, Glenn; Trapp, Tim; Comley, Peter

    2010-06-01

    A study was undertaken to simulate the thinning behavior of titanium 6Al-4V alloy sheet during Superplastic Forming and to evaluate the feasibility of controlling thinning in areas of interest with Friction Stir Processing (FSP) of the material. The commercially available Finite Element Analysis software ABAQUS was used to execute these simulations. Material properties of the parent sheet and the Friction Stir Processed regions input into the models were determined experimentally by elevated temperature tensile testing. The results of these simulations were compared to experimental test results via Superplastically Forming representative aerospace parts and analytical computations for validation. It was found that numerical simulations can be used to predict the thin-out characteristics of superplastically formed titanium parts and the thin-out can be controlled in desired areas by FSP, locally, prior to forming.

  18. Superplastic forming and diffusion bonding: Progress and trends

    Directory of Open Access Journals (Sweden)

    Zhiqiang Li

    2015-01-01

    Full Text Available This paper summarized recent progress in metal superplasticity and the application of Superplastic Forming/Diffusion Bonding (SPF/DB or SPF/Welding in typical structures. Various aerospace components such as three dimensional lattice structures made by SPF/DB have been demonstrated. In addition, some newly developed technologies, such as melt droplet spreading/thermo-mechanical forming (MDS/TMF, were also included. Finally, the future potential of SPF/DB technology was predicted.

  19. Superplasticity of Ti2448 Alloy with Nanostructured Grains

    Institute of Scientific and Technical Information of China (English)

    M.J. Xiao; Y.X. Tian; G.W. Mao; S.J. Li; Y.L. Hao; R. Yang

    2011-01-01

    Ti-24Nb-4Zr-8Sn, abbreviated as Ti2448 from its chemical composition in weight percent, is a multifunctional β type titanium alloy with body centered cubic (bcc) crystal structure, and its highly localized plastic deformation behavior contributes significantly to grain refinement during conventional cold processing. In the paper, the nanostructured (NS) alloy with grain size less than 50 nm produced by cold rolling has been used to investigate its superplastic deformation behavior by uniaxial tensile tests at initial strain rates of 1.5×10-2, 1.5×10-3 and 1.6×10-4 s-1 and temperatures of 600, 650 and 700℃. The results show that, in comparison with the coarse-grained alloy with size of 50 μm, the NS alloy has better superplasticity with elongation up to ~275% and ultimate strength of 50-100 Mpa. Strain rate sensitivity (m) of the NS alloy is 0.21, 0.30 and 0.29 for 600, 650 and 700℃, respectively. These results demonstrate that grain refinement is a valid way to enhance the superplasticity of Ti2448 alloy.

  20. Superplastic behavior of coarse-grained aluminum alloys

    NARCIS (Netherlands)

    Chezan, AR; De Hosson, JTM

    2005-01-01

    In this paper we concentrate on the superplastic behavior and the microstructural evolution of two coarse-grained Al alloys: Al-4.4w/oMg and Al-4.4w/oMg-0.4w/oCu. The values for the strain rate sensitivity index and activation energy suggest that solute drag on dislocation motion is an important phe

  1. Deformation and reconstruction mechanisms in coarse-grained superplastic Al-Mg alloys

    NARCIS (Netherlands)

    Soer, W. A.; Chezan, A. R.; De Hosson, J. Th. M.

    2006-01-01

    This paper concentrates on the superplastic response of fine-grained and coarse-grained Al-Mg alloys under uniaxial tension. To identify the main characteristics of superplastic deformation and to determine the optimum deformation parameters, the microstructure and dislocation substructure of the al

  2. High strain rate superplastic aluminium alloys: the way forward?

    Energy Technology Data Exchange (ETDEWEB)

    Grimes, R.; Dashwood, R.J.; Flower, H.M. [Imperial Coll. of Science, Technology and Medicine, London (United Kingdom). Dept. of Materials

    2001-07-01

    The technical and commercial barriers to the development and successful exploitation of a high strain rate superplastically deformable aluminium alloy for use in the automotive industry are considered in this paper. Batch processing routes, such as mechanical alloying or equal channel angular extrusion, employed to deliver appropriate chemistry and structure, are inherently costly and unlikely to deliver either the quantity or the size of strip required commercially. There is evidence that there is still scope for development of conventional casting and rolling routes, but a particulate casting route combined with roll consolidation offers the prospect of a commercially viable Al-Mg-Zr product. The use of alloying additions, including zirconium, is also discussed and comparative costs are presented: on this basis the use of scandium appears economically prohibitive. (orig.)

  3. Superplasticity of the aluminum alloys containing the Al{sub 3}Ni eutectic particles

    Energy Technology Data Exchange (ETDEWEB)

    Portnoy, V.K. [Department of Physical Metallurgy Non-Ferrous Metals, National University of Science and Technology ' ' MISIS' ' , Moscow (Russian Federation); Mikhaylovskaya, A.V.

    2012-09-15

    The structures and parameters of superplasticity of aluminum alloys containing fine and coarse eutectic Al{sub 3}Ni particles were investigated. Traditional hot and cold rolling were used for sheet producing. The research alloys have low- or high - alloying solid solution. Superplasticity characterization of the alloy with high-alloying solid solution is much better beside alloys with low-alloying solid solution. Alloying by zirconium improves superplasticity in some investigated alloys. Some alloys with partially recrystallized structure show d = 500-700% at T = 0.95 Tm with the constant strain rates to the range of (1.10{sup -3}-1.10{sup -2}) s{sup -1}. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  4. Boronization and Carburization of Superplastic Stainless Steel and Titanium-Based Alloys

    Directory of Open Access Journals (Sweden)

    Masafumi Matsushita

    2011-07-01

    Full Text Available Bronization and carburization of fine-grain superplastic stainless steel is reviewed, and new experimental results for fine grain Ti88.5Al4.5V3Fe2Mo2 are reported. In superplastic duplex stainless steel, the diffusion of carbon and boron is faster than in non-superplastic duplex stainless steel. Further, diffusion is activated by uniaxial compressive stress. Moreover, non-superplastic duplex stainless steel shows typical grain boundary diffusion; however, inner grain diffusion is confirmed in superplastic stainless steel. The presence of Fe and Cr carbides or borides is confirmed by X-ray diffraction, which indicates that the diffused carbon and boron react with the Fe and Cr in superplastic stainless steel. The Vickers hardness of the carburized and boronized layers is similar to that achieved with other surface treatments such as electro-deposition. Diffusion of boron into the superplastic Ti88.5Al4.5V3Fe2Mo2 alloy was investigated. The hardness of the surface exposed to boron powder can be increased by annealing above the superplastic temperature. However, the Vickers hardness is lower than that of Ti boride.

  5. Superplasticity of a Ti-24Al-14Nb-3V-0.5Mo Intermetallic Alloy

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Superplastic properties and microstructural evolution of a Ti-24Al-14Nb-3V-0.5Mo (at. pct)intermetallic alloy were studied. Optimum superplastic properties were obtained for temperatures in the interval 960°C< T<980°C. The apparent activation energy in the superplastic regime was determined and the deformation mechanism was also discussed. Based on the studies, a curve panel with three sheets sandwich structure was fabricated successfully. The microstructures corresponding to different strain in the part were also studied.

  6. High Temperature Creep and Superplasticity in a Mg-Zn-Zr Alloy

    Institute of Scientific and Technical Information of China (English)

    S. Spigarelli; M. El Mehtedi; M. Regev; E. Gariboldi; N. Lecis

    2012-01-01

    Creep and superplasticity were investigated by testing a fine-grained extruded Mg–Zn–Zr magnesium alloy under a wide range of applied stress in the temperature range between 100 and 300 ℃. Grain boundary sliding became the dominating mechanism at 200 ℃, leading to a true superplastic behaviour at 300 ℃, where superplasticity was attained even under relatively high strain rates (5×10-3 s-1 ). By contrast, for lower temperatures, the straining process was controlled by dislocation climb. A comprehensive model, taking into account the simultaneous operation of the different mechanisms, was developed to describe the strain rate dependence on applied stress.

  7. Achieving superplastic properties in a ZK10 magnesium alloy processed by equal-channel angular pressing

    Directory of Open Access Journals (Sweden)

    Roberto B. Figueiredo

    2017-04-01

    Full Text Available Equal-channel angular pressing provides an opportunity for refining the grain structure and introducing superplastic properties in magnesium alloys. This report describes the use of this processing technique with a ZK10 (Mg–1.0 wt.% Zn–0.26 wt.% Zr alloy. The grain structure was successfully refined from ∼12.9 to ∼5.2 μm after 4 passes and superplastic elongations were observed when testing at low strain rates at temperatures of 473 and 523 K. An analysis shows that the superplastic behavior is consistent with the conventional theoretical model for superplastic flow and at higher stresses and strain rates there is a transition to control by a viscous glide process.

  8. Elastic constants for superplastically formed/diffusion-bonded sandwich structures

    Science.gov (United States)

    Ko, W. L.

    1979-01-01

    Formulae and the associated graphs are presented for contrasting the effective elastic constants for a superplastically formed/diffusion-bonded (SPF/DB) corrugated sandwich core and a honeycomb sandwich core. The results used in the comparison of the structural properties of the two types of sandwich cores are under conditions of equal sandwich density. It was found that the stiffness in the thickness direction of the optimum SPF/DB corrugated core (i.e., triangular truss core) was lower than that of the honeycomb core, and that the former had higher transverse shear stiffness than the latter.

  9. 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.

  10. Formability and cavitation behavior of superplastic AA5083 aluminum alloy under biaxial tension

    Institute of Scientific and Technical Information of China (English)

    LUO Ying-bing; LI Da-yong; PENG Ying-hong

    2006-01-01

    The superplastic forming potential of two fine-grained 5083 aluminum alloys were studied under biaxial tension using a pneumatic bulge test. Experiments were performed at temperatures ranging from 475 to 525 ℃ with three different strain paths ranging from equi-biaxial to approaching plane strain. The shape of the forming limited diagram(FLD) is found to be significantly different from FLDs commonly used in room temperature stamping. The effects of temperature on final thickness distribution, dome height and cavitation were investigated for the case of equi-biaxial stretching. Increasing temperature in free bulge forming can improve the thickness distribution of final parts but have no significant effect on dome height. The results indicate that determination of forming limits in SPF cannot be represented with a simple FLD and additional metrics such as external thinning and internal cavitation needed to determine the SPF potential of a material.

  11. Effect of equal channel angular extrusion on the microstructure and superplasticity of an Al-Li alloy

    Science.gov (United States)

    Salem, H. G.; Lyons, J. S.

    2002-08-01

    This research investigates the use of equal channel angular extrusion (ECAE) processing to produce a superplastic form of the aluminum alloy 2098. The starting material was a hot-rolled and precipitation-hardened plate with elongated grains of width 67-92 µm, and a composition in weight percent of 2.2% Li, 1.3% Cu, 0.73% Mg, 0.05% Zr, balance Al. Microstructural evolution was investigated with optical and transmission electron microscopy (TEM) and microhardness measurements after each step of a multipass ECAE process. ECAE produced a submicron grain structure with an average size of about 0.5 µm. The sub-grain microstructure size was a function of the magnitude of the input strain and the extrusion temperature. Misorientation angles of the developed submicron structure increase with increasing number of passes at warm working temperatures. Superplastic behavior of the ECAE-processed alloy was achieved. However, the low zirconium content of the 2098 alloy resulted in grain growth of the refined structure at the superplastic processing temperatures, placing a lower limit on the deformation rates that can be used.

  12. Ultrafine-grained magnesium–lithium alloy processed by high-pressure torsion: Low-temperature superplasticity and potential for hydroforming

    Energy Technology Data Exchange (ETDEWEB)

    Matsunoshita, Hirotaka [Department of Materials Science and Engineering, Faculty of Engineering, Kyushu University, Fukuoka 819-0395 (Japan); Edalati, Kaveh, E-mail: kaveh.edalati@zaiko6.zaiko.kyushu-u.ac.jp [Department of Materials Science and Engineering, Faculty of Engineering, Kyushu University, Fukuoka 819-0395 (Japan); WPI, International Institute for Carbon-Neutral Energy Research (WPI-I2CNER), Kyushu University, Fukuoka 819-0395 (Japan); Furui, Mitsuaki [Graduate School of Science and Engineering for Research, University of Toyama, Toyama 930-8555 (Japan); Horita, Zenji [Department of Materials Science and Engineering, Faculty of Engineering, Kyushu University, Fukuoka 819-0395 (Japan); WPI, International Institute for Carbon-Neutral Energy Research (WPI-I2CNER), Kyushu University, Fukuoka 819-0395 (Japan)

    2015-07-29

    A Mg–Li alloy with 8 wt% Li was processed by severe plastic deformation (SPD) through the process of high-pressure torsion (HPT) to achieve ultrafine grains with an average grain size of ~500 nm. Tensile testing with an initial strain rate of 10{sup −3} s{sup −1} showed that the alloy exhibited superplasticity at a temperature of 323 K or higher. Tensile testing in boiling water confirmed that the specimens were elongated to 350–480% at 373 K under the initial strain rates of 10{sup −3} s{sup −1} to {sup 1}0{sup −2} s{sup −1} with a strain rate sensitivity of ~0.3. The current study suggests that not only superplastic forming but also superplastic hydroforming should be feasible after the grain refinement using the HPT method.

  13. Superplastic Deformation Behavior of Hot-rolled AZ31 Magnesium Alloy Sheet at Elevated Temperatures

    Institute of Scientific and Technical Information of China (English)

    ZHANG Kaifeng; YIN Deliang; WANG Guofeng; HAN Wenbo

    2006-01-01

    Uniaxial tensile tests were carried out in the temperature range of 250-450 ℃ and the strain rate range of 0.7×10-3-1.4×10-1s-1 to evaluate the superplasticity of AZ31 Mg alloy. The threshold stress which characterizes the difficulty for grain boundary sliding was calculated at various temperatures. The surface relieves of superplastically deformed specimens were observed by using a scanning electronic microscope (SEM). Results show that, at the temperature of 400 ℃ and strain rate of 0.7×10-3 s-1, the strain rate sensitivity exponent, i e, m value reaches 0.47 and the maximum elongation of 362.5% is achieved. Grain boundary sliding (GBS) is the primary deformation mechanism and characterized by a pronounced improvement in the homogeneity with increasing temperatures. A large number of filaments were formed at the end of deformation and intergranular cavities were produced with the necking and fracture of filaments. Finally, the model for the formation of intergranular cavities was proposed.

  14. Early stages of superplasticity and positron lifetime spectroscopy in an Al-Mg-Cu alloy

    Energy Technology Data Exchange (ETDEWEB)

    Ayciriex, M.D.; Romero, R.; Somoza, A. [Universidad Nacional del Centro de la Provincia de Buenos Aires (Argentina). Instituto de Fisica de Materiales Tandil

    1996-07-01

    In the present paper, by using positron lifetime technique, a careful study is carried out to analyze the microstructural changes induced on samples of an Al-based commercial alloy (Al-Mg-Cu-Mn-Cr) by superplastic deformation in the early stages of superplastic behavior of the alloy (strain range from 0.2% to 100%). These results are compared with those obtained on specimens only heat treated at the same temperature and for a time equivalent to the elapsed time during each tensile test, in order to evaluate the thermal contribution to the microstructural changes induced during the superplastic deformation process. Moreover, the positron results were linked with the microstructural evolution of the samples followed by means of optical microscopy and Vickers microhardness technique.

  15. Enhanced superplasticity in an extruded high strength Mg–Gd–Y–Zr alloy with Ag addition

    Energy Technology Data Exchange (ETDEWEB)

    Movahedi-Rad, A. [School of Metallurgical and Materials Engineering, College of Engineering, University of Tehran, Tehran (Iran, Islamic Republic of); Mahmudi, R., E-mail: mahmudi@ut.ac.ir [School of Metallurgical and Materials Engineering, College of Engineering, University of Tehran, Tehran (Iran, Islamic Republic of); Wu, G.H.; Jafari Nodooshan, H.R. [National Engineering Research Center of Light Alloy Net Forming, Shanghai Jiao Tong University, Shanghai 200240 (China)

    2015-03-25

    Highlights: • Addition of 2% Ag to the base alloy refined the microstructure and increased m-value. • Volume fractions of both high angle grain boundaries and particles increased after Ag addition. • Ag-containing alloy had an m-value of 0.51, typical of superplastic materials. • Grain boundary sliding accommodated by lattice diffusion was the dominant deformation mechanism. - Abstract: The effect of 2 wt% Ag addition on the superplastic behavior of an extruded Mg–8.5Gd–2.5Y–0.5Zr (wt%) alloy was investigated by impression testing in the temperature range of 523–598 K. The average sizes of the dynamically recrystallized grains of the Ag-free and Ag-containing alloys were about 8 and 3 μm, respectively. Analysis of electron backscattered diffraction (EBSD) data confirmed the higher fractions of high-angle grain boundaries (HAGBs) in the Ag-containing alloy. The deformation response of this alloy in proper temperature range conforms to regions I, II and III, typical of superplastic deformation behavior. The addition of Ag to the base alloys led to enhanced superplasticity in region II by increasing the strain rate sensitivity (SRS) indices (m-values) from 0.25 to 0.51 and 0.36 to 0.46 at 573 and 598 K, respectively. These high m-values together with the activation energy of 181 kJ/mol suggest that the major mechanism involved in superplastic deformation is grain boundary sliding (GBS) accommodated by lattice diffusion at temperatures above 573 K.

  16. Continuous recrystallization during thermomechanical processing of a superplastic Al-10Mg-0.1Zr alloy

    Science.gov (United States)

    Hales, S. J.; Mcnelley, T. R.; Crooks, R.

    1990-01-01

    Microstructural evolution via static continuous recrystallization during thermomechanical processing of an Al-Mg-Zr alloy is addressed. Mechanical property data demonstrated that as-rolled material was capable of superplastic response without further treatment. Further, superplastic ductility at 300 C was enhanced by a factor of five by increasing the reheating time between rolling passes during processing also at 300 C. This enhanced ductility was associated with a Cu-texture and a microstructure consisting of predominantly high-angle boundaries. Processing to minimize recovery resulted in a strong Brass-texture component, a predominantly low-angle boundary microstructure and poorer ductility.

  17. Continuous recrystallization during thermomechanical processing of a superplastic Al-10Mg-0.1Zr alloy

    Science.gov (United States)

    Hales, S. J.; Mcnelley, T. R.; Crooks, R.

    1990-01-01

    Microstructural evolution via static continuous recrystallization during thermomechanical processing of an Al-Mg-Zr alloy is addressed. Mechanical property data demonstrated that as-rolled material was capable of superplastic response without further treatment. Further, superplastic ductility at 300 C was enhanced by a factor of five by increasing the reheating time between rolling passes during processing also at 300 C. This enhanced ductility was associated with a Cu-texture and a microstructure consisting of predominantly high-angle boundaries. Processing to minimize recovery resulted in a strong Brass-texture component, a predominantly low-angle boundary microstructure and poorer ductility.

  18. Effect of Post-Rolling after ECAP on Superplastic Behavior of Commercial Al-Mg Alloy

    Institute of Scientific and Technical Information of China (English)

    Dong Hyuk Shin; Byung Du Ahn; Hyun Soo; Woo Kyeom Kim; Kyung-Tae Park

    2004-01-01

    A commercial Al-Mg alloy was subjected to equal channel angular pressing of 4 passes with and without postrolling, and the effects of post-rolling on the deformation characteristics of the alloy at 723 K were examined. Post-rolling was found to influence the deformation behavior significantly. The deformation behavior of the alloy processed only by equal channel angular pressing was characterized by (a) localized deformation indicated by severe surface prominence and depression, (b) the strain rate sensitivity of 0.33, and (c) moderate high strain rate superplastic elongations. By contrast, that of the alloy processed by equal channel angular pressing and post-rolling (70 % thickness reduction) was manifested by (a) uniform deformation associated with grain boundary sliding throughout the sample, (b) a sigmoidal behavior showing the strain rate sensitivity of 0.45 at the intermediate strain rates in the logarithmic stress-strain rate curve, and (c) very large high strain rate superplastic elongations.

  19. Recrystallization and superplasticity at 300 C in an aluminum-magnesium alloy

    Science.gov (United States)

    Hales, S. J.; Mcnelley, T. R.; Mcqueen, H. J.

    1991-01-01

    Variations in thermomechanical processing (TMP) which regulate the microstructural characteristics and superplastic response of an Al-10Mg-0.1Zr alloy at 300 C were evaluated. Mechanical property data revealed that the superplastic ductility can be enhanced by simultaneously increasing the total rolling strain, the reduction per pass, and the duration of reheating intervals between passes during isothermal rolling. Texture and microscopy data were consistent with the development of a refined microstructure by recovery-dominated processes, i.e., continuous recrystallization, during the processing. The mechanisms by which a refined substructure can be progressively converted into a fine-grained structure during repeated cycles of deformation and annealing are addressed. A qualitative description of the complex sequence of developments leading to a microstructure better suited to support superplastic response is presented.

  20. Recrystallization and superplasticity at 300 °C in an aluminum-magnesium alloy

    Science.gov (United States)

    Hales, S. J.; McNelley, T. R.; McQueen, H. J.

    1991-05-01

    Variations in thermomechanical processing (TMP) which regulate the microstructural characteristics and superplastic response of an Al-lOMg-0.1Zr alloy at 300 °C were evaluated. Mechanical property data revealed that the superplastic ductility can be enhanced by simultaneously increasing the total rolling strain, the reduction per pass, and the duration of reheating intervals between passes during isothermal rolling. Texture and microscopy data were consistent with the development of a refined microstructure by recovery-dominated processes, i.e., continuous recrystallization, during the processing. The mechanisms by which a refined substructure can be progressively converted into a fine-grained structure during repeated cycles of deformation and annealing are addressed. A qualitative description of the complex sequence of developments leading to a microstructure better suited to support superplastic response is presented.

  1. Influence of fluoridation on the strength of superplastic Zn-21Al-2Cu alloy deformed in a saline medium

    Energy Technology Data Exchange (ETDEWEB)

    Elizalde-Torres, J.; Torres-Villasenor, G. [UNAM, Mexico Distrito Federal (Mexico); Sandoval-Jimenez, A. [Instituto Nacional de Investigaciones Nucleares, Mexico Distrito Federal (Mexico)

    1999-04-09

    The interest in Zi-Al-Cu alloys has intensified in recent years because they possess the highest known yield strengths among the entire series of Zn-Al superplastic alloys. The superplastic materials are generally fine-grained materials and the deformation is associated with the grain boundary processes. Because of this, the superplastic alloys are exposed to a potential danger of intergranular stress corrosion cracking under susceptible service conditions. Consequently, the study of enhancing the strength and increasing the corrosion resistance of the material at room temperature is an important research area. Fluorine passivation technology of metal surfaces (fluoridation) has been proved to be very effective in the protection of several metals such as austenitic stainless steel and aluminum. In the present investigation the superplastic Zn-Al-Cu alloy has been studied to evaluate the effects of fluoridation and the stress corrosion damage.

  2. The development of a high strain rate superplastic Al-Mg-Zr alloy

    Energy Technology Data Exchange (ETDEWEB)

    Dashwood, R.J.; Grimes, R.; Harrison, A.W.; Flower, H.M. [Imperial Coll. of Science, Technology and Medicine, London (United Kingdom). Dept. of Materials

    2001-07-01

    In order for superplastic forming of aluminium to break out of the niche market low cost alloys are required that exhibit higher strain rate capability that are capable of volume production. This paper describes an investigation into the feasibility of producing such an alloy. A series of Al-4Mg alloys with 0, 0.25, 0.5, 0.75 and 1% Zr additions was prepared using a cheap particulate casting route, in an attempt to achieve higher levels of Zr supersaturation than are possible with conventional casting. The particulate was processed into a sheet product via hot extrusion followed by cold rolling and the effect of a number of process variables on the SPF performance of the sheet was investigated. It was found that increasing the Zr content, and manipulation of the thermomechanical processing conditions improved the SPF performance. Ductilities in excess of 600% have been achieved at a strain rate of 0.01 s{sup -1}, together with flow stresses less than 15 MPa. (orig.)

  3. Thermomechanical Processing and Superplasticity of AZ91 Magnesium Alloy

    Institute of Scientific and Technical Information of China (English)

    Rongshi CHEN; J.J. Blandin; M.Suéry; Qudong WANG; Enhou HAN

    2004-01-01

    The effect of extrusion on grain refinement has been studied in the AZ91 cast ingots. It is found that grain size smaller than 10 μm can be obtained by the extrusion processing. Vickers hardness measurements were also carried out to evaluate the effect of these processes on the room temperature mechanical properties. The experimental results of high temperature tensile tests revealed that the stress was inversely proportional to the square of the grain size and that the activation energy for superplastic flow was higher than that for grain boundary diffusion.

  4. Investigation on the factors influencing the thickness distribution of superplastic-formed components

    Institute of Scientific and Technical Information of China (English)

    GAO Chong-yang; FANG You-tong

    2005-01-01

    In the superplastic sheet forming process, the uniformity of the sheet's final thickness distribution is vital for ensuring the good mechanical quality of the formed components. The influences of the component shape and the contact friction on the final thickness distribution were investigated in this work by using finite element method on a series of axisymmetric models. It was concluded that shape optimization and friction elimination are required to get uniform thickness distribution, and eventually to improve the mechanical quality of the formed components. The constitutive equation of the Ti-6A1-4V superplastic material was also determined on the basis of experimental data.

  5. Effect of two-stage aging on superplasticity of Al-Li alloy

    Institute of Scientific and Technical Information of China (English)

    LUO Zhi-hui; ZHANG Xin-ming; DU Yu-xuan; YE Ling-ying

    2006-01-01

    The effect of two-stage aging on the microstructures and superplasticity of 01420 Al-Li alloy was investigated by means of OM, TEM analysis and stretching experiment. The results demonstrate that the second phase particles distributed more uniformly with a larger volume fraction can be observed after the two-stage aging (120 ℃, 12 h+300 ℃, 36 h) compared with the single-aging(300 ℃, 48 h). After rolling and recrystallization annealing, fine grains with size of 8-10 μm are obtained, and the superplastic elongation of the specimens reaches 560% at strain rate of 8×10-4 s-1 and 480 ℃. Uniformly distributed fine particles precipitate both on grain boundaries and in grains at lower temperature. When the sheet is aged at high temperature, the particles become coarser with a large volume fraction.

  6. Cryogenic mechanical properties of low density superplastically formable Al-Li alloys

    Science.gov (United States)

    Verzasconi, S. L.; Morris, J. W., Jr.

    1989-01-01

    The aerospace industry is considering the use of low density, superplastically formable (SPF) materials, such as Al-Li alloys in cryogenic tankage. SPF modifications of alloys 8090, 2090, and 2090+In were tested for strength and Kahn tear toughness. The results were compared to those of similar tests of 2219-T87, an alloy currently used in cryogenic tankage, and 2090-T81, a recently studied Al-Li alloy with exceptional cryogenic properties (1-9). With decreasing temperature, all materials showed an increase in strength, while most materials showed an increase in elongation and decrease in Kahn toughness. The indium addition to 2090 increased alloy strength, but did not improve the strength-toughness combination. The fracture mode was predominantly intergranular along small, recrystallized grains, with some transgranular fracture, some ductile rupture, and some delamination on large, unrecrystallized grains.

  7. Stored energy analysis of Zn-5Al eutectic alloy in superplastic deformation

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The stored energy and the energy release during SPD (superplastic deformation) ofa Zn-5Al alloy were studied. The alloy after rolling process gains more stored energy, and the as-rolled specimen can obtain maximum elongation and minimum flow stress without hot holding treatment before SPD. Experimental results show that stored energy release process is along with SPD process and is also an impetus to SPD. The as-rolled Zn-5Al alloy has 48 J/mol stored energy which was measured with DSC (differential scanning calorimeter) and conforms well to the calculated value. The as-rolled Zn-5Al alloy after SPD with an elongation of 2 500% releases 112 J/mol stored energy. Analysis shows that the strain rate is in direct ratio to the rate of stored energy release.

  8. Microstructure evolution and fracture behavior in superplastic deformation of hot-rolled AZ31 Mg alloy sheet

    Energy Technology Data Exchange (ETDEWEB)

    Yin, D.L.; Zhang, K.F.; Wang, G.F. [School of Material Science and Technology, Harbin Inst. of Tech. (China)

    2005-07-01

    Fine-grained AZ31 magnesium alloy sheets were prepared through hot rolling process. The superplastic properties of hot-rolled AZ31 Mg alloy was examined by uniaxial tensile tests at a temperature range 250{proportional_to}450 C and strain rate range 0.7 x 10{sup -3}{proportional_to}1.4 x 10{sup -1} s{sup -1}. Optical and scanning electronic microscope (SEM) were used to observe the microstructure evolution and fracture behavior in superplastic deformation of AZ31 Mg alloy and the values of deformation activation energy at various temperatures were calculated. It is demonstrated that, the hot-rolled AZ31 alloy begins to exhibit superplasticity from 300 C and a maximum elongation of 362.5% is obtained at 400 C and 0.7 x 10{sup -3} s{sup -1}. In the temperature range 300{proportional_to}400 C, the dominant superplastic deformation mechanism is grain boundary sliding (GBS) controlled by grain boundary diffusion and the influence of temperature on the fracture behavior of AZ31 Mg alloy is characterized by the change from dimple-aggregating type to intercrystalline one. (orig.)

  9. Superplastic behaviour of AZ91 magnesium alloy processed by high-pressure torsion

    Energy Technology Data Exchange (ETDEWEB)

    Al-Zubaydi, Ahmed S.J., E-mail: asaz1e11@soton.ac.uk [Materials Research Group, Faculty of Engineering and the Environment, University of Southampton, Southampton SO17 1BJ (United Kingdom); Branch of Materials Science, Department of Applied Sciences, University of Technology, Baghdad (Iraq); Zhilyaev, Alexander P. [Institute for Problems of Metals Superplasticity, Russian Academy of Sciences, Khalturina 39, Ufa 450001 (Russian Federation); Wang, Shun C.; Reed, Philippa A.S. [Materials Research Group, Faculty of Engineering and the Environment, University of Southampton, Southampton SO17 1BJ (United Kingdom)

    2015-06-18

    An investigation has been conducted on the tensile properties of a fine-grained AZ91 magnesium alloy processed at room temperature by high pressure torsion (HPT). Tensile testing was carried out at 423 K, 473 K and 573 K using strain rates from 1×10{sup −1} s{sup −1} to 1×10{sup −4} s{sup −1} for samples processed in HPT for N=1, 3, 5 and 10 turns. After testing was completed, the microstructures were investigated by scanning electron microscopy and energy dispersive spectroscopy. The alloy processed at room temperature in HPT exhibited excellent superplastic behaviour with elongations higher than elongations reported previously for fine-grained AZ91 alloy produced by other severe plastic deformation processes, e.g. HPT, ECAP and EX-ECAP. A maximum elongation of 1308% was achieved at a testing temperature of 573 K using a strain rate of 1×10{sup −4} s{sup −1}, which is the highest value of elongation reported to date in this alloy. Excellent high-strain rate superplasticity (HSRSP) was achieved with maximum elongations of 590% and 860% at temperatures of 473 K and 573 K, respectively, using a strain rate of 1×10{sup −2} s{sup −1}. The alloy exhibited low-temperature superplasticity (LTSP) with maximum elongations of 660% and 760% at a temperature of 423 K and using strain rates of 1×10{sup −3} s{sup −1} and 1×10{sup −4} s{sup −1}, respectively. Grain-boundary sliding (GBS) was identified as the deformation mechanism during HSRSP, and the glide-dislocation creep accommodated by GBS dominated during LTSP. Grain-boundary sliding accommodated with diffusion creep was the deformation mechanism at high test temperature and slow strain rates. An enhanced thermal stability of the microstructure consisting of fine equiaxed grains during deformation at elevated temperature was attributed to the extremely fine grains produced in HPT at room temperature, a high volume fraction of nano β-particles, and the formation of β-phase filaments.

  10. Mechanical problems of superplastic fill-forming bulge solved by one-dimensional tensile and two-dimensional free bulging constitutive equations

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Because of the strong structural sensitivity of superplasticity, the deformation rule must be affected by stress-state. It is necessary to prove whether one-dimensional tensile constitutive equation can be directly generalized to deal with the two-dimensional mechanical problems or not. In this paper, theoretical results of fill-forming bulge have been derived from both one-dimensional tensile and two-dimensional bulging constitutive equation with variable m value. By comparing theoretical analysis and experimental results made on typical superplastic alloy Zn-wt22%Al, it is shown that one-dimensional tensile constitutive equation cannot be directly generalized to deal with two-dimensional mechanical questions. A method to correct deviation between theoretical and experimental results is also proposed.

  11. Effect of electric current pulse on grain growth in superplastic deformation of 2091 Al-Li alloy

    Institute of Scientific and Technical Information of China (English)

    刘志义; 许晓嫦; 崔建忠

    2003-01-01

    The effect of electric current pulse on the grain growth in the superplastic deformation of 2091 Al-Li alloy was investigated. Optical metallographic microstructure observation and average linear intercept measuring results show that at same strain, the grain size in the superplastic deformation loaded with electric current pulse is smaller than that unemploying electric current pulse, and so does the grain growth rate. TEM observation shows that the dislocation density at grain boundary in the superplastic deformation applied with electric current pulse is lower than that unemploying electric current pulse.It indicates that electric current pulse increases the rate of dislocation slip and climb in grain boundary, which leads to a decrease of both the density of the dislocation slipping across grain boundary at same strain rate and the driving force for grain growth, therefore the rate of grain growth decreases.The established model for grain growth shows an exponential relation of grain size with strain.

  12. The effect of composition on the mechanism of continuous recrystallization and superplastic response of aluminum-scandium alloys

    Energy Technology Data Exchange (ETDEWEB)

    Bradley, E.L. III

    1993-05-01

    The continuous recrystallization (CRX) appears to be fundamental in Al-Sc because it occurs irrespective of solute composition. It appears to be due to a combination of subgrain coalescence at low strains and incorporation of additional dislocations generated during grain boundary sliding at higher strains when the misorientation has increased sufficiently. Alloying additives such as Mg, Li are more important with respect to deformation after CRX is completed. Mg, and to a lesser extent Li, affect the max m-values (strain-rate sensitivities) in Al-Sc by changing the melting points (mp). Max m- values correlate inversely with mp so that the alloy with the greatest Mg had the highest m-values and lowest mp; the stress is raised at which power-law creep and breakdown occurs. The power-law breakdonw at much lower stresses in Al-0.5Sc and Al-1.2Li-0.5Sc causes the m-value to decrease more rapidly with strain rate. Al alloys for commercial superplastic applications should contain elements that raise the power-law strength so that the m-values are maximized while preserving the post-formed mechanical properties. Refs, figs, tabs.

  13. Superplastic behavior of hot extruded gamma TiAl (Mo, Si) alloys

    Energy Technology Data Exchange (ETDEWEB)

    Jimenez, J.A.; Carsi, M.; Ruano, O.A. [Dept. of Physical Metallurgy, Centro Nacional de Investigaciones Metalurgicas, C.S.I.C., Madrid (Spain); Frommeyer, G.; Knippscher, S. [Dept. of Materials Engineering, Max Planck Inst. fuer Eisenforschung, Duesseldorf (Germany); Wittig, J. [Dept. of Materials Science and Engineering, Vanderbilt Univ., Nashville (United States)

    2003-07-01

    Superplastic behavior of hot extruded intermetallic Ti-46Al-1.7(Mo,Si) (at%) alloys was studied by stress change tests in compression and tensile tests at temperatures ranging from 700 to 1050 C. The material produced by arc melting exhibited a structure of coarse lamellar grains in the as-cast condition that transforms to an equiaxic near {gamma} microstructure after processing by hot extrusion at 1250 C. This microstructure consists of zones of {gamma} grains finer than 1 {mu}m and band like regions with coarser grains, ranging from 5 to 20 {mu}m. In addition to {gamma} grains, a volume fraction of more than 20 vol% of {alpha}{sub 2}-Ti{sub 3}Al particles finely dispersed are also present in the fine-grained zones. Compression tests of the extruded material at stresses ranging from 4 to 825 MPa showed values of the strain-rate-sensitivity exponent near 0.5 at low stresses and/or high temperatures. The microstructure in the fine-grained areas remains essentially constant during deformation. TEM analysis of deformed samples in this regime leads to relate grain boundary sliding as the mechanism controlling the deformation process. High elongation to failure, characteristic of superplasticity, was achieved at 975 and 1050 C at an initial strain rate of 4.6 x 10{sup -4} and 4.6 x 10{sup -3} s{sup -1}. (orig.)

  14. Forming of a super plastic sheet metal made of MgAZ31 alloy

    Science.gov (United States)

    Zaid, Adnan I. O.; Al-Matari, Mustafa A. A.; Nazzal, M. A. H.

    2016-08-01

    Metal forming industries are constantly looking for advanced innovation, economical and energy efficient techniques. Superplastic forming has a great potential to be one of those advanced forming methods. It is a near net shape forming process which uses a unique type of materials where elongation exceeds 200% during a controlled forming conditions, e.g. temperature, pressure, and strain rate. Most of superplastic materials are formed by gas technique at elevated temperature. The main objectives of the research work in this paper were: to study the effects of the forming schemes on the forming time and thickness distribution of the formed and device a method to improve the forming part thickness and its uniformity distribution and the forming time. In this paper, a hydraulic and heating system were designed and manufactured to facilitate the experimental investigation. The superplastic magnesium alloy AZ31, Mg AZ31, was formed at 350°C with different strain rates to investigate the effect of the forming pressure profiles on the thickness uniformity of the superplastic formed part. The pressure profiles were generated based on Dutta and Mukherjee analytical approach. Finally, a variable strain rate method is modified to improve the uniformity of the thickness distribution of the formed part and reduce the forming time; which is a major limitation of superplastic forming.

  15. The measurement of friction for superplastic forming of Ti-6Al-4V

    Energy Technology Data Exchange (ETDEWEB)

    Kelly, R.B.; Leen, S.B.; Pashby, I.R.; Kennedy, A.R. [School of M3EM, Univ. of Nottingham (United Kingdom)

    2004-07-01

    An experimental test for measuring the friction between Ti-6Al-4V sheet material and S310 stainless steel tool material at 900 C is presented. The test is intended for application to Ti-6Al-4V superplastic forming for the manufacture of aeroengine components. The work is motivated by the need for accurate, representative data for process modelling, where accurate simulation is critical to formed component dimensions. The results show a time dependency of friction. The effects of boron nitride density, applied normal load and die surface roughness are investigated. (orig.)

  16. Superplasticity in a lean Fe-Mn-Al steel.

    Science.gov (United States)

    Han, Jeongho; Kang, Seok-Hyeon; Lee, Seung-Joon; Kawasaki, Megumi; Lee, Han-Joo; Ponge, Dirk; Raabe, Dierk; Lee, Young-Kook

    2017-09-29

    Superplastic alloys exhibit extremely high ductility (>300%) without cracks when tensile-strained at temperatures above half of their melting point. Superplasticity, which resembles the flow behavior of honey, is caused by grain boundary sliding in metals. Although several non-ferrous and ferrous superplastic alloys are reported, their practical applications are limited due to high material cost, low strength after forming, high deformation temperature, and complicated fabrication process. Here we introduce a new compositionally lean (Fe-6.6Mn-2.3Al, wt.%) superplastic medium Mn steel that resolves these limitations. The medium Mn steel is characterized by ultrafine grains, low material costs, simple fabrication, i.e., conventional hot and cold rolling, low deformation temperature (ca. 650 °C) and superior ductility above 1300% at 850 °C. We suggest that this ultrafine-grained medium Mn steel may accelerate the commercialization of superplastic ferrous alloys.Research in new alloy compositions and treatments may allow the increased strength of mass-produced, intricately shaped parts. Here authors introduce a superplastic medium manganese steel which has an inexpensive lean chemical composition and which is suited for conventional manufacturing processes.

  17. Elastic stability of superplastically formed/diffusion-bonded orthogonally corrugated core sandwich plates

    Science.gov (United States)

    Ko, W. L.

    1980-01-01

    The paper concerns the elastic buckling behavior of a newly developed superplastically formed/diffusion-bonded (SPF/DB) orthogonally corrugated core sandwich plate. Uniaxial buckling loads were calculated for this type of sandwich plate with simply supported edges by using orthotropic sandwich plate theory. The buckling behavior of this sandwich plate was then compared with that of an SPF/DB unidirectionally corrugated core sandwich plate under conditions of equal structural density. It was found that the buckling load for the former was considerably higher than that of the latter.

  18. Elastic constants for superplastically formed/diffusion-bonded corrugated sandwich core

    Science.gov (United States)

    Ko, W. L.

    1980-01-01

    Formulas and associated graphs for evaluating the effective elastic constants for a superplastically formed/diffusion bonded (SPF/DB) corrugated sandwich core, are presented. A comparison of structural stiffnesses of the sandwich core and a honeycomb core under conditions of equal sandwich core density was made. The stiffness in the thickness direction of the optimum SPF/DB corrugated core (that is, triangular truss core) is lower than that of the honeycomb core, and that the former has higher transverse shear stiffness than the latter.

  19. Use of laser(s) in the process of superplastic forming and diffusion bonding

    Energy Technology Data Exchange (ETDEWEB)

    Jocelyn, A.; Jonik, M.; Keevil, A.; Ackerman, M.; Way, J.; Flower, T. [Aerospace Mfg. Research Centre, Faculty of Computing, Engineering and Mathematical Sciences, Coldharbour Lane, Bristol (United Kingdom); Kar, A. [Univ. of Central Florida, School Optics/CREOL, Orlando, FL (United States)

    2004-07-01

    Superplastic forming and diffusion bonding (SPF/DB) has permitted the manufacture of some of the lightest, strongest, corrosion resistant, complex, and yet often elegant structures ever to be produced. For the last 30 years, all such components have been made by some form of high thermal-mass, isothermal method of production using conventional equipment, such as hot platen presses or furnaces. However, if laser(s) could be used just to heat the material to be superplastically formed, this could provide a novel, low thermal-mass, means of production which could, relatively easily, be integrated into a laser based manufacturing centre. In this paper, a concept is described of how a laser based manufacturing centre, comprised of a number of individual process cells, together with integrated pre and post SPF/DB operations, would work and the benefits that would result. The concept is based on four considerations. Firstly, that it is essential to heat the material directly and quickly. Secondly, the environment must be completely inert so that there is no contamination of components. Thirdly, the complete process of diffusion bonding must only entail the use of laser(s). Lastly, established laser activities such as cutting, welding, hole drilling or trepanning and the removal of surplus material, must be integrated into the process. In addition, the envisaged cells need to be modular in concept so industry can acquire capital plant progressively, thereby spreading the cost over time. (orig.)

  20. A high-strain-rate superplastic ceramic.

    Science.gov (United States)

    Kim, B N; Hiraga, K; Morita, K; Sakka, Y

    2001-09-20

    High-strain-rate superplasticity describes the ability of a material to sustain large plastic deformation in tension at high strain rates of the order of 10-2 to 10-1 s-1 and is of great technological interest for the shape-forming of engineering materials. High-strain-rate superplasticity has been observed in aluminium-based and magnesium-based alloys. But for ceramic materials, superplastic deformation has been restricted to low strain rates of the order of 10-5 to 10-4 s-1 for most oxides and nitrides with the presence of intergranular cavities leading to premature failure. Here we show that a composite ceramic material consisting of tetragonal zirconium oxide, magnesium aluminate spinel and alpha-alumina phases exhibits superplasticity at strain rates up to 1 s-1. The composite also exhibits a large tensile elongation, exceeding 1,050 per cent for a strain rate of 0.4 s-1. The tensile flow behaviour and deformed microstructure of the material indicate that superplasticity is due to a combination of limited grain growth in the constitutive phases and the intervention of dislocation-induced plasticity in the zirconium oxide phase. We suggest that the present results hold promise for the application of shape-forming technologies to ceramic materials.

  1. Superplasticity in an Aluminum Alloy 6061/A12O3p Composite

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The superplasticity of an Al2O3p/6061Al composite, fabricated by powder metallurgy techniques,has been investigated. Instead of any special thermomechanical processing or hot rolling, simple hot extrusion has been employed to obtain a fine grained structure before superplastic testing.Superplastic tensile tests were performed at strain rates ranging from 10-2 to 10-4 s-1 and at temperatures from 833 to 893 K. A maximum elongation of 200% was achieved at a temperature of 853 K and an initial strain rate of 1.67×10-3 s-1. The highest value obtained for the strain rate sensitivity index (m) was 0.32. Differential scanning calorimeter was used to ascertain the possibility of any partial melting in the vicinity of optimum superplastic temperature. These results suggested that no liquid phase existed where maximum elongation was achieved and deformation took place entirely in the solid state.

  2. Hot Workability and Superplasticity of Low-Al and High-Nb Containing TiAl Alloys

    Science.gov (United States)

    Tang, Bin; Zhao, Fengtong; Chu, Yudong; Kou, Hongchao; Li, Jinshan

    2017-09-01

    The superplastic deformation mechanism of low-Al and high-Nb containing TiAl alloy was investigated in compression mode. The experimental results showed that intense dynamic recrystallization (DRX) breaks the balance and leads to a significant drop in flow stress after the peak when deforming below 950°C. Arrhenius kinetic analysis revealed that the activation energy for superplastic compression first increased then decreased with temperature, suggesting a change in the deformation mechanism. Microstructure observations showed that, when deformed at 850°C, the deformation mechanism was grain-boundary sliding accommodated by γ-DRX, γ-intragranular deformation, and β/B2-phase decomposition, while the mechanism was grain-boundary sliding accommodated by γ-DRX, β/B2-DRX, and γ → β/B2 + α 2 phase transformation when deformed at 1000°C. After compression, the microstructure tended to be uniform, which may yield important information for the development of new deformation techniques for TiAl alloys.

  3. Cooperative grain boundary sliding at room temperature of a Zn-20.2%Al-1.8%Cu superplastic alloy

    Energy Technology Data Exchange (ETDEWEB)

    Munoz-Andrade, J.D. [Dept. de Materiales, Univ. Autonoma Metropolitana Unidad Azcapotzalco (Mexico); Mendoza-Allende, A.; Montemayor-Aldrete, J.A. [Inst. de Fisica, Univ. Nacional Autonoma de Mexico (Mexico); Torres-Villasenor, G. [Inst. de Investigacion en Materiales, Univ. Nacional Autonoma de Mexico (Mexico)

    2001-07-01

    By applying a new technique [1-2] which provides a mesoscopic coordinate system inscribed on the surface of a tensile specimen, with 371 {mu}m gage length for a Zn-20.2%Al-1.8%Cu superplastic alloy deformed at room temperature it is possible to show that: Deformation of the sample it is homogeneous at macroscopic level, but inhomogeneous at mesoscopical level. The inhomogeneity is ascribed to the sliding of grain blocks. For 28.5% of deformation the distribution function for the block sizes is described by: N(x) = 1.37 x{sup 3}exp(-3x/12.2 {mu}m), where, N(x) is the number of blocks of size x, inside an area of about 172 x 244 ({mu}m){sup 2}. (orig.)

  4. Effects of Heating Rate on the Process Parameters of Superplastic Forming for Zr55Cu30Al10Ni5

    Institute of Scientific and Technical Information of China (English)

    YANG Fan; SHI Tielin; LIAO Guanglan

    2014-01-01

    We investigated the effects of heating rate on the process parameters of superplastic forming for Zr55Cu30Al10Ni5 by differential scanning calorimetry. The continuous heating and isothermal annealing analyses suggested that the temperatures of glass transition and onset crystallization are heating rate-dependent in the supercooled liquid region. Then, the time-temperature-transformation diagram under different heating rates indicates that increasing the heating rate can lead to an increase of the incubation time at the same anneal temperature in the supercooled liquid region. Based on the Arrhenius relationship, we discovered that the incubation time increases by 1.08-1.11 times with double increase of the heating rate at the same anneal temperature, and then verified it by the data of literatures and the experimental results. The obtained curve of the max available incubation time reveals that the incubation time at a certain anneal temperature in the supercooled liquid region is not infinite, and will increase with increasing heating rate until this temperature shifts out of the supercooled liquid region because of exceeding critical heating rate. It is concluded that heating rate must be an important processing parameter of superplastic forming for Zr55Cu30Al10Ni5.

  5. Superplastic Behavior of Ti-6Al-4V-0.1B Alloy (Preprint)

    Science.gov (United States)

    2011-10-01

    Galeyev, O.R. Valiakhmetov, F.H. (Sam) Froes, Journal of Alloys and Compounds 345 (2002) 221–227. 8. A.V. Sergueeva, V.V. Stolyarov, R.Z. Valiev... Journal of Alloys and Compounds 490 (2010) 118–123. 7 Approved for public release; distribution unlimited. 17. S. Tamirisakandala, R.B. Bhat

  6. Cavity coalescence in superplastic deformation

    Energy Technology Data Exchange (ETDEWEB)

    Stowell, M.J.; Livesey, D.W.; Ridley, N.

    1984-01-01

    An analysis of the probability distribution function of particles randomly dispersed in a solid has been applied to cavitation during superplastic deformation and a method of predicting cavity coalescence developed. Cavity size distribution data were obtained from two microduplex nickel-silver alloys deformed superplastically to various extents at elevated temperature, and compared to theoretical predictions. Excellent agreement occurred for small void sizes but the model underestimated the number of voids in the largest size groups. It is argued that the discrepancy results from a combination of effects due to non-random cavity distributions and to enhanced growth rates and incomplete spheroidization of the largest cavities.

  7. Sputter deposition of pure titanium onto complete denture base of Ti-6Al-4V deformed by superplastic forming. Chososei keiseishita Ti-6Al-4V gishi zenbusho eno sputter jochaku ni yoru jun Ti no hifuku

    Energy Technology Data Exchange (ETDEWEB)

    Kato, M.; Sonoda, T. (Government Industrial Research Institute, Nagoya, Nagoya (Japan))

    1991-07-01

    In order to improve the biocompatibility of TiNi shape memory alloy and Ti-6Al-4V alloy of functional Ti base alloys which are paid attention as the dental materials or implant materials, the sputter deposition coating using bio-inactive Ti metal was studied. DC source was superior to RF source in characteristics of sputtered film and the rate of deposition. The wiping with gauze impregnated by acetone followed by the ultrasonic cleaning was more effective for the precleaning of the substrate. The sputtered Ti film thickness was nearly proportional to electric power and showed the orientation which depended highly on the heating temperature of the substrate. The complete surface of denture base of Ti-6Al-4V deformed by superplastic forming was well coated with pure Ti and the prospect of biocompatibility of this Ti alloy could be obtained. But the film deposited by the heating condition showed the different characteristics of film compared with that formed under the cooling condition, and it is necessary that the effect of this on the biocompatibility must be investigated. 10 refs., 11 figs.

  8. The role of microstructural aspects on the performance of coarse-grained superplastic Al alloys

    NARCIS (Netherlands)

    Chezan, AR; De Hosson, JTM; Houtte, PV; Kestens, L

    2005-01-01

    Deformed under optimum conditions of temperature and strain rate, coarse-grained aluminum alloys show elongation to failure in excess of 300%. The strain rate sensitivity index and the activation energy point to solute drag creep as the principal mechanism, a mechanism that has virtually no grain si

  9. Superplasticity of a fine-grained Mg–9Gd–4Y–0.4Zr alloy evaluated using shear punch testing

    Directory of Open Access Journals (Sweden)

    Reza Alizadeh

    2014-07-01

    Full Text Available The superplasticity of an extruded fine-grained Mg–9Gd–4Y–0.4Zr alloy was investigated by measuring the strain rate sensitivity using shear punch testing (SPT. Shear punch tests were conducted at shear strain rates in the range of 3 × 10−3–2 × 10−1 s−1 and at temperatures in the range of 573–773 K. The results indicate the strain rate sensitivity, m, increases from about 0.11 at 573 K to about 0.40 at 723 K and then decreases to 0.32 with a further increase in test temperature. A strain rate sensitivity of 0.40 and an activation energy of 140 kJ/mol are indicative of a superplastic deformation behavior dominated by grain boundary sliding accommodated by lattice diffusion at temperatures above 673 K.

  10. New method for making super-plastic glasses

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    @@ It was a long-cherished dream for materials scientists to find a nearly ideal metallic alloy with high strength and super-plasticity concurrently as a super-material both extremely strong and exceptionally hard for human use.

  11. Enhanced foaming of cellular metals by internal stress superplasticity

    Energy Technology Data Exchange (ETDEWEB)

    Kitazono, K.; Sato, E.; Kuribayashi, K. [The Inst. of Space and Astronautical Science, Kanagawa (Japan)

    2004-07-01

    Effects of internal stress superplasticity on solid-state foaming process were examined using Al-8.69Si alloy and pure zinc compacts produced by the powder metallurgical (P/M) route. Isothermal and thermal cycling compression creep behaviors revealed that composite CTE (coefficient of thermal expansion)-mismatch superplasticity was induced in P/M Al-Si alloy, however, no difference was shown in the solid-state foaming. On the other hand, the foaming rate of P/M zinc was enhanced by anisotropic CTE-mismatch superplasticity. The cell morphology of the foamed zinc has anisotropy due to the original powder compact produced by hot-extrusion. (orig.)

  12. Effect of state of stress on the cavitation behavior of Al 5083 superplastic material

    Energy Technology Data Exchange (ETDEWEB)

    Chandra, Namas; Kalu, Peter [Dept. of Mech. Eng., Florida State Univ., Tallahassee, FL (United States); Khraisheh, Marwan K. [Dept. of MEch. Eng., Univ. of Kentucky, Lexington, KY (United States)

    2005-07-01

    In this paper we address the controversial issue of nucleation of cavities in Al 5083 alloys and their subsequent growth to coalescence and failure. We focus on the origin and growth of cavities not only during the primary processing of Al 5083 in sheet forms, but also during the manufacture of these sheets into SPF (superplastic forming) components. Experimental observations of pre-existing cavities in this alloy are made using optical and electron microscopy. The role of sheet rolling direction, and the state of stress during superplastic deformation on the cavity formation and coalescence are also discussed. The effect of the state of stress (uniaxial, plane strain, balanced biaxial, and tri-axial) on the growth characteristics of cavitation is also examined. It is found that the uniaxial model based cavitation cannot directly be extended to predict the behavior of more complex stress states, unless great care is taken to identify the right strain measure for the mapping process. (orig.)

  13. Super plastic forming of the Cd-17.4 Zn alloy; Conformado superplastico de la aleacion Cd-17.4 Zn

    Energy Technology Data Exchange (ETDEWEB)

    Llanes Briceno, J. A.; Torres Villasenor, G. [Instituto de Investigaciones en Materiales, UNAM, Mexico, D.F. (Mexico)

    2000-06-01

    In the present work the necessary steps to carry on the superplastic forming of the Cd-17.4 Zn alloy are defined. The use of either atmospheric pressure or gas pressure as forming tools is analyzed. The optimum values of the variables involved (temperature, maximum strain and sensitivity index) are determined while a method for the characterization of future superplastic alloys is set forth. The experimental characterization of the superplastic forming is achieved with free bulging of circular membranes of 12, 16, 24, 32 and 40 mm in diameter and with three different membrane thicknesses (0.4, 0.6 and 0.8 mm). [Spanish] Se definen los pasos necesarios para el conformado superplastico de la aleacion Cd-17.4Zn. Se comparan la presion atmosferica y el gas a presion como herramientas de conformado. Se determinan los valores optimos de las variables involucradas (temperatura, deformacion maxima e indice de sensibilidad) y se plantea una metodologia para la caracterizacion de futuras aleaciones superplasticas. El conformado superplastico se caracteriza experimentalmente mediante el inflado libre de membranas circulares de 12, 16, 24, 32 y 40 mm de diametro y tres diferentes espesores (0.4, 0.6 y 0.8 mm).

  14. Gas-pressure forming of an AlMg-alloy sheet at elevated temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Rauscher, B.; Goesling, M.; Homberg, W.; Kleiner, M. [Dortmund Univ. (DE). Inst. of Forming Technology and Lightweight Construction (IUL)

    2005-12-01

    Forming of automotive leightweight parts using aluminium offers numerous advantages. Compared to other wrought aluminium alloys, in particular AlMg-alloys generally show a good formability which is favourable for the production of complex parts. However, forming of Mg-containing alloys at room temperature leads to yielding patterns preventing their implementation for class-A-surface applications. Furthermore, the formability of steel still exceeds that of AlMg-alloys at room temperature. Thus, in the present study, sheet metal forming is applied at a temperature range that is typical for warm forming. It is supposed to profit from the advantages of warm forming like high achievable strains and improved surface quality of the formed part, while not having the disadvantages of long production times and high energy consumption, which is correlated with superplastic forming. Applying fluid-based sheet metal forming in this paper, nitrogen is used as fluid working medium to satisfy the demand on high temperature resistance. Concerning the blank material used, formability of Mg-containing aluminium alloys shows strong strain rate sensitivity at elevated temperatures. To figure out the optimal strain rates for this particular process, a control system for forming processes is developed within the scope of this paper. Additionally, FE-simulations are carried out and adapted to the experiment, based on the generated process data. FE-investigations include forming of domes (bulging) as well as shape-defined forming, having the objective to increase formability in critical form elements by applying optimal strain rates. Here, a closed-loop process control for gas-pressure forming at elevated temperatures is to be developed in the next stages of the project. (orig.)

  15. Scaling up of High-Pressure Sliding (HPS) for Grain Refinement and Superplasticity

    Science.gov (United States)

    Takizawa, Yoichi; Masuda, Takahiro; Fujimitsu, Kazushige; Kajita, Takahiro; Watanabe, Kyohei; Yumoto, Manabu; Otagiri, Yoshiharu; Horita, Zenji

    2016-09-01

    The process of high-pressure sliding (HPS) is a method of severe plastic deformation developed recently for grain refinement of metallic materials under high pressure. The sample for HPS is used with a form of sheet or rod. In this study, an HPS facility with capacities of 500 tonnes for vertical pressing and of 500 and 300 tonnes for horizontal forward and backward pressings, respectively, was newly built and applied for grain refinement of a Mg alloy as AZ61, Al alloys such as Al-Mg-Sc, A2024 and A7075 alloys, a Ti alloy as ASTM-F1295, and a Ni-based superalloy as Inconel 718. Sheet samples with dimensions of 10 to 30 mm width, 100 mm length, and 1 mm thickness were processed at room temperature and ultrafine grains with sizes of ~200 to 300 nm were successfully produced in the alloys. Tensile testing at elevated temperatures confirmed the advent of superplasticity with total elongations of more than 400 pct in all the alloys. It is demonstrated that the HPS can make all the alloys superplastic through processing at room temperature with a form of rectangular sheets.

  16. Free Bulging at Constant Pressure of Superplastic Sheet Metal

    Directory of Open Access Journals (Sweden)

    Costanzo Bellini

    2015-08-01

    Full Text Available This work intends to establish, by means of analytical modelling, a practical definition of the superplastic behaviour by using the results of the free bulging of sheet metal instead of the results of the traditional tensile test. In particular this paper analyses the superplastic flow of PbSn60 alloy and it focuses the attention on the value of H parameter corresponding to the maximum value of dt/dH, never considered in the literature. This parameter can represent a practical tool in industrial applications to establish the superplastic behaviour of a sheet metal.

  17. Quantitative determination of homogeneous strain value in superplastic tension

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    After load instability, a passage of homogeneous strain ε can be still continued in superplastic tensile deformation. But untill now, no one has given the precise value of ε corresponding to actual materials, neither in experimental measurements nor in theoretical calculations. Using the elaborate experimental measuring methods of m value and its function expressions, the note first gives the method to determine homogeneous ε, and the homogeneous ε value of typical superplastic alloy Zn-5% Al under 18℃ and 340℃ respectively.

  18. Super plastic forming technology applied to aeroengine and space equipment

    Science.gov (United States)

    Mandai, Katsumi

    1992-03-01

    Titanium alloys, especially Ti-6Al-4V, are widely used for the aeroengine and space equipment because of their high strength ratio and excellent resistance to heat and corrosion. But this material is difficult to manufacture by conventional plastic forming technology. It has been reported that Ti-6Al-4V shows extensive ductility (superplasticity), more than 1000 percent under the condition of both low straining rate and high temperature ranges. Superplastic forming technology applying this characteristic is widely known as one of the most cost-effective methods to save material. At the plant, gas argon blowing equipment for the superplastic forming technology has been developed and 'V2500 nose fairing' and 'fuel tank of the H-II rocket second stage reaction control system' have been manufactured. This paper describes the superplastic forming equipment and the two products above.

  19. Superplastic flow lubricates carbonate faults during earthquake slip

    Science.gov (United States)

    De Paola, Nicola; Holdsworth, Robert; Viti, Cecilia; Collettini, Cristiano; Faoro, Igor; Bullock, Rachael

    2014-05-01

    Tectonic earthquakes are hosted in the shallower portion of crustal fault zones, where fracturing and cataclasis are thought to be the dominant processes during frictional sliding. Aseismic shear in lower crust and lithospheric mantle shear zones is accomplished by crystal plasticity, including superplastic flow acting at low strain rates on ultrafine-grained rocks. Superplasticity has also been observed at high strain rates for a range of nano-phase alloys and ceramics, and could potentially occur in fine-grained geological materials, if deformed at high strain rates and temperatures. We performed a set of displacement-controlled experiments to explore whether superplastic flow can effectively weaken faults, and facilitate earthquake propagation. The experiments were performed on fine-grained synthetic gouges (63 lubrication mechanisms. When T ≥ 800 °C are attained, micro-textures diagnostic of diffusion-dominated grain boundary sliding are widespread within the slip zone, and suggest bulk superplastic flow. Flow stresses predicted by superplasticity constitutive laws at the slip zone temperatures, grain sizes and strain rates attained during the experiments match those we measured in the laboratory (μ = 0.16). We propose therefore that the activation of diffusion creep at high temperatures (T ≥ 800 °C) leads to slip zone-localised superplastic flow and that this causes the dynamic weakening of carbonate faults at seismic slip rates. Note, however, that both cataclasis and dislocation creep operating at lower temperatures, during the earlier stages of slip, are critical, precursory processes needed to produce the nanoscale grain sizes required to activate grainsize sensitive mechanisms during superplastic flow. Finally, the re-strengthening observed during the decelerating phase of deformation can be explained by the falling temperature "switching off" slip zone-localized superplasticity, leading to a return to frictional sliding. These results indicate

  20. Rheology of Superplastic Ceramics

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Constitutive equation of rheglogy describing a phenomenological level of superplastic deformation as functional correlation between tensor components of stress and strain rate has been analyzed for the case of superplastic ceramic flow. Rheological properties of material are taken into account by means of scalar rheological coefficients of shear and volume viscosity, which are functions of temperature, effective stress (or strain rate) and density of material.

  1. Grain boundary dynamics in ceramics superplasticity

    Directory of Open Access Journals (Sweden)

    Wakai, E.

    2001-04-01

    Full Text Available Superplasticity refers to an ability of polycrystalline solids to exhibit exceptionally large elongation in tension. The application of superplasticity makes it possible to fabricate ceramic components by superplastic forming (SPF, concurrent with diffusion bonding, and superplastic sinter-forging just like superplastic metals. Furthermore the superplastic deformation plays an important role in stress-assisted densification processes such as hot isostatic pressing (HIP and hot pressing (HP. The ceramics superplasticity has been one of intensive research fields in the last decade. Although most of reports are still limited to those of zirconia[1], new developments have been achieved in superplasticity of Si3N4 and SiC in recent years. It is clearly demonstrated that the superplasticity is one of the common natures of fine-grained ceramics and nanocrystalline ceramics at elevated temperatures.

    La superplaticidad se refiere a la capacidad que posee un sólido policristalino de presentar alargamientos excepcionalmente elevados en tracción. La aplicación de la superplasticidad hace posible la fabricación de componentes cerámicos por conformado superplástico, soldadura por difusión y forja-sinterizado superplástica, igual que en metales superplásticos. Además, la deformación superplástica tiene un rol importante en los procesos de densificación asistidos por tensiones, tales como la compactación isostática en caliente y el prensado en caliente. Las cerámicas superplásticas han sido uno de los campos donde se ha realizado una investigación más intensa en la última década. Aunque, la mayoría de los informes se limitan a la circonia[1] se han alcanzado nuevos desarrollos en superplasticidad de Si3N4 y SiC. Está claramente demostrado que la superplasticidad es una propiedad intrínseca de las cerámicas de pequeño tamaño de grano y de las cer

  2. 粉末冶金法制备超细晶AZ31镁合金及超塑性变形研究%Powder Metallurgy Prepared Ultra-fine Grain AZ31 Alloy and Its Superplastic Deformation

    Institute of Scientific and Technical Information of China (English)

    林莺莺; 胡杰仁

    2013-01-01

    采用粉末冶金法制备超细晶AZ31镁合金材料,并对其微观组织形貌及相成分进行研究;利用单向拉伸试验研究了该材料在不同条件下超塑性变形.结果表明,采用球磨、冷压制坯和热挤压法可获得晶粒尺寸在1微米以下的超细晶组织,该材料在250℃,1×10-3s-1的应变速率条件下获得了最大伸长率,基本达到超塑性状态.%Ultra-fine grain AZ31 alloy bars were fabricated by power metallurgy process,and the microstructure and phase composition were also researched.The superplastic deformation was studied by simple tension test.According to the results,AZ31 alloy with the grain size under 1 μm was prepared by the process of high energy ball milling,cold compacting and hot extrusion.The superplastic deformation was achieved under the temperature of 250 ℃ and strain rate of 1 × 10-3 s-1.

  3. Numerical Simulation of Superplastic Forming and Diffusion Bonding of Ti Alloys

    Institute of Scientific and Technical Information of China (English)

    Kaifeng ZHANG; Wenbo HAN; Wei WU; Guofeng WANG; Dezhong WU

    2003-01-01

    The research on numerical simulation for combinative process of SPF/DB is carried out in this paper. The contacting problem of sheets is analyzed by using the penalty method. In order to solve the contact problem of different parts of the sheet, a new alg

  4. Superplastic Deformation and Microstructural Evolution of Ti-6Al-4V Alloy%Ti-6Al-4V合金超塑性变形及微观组织演变

    Institute of Scientific and Technical Information of China (English)

    朱堂葵; 李淼泉

    2012-01-01

    通过高温拉伸试验研究了Ti-6Al-4V合金的高温变形力学行为和超塑性,并对试样断口附近的组织进行了观察.结果表明,随着变形温度的升高或初始应变速率的降低,Ti-6Al-4V合金的流动应力明显减小 ;Ti-6Al-4V合金的最佳超塑性变形工艺参数为880℃/0.001 s-1,最大延伸率为689%,峰值应力仅为30.03 MPa ;在超塑性拉伸过程中,试样变形区发生明显的动态再结晶,使片层状的α相晶粒破碎、细化和等轴化,促进超塑性的增加;随着变形温度的提高、变形量增大和变形时间的加长,再结晶α相发生了聚集长大,从而使显微组织明显粗化.对于双态组织的两相钛合金,最佳超塑性变形温度应低于或等于片层状α→β转变的终了温度.%The deformation behavior and superplasticity of Ti-6A1-4V alloy at elevated temperature have been investigated through tensile tests. The microstructures near the fracture of the specimen have been observed by optical microscopy. The results show that the flow stress of Ti-6AI-4V alloy decreases obviously with increasing of the temperature or decreasing of the initial strain rate. The temperature and the initial strain rate of optimal superplastic deformation are 880 ℃ and 0.001 s-1, respectively. Under this optimal condition, the maximum elongation is 689%; however, the peak stress is only 30.03 MPa. During the superplastic tensile deformation, the dynamic recrystallization occurs obviously in the deformation zone of the specimen and the lamellar α grain is broken, refined and spheroidized, so that the superplasticity can be improved. With increasing of the deformation temperature, the deformation amount and the deformation time, the recrystal α grain will merge and grow up, causing obvious coarsening of the microstructure. The temperature of optimal superplastic deformation should not exceed the ceasing temperature of lamellar α→β phase transformation for the α+β titanium alloy

  5. Superplasticity of metals: phenomenology based on rheological properties and structural dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Smirnov, O.M. [Moscow State Steel and Alloys Inst. (Russian Federation). Lab. of Superplastic Mater. Deformation

    1997-12-31

    Fine structure superplasticity (FSSP), high strain rate superplasticity (HSRSP) and phase transformation superplasticity (PTSP) as well as superplastic-like behaviour of some natural and industrial materials evidently belong to the same type of rheological behaviour i.e. non-linear viscoplastic flow. Temperature map has been proposed as a base for rheological analysis of various types of superplastic and superplastic-like flow of metallic materials. A phenomenological model has been developed to describe deformation of polycrystalline materials at elevated temperatures in a wide range of strain rates with respect to structure evolution during deformation. Rheological analysis of FSSP, HSRSP and PTSP materials along with a slurry during rheocasting shows similarities and peculiarities of superplastic and superplastic-like behaviour. The value of apparent viscosity seems to be an informative index for estimation of rheological and physical state of grain boundaries as a viscous phase and of polycrystalline material as a whole. A new process of impulse bulk forming is presented to show unique possibility of joining in one process two stages of a regular superplastic technology, i.e. preparation of ultrafine grain structure followed by HSRSP deformation. (orig.) 37 refs.

  6. Superplasticity in ceramic and metal matrix composites and the role of grain size, segregation, interfaces, and second phase morphology

    Energy Technology Data Exchange (ETDEWEB)

    Wadsworth, J.; Nieh, T.G.

    1992-10-01

    Structural ceramics and ceramic composites have been shown to exhibit superplasticity in recent times and this discovery has attracted tremendous interest. Although the number of ceramics exhibits superplasticity is now quite large, there are gaps in understanding the requirements for superplasticity in ceramics. Also, superplastic behavior at very high strain rates (1 s{sup {minus}1}) in metallic-based materials is an area of increasing research. In this case, the phenomenon has been observed quite extensively in aluminum alloy-based metal matrix composites and mechanically alloyed aluminum- and nickel-based materials. Again, the details of the structural requirements of this phenomenon are not yet understood. In the present paper, experimental results on superplasticity in ceramic-based materials and on high strain rate behavior in metallic-based materials are presented. The roles of grain size, grain boundary and interface chemistry, and second phase morphology and compatibility with the matrix material will be emphasized.

  7. Forming of aluminium alloy friction stir welds

    Science.gov (United States)

    Bruni, Carlo

    2016-10-01

    The present paper aims at investigating, through analytical models, numerical models and experiments, the effect of the warm deformation phase, realised with an in temperature upsetting, on the weld previously performed by friction stir lap welding on aluminium alloy blanks. The investigation allows to show the deformation zones after upsetting that determine the homogenisation of the weld section. The analytical model allows to relate the friction factor with the upsetting load. The presence on the weld of not elevated friction factor values determines the deformation and localisation levels very useful for the weld. Such methodology allows to improve the weld itself with the forming phase.

  8. Micrograin Superplasticity: Characteristics and Utilization

    Directory of Open Access Journals (Sweden)

    Farghalli A. Mohamed

    2011-07-01

    Full Text Available Micrograin Superplasticity refers to the ability of fine-grained materials (1 µm < d < 10 μm, where d is the grain size to exhibit extensive neck-free elongations during deformation at elevated temperatures. Over the past three decades, good progress has been made in rationalizing this phenomenon. The present paper provides a brief review on this progress in several areas that have been related to: (a the mechanical characteristics of micrograin superplasticity and their origin; (b the effect of impurity content and type on deformation behavior, boundary sliding, and cavitation during superplastic deformation; (c the formation of cavity stringers; (d dislocation activities and role during superplastic flow; and (e the utilization of superplasticity.

  9. Recent Advances in the Hot Working of Titanium Alloys

    Institute of Scientific and Technical Information of China (English)

    DANG Xiao-ling

    2012-01-01

    In this paper, recent advances in titanium alloy processing are reviewed. The casting, superplastic forming, friction stir welding and thermohydrogen processing of titanium alloys are developed. The great cost saving results from using casting comparing with the conventional machining for rings. The superplastic forming of titanium alloys is a feasible manufacturing technology for civil and military aircraft. The friction stir welding leds to the production of fully-formed, high quality friction stirwelds. In thermohydrogen processing, the high diffusivity of hydrogen in titanium is firstly used to add hydrogen to titanium alloys by controlled diffusion from a hydrogen environment , after thermohydrogen processing, to remove it by a controlled vacuum anneal so as to improve processing and mechanical properties.

  10. Alloy substantially free of dendrites and method of forming the same

    Science.gov (United States)

    de Figueredo, Anacleto M.; Apelian, Diran; Findon, Matt M.; Saddock, Nicholas

    2009-04-07

    Described herein are alloys substantially free of dendrites. A method includes forming an alloy substantially free of dendrites. A superheated alloy is cooled to form a nucleated alloy. The temperature of the nucleated alloy is controlled to prevent the nuclei from melting. The nucleated alloy is mixed to distribute the nuclei throughout the alloy. The nucleated alloy is cooled with nuclei distributed throughout.

  11. Alloy

    Science.gov (United States)

    Cabeza, Sandra; Garcés, Gerardo; Pérez, Pablo; Adeva, Paloma

    2014-07-01

    The Mg98.5Gd1Zn0.5 alloy produced by a powder metallurgy route was studied and compared with the same alloy produced by extrusion of ingots. Atomized powders were cold compacted and extruded at 623 K and 673 K (350 °C and 400 °C). The microstructure of extruded materials was characterized by α-Mg grains, and Mg3Gd and 14H-LPSO particles located at grain boundaries. Grain size decreased from 6.8 μm in the extruded ingot, down to 1.6 μm for powders extruded at 623 K (350 °C). Grain refinement resulted in an increase in mechanical properties at room and high temperatures. Moreover, at high temperatures the PM alloy showed superplasticity at high strain rates, with elongations to failure up to 700 pct.

  12. Phase boundary sliding model controlled by diffusion-solution zone in superplastic deformation

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    With scanning electron microscope (SEM), the surface morphology of phase boundary sliding (PBS) in superplastic deformation (SPD) of Zn-Al alloy and the diffusion behavior of Zn, Al interfaces in their powers' sintering have been investigated. The results show that Zn-Al eutectoid microstructure can be achieved through their powders' sintering, and the diffusion characteristic between Zn and Al is just a demonstration of Kirkendall effect, in which Zn can dissolve into Al whereas A1 can hardly dissolve into Zn. During sintering, a diffusion-solution zone ?′ has formed and subsequently transformed into a eutectoid microstructure in the cooling process. The superplastic deformation mechanism of Zn-Al eutectic alloy is phase boundary sliding which is controlled by the diffusion-solution zone ?′. If the diffusion-solution zone ?′ is unsaturated, it will have much more crystal defects and the combination between ?′ and phase ? is weak, thus the process of phase boundary sliding becomes easily; on the contrary, if the diffusion-solution zone ?′ becomes thick and saturated, the sliding will be difficult.

  13. Super-plastic forming process of Zr-based bulk metallic glass%Zr基非晶合金超塑性成形工艺研究

    Institute of Scientific and Technical Information of China (English)

    廖广兰; 王俊; 喻强; 朱志靖

    2011-01-01

    采用感应耦合等离子体刻蚀工艺制备了微型硅模具,基于硅模具研究了非晶合金Zr41.25Ti13.75Ni10Cu12.5Be22.5的超塑性微零件成形工艺.采用差示扫描量热仪测定了Zr41.25Ti13.75Ni10Cu12.5Be22.5的过冷液相区间为360~440℃,在过冷液相区间热压成形非晶合金微零件、机械研磨去除零件飞边和采用40%的KOH溶液腐蚀去除硅模具,得到非晶合金微型零件.自主研制了成形设备,仿真分析与实验相结合,解决了成形过程中设备的温度控制问题,比较分析了不同温度下的成形结果,实验与仿真结果符合较好.在410℃条件下成功制备出模数0.03、齿数66和厚度500μm的微型内齿轮,齿形轮廓清晰,X射线衍射仪扫描结果显示该微齿轮为非晶结构,从而验证了采用该工艺制备微型零件的可行性.%Super-plastic micro-forming process of bulk metallic glasses Zr41.25Ti13.75Ni10Cu12.5Be22.5 utilizing micro silicon molds was investigated,where the micro silicon molds were fabricated by inductively coupled plasma etching.The super-cooled liquid region,360~440 ℃,was measured by differential scanning calorimeter.Micro components were thermoformed in the super-cooled liquid region.The flash of micro components was removed by mechanical grinding,and the silicon molds were resolved with 40% KOH.Forming equipment was developed on the basis of the super-plastic process,and the temperature-control was solved by simulation analysis and experiments.Subsequently,the forming results in different temperatures were analyzed,which confirmed the simulation results.Finally,an internal gear with 0.03 module,66 teeth and 500 μm thickness was obtained with good dimensional accuracy at 410 ℃.The gear had a relatively good profile with an amorphous structure proved by X-ray diffraction scanning,which substantiated the feasibility of the process.

  14. Recent Achievements in Developing Low Temperature and High Strain Rate Superplastic Materials

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    This paper is to briefly outline our recent activities in developing low temperature or high strain rate superplastic materials, including aircraft-used and general-purpose Al- and Mg-base alloys or composites, as well as Ti3Al base intermetallic alloys. The processing routes applied included the thermomechanical treatment, equal channel angular pressing and other extrusion or forging methods.

  15. Ti-Pt Alloys form mechanical milling

    CSIR Research Space (South Africa)

    Nxumalo, S

    2009-12-01

    Full Text Available orthorhombic structure at a temperature of approximately 1000oC. The martensite phase results in shape memory effect being observed in this alloy at this temperature. Other alloys such as TiNi and TiPd have also been investigated for the martensitic...

  16. Reference Alloy Waste Form Fabrication and Initiation of Reducing Atmosphere and Reductive Additives Study on Alloy Waste Form Fabrication

    Energy Technology Data Exchange (ETDEWEB)

    S.M. Frank; T.P. O' Holleran; P.A. Hahn

    2011-09-01

    This report describes the fabrication of two reference alloy waste forms, RAW-1(Re) and RAW-(Tc) using an optimized loading and heating method. The composition of the alloy materials was based on a generalized formulation to process various proposed feed streams resulting from the processing of used fuel. Waste elements are introduced into molten steel during alloy fabrication and, upon solidification, become incorporated into durable iron-based intermetallic phases of the alloy waste form. The first alloy ingot contained surrogate (non-radioactive), transition-metal fission products with rhenium acting as a surrogate for technetium. The second alloy ingot contained the same components as the first ingot, but included radioactive Tc-99 instead of rhenium. Understanding technetium behavior in the waste form is of particular importance due the longevity of Tc-99 and its mobility in the biosphere in the oxide form. RAW-1(Re) and RAW-1(Tc) are currently being used as test specimens in the comprehensive testing program investigating the corrosion and radionuclide release mechanisms of the representative alloy waste form. Also described in this report is the experimental plan to study the effects of reducing atmospheres and reducing additives to the alloy material during fabrication in an attempt to maximize the oxide content of waste streams that can be accommodated in the alloy waste form. Activities described in the experimental plan will be performed in FY12. The first aspect of the experimental plan is to study oxide formation on the alloy by introducing O2 impurities in the melt cover gas or from added oxide impurities in the feed materials. Reducing atmospheres will then be introduced to the melt cover gas in an attempt to minimize oxide formation during alloy fabrication. The second phase of the experimental plan is to investigate melting parameters associated with alloy fabrication to allow the separation of slag and alloy components of the melt.

  17. Standard test method for determining the superplastic properties of metallic sheet materials

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2008-01-01

    1.1 This test method describes the procedure for determining the superplastic forming properties (SPF) of a metallic sheet material. It includes tests both for the basic SPF properties and also for derived SPF properties. The test for basic properties encompasses effects due to strain hardening or softening. 1.2 This test method covers sheet materials with thicknesses of at least 0.5 mm but not greater than 6 mm. It characterizes the material under a uni-axial tensile stress condition. Note 1—Most industrial applications of superplastic forming involve a multi-axial stress condition in a sheet; however it is more convenient to characterize a material under a uni-axial tensile stress condition. Tests should be performed in different orientations to the rolling direction of the sheet to ascertain initial anisotropy. 1.3 This method has been used successfully between strain rates of 10-5 to 10-1 per second. 1.4 This method has been used successfully on Aluminum and Titanium alloys. The use of the method wi...

  18. Superplasticity and joining of zirconia-based ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Dominguez-Rodriguez, A.; Gutierrez-Mora, F.; Jimenez-Melendo, M.; Chaim, R.; Routbort, J. L.

    1999-12-10

    Steady-state creep and joining of alumina/zirconia composites containing alumina volume fractions of 20, 60, and 85% have been investigated between 1,250 and 1,350 C. Superplasticity of these compounds is controlled by grain-boundary sliding and the creep rate is a function of alumina volume fraction, not grain size. Using the principles of superplasticity, pieces of the composite have been joined by applying the stress required to achieve 5 to 10% strain to form a strong interface at temperatures as low as 1,200 C.

  19. Property measurements on spray formed Si-Al alloys

    Institute of Scientific and Technical Information of China (English)

    WEI Yan-guang; XIONG Bai-qing; ZHANG Yong-an; LIU Hong-wei; WANG Feng; ZHU Bao-hong

    2007-01-01

    A novel Si-Al alloy was prepared by spray forming process for electronic packaging. Property measurements on spray-formed Si-Al alloys after hot pressing were carried out. The results indicate that the alloys (Si-(30%-40%)Al) have advantageous physical and mechanical characteristics, including low coefficient of thermal expansion (6.9×10-6-8.7×10-6/K), high thermal conductivity (118-127 W/(m·K)), low density (2.421×103-2.465×103 kg/m3), high ultimate flexural strength (180-220 MPa) and Brinell hardness (162-261). The alloys are easy to machine to tight tolerances using standard machine tools and they can be electroplated with gold finishes and soldered with Sn-Pb alloy without any difficulty.

  20. Superplastic Micro-forming Mechanism and Size Effects of Micro-array Made of Nanocrystalline Material%纳米材料微阵列超塑微成形机理与尺度效应

    Institute of Scientific and Technical Information of China (English)

    王国峰; 李优; 刘奇; 赵相禹

    2015-01-01

    微成形技术是未来批量制造高精密微小零件的关键技术,但是,微小尺度下材料的塑性变形行为不仅表现出明显的尺度效应,而且零件尺度已经接近常规材料的晶粒尺寸,每个晶粒的形状、取向、变形特征对整体变形产生复杂的影响,难以保证微成形的工艺稳定性。本项目采用纳米材料进行微成形,制造微阵列,零件内部包含大量的晶粒,可以排除晶粒复杂性的影响,而且纳米材料具有超塑性,在超塑状态下,变形抗力和摩擦力都明显降低,从而显著降低微成形工艺对模具性能的苛刻要求,提高工艺稳定性和成形精度。目前,纳米材料超塑性微成形技术方面的研究极少,变形时纳米材料的力学行为、变形机理、尺度效应、位错演化、力学模型等关键问题还有待研究。采用电沉积技术制备晶粒尺寸可控的纳米材料,将工艺实验研究、性能测试、组织分析、力学性能表征、数值模拟相结合,深入探究了纳米材料微阵列超塑性微成形机理和成形规律,以促进该技术的广泛应用。%ABSTRACT:Micro-forming is a key technique for fabricating high-precision micro-part in large volume. However, plastic deformation at small scale has obvious size effects. The shape, orientation and deformation behavior of each grain have complicated influence on the micro-forming, since the scale of the parts approaches to the size of grain in common materi-als. Consequently, it is very hard to ensure the processing stability of micro-forming. In the current project, nanocrystalline materials were used to form micro-array. The influence of grain complexity could be eliminated since there were a lot of grains in the micro-part. In addition, nanocrystalline materials usually have superplasticity. Under this condition, the de-formation force and friction decrease obviously, which decreases the requirement on the mechanical

  1. AN ELECTROPLATING METHOD OF FORMING PLATINGS OF NICKEL, COBALT, NICKEL ALLOYS OR COBALT ALLOYS

    DEFF Research Database (Denmark)

    1997-01-01

    An electroplating method of forming platings of nickel, cobalt, nickel alloys or cobalt alloys with reduced stresses in an electrodepositing bath of the type: Watt's bath, chloride bath or a combination thereof, by employing pulse plating with periodic reverse pulse and a sulfonated naphthalene...... additive. This method makes it possible to deposit nickel, cobalt, nickel or cobalt platings without internal stresses....

  2. Bonding theory for metals and alloys

    CERN Document Server

    Wang, Frederick E

    2005-01-01

    Bonding Theory for Metals and Alloys exhorts the potential existence of covalent bonding in metals and alloys. Through the recognition of the covalent bond in coexistence with the 'free' electron band, the book describes and demonstrates how the many experimental observations on metals and alloys can all be reconciled. Subsequently, it shows how the individual view of metals and alloys by physicists, chemists and metallurgists can be unified. The physical phenomena of metals and alloys covered in this book are: Miscibility Gap between two liquid metals; Phase Equilibrium Diagrams; Phenomenon of Melting. Superconductivity; Nitinol; A Metal-Alloy with Memory; Mechanical Properties; Liquid Metal Embrittlement; Superplasticity; Corrosion; The author introduces a new theory based on 'Covalon' conduction, which forms the basis for a new approach to the theory of superconductivity. This new approach not only explains the many observations made on the phenomenon of superconductivity but also makes predictions that ha...

  3. Effect of partial melting on superplasticity ofAlNp/6061Al composite

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    AlN particulate reinforced 6061 aluminum alloy composite was fabricated by powder metallurgy method and hot-rolled after extrusion. Tensile strength and elongation at elevated temperature were measured by tensile test at initial strain rates between 10-2 s-1 and 100 s-1. The AlNp/6061Al composite exhibits an m-value of 0.42 and a maximum elongation of 450% at 863?K. Differential scanning calorimeter was used to ascertain the possibility of any partial melting in the vicinity of optimum superplastic temperature. Partial melting resulting from solute segregation at interfaces has much influence on superplasticity of the composite. It is postulated that AlNp/matrix interface sliding occurs along with grain boundary in superplastic deformation.

  4. Creep study of mechanisms involved in low-temperature superplasticity of UFG Ti-6Al-4V processed by SPD

    Energy Technology Data Exchange (ETDEWEB)

    Kral, Petr, E-mail: pkral@ipm.cz [Institute of Physics of Materials, ASCR, Zizkova 22, CZ -61662 Brno (Czech Republic); CEITEC – IPM ASCR, v.v.i., Zizkova 22, CZ-61662 Brno (Czech Republic); Dvorak, Jiri [Institute of Physics of Materials, ASCR, Zizkova 22, CZ -61662 Brno (Czech Republic); CEITEC – IPM ASCR, v.v.i., Zizkova 22, CZ-61662 Brno (Czech Republic); Blum, Wolfgang [Inst. f. Werkstoffwissenschaften, University of Erlangen-Nürnberg, D-91058 Erlangen (Germany); Kudryavtsev, Egor; Zherebtsov, Sergey; Salishchev, Gennady [Belgorod State University, Laboratory of Bulk Nanostructured Materials, Pobeda Str. 85, 308015 Belgorod (Russian Federation); Kvapilova, Marie; Sklenicka, Vaclav [Institute of Physics of Materials, ASCR, Zizkova 22, CZ -61662 Brno (Czech Republic); CEITEC – IPM ASCR, v.v.i., Zizkova 22, CZ-61662 Brno (Czech Republic)

    2016-06-15

    The deformation kinetics of ultrafine-grained Ti-6Al-4V with mean (sub)grain size about 150 nm (produced by isothermal multiaxial forging) and superplastic properties at the relatively low temperature of 873 K was investigated in compression and tension over a large range of strain rates from 10{sup −7} to 10{sup −2} s{sup −1}. Electron microscopic observations showed that the grains coarsen during deformation towards the quasi-stationary spacing w{sub qs} of strain induced boundaries. In spite of the grain coarsening the grains were generally smaller than w{sub qs} allowing high-angle boundaries to dominate the quasi-stationary strength. Texture measurements indicate that dislocation glide plays a large role in deformation. Glide in this alloy is significantly influenced by solid solution strengthening leading to a stress sensitivity of strain rate of n = 3. The present ultrafine-grained Ti alloy displays a stress sensitivity exponent n = 2 over an extended stress range where its superplastic behavior is optimal. While the deformation kinetics of present ultrafine-grained Ti alloy can be roughly explained by the traditional formula for superplastic flow, the significant discrepancy to the measured values suggests that solid solution strengthening must be taken into account to get a complete insight. - Highlights: • The UFG Ti-6Al-4V alloy behaves superplastically at low temperature of 873 K. • Grain coarsening at low stresses limits superplasticity of UFG Ti alloy. • Solute strengthening plays an important role in low-temperature superplasticity. • Acceleration of creep in UFG Ti alloy is caused by processes related to hab.

  5. NUMERICAL SIMULATION FOR FORMED PROJECTILE OF DEPLETED URANIUM ALLOY

    Institute of Scientific and Technical Information of China (English)

    宋顺成; 高平; 才鸿年

    2003-01-01

    The numerical simulation for forming projectile of depleted uranium alloy with the SPH ( Smooth Particle Hydrodynamic ) algorithm was presented. In the computations the artificial pressures of detonation were used, i. e. , the spatial distribution and time distribution were given artificially. To describe the deformed behaviors of the depleted uranium alloy under high pressure and high strain rate, the Johnson-Cook model of materials was introduced. From the numerical simulation the formed projectile velocity,projectile geometry and the minimum of the height of detonation are obtained.

  6. Influence of Grain Coarsening on the Creep Parameters During the Superplastic Deformation of a Severely Friction Stir Processed Al-Zn-Mg-Cu Alloy

    Science.gov (United States)

    Orozco-Caballero, Alberto; Ruano, Oscar A.; Carreño, Fernando

    2017-09-01

    During grain boundary sliding in ultrafine-grain materials at intermediate temperatures and high strain rates ( 10-2 s-1), apparent creep parameters usually deviate from the theoretical values, due to microstructural coarsening. An analysis has been carried out in a severely friction stir processed (FSP) 7075 alloy with three different ultra-fine grain sizes ( L), obtaining explicit grain size dependence of the creep parameters n ap = n ap( L) and Q ap = Q ap( L), confirming the validity of the theoretical values of these parameters in the constitutive equation.

  7. New developments in rapidly solidified magnesium alloys

    Energy Technology Data Exchange (ETDEWEB)

    Das, S.K. [Allied-Signal, Inc., Morristown, NJ (United States); Chang, C.F. [Allied-Signal, Inc., Morristown, NJ (United States); Raybould, D. [Allied-Signal, Inc., Morristown, NJ (United States); King, J.F. [Magnesium Elektron Ltd., Manchester (United Kingdom); Thistlethwaite, S. [Magnesium Elektron Ltd., Manchester (United Kingdom)

    1992-12-31

    In the present paper, we will examine the new developments in the rapidly solidified Mg-Al-Zn-Nd (EA55RS) alloy. We shall first briefly review the process scale-up currently employed for producing rapidly solidified magnesium alloys in large quantities, and then discuss the effect of billet size and processing parameters on the mechanical properties of various mill product forms such as extrusions and sheets. The superplastic behavior of EA55RS extrusions and rolled sheets are also discussed. Finally, some results on magnesium metal-matrix composites using rapidly solidified EA55RS matrix powders and SiC particulates are presented. (orig.)

  8. Constitutive modelling of aluminium alloy sheet at warm forming temperatures

    Science.gov (United States)

    Kurukuri, S.; Worswick, M. J.; Winkler, S.

    2016-08-01

    The formability of aluminium alloy sheet can be greatly improved by warm forming. However predicting constitutive behaviour under warm forming conditions is a challenge for aluminium alloys due to strong, coupled temperature- and rate-sensitivity. In this work, uniaxial tensile characterization of 0.5 mm thick fully annealed aluminium alloy brazing sheet, widely used in the fabrication of automotive heat exchanger components, is performed at various temperatures (25 to 250 °C) and strain rates (0.002 and 0.02 s-1). In order to capture the observed rate- and temperature-dependent work hardening behaviour, a phenomenological extended-Nadai model and the physically based (i) Bergstrom and (ii) Nes models are considered and compared. It is demonstrated that the Nes model is able to accurately describe the flow stress of AA3003 sheet at different temperatures, strain rates and instantaneous strain rate jumps.

  9. Simulation study for atomic size and alloying effects during forming processes of amorphous alloys

    Institute of Scientific and Technical Information of China (English)

    ZHENG Caixing; LIU Rangsu; PENG Ping; ZHOU Qunyi

    2004-01-01

    A molecular dynamics (MD) simulation study has been performed for the solidification processes of two binary liquid alloys Ag6Cu4 and CuNi by adopting the quantum Sutton-Chen many-body potentials. By analyzing bond-types, it is demonstrated that at the cooling rate of 2×1012K/s, the CuNi forms fcc crystal structures, while the Ag6Cu4 forms amorphous structures. The original reason is that the atomic radius ratio (1.13) of the CuAg is bigger than that (1.025) of the CuNi. This shows that the atomic size difference is indeed the main factor for forming amorphous alloys. Moreover, for Ag60Cu40,corresponding to the deep eutectic point in the phase diagram, it forms amorphous structure easily. This confirms that as to the forming tendency and stability of amorphous alloys, the alloying effect plays a key role. In addition, having analyzed the transformation of microstructures by using the bond-type index and cluster-type index methods, not only the key role of the icosahedral configuration to the formation and stability of amorphous alloys can be explained, but also the solidification processes of liquid metals and the characteristics of amorphous structures can be further understood.

  10. Titanium Alloys and Processing for High Speed Aircraft

    Science.gov (United States)

    Brewer, William D.; Bird, R. Keith; Wallace, Terryl A.

    1996-01-01

    Commercially available titanium alloys as well as emerging titanium alloys with limited or no production experience are being considered for a variety of applications to high speed commercial aircraft structures. A number of government and industry programs are underway to improve the performance of promising alloys by chemistry and/or processing modifications and to identify appropriate alloys and processes for specific aircraft structural applications. This paper discusses some of the results on the effects of heat treatment, service temperatures from - 54 C to +177 C, and selected processing on the mechanical properties of several candidate beta and alpha-beta titanium alloys. Included are beta alloys Timetal 21S, LCB, Beta C, Beta CEZ, and Ti-10-2-3 and alpha-beta alloys Ti-62222, Ti-6242S, Timetal 550, Ti-62S, SP-700, and Corona-X. The emphasis is on properties of rolled sheet product form and on the superplastic properties and processing of the materials.

  11. Forming analysis and application for aluminum-alloy material

    Institute of Scientific and Technical Information of China (English)

    Wei Yuansheng

    2012-01-01

    The increase in car ownership brought about by energy shortages, and environmental crises became more acute. The most effective way to achieve energy saving and emission reduction of car is to improve engine efficiency. In addition to that, lightweight body is the key. Aluminum, magnesium alloy as significant materials of lightweight, and the application amount in the car body is a significant upward trend. However, there is high cost of material, with im- mature applied technology and a series of bottleneck problems. All of them affect general application of lightweight mate- rials. This paper focuses on forming process issues for aluminum, magnesium alloy and the solutions to achieve.

  12. Incremental forming of aluminium alloys in cryogenic environment

    Science.gov (United States)

    Vanhove, Hans; Mohammadi, Amirahmad; Duflou, Joost R.

    2016-10-01

    Incremental Sheet Forming processes suffer from stringent forming limits, restricting the range of producible geometries. Through in-process cooling of the sheet to cryogenic level, this paper explores the potential of altering material properties benefiting the formability and residual hardness of different aluminium alloys. Global cooling of aluminium sheets with liquid nitrogen and dry ice allows to reach temperatures of 78K and 193K respectively. Extended with experiments at room temperature (293K), these tests form a base for comparison of surface quality, formability and residual hardness. As an aluminium alloy commonly used for its high strength to weight ratio, but suffering from limited formability compared to draw-quality steels, AA5083-H111 is of interest for cryogenic treatment. AA1050-H24 is included in the test campaign as a base for commercially pure aluminium.

  13. Low-Temperature Forming of Beta Titanium Alloys

    Science.gov (United States)

    Kaneko, R. S.; Woods, C. A.

    1983-01-01

    Low cost methods for titanium structural fabrication using advanced cold-formable beta alloys were investigated for application in a Mach 2.7 supersonic cruise vehicle. This work focuses on improving processing and structural efficiencies as compared with standard hot formed and riveted construction of alpha-beta alloy sheet structure. Mechanical property data and manufacturing parameters were developed for cold forming, brazing, welding, and processing Ti-15V-3Cr-3Sn-3Al sheet, and Ti-3Al-8V-6Cr-4Zr on a more limited basis. Cost and structural benefits were assessed through the fabrication and evaluation of large structural panels. The feasibility of increasing structural efficiency of beta titanium structure by selective reinforcement with metal matrix composite was also explored.

  14. Carburizing of Duplex Stainless Steel (DSS) Under Compression Superplastic Deformation

    Science.gov (United States)

    Ahamad, Nor Wahida; Jauhari, Iswadi

    2012-12-01

    A new surface carburizing technique which combines superplastic deformation with superplastic carburizing (SPC) is introduced. SPC was conducted on duplex stainless steel under compression mode at a fixed 0.5 height reduction strain rates ranging from 6.25 × 10-5 to 1 × 10-3 s-1 and temperature ranging from 1173 K to 1248 K (900 °C to 975 °C). The results are compared with those from conventional and non-superplastic carburizing. The results show that thick hard carburized layers are formed at a much faster rate compared with the other two processes. A more gradual hardness transition from the surface to the substrate is also obtained. The highest carburized layer thickness and surface hardness are attained under SPC process at 1248 K (975 °C) and 6.25 × 10-5 s-1 with a value of (218.3 ± 0.5) μm and (1581.0 ± 5.0) HV respectively. Other than that, SPC also has the highest scratch resistance.

  15. Numerical Modelling of Drawbeads for Forming of Aluminium Alloys

    DEFF Research Database (Denmark)

    Joshi, Y; Christiansen, Peter; Masters, I

    2016-01-01

    The drawbeads in stamping tools are usually designed based on experience from the forming of steel. However, aluminium alloys display different forming behaviour to steels, which is not reflected in the drawbead design for tools used for stamping aluminium. This paper presents experimental results...... from different semi-circular drawbead geometries commonly encountered in automotive dies and compares them to those obtained from Stoughton’s analytical drawbead model and the 2D plane strain drawbead model set up using LS-DYNA.The study was conducted on lubricated NG5754 strips. The results presented...

  16. QuikForm: Intelligent deformation processing of structural alloys

    Energy Technology Data Exchange (ETDEWEB)

    Bourcier, R.J.; Wellman, G.W.

    1994-09-01

    There currently exists a critical need for tools to enhance the industrial competitiveness and agility of US industries involved in deformation processing of structural alloys. In response to this need, Sandia National Laboratories has embarked upon the QuikForm Initiative. The goal of this program is the development of computer-based tools to facilitate the design of deformation processing operations. The authors are currently focusing their efforts on the definition/development of a comprehensive system for the design of sheet metal stamping operations. The overall structure of the proposed QuikForm system is presented, and the focus of their thrust in each technical area is discussed.

  17. Damage percolation during stretch flange forming of aluminum alloy sheet

    Science.gov (United States)

    Chen, Zengtao; Worswick, Michael J.; Keith Pilkey, A.; Lloyd, David J.

    2005-12-01

    A multi-scale finite element (FE)-damage percolation model was employed to simulate stretch flange forming of aluminum alloys AA5182 and AA5754. Material softening and strain gradients were captured using a Gurson-based FE model. FE results were then fed into the so-called damage percolation code, from which the damage development was modelled within measured microstructures. The formability of the stretch flange samples was predicted based upon the onset of catastrophic failure triggered by profuse void coalescence within the measured second-phase particle field. Damage development is quantified in terms of crack and void areal fractions, and compared to metallographic results obtained from interrupted stretch flange specimens. Parametric study is conducted on the effect of void nucleation strain in the prediction of formability of stretch flanges to "calibrate" proper nucleation strains for both alloys.

  18. Microstructure and Properties of Superplastic Welding between 4OCr and CrWMn Steels

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Superplastic welding of tool steel and structural steel was investigated. The welding between 40Cr and CrWMn steels was carried out under the conditions of temperature 750~780°C, strain rate 2×10-4 s-1, compressive stress 50~90 MPa for 3~5 min. The joints show similar strength to that of 40Cr steel and the good metallurgical joining is formed. The structural change occurring during superplastic welding was analyzed by metallography and distribution of carbon content in the vicinity of the welding joint was also determined. The mechanism of superplastic welding for steels is proposed to be the disappearance of original bond interfaces caused by atomic diffusion and the grain sliding.

  19. Tribological Behaviour of the Ceramic Coating Formed on Magnesium Alloy

    Institute of Scientific and Technical Information of China (English)

    CHEN Fei; ZHOU Hai; CHEN Qiang; GE Yuanjing; LV Fanxiu

    2007-01-01

    Micro-arc oxidation is a recently developed surface treatment technology under anodic oxidation. Through micro-arc oxidation, a ceramic coating is directly formed on the surface of magnesium alloy, by which its surface property is significantly improved. In this paper, a dense ceramic oxide coating was prepared on an AZ31 magnesium alloy by micro-arc oxidation in a NaOH-Na2SiO3-NaB4O7-(NaPO3)6 electrolytic solution. Micro-structure, surface morphology and phase composition were analysed using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The tribological behavior of the micro-arc oxidation ceramic coating under dry sliding against GCrl5 steel was evaluated on a ball-on-disc test rig. The results showed that the AZ31 alloy was characterized by adhesion wear and scuffing under dry sliding against the steel, while the surface micro-arc oxidation ceramic coating experienced much abated adhesion wear and scuffing under the same testing conditions. The micro-arc oxidation ceramic coating showed good friction-reducing and fair antiwear ability in dry sliding against the steel.

  20. TOPICAL REVIEW On the glass forming ability of liquid alloys

    Directory of Open Access Journals (Sweden)

    Yoshio Waseda et al

    2008-01-01

    Full Text Available By using the concepts of the short-range order (SRO and middle-range order (MRO characterizing structures, an attempt has been made to describe the glass forming ability (GFA of liquid alloys. This includes the effect of more than two kinds of SRO in the liquid caused by the addition of second and third elements to a metallic solvent. The minimum solute concentration is related to the atomic volume mismatch estimated from the cube of the atomic radius. The optimum solute concentration for good glass formability in several binary and some ternary alloys is discussed on the basis of the empirical guideline. A new approach to obtaining good GFA of liquid alloys is based on four main factors: (i formation of new SRO and coexistence of two or more kinds of SRO, (ii stabilization of dense random packing structure by restraining the atomic redistribution for initiating the nucleation and growth process, (iii formation of a stable cluster (SC or the MRO by the harmonious coupling of SROs, and (iv difference between SRO characterizing the liquid structure and the near-neighbor environment in the corresponding equilibrium crystalline phases. The use of interaction parameters, widely used in the thermodynamics of multicomponent metallic solutions, is proposed for effectively selecting the third solute element (X3 for enhancing the GFA of a metallic liquid (M containing the second solute (X2. Fe70-B20-(X310 alloys (X3=Cr, W, Nb, Zr and Hf are used for illustration. Two typical model structures denoted by the Bernal and chemical-order types are used in describing the new glass structure as a function of solute concentration.

  1. Microstructurally Controlled Mechanical Properties of Al-Mg-Si Alloys for Warm Forming Applications

    NARCIS (Netherlands)

    Ghosh, M.

    2011-01-01

    Owing to their light weight and excellent corrosion resistance the use of aluminium alloys in automotive industries is increasing progressively. However, aluminium alloys remain mainly handicapped by poor room temperature formability compared to steel. Increasing temperature during forming, but stil

  2. Age hardening characteristics and mechanical behavior of Al-Cu-Li-Zr-In alloys

    Science.gov (United States)

    Wagner, John A.

    1989-01-01

    An investigation was conducted to determine the age-hardening response and cryogenic mechanical properties of superplastic Al-Cu-Li-Zr-In alloys. Two alloys with compositions Al-2.65Cu-2.17Li-O.13Zr (baseline) and Al-2.60Cu-2.34Li-0.16Zr-0.17In were scaled-up from 30 lb permanent mold ingots to 350 lb DC (direct chill) ingots and thermomechanically processed to 3.2 mm thick sheet. The microstructure of material which contained the indium addition was partially recrystallized compared to the baseline suggesting that indium may influence recrystallization behavior. The indium-modified alloy exhibited superior hardness and strength compared to the baseline alloy when solution-heat-treated at 555 C and aged at 160 C or 190 C. For each alloy, strength increased and toughness was unchanged or decreased when tested at - 185 C compared to ambient temperature. By using optimized heat treatments, the indium-modified alloy exhibited strength levels approaching those of the baseline alloy without deformation prior to aging. The increase in strength of these alloys in the T6 condition make them particularly attractive for superplastic forming applications where post-SPF parts cannot be cold deformed to increase strength.

  3. Stress releasement by transformation superplasticity. Part 2. ; Effect of alloying elements and transformation temperature on stress releasement. Hentai chososei ni yoru oryoku kanwa. 2. ; Oryoku kanwa ni oyobosu gokin genso oyobi hentai ondo no eikyo

    Energy Technology Data Exchange (ETDEWEB)

    Murata, H. (Yokogawa Medical System, Ltd., Tokyo (Japan)); Kato, N. (Tokyo Institute of Technology, Tokyo (Japan)); Tamura, H. (Nihon University, Tokyo (Japan))

    1991-02-05

    Steel test pieces having various transformation temperatures (M {sub S}) were fabricated varying Ni and Cr contents, and tests were done on their torsional transformation resistance in cooling process, and stress relaxing characteristics due to transformation superplasticity, using a forced twisting equipment. The test pieces, while being twisted, were heated by high frequency induction from an external source to 1000 {degree} C in 50 seconds, retained for 50 seconds, and then their transformation resistance was detected during cooling. The motor was so controlled in five steps that the added shear distortion speed is constant per unit temperature reduction. The Ni and Cr contents and M {sub S} are in linear relation, and its experimental formula was sought. Even if Ni and Cr contents differ, similar stress relaxing characteristics were presented as long as the M {sub S} points are identical. Therefore, hardness and corrosion resistance can be controlled in welding metals by means of so varying Ni and Cr contents that the M {sub S} point is maintained in a certain range. The transformation resistance showed the minimum value lower by 70 to 80 {degree} C than the M {sub S} point. To apply the phenomena of transformation superplasticity, the temperature difference between preheating paths is important in addition to chemical constituents. 18 refs., 8 figs., 1 tab.

  4. The Neighbor Switching Mechanism of Superplastic Deformation

    Science.gov (United States)

    Sherwood, David John

    At one time the notion that crystal plasticity resulted from the simultaneous motion of lattice planes over one another was entertained. This idea was displaced by the concept that relative atomic motions occur sequentially when dislocations move through the crystal. Similarly, McLean suggested that grains switch neighbors sequentially in a polycrystalline material undergoing superplastic flow. Morral and Ashby observed that the neighbor switching reactions in a froth occurred at irregular cells, and that these irregularities were associated with dislocations in the cellular array. They introduced cellular dislocation glide as a model for superplastic flow, and suggested that if the concentration of these defects required to make the froth flow increased with the flow stress, then the froth would have a non-Newtonian viscosity, like many superplastic materials. Cahn and Padawer pointed out that cellular dislocation climb was used as a model for grain growth by Hillert; this process results in the elimination of cells from the froth. Sato, Kuribayashi and Horiuchi used cellular dislocation climb to model both grain motion and the deformation-enhanced grain growth which can accompany superplastic flow. Here, the neighbor switching mechanism of superplastic deformation is developed as a topic in dislocation theory. The compatibility theory of dislocations is developed at an introductory level with exterior calculus. "Compatibility" of a cellular array corresponds to statements, a la Rivier, about the distribution of edges amongst the cells. The theory of dislocation motion, or crystal plasticity, is also developed with exterior calculus. Morral and Ashby's constitutive relationship for superplastic flow is analyzed and two models for deformation-enhanced grain growth are developed. The constitutive relationship and grain growth kinetics for superplastic flow are illustrated by modelling the behavior exhibited by single phase (Sn-1% Bi) and quasi -single phase (7475 Al

  5. Low temperature superplasticity through grain refinement in Ti-6Al-4V by a novel route of quench-roll-recrystallise

    Directory of Open Access Journals (Sweden)

    Jalumedi Babu

    2015-07-01

    Full Text Available A ‘quench + roll + recrystallise’ method was simulated through compression testing of initially ‘water quenched’ Ti-6Al-4V alloy at a temperature of 973 K and rolling strain-rate 100 s−1 in order to achieve superplasticity at lower temperature through grain refinement, with a view to increase die life. Subsequent annealing of wire-cut specimens of a rolled sheet at temperatures 1023, 1073, 1123, and 1173 K revealed that, the structures became finer and equi-axial in the range of 1–2 μm, when annealed at 1073 and 1123 K. In compliance to this behavior, a tensile sample from industrially ‘quenched + rolled’ sheet at 973 K could produce an elongation of 740% at a temperature of 1073 K under a strain-rate of 10−3 s−1. Significant elongation of 652% was obtained at further lower temperature of 1023 K under a strain-rate of 10−3 s−1. Quench-roll-recrystallise technique pushes down superplastic forming temperature to 1023 K.

  6. Effects of Alloying Element Ca on the Corrosion Behavior and Bioactivity of Anodic Films Formed on AM60 Mg Alloys

    Directory of Open Access Journals (Sweden)

    Anawati Anawati

    2016-12-01

    Full Text Available Effects of alloying element Ca on the corrosion behavior and bioactivity of films formed by plasma electrolytic oxidation (PEO on AM60 alloys were investigated. The corrosion behavior was studied by conducting electrochemical tests in 0.9% NaCl solution while the bioactivity was evaluated by soaking the specimens in simulated body fluid (SBF. Under identical anodization conditions, the PEO film thicknesses increased with increasing Ca content in the alloys, which enhanced the corrosion resistance in NaCl solution. Thicker apatite layers grew on the PEO films of Ca-containing alloys because Ca was incorporated into the PEO film and because Ca was present in the alloys. Improvement of corrosion resistance and bioactivity of the PEO-coated AM60 by alloying with Ca may be beneficial for biodegradable implant applications.

  7. Superplastic Formed Aluminum-Lithium Aircraft Structure

    Science.gov (United States)

    1988-10-01

    sulfide (Ryton-PPS, Nylon 11, polyester, and polyetherimide ( Ultem ). These thermoplastics are used as a powder for flame-spraying. Preliminary tests...the necessary thermal requirements to support the program and were eliminated as possible adhesives. A polyetherimide powder ( Ultem or related to it

  8. Durability and degradation of HT9 based alloy waste forms with variable Ni and Cr content

    Energy Technology Data Exchange (ETDEWEB)

    Olson, L. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

    2016-12-31

    Short-term electrochemical and long-term hybrid electrochemical corrosion tests were performed on alloy waste forms in reference aqueous solutions that bound postulated repository conditions. The alloy waste forms investigated represent candidate formulations that can be produced with advanced electrochemical treatment of used nuclear fuel. The studies helped to better understand the alloy waste form durability with differing concentrations of nickel and chromium, species that can be added to alloy waste forms to potentially increase their durability and decrease radionuclide release into the environment.

  9. THE FORMING OF MAGNESIUM ALLOY FORGINGS FOR AIRCRAFT AND AUTOMOTIVE APPLICATIONS

    Directory of Open Access Journals (Sweden)

    Anna Dziubińska

    2016-09-01

    Full Text Available The paper presents the theoretical and technological aspects of forming magnesium alloy parts for aircraft and automotive applications. The main applications of magnesium alloys in the aircraft and automotive industries are discussed. In addition, the forging technology for magnesium alloys is generally described, with a particular emphasis on wrought alloys. A brief outline of the state of the art in the forging of magnesium alloys is given based on a survey of the specialist literature and the results of previous research by the authors.

  10. Surface properties and activation energy of superplastically carburized duplex stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Ahamad, Nor Wahida, E-mail: wahida_um@yahoo.com [Department of Mechanical and Materials Engineering, Faculty of Engineering, University Malaya, Lembah Pantai, 50603 Kuala Lumpur (Malaysia); Jauhari, Iswadi, E-mail: iswadi@um.edu.my [Department of Mechanical and Materials Engineering, Faculty of Engineering, University Malaya, Lembah Pantai, 50603 Kuala Lumpur (Malaysia); Azis, Sharidah Azuar Abdul, E-mail: sharidah_azuar@yahoo.com [Department of Mechanical and Materials Engineering, Faculty of Engineering, University Malaya, Lembah Pantai, 50603 Kuala Lumpur (Malaysia); Aziz, Nur Hafizah Abd, E-mail: phiza_aziz@yahoo.com [Department of Mechanical and Materials Engineering, Faculty of Engineering, University Malaya, Lembah Pantai, 50603 Kuala Lumpur (Malaysia)

    2010-08-01

    A new surface carburizing technique which combines superplastic phenomenon and carburizing process called superplastic carburizing (SPC) was introduced and compared with conventional carburizing (CC) process. Thermomechanically treated duplex stainless steel (DSS) with a fine grain microstructure that exhibits superplasticity was used as the superplastic material. SPC was carried out at temperatures of 1198-1248 K and a compression rate of 1 x 10{sup -4} s{sup -1} for various durations. Metallographic studies revealed that a carbon layer with a uniform, dense and smooth morphology formed on all carburized specimens. The case depth of the carbon layer was between 50.8 and 159.1 {mu}m. A remarkable increase in surface hardness was observed in the range 389.9-1129.0 HV. Activation energy for SPC was determined as 183.4 kJ mol{sup -1}, which is lower compare to CC process. The results indicate that SPC accelerates the diffusion of carbon atoms into the surface of DSS, thus increasing the thickness of the carburized layer and the surface hardness, at lower activation energy.

  11. Numerical simulation of high speed incremental forming of aluminum alloy

    Science.gov (United States)

    Giuseppina, Ambrogio; Teresa, Citrea; Luigino, Filice; Francesco, Gagliardi

    2013-12-01

    In this study, an innovative process is analyzed with the aim to satisfy the industrial requirements, such as process flexibility, differentiation and customizing of products, cost reduction, minimization of execution time, sustainable production, etc. The attention is focused on incremental forming process, nowadays used in different fields such as: rapid prototyping, medical sector, architectural industry, aerospace and marine, in the production of molds and dies. Incremental forming consists in deforming only a small region of the workspace through a punch driven by a NC machine. SPIF is the considered variant of the process, in which the punch gives local deformation without dies and molds; consequently, the final product geometry can be changed by the control of an actuator without requiring a set of different tools. The drawback of this process is its slowness. The aim of this study is to assess the IF feasibility at high speeds. An experimental campaign will be performed by a CNC lathe with high speed to test process feasibility and the influence on materials formability mainly on aluminum alloys. The first results show how the material presents the same performance than in conventional speed IF and, in some cases, better material behavior due to the temperature field. An accurate numerical simulation has been performed to investigate the material behavior during the high speed process substantially confirming experimental evidence.

  12. Effect of the Fine-Grained Structure on the Fatigue Properties of the Heat-Resistant Nickel-Iron Alloy Inconel 718

    Science.gov (United States)

    Mukhtarov, Sh. Kh.; Shakhov, R. V.

    2015-10-01

    It is well known that ultrafine-grained nickel alloys with average grain sizes d = 0.1-1 μm possess improved hot workability and can be used for superplastic forming or rolling. However, microstructure refinement can worsen some performance characteristics of the alloy, for example, heat-resistant or fatigue properties. In the present work, fatigue characteristics of the fine-grained alloy Inconel 718 are investigated. Ultrafine-grained alloys with average grain sizes d = 0.1-1 μm were manufactured by multiple forging with stage-by-stage deformation temperature decrease. During standard heat treatment of the alloy performed to obtain the desired properties, the γ-grain size was controlled by precipitations of δ-phase particles along the boundaries. Results of low-cycle fatigue tests of the fine-grained alloy at room and elevated temperatures are compared with the properties of the coarse-grained alloy.

  13. The Properties of 7xxx Series Alloys Formed by Alloying Additions

    Directory of Open Access Journals (Sweden)

    Kwak Z.

    2015-06-01

    Full Text Available Currently there is a constant development in the field of aluminium alloys engineering. This results from, i.a., better understanding of the mechanisms that direct strengthening of these alloys and the role of microalloying. Now it is microalloying in aluminum alloys that is receiving a lot of attention. It affects substantially the macro- and microstructure and kinetics of phase transformation influencing the properties during production and its exploitation. 7xxx series aluminum alloys, based on the Al-Zn-Mg-Cu system, are high-strength alloys, moreover, the presence of Zr and Sr further increases their strength and improves resistance to cracking.

  14. Microstructure Evolution and Mechanical Behavior of Ultrafine Ti-6Al-4V During Low Temperature Superplastic Deformation (Postprint)

    Science.gov (United States)

    2016-09-13

    alloys , Russ. J. Non- Ferrous Met. 56 (2016) 437e441. [40] B.B. Straumal, X. Sauvage, B. Baretzky, A.A. Mazilkin, R.Z. Valiev, Grain boundary films in...dynamic coarsening response and plastic-flow behavior of the alloy with a mean size of α (sub)grains and β particles of 0.1–0.4 μm were determined via a...Very limited cavitation was observed in the specimens after superplastic deformation under optimal conditions. 15. SUBJECT TERMS Titanium alloy ; Low

  15. Superplastic Deformation and Viscous Flow in an Zr-Based Metallic Glass at 410 Degrees C

    Energy Technology Data Exchange (ETDEWEB)

    Liu, C.T.; Mukai, T.; Nieh, T.G.; Wadsworth, J.; Wang, J.G.

    1998-12-01

    The thermal properties of an amorphous alloy (composition in at.%: Zr-l0Al-5Ti-l7.9Cu-14.6Ni), and particularly the glass transition and crystallization temperature as a function of heating rate, were characterized using Differential Scanning Calorimetry (DSC). X-ray diffraction analyses and Transmission Electron Microscopy were also conducted on samples heat-treated at different temperatures for comparison with the DSC results. Superplasticity in the alloy was studied at 410 degrees C, a temperature within the supercooled liquid region. Both single strain rate and strain rate cycling tests in tension were carried out to investigate the deformation behavior of the alloy in the supercooled liquid region. The experimental results indicated that the alloy did not behave like a Newtonian fluid.

  16. Discontinuous Dynamic Recrystallization of Inconel 718 Superalloy During the Superplastic Deformation

    Science.gov (United States)

    Huang, Linjie; Qi, Feng; Hua, Peitao; Yu, Lianxu; Liu, Feng; Sun, Wenru; Hu, Zhuangqi

    2015-09-01

    The superplastic behavior of Inconel 718 superalloy with particular emphasis on the microstructural evolution has been systematically investigated through tensile tests at the strain rate of 10-3 s-1 and the temperatures ranging from 1223 K to 1253 K (950 °C to 980 °C). Its elongations exceeded 300 pct under all of the experimental conditions and peaked a maximum value of 520 pct at 1223 K (950 °C). Moreover, the stress reached the top value at the strain of 0.3, and then declined until the tensile failure. In addition, we have found that the grain size reduced after deformation while the δ phase precipitation increased. Microstructural evolution during the superplasticity was characterized via transmission electron microscope, and the randomly distributed dislocation, dislocation network, dislocation arrays, low-angled subgrains, and high-angled recrystallized new grains were observed in sequence. These new grains were found to nucleate at the triple junction, twin boundary, and near the δ phase. Based on these results, it is deemed that the discontinuous dynamic recrystallization occurred as the main mechanism for the superplastic deformation of Inconel 718 alloy.

  17. CONSTITUTE EQUATIONS OF 40Cr STEEL UNDER SUPERPLASTIC COMPRESSIVE DEFORMATION

    Institute of Scientific and Technical Information of China (English)

    K.K. Zhang; Y.L. Yang; S.Z. Liu; C.X. Han; D. Xu

    2003-01-01

    The microstructure of 40Cr steel sample and its surface is ultra-fined through saltbath cyclic quenching and high frequency hardening, then the superplasticity is studied under isothermal superplastic compressive deformation condition. The experimental results indicate that the stress-strain curves are shown to take place obvious superplastic flow characteristic at the temperature of 730-770℃ and at the initial strain rate of (1.7-5.0)× 10-4s-1. Its strain rate sensitivity is 0.30-0.38, the steady superplastic flow stress is 60-70MPa, the superplastic flow activation energy is 198-217kJ/mol,and it is close to α-Fe grain boundary self-diffusion activation energy. The superplastic compressive constitute equations of this steel are correspondingly set up. Due to the finer microstructure of high frequency hardening, it appears bigger strain rate sensitivity value, smaller the steady superplastic flow stress and the superplastic flow activation energy, so it has better superplastic deformation capability.

  18. Dual-Alloy Disks are Formed by Powder Metallurgy

    Science.gov (United States)

    Harf, F. H.; Miner, R. V.; Kortovich, C. S.; Marder, J. M.

    1982-01-01

    High-performance disks have widely varying properties from hub to rim. Dual property disk is fabricated using two nickel-base alloys, AF-115 for rim and Rene 95 for hub. Dual-alloy fabrication may find applications in automobiles, earth-moving equipment, and energy conversion systems as well as aircraft powerplants. There is potential for such applications as shafts, gears, and blades.

  19. Laser rapid forming of low cost hydride-dehydride titanium alloy powder

    Institute of Scientific and Technical Information of China (English)

    CHEN Jing; ZHANG Feng-ying; LIN Xin; TAN Hua; HUANG Wei-dong

    2006-01-01

    Low cost hydride-dehydride (HDH) Ti-6Al-4V (Ti-64) alloy powder was employed to investigate the metallurgical quality and mechanical properties of laser formed samples. With appropriate control of the laser forming processing parameters and the loose density of HDH powder, two kinds of defect, i.e. porosity and ill-bonding, can be avoided. Rare earth Nd powder was added to HDH Ti-64 powder to purify laser formed alloy. The results show that with a few additive of Nd, the microstructure of laser formed alloy changes from Widmanst-tten morphology to a basket weave microstructure. Accordingly an appropriate addition of Nd is effective to improve both the strength and ductility of laser formed HDH Ti-64 alloy. The values of tensile test meet the wrought specification with the content of Nd ranging from 0.1%-0.2%(mass fraction).

  20. Ultrahigh carbon steels, Damascus steels, and superplasticity

    Energy Technology Data Exchange (ETDEWEB)

    Sherby, O.D. [Stanford Univ., CA (United States). Dept. of Materials Science and Engineering; Wadsworth, J. [Lawrence Livermore National Lab., CA (United States)

    1997-04-01

    The processing properties of ultrahigh carbon steels (UHCSs) have been studied at Stanford University over the past twenty years. These studies have shown that such steels (1 to 2.1% C) can be made superplastic at elevated temperature and can have remarkable mechanical properties at room temperature. It was the investigation of these UHCSs that eventually brought us to study the myths, magic, and metallurgy of ancient Damascus steels, which in fact, were also ultrahigh carbon steels. These steels were made in India as castings, known as wootz, possibly as far back as the time of Alexander the Great. The best swords are believed to have been forged in Persia from Indian wootz. This paper centers on recent work on superplastic UHCSs and on their relation to Damascus steels. 32 refs., 6 figs.

  1. Stress Relaxation Behavior and Springback Equation of 7050 Aluminum Alloys During Age-forming Process

    Directory of Open Access Journals (Sweden)

    REN Wei-wei

    2016-09-01

    Full Text Available The stress relaxation behavior and springback equation of 7050 aluminum alloys during the age-forming process were studied through self-designed uniaxial tension device. The results show that in traditional aging temperature, the stress relaxation curve of 7050 aluminum alloys exhibits a classical logarithmic decrement curve. The stress relaxation process can be divided into three stages, which are the initial stress decayed fast stage, the subsequent stress slowly decayed stage and the stress constantly maintained stage, respectively. Stress relaxation limit of 7050 aluminum alloys decreases with increasing aging temperature. The threshold stress presents during the stress relaxation process due to the interaction between precipitation behavior and dislocation creep of 7050 aluminum alloys. The stress relaxation equation of 7050 aluminum alloys is obtained through resolving the feature and Taylor equation of relaxation process, and using the stress relaxation equation can precisely predict the springback of workpiece after age-forming.

  2. Effect of temperature on vacuum hot bulge forming of BT20 titanium alloy cylindrical workpiece

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Temperature is one of the key parameters for BT20 titanium alloy cylindrical workpiece manufactured by vacuum hot bulge forming. A two-dimensional nonlinear thermo-mechanical coupled FE model was established. Numerical simulation of vacuum hot bulge forming process of titanium alloy cylindrical workpiece was carried out using FE analysis software MSC Marc. The effects of temperature on vacuum hot bulge forming of BT20 titanium alloy cylindrical workpiece were analyzed by numerical simulation.The simulated results show that the Y-direction displacement and the equivalent plastic strain of the workpiece increase with increasing bulge temperature. The residual stress decreases with increasing bulge temperature. The optimal temperature range of BT20 titanium alloy during vacuum hot bulge forming is 750-850 ℃. The corresponding experiments were carried out. The simulated results agreed well with the experimental results.

  3. Density and glass forming ability in amorphous atomic alloys: The role of the particle softness

    Science.gov (United States)

    Douglass, Ian; Hudson, Toby; Harrowell, Peter

    2016-04-01

    A key property of glass forming alloys, the anomalously small volume difference with respect to the crystal, is shown to arise as a direct consequence of the soft repulsive potentials between metals. This feature of the inter-atomic potential is demonstrated to be responsible for a significant component of the glass forming ability of alloys due to the decrease in the enthalpy of fusion and the associated depression of the freezing point.

  4. Isothermal and Near Isothermal Processing of Titanium Alloys

    Directory of Open Access Journals (Sweden)

    T. Raghu

    2011-01-01

    Full Text Available Isothermal and near isothermal forging are specialized metal processing techniques which are used for producing critical aeroengine components out of advanced materials such as titanium alloys. The process can be used to produce net / near net shape components leading to optimum utilization of materials. As titanium alloys are highly sensitive to temperature and strain rate, these processes help to deform them under slow and controlled strain rates.  Further, these processes can be combined with other conventional and non conventional metal forming processes to refine the microstructure. For example, multiaxial isothermal forging coupled with pack rolling can be used to produce thin sheets out of titanium alloys with submicron grain size. The refined structure exhibits superplastic characteristics at low temperatures and high strain rates. This lower temperature superplastic characteristic can be exploited to establish technologies for producing various components. The paper throws light on the capabilities of isothermal forging process and its variants.Defence Science Journal, 2011, 61(1, pp.72-80, DOI:http://dx.doi.org/10.14429/dsj.61.321

  5. Microstructure evolution model based on deformation mechanism of titanium alloy in hot forming

    Institute of Scientific and Technical Information of China (English)

    LI Xiao-li; LI Miao-quan

    2005-01-01

    The microstructure evolution in hot forming will affect the mechanical properties of the formed product.However, the microstructure is sensitive to the process variables in deformation process of metals and alloys. A microstructure evolution model of a titanium alloy in hot forming, which included dislocation density rate and primary α phase grain size, was presented according to the deformation mechanism and driving forces, in which the effect of the dislocation density rate on the grain growth was studied firstly. Applying the model to the high temperature deformation process of a TC6 alloy with deformation temperature of 1 133 - 1 223 K, strain rate of 0.01 -50 s-1 and height reduction of 30%, 40% and 50%, the material constants in the present model were calculated by the genetic algorithm(GA) based objective optimization techniques. The calculated results of a TC6 alloy are in good agreement with the experimental ones.

  6. Electrical resistivity of NaPb compound-forming liquid alloy using ab initio pseudopotentials

    Indian Academy of Sciences (India)

    Anil Thakur; N S Negi; P K Ahluwalla

    2005-08-01

    The study of electrical resistivity of compound-forming liquid alloy, NaPb, is presented as a function of concentration. Hard sphere diameters of Na and Pb are obtained through the interionic pair potentials evaluated using Troullier and Martins ab initio pseudopotential, which have been used to calculate the partial structure factors (). Considering the liquid alloy to be a ternary mixture, Ziman formula, modified for complex formation has been used for calculating resistivity of binary liquid alloys. Form factors are calculated using ab initio pseudopotentials. The results suggest that Ziman formalism, when used with ab initio pseudopotentials, are quite successful in explaining the electrical resistivity data of compound-forming binary liquid alloys.

  7. On the origin of bulk glass forming ability in Cu-Hf, Zr alloys

    Science.gov (United States)

    Ristić, Ramir; Zadro, Krešo; Pajić, Damir; Figueroa, Ignacio A.; Babić, Emil

    2016-04-01

    Understanding the formation of bulk metallic glasses (BMG) in metallic systems and finding a reliable criterion for selection of BMG compositions are among the most important issues in condensed-matter physics and material science. Using the results of magnetic susceptibility measurements performed on both amorphous and crystallized Cu-Hf alloys (30-70 at% Cu) we find a correlation between the difference in magnetic susceptibilities of corresponding glassy and crystalline alloys and the variation in the glass forming ability (GFA) in these alloys. Since the same correlation can be inferred from data for the properties associated with the electronic structure of Cu-Zr alloys, it seems quite general and may apply to other glassy alloys based on early and late transition metals. This correlation is plausible from the free-energy considerations and provides a simple way to select the compositions with high GFA.

  8. Numerical Simulation and Experiment on Material Flow Regulation During Superplastic Forming Process of Box-Shaped Part%盒形件超塑成形过程中材料流动规律的数值模拟与实验

    Institute of Scientific and Technical Information of China (English)

    段奇锐; 原晓明

    2012-01-01

    利用有限元软件MSC.Marc2010对钛合金盒形件超塑成形过程进行了有限元模拟,控制目标应变速率,得到优化的压力-时间曲线,并据此进行实验研究,沿实验曲线分别加裁至6个不同的标定压力值(分别为0.5,1.0,1.5,2.0,2.3和2.5 MPa)得到成形过程中的零件.测量6个实验零件的外形轮廓和厚度,并分剐与相对应的模拟结果进行对比,验证实验与模拟的一致性,并分析整个成形过程中的材料流动规律,得出在自由胀形、底部贴模、充填圆角3阶段盒形件不同区域的应力、应变和变薄率分布,为复杂零件的起塑成形工艺的制定奠定了一定的理论基础.%The superplastic forming process of the box-shaped part is simulated by using finite element software MSC. Marc2010 to optimize the curve of pressure-time under the control of the target strain rate. The fitted curve used in the experiment is based on the simulated pressure-time (p-t) curve. The six parts are obtained along the same optimal experiment p-t curve at six selected pressure respectively (0- 5, 1.0, 1-5, 2. 0, 2. 3 and 2. 5 MPa). By measuring the outline and thickness of the six parts, the experimental result is compared with the numerical simulation result to verify if they agree with each other, and the material flow regulation can be analyzed. The distribution results of stress, strain and reduction rate of the three periods of free bulging, closing up to the cavity and corner fiuing are obtained, which lays the theoretical foundation for the superplastic forming process design of complex parts.

  9. Superplastic deformation of commercial 00Cr22Ni5Mo3N0.17 duplex stainless steel

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    The superplastic behavior of a commercial duplex stainless steel has been studied by means of isothermal hot tensile testat temperatures of 850-1050℃ for the initial strain rates ranging from 3×l0-4 s-1 to 5X10-2 s-1. At 960℃, the best superplastic de-formation that caused the maximum elongation greater than 840% was obtained for an initial strain rate of 1.2×10-3 s-1. At 850℃, thebest elongation 500% was achieved for an initial strain rate of 2.5×10-3 s-1. During the deformation in higher temperature region,coarse γ grains formed during the prior treatments were broken into spherical particles, resulting in a homogeneous dispersion of γparticles within the δ-ferrite matrix. However, at lower temperatures between 800 and 950℃, the σ phase was formed through theeutectoid decomposition of δ→γ+σ, resulting finally in the stable equiaxed micro-duplex structures with δ/γ and γ/σ, respectively.The precipitation of the σ phase played an important role in improving the superplasticity at 850℃. The strain-rate sensitivity coeffi-cient, m-values, were also determined by the strain rate change tests. The microstructure studies show that the superplastic processoccurs mainly by the local work hardening and the subsequent dynamic recrystallization and a grain boundary sliding and grain switching mechanism.

  10. Effect of Aging Treatments on the Mechanical and Corrosive Behaviors of Spray-Formed 7075 Alloy

    Science.gov (United States)

    Su, Rui-ming; Qu, Ying-dong; Li, Rong-de

    2014-11-01

    Mechanical properties, microstructure, exfoliation corrosion (EXCO), and intergranular corrosion (IGC) behaviors of the spray-formed 7075 aluminum alloy after T6, T73, retrogression (R), and re-aging (RRA) treatment, respectively, were studied by using tensile tester, transmission electron microscope, and scanning electron microscope. The results show that the T6 process can increase the ultimate tensile strength (UTS) up to 760 MPa, while it decreases the elongation, the EXCO, and the IGC resistance of the alloy. The T73 process can improve elongation, the EXCO, and the IGC resistance of the alloy. The corrosion resistance of the alloy can also be improved by R and RRA processes with retrogression times increase. The tiny precipitated phases distributed homogeneously in the matrix can increase the UTS. The close-connected discrete grain boundary phases (GBP) and the narrow precipitate free zones (PFZ) will lower the elongation, the EXCO, and the IGC resistance of the alloy. Contrarily, the discrete GBP and wide PFZ can improve the elongation, the EXCO, and the IGC resistance of the alloy. The EXCO and the IGC behaviors for the spray-formed 7075 alloy after different aging treatments have been established according to the standards of ASTM G34-2001 (2007) and ASTM G110-1992 (2009).

  11. System and method of forming nanostructured ferritic alloy

    Energy Technology Data Exchange (ETDEWEB)

    Dial, Laura Cerully; DiDomizio, Richard; Alinger, Matthew Joseph; Huang, Shenyan

    2016-07-26

    A system for mechanical milling and a method of mechanical milling are disclosed. The system includes a container, a feedstock, and milling media. The container encloses a processing volume. The feedstock and the milling media are disposed in the processing volume of the container. The feedstock includes metal or alloy powder and a ceramic compound. The feedstock is mechanically milled in the processing volume using metallic milling media that includes a surface portion that has a carbon content less than about 0.4 weight percent.

  12. Storing hydrogen in the form of light alloy hydrides

    Science.gov (United States)

    Freund, E.; Gillerm, C.

    1981-01-01

    Different hydrides are investigated to find a system with a sufficiently high storage density (at least 3%). The formation of hydrides with light alloys is examined. Reaction kinetics for hydride formation were defined and applied to the systems Mg-Al-H, Mg-Al-Cu-H, Ti-Al-H, Ti-Al-Cu-H, and Ti-Al-Ni-H. Results indicate that the addition of Al destabilizes MgH2 and TiH2 hydrides while having only a limited effect on the storage density.

  13. Superplasticity and Superplastic Forming: Proceedings of an International Conference on Superplasticity and Superplastic Forming Held in Blaine, Washington on 1-4 August 1988

    Science.gov (United States)

    1988-01-01

    315 Chen Bingkin and Hai Jintao Theoretical and Experimental Studies on the Pressure Thermoforming of Hemispheres of... packages , has conciuded that anelasticity may have a strong influence on joint life at different cycle frequencies (11]. Independent work (121 has shown...34Solder Modelling for SMT" (Paper Presented at C4MT-IEEE VLSI Packaging Workshop, Paris, 17-18 November 1986). 37 THE ROLE OF GRAIN BOUNDARY

  14. Technological aspects regarding machining the titanium alloys by means of incremental forming

    Directory of Open Access Journals (Sweden)

    Bologa Octavian

    2017-01-01

    Full Text Available Titanium alloys are materials with reduced formability, due to their low plasticity. However, today there are high demands regarding their use in the automotive industry and in bio-medical industry, for prosthetic devices. This paper presents some technological aspects regarding the machinability of titanium alloys by means of incremental forming. The research presented in this paper aimed to demonstrate that the parts made from these materials could be machined at room temperature, in certain technological conditions.

  15. Rare earth oxide coatings to decrease high temperature degradation of chromia forming alloys

    Directory of Open Access Journals (Sweden)

    Stela Maria de Carvalho Fernandes

    2004-03-01

    Full Text Available The addition of small quantities of reactive elements such as rare earths (RE to chromia or alumina forming alloys improves the high temperature oxidation resistance. Traditionally, these elements are alloying additions or are added as oxides to form a dispersion. The alloys can also be coated with RE oxides. Several methods can be used to coat alloy substrates with RE oxides and the sol-gel process is considered to be quite efficient, as it generates the very small oxide particles. This paper presents the influence of surface coatings of Ce, La, Pr, and Y oxide gels on the oxidation behavior of an Fe-20Cr alloy at 1000 °C. The morphology of the rare earth (RE oxide coatings varied with the nature of RE. The oxidation rate of RE oxide coated Fe-20Cr was significantly less than that of the uncoated alloy. The extent of influence the RE oxide coating exercised on the oxidation rate decreased in the following order: La, Ce, Pr, Y. The scale formed in the presence of RE oxide was very thin, fine grained and adherent chromia. A direct correlation between rare earth ion radius and the extent of influence on chromia growth rate at 1000 °C was observed.

  16. Spray Forming of NiTi and NiTiPd Shape-Memory Alloys

    Science.gov (United States)

    Mabe, James; Ruggeri, Robert; Noebe, Ronald

    2008-01-01

    In the work to be presented, vacuum plasma spray forming has been used as a process to deposit and consolidate prealloyed NiTi and NiTiPd powders into near net shape actuators. Testing showed that excellent shape memory behavior could be developed in the deposited materials and the investigation proved that VPS forming could be a means to directly form a wide range of shape memory alloy components. The results of DSC characterization and actual actuation test results will be presented demonstrating the behavior of a Nitinol 55 alloy and a higher transition temperature NiTiPd alloy in the form of torque tube actuators that could be used in aircraft and aerospace controls.

  17. Spray Forming of NiTi and NiTiPd Shape-Memory Alloys

    Science.gov (United States)

    Mabe, James; Ruggeri, Robert; Noebe, Ronald

    2008-01-01

    In the work to be presented, vacuum plasma spray forming has been used as a process to deposit and consolidate prealloyed NiTi and NiTiPd powders into near net shape actuators. Testing showed that excellent shape memory behavior could be developed in the deposited materials and the investigation proved that VPS forming could be a means to directly form a wide range of shape memory alloy components. The results of DSC characterization and actual actuation test results will be presented demonstrating the behavior of a Nitinol 55 alloy and a higher transition temperature NiTiPd alloy in the form of torque tube actuators that could be used in aircraft and aerospace controls.

  18. A study on the boss forming process of AZ31 Mg alloy sheet

    Science.gov (United States)

    Park, Ji Eon; Kim, Hyung Rae; Ahn, Sang Ho; Chang, Young Won

    2009-06-01

    A series of boss forming tests has been carried out using an AZ31 Mg alloy sheet at 250 °C, 300 °C, and 350 °C with various lubrication conditions to obtain optimum process conditions. The Mg alloy sheet had a homogeneous distribution of very fine sized grains. Surface defects generated during boss forming process could be reduced by changing the friction conditions, as prescribed by FEM analysis using the DEFORM 2D program. The modified boss forming process, lubricating only on the front side, was found to be successful in manufacturing the boss without defects.

  19. Thermodynamics and fragility of glass-forming alloys

    Energy Technology Data Exchange (ETDEWEB)

    Battezzati, L., E-mail: livio.battezzati@unito.it [Dipartimento di Chimica e Centro NIS, Università di Torino, Via P. Giuria 7, 10125 Torino (Italy); Dalla Fontana, G. [Dipartimento di Chimica e Centro NIS, Università di Torino, Via P. Giuria 7, 10125 Torino (Italy)

    2014-02-15

    Highlights: ► Thermodynamic and dynamic properties of metallic melts compared with those of other glass formers. ► Relationships between ΔS{sub g}/ΔC{sub p,g} and relevant temperatures for the glass demonstrated. ► Correspondence with either hyperbolic or Gaussian distribution of the states in the PEL shown. ► Correlations allow estimate of unknown quantities and pinpoint peculiar behavior of liquid. -- Abstract: The existing correlation between the extensive properties, ΔH and ΔS, the enthalpy and entropy difference between liquid and crystal phases has been checked to relate metallic glasses to other classes of amorphous materials. Expressing the specific heat difference, ΔC{sub p}, of molten and crystalline metallic glass-formers as a function of temperature with different functional trends, parametric expressions of fragility are derived using relevant temperatures for alloys. It is shown that relationships between the ΔS{sub g}/ΔC{sub p,g} ratio and such temperatures are useful to estimate unknown quantities when the experimental determination of the specific heat is possible. Thermodynamic indicators of fragility are compared to the kinetic fragility obtained from viscosity data accounting for the estimated errors on parameters which are derived from extrapolations. The outcome of the analysis indicates that a relationship between thermodynamic and kinetic parameters exists. Moreover a systematic scatter for some alloys indicates a diverse behavior which can be ascribed to structure modification either in the liquid or in the solid reference state.

  20. Microstructure behavior and metal flow during continuously extending-extrusion forming of semisolid A2017 alloy

    Institute of Scientific and Technical Information of China (English)

    GUAN Ren-guo; WEN Jing-lin; WANG Shun-cheng; LIU Xiang-hua

    2006-01-01

    A self-designed test machine of continuously semisolid extending extrusion was made to produce the flat bar of A2017 alloy. The slurry of A2017 alloy with spherical or elliptical structures was obtained. During manufacturing semisolid A2017 alloy by the proposed process, the spherical grain was formed with the application of the large force provided by the rough roll. By controlling the casting temperature, the products of A2017 alloy with fine surfaces and rectangular transections of 14 mn×25 mm were produced. The microstructure of the product is fine with the stripped appearance. The fracture strength and elongation of the product are increased by 100 MPa and 29%, respectively.

  1. Ductile Bulk Aluminum-Based Alloy with Good Glass-Forming Ability and High Strength

    Institute of Scientific and Technical Information of China (English)

    ZHUO Long-Chao; PANG Shu-Jie; WANG Hui; ZHANG Tao

    2009-01-01

    Based on a new approach for designing glassy alloy compositions,bulk Al-based alloys with good glass-forming ability (GFA) are synthesized.The cast Al86Si0.5Ni4.06Co2.94 Y6Sc0.5 rod with a diameter of 1 mm shows almost fully amorphous structure besides about 5% fcc-Al nucleated in the center of the rod.The bulk alloy with high Al concentration exhibits an ultrahigh yield strength of 1.18 Gpa and maximum strength of 1.27 Gpa as well as an obvious plastic strain of about 2.4% during compressive deformation.This light Al-based alloy with good GFA and mechanical properties is promising as a new high specific strength material with good deformability.

  2. Forming of magnesium alloy microtubes in the fabrication of biodegradable stents

    Institute of Scientific and Technical Information of China (English)

    Lixiao Wang; Gang Fang; Lingyun Qian; Sander Leeflang; Jurek Duszczyk; Jie Zhou

    2014-01-01

    Magnesium alloys have, in recent years, been recognized as highly promising biodegradable materials, especially for vascular stent applications. Forming of magnesium alloys into high-precision thin-wall tubes has however presented a technological barrier in the fabrication of vascular stents, because of the poor workability of magnesium at room temperature. In the present study, the forming processes, i.e., hot indirect extrusion and multi-pass cold drawing were used to fabricate seamless microtubes of a magnesium alloy. The magnesium alloy ZM21 was selected as a representative biomaterial for biodegradable stent applications. Microtubes with an outside diameter of 2.9 mm and a wall thickness of 0.2 mm were successfully produced at the fourth pass of cold drawing without inter-pass annealing. Dimensional evaluation showed that multi-pass cold drawing was effective in correcting dimensional non-uniformity arising from hot indirect extrusion. Examinations of the microstructures of microtubes revealed the generation of a large number of twins as a result of accumulated work hardening at the third and fourth passes of cold drawing, corresponding to the significantly raised forming forces. The work demonstrated the viability of the forming process route selected for the fabrication of biodegradable magnesium alloy microtubes.

  3. Hydroxyapatite precipitation on nanotubular films formed on Ti-6Al-4V alloy for biomedical applications

    Energy Technology Data Exchange (ETDEWEB)

    Jo, Chae-Ik; Jeong, Yong-Hoon [Department of Dental Materials, Research Center of Nano-Interface Activation for Biomaterials, and Research Center for Oral Disease Regulation of the Aged, School of Dentistry, Chosun University, Gwangju (Korea, Republic of); Choe, Han-Cheol, E-mail: hcchoe@chosun.ac.kr [Department of Dental Materials, Research Center of Nano-Interface Activation for Biomaterials, and Research Center for Oral Disease Regulation of the Aged, School of Dentistry, Chosun University, Gwangju (Korea, Republic of); Brantley, William A. [Division of Restorative, Prosthetic and Primary Care Dentistry, College of Dentistry, The Ohio State, University, Columbus, OH (United States)

    2013-12-31

    In this study, hydroxyapatite precipitation on nanotubular film-formed Ti-6Al-4V alloy for biomedical applications has been investigated using a variety of techniques. To prepare the substrate samples for hydroxyapatite (HA) deposition, the starting Ti-6Al-4V alloy was polished and heat-treated for 12 h at 1050 °C in an Ar atmosphere, followed by water-quenching at 0 °C. Nanotube formation on the titanium alloy was performed using anodization with a DC power supply at 30 V for 1 h in 1 M H{sub 3}PO{sub 4} + 0.8 wt.% NaF at 25 °C. Subsequent HA precipitation treatment was carried out by cyclic voltammetry over a potential range of −1.5 V to 0 V using a scanning rate of 100 mV/s in 0.03 M Ca(NO{sub 3}){sub 2} ∙ 4 H{sub 2}O + 0.018 M NH{sub 4}H{sub 2}PO{sub 4} at 80° ± 1 °C. Four different numbers of cycles were employed: 10, 20, 30, and 50. Surface morphology and structure were examined by field-emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. The heat-treated Ti–6Al–4V alloy has a needle-like duplex microstructure containing the martensitic α′ phase and β phase. Plate-like precipitates were formed on bulk Ti–6Al–4V alloy, and the size of these precipitates increased with the number of deposition cycles. The HA precipitates on the nanotube surface showed a mixture of plate-like and flower-like particles with more deposition cycles. The deposited HA phase in the coated layer had an amorphous structure, with particle composition in good agreement with Ca{sub 10}(PO{sub 4}){sub 6}(OH){sub 2}. - Highlights: • Hydroxyapatite (HA) precipitation on nanotubular films formed on Ti–6Al–4V alloy was investigated using a variety of experimental methods. • HA precipitation treatment was carried out using a cyclic voltammetry method after nanotube formation on Ti–6Al–4V alloy. • Plate-like precipitates were formed on the bulk (not anodized) alloy, and the

  4. Chemical durability and degradation mechanisms of HT9 based alloy waste forms with variable Zr content

    Energy Technology Data Exchange (ETDEWEB)

    Olson, L. N. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

    2015-10-30

    In Corrosion studies were undertaken on alloy waste forms that can result from advanced electrometallurgical processing techniques to better classify their durability and degradation mechanisms. The waste forms were based on the RAW3-(URe) composition, consisting primarily of HT9 steel and other elemental additions to simulate nuclear fuel reprocessing byproducts. The solution conditions of the corrosion studies were taken from an electrochemical testing protocol, and meant to simulate conditions in a repository. The alloys durability was examined in alkaline and acidic brines.

  5. Investigation on inductive heating of A356 alloy for thixo-forming

    Institute of Scientific and Technical Information of China (English)

    Kai-kun Wang; Jian-lin Sun; Yong-lin Kang; Qi Zhang; Lei Yang; Chun-mei Ma

    2009-01-01

    To meet the demands of continuous stream-line for component production in the thixo-forming industry, billet heating should be of high quality and in a controllable way. A 4-step inductive heating strategy for aluminum alloy A356 was performed. Thixotropic testing and microstructure analysis showed that a homogenous temperature distribution was achieved after tempera-ture-power-time optimization. Theoretical analysis was given concerning the thermal conductivity and heat capacity of A356 be-tween conventional and semisolid casting microstructures. The experimental results show that the optimized 4-step strategy could bethe best strategy for billet heating during the thixo-forming of aluminum alloy A356.

  6. Superplasticity of low carbon HSLA steel during bainite transformation. Teitanso teigokinko no beinaito hentai ni okeru chososei kyodo

    Energy Technology Data Exchange (ETDEWEB)

    Nakajima, H.; Yamamoto, S.; Miyaji, H.; Furubayashi, E. (National Research Inst. for Metals, Tsukuba, Ibaraki (Japan))

    1993-12-01

    Recently, the development of high strength low alloy steel (HSLA steel) of untempered type is advanced by using the comparatively high strength and excellent tenacity of the bainite or martensite of carbon remained being transformed. In the present researches, the superplasticity during the bainite transformation due to the continuous cooling and changes of the structure as well as the mechanical properties due to the superplastic deformation are examined with the samples of Mn-Cr-Mo system HSLA steel. The results obtained therefrom are shown as follows. The temperatre range of B[sub S] and bainite transformation is moving to the higher temperature side along with the increasing of the applied stress when it is over 60 MPa. The bainitic structure is composed of the mixture lath-like bainitic ferrite and granular bainitic ferrite in the use of having no applied stress, while the percentage of the latter increases simultaneously with the increasing of the applied stress. Transformation superplastic strain is increasing together with the increasing of the applied stress, and its increasing is over the linear function when the applied stress is above about 50 MPa. 22 refs., 9 figs., 2 tabs.

  7. Evaluation of forming limit in viscous pressure forming of automotive aluminum alloy 6k21-T4 sheet

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    A ductile fracture criterion is introduced into numerical simulation to predict viscous pressure forming limit of the automotive body aluminum alloy 6k21-T4. The material constant in the ductile fracture criterion is determined by the combination of the viscous pressure bulging (VPB) test with numerical simulation. VPB tests of the aluminum alloy sheet are carried out by using various elliptical dies with different ratios of major axis to minor axis(β), and the bugling processes are simulated by the aid of the finite element method software LS-DYNA3D. On the basis of the stress and strain calculated from numerical simulations, the forming limits of bulging specimens obtained are predicted by the ductile fracture criterion, and compared with experimental results.The fracture initiation site and the minimal thickness predicted by the ductile fracture criterion are in good agreement with the experimental results.

  8. Processing of magnesium alloys with ultrafine grain structure

    Science.gov (United States)

    Figueiredo, Roberto Braga

    The relationship between processing, structure and properties is analyzed in magnesium alloys subjected to equal-channel angular pressing. Finite element modeling is used to show that the flow softening behavior associated with grain refinement might cause shear localization and billet failure in magnesium alloys processed by ECAP. It also shows that increasing the angle between the channels of the die reduces the accumulated damage in the billets and increasing the material strain rate sensitivity reduces the tendency for shear localization. Both procedures reduce the tendency for billet cracking. The mechanism of grain refinement in magnesium alloys deformed at moderate temperatures differs from that observed in other metals such as copper and aluminum. Fine grains nucleate along pre-existing grain boundaries in a necklace pattern in coarse-grained magnesium while homogeneous nucleation of fine grains is observed in fine-grained. A bimodal grain size distribution is observed after processing alloys from an initial coarse structure and a homogeneous distribution of ultrafine grains is the outcome of a starting fine one. Experiments and simulations are used to analyze the evolution of texture. It is shown that different components are formed depending on the activity ratio of non-basal slip and processing route. The measured pole figures exhibit features characteristic of high activity of non-basal slip. It is also shown that the development of some texture components and their orientation depends on the initial texture and the die angle which provide the basis for future texture engineering. Excellent superplastic properties, including a record elongation for a magnesium alloy, were observed after ECAP. Systematic research showed that the structure characteristics prior and after ECAP play significant role on these properties. Grain growth during superplastic deformation causes a strain hardening effect. The experimental results showed good agreement with the

  9. Semiconductor structures having electrically insulating and conducting portions formed from an AlSb-alloy layer

    Science.gov (United States)

    Spahn, Olga B.; Lear, Kevin L.

    1998-01-01

    A semiconductor structure. The semiconductor structure comprises a plurality of semiconductor layers formed on a substrate including at least one layer of a III-V compound semiconductor alloy comprising aluminum (Al) and antimony (Sb), with at least a part of the AlSb-alloy layer being chemically converted by an oxidation process to form superposed electrically insulating and electrically conducting portions. The electrically insulating portion formed from the AlSb-alloy layer comprises an oxide of aluminum (e.g. Al.sub.2 O.sub.3), while the electrically conducting portion comprises Sb. A lateral oxidation process allows formation of the superposed insulating and conducting portions below monocrystalline semiconductor layers for forming many different types of semiconductor structures having particular utility for optoelectronic devices such as light-emitting diodes, edge-emitting lasers, vertical-cavity surface-emitting lasers, photodetectors and optical modulators (waveguide and surface normal), and for electronic devices such as heterojunction bipolar transistors, field-effect transistors and quantum-effect devices. The invention is expected to be particularly useful for forming light-emitting devices for use in the 1.3-1.6 .mu.m wavelength range, with the AlSb-alloy layer acting to define an active region of the device and to effectively channel an electrical current therein for efficient light generation.

  10. Modeling and optimization of shape change in shell spatial cross-sections under superplastic moulding

    Science.gov (United States)

    Chumachenko, E. N.

    2008-08-01

    The necessity to develop and optimize new technological processes of gas moulding of shells under the superplasticity conditions, which ensure large elongation and complexity of the shape of end items, makes the specialists in the field of mathematical simulation to pose and solve problems of constant improvement of the imitation models. Because of a large number of "embedded" nonlinearities (the physical properties of the material, friction, and unknown boundaries), the solution of such problems requires large computer resources, high qualification of designers, and large amount of labor. In the present paper, we consider the problems of express analysis of pattern change of spatial shells on the basis of estimation of the behavior of their critical cross-sections. We solve problems of moulding of titan shells (made of VT6 alloy) in a matrix of complicated shape. We theoretically and experimentally justify the methods for predicting and constructing the optimal technological processes of shell deformation under conditions close to superplasticity by using the 2.5D designing procedures.

  11. FE simulation and process analysis on forming of aluminum alloy multi-layer cylinder parts with flow control forming

    Institute of Scientific and Technical Information of China (English)

    WANG Xin-yun; WU You-sheng; XIA Ju-chen; HU Guo-an

    2005-01-01

    The aluminum alloy parts used in airbag of car were studied with flow control forming(FCF) method,which was a good way to low forming force and better mechanical properties. The key technology of FCF was the design of control chamber to divide metal flow. So, the design method of FCF was analyzed and two type of control chamber were put forward. According to divisional principle, calculation model of forming force and approximate formula were given. Then forming process of aluminum alloy multi-layer cylinder parts was simulated. The effect of friction factor, die radius and punch velocity on metal flow and forming force was obtained. Finally, the experiment was preformed under the direction of theory and finite element(FE) simulation results. And the qualified parts were manufactured. The simulation data and experimental results show that the forming sequence of inner wall and outer wall, and then the force step, can be controlled by adjusting the process parameters. And the FCF technology proposed has very important application value in precision forging.

  12. Laser forming of structures of zinc oxide on a surface of products from copper alloys

    Science.gov (United States)

    Abramov, D. V.; Gorudko, T. N.; Koblov, A. N.; Nogtev, D. S.; Novikova, O. A.

    Laser formation of a protective zinc oxide layer on a surface of products from copper alloys is present. This layer is formed with using of carbon nanotubes. Destructions of the basic material are avoided or minimized at laser nanostructuring of product surfaces. Such laser processing can be made repeatedly. Offered covering have self-clearing and water-repellent properties.

  13. High strength microstructural forms developed in titanium alloys by rapid heat treatment

    Energy Technology Data Exchange (ETDEWEB)

    Ivasishin, O.M. [Institute of Metal Physics, Kiev (Ukraine)

    2001-09-01

    It is shown that rapid heat treatment of alpha+beta and beta titanium alloys, which includes rapid heating of alloys with initial equiaxed microstructure into single-phase beta field is able to produce microstructural forms in which high strength can be well balanced with other mechanical properties. Main advantage of rapid heating approach comes from the possibility to extend the level of ''useful'' strength. Desirably high strength is provided by intragranular morphology and microchemistry while beta-grain refinement permits a reliability of such high strength conditions. (orig.)

  14. The fluidity and molding ability of glass-forming Zr-based alloy melt

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The fluidity and filling ability of glass-forming Zr-based alloy melt in copper mould were investigated both theoretically and experimentally. The major factors which affected the flowing behavior of the metallic melt in the mold were determined,which provides the foundation for overcoming the contradiction between the filling and formation of amorphous alloy during the rapid cooling process of the metallic melts. The casting factors to prepare a metallic ring were discussed and selected. As a result,a Zr-based bulk metallic glass ring was prepared successfully.

  15. Comparative study of patinas formed on statuary alloys by means of electrochemical and surface analysis techniques

    Energy Technology Data Exchange (ETDEWEB)

    Cicileo, Gabriela P.; Crespo, Miguel A.; Rosales, Blanca M

    2004-04-01

    A comparative evaluation of natural patinas and those formed during acid rain laboratory tests was applied to predict patina stability in corrosive urban environments. SEM-EDX analyses of various statuary alloys after the laboratory tests distinguished areas of correlative intensity of attack and S percentage, depending on the alloy. Moreover, EDX and X-ray diffraction (XRD) determined the chemical composition of different coloured patina carefully scraped from a bronze monument, submitted to 75 years outdoors exposure. To analyse the electrochemical potential evolution with time the in situ Pourbaix technique was applied on the laboratory-exposed samples and over representative areas of the monument, at 2 years interval.

  16. Ferromagnetic Fe-based Amorphous Alloy with High Glass-forming Ability

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    A ferromagnetic amorphous Fe73Al4Ge2Nb1P10C6B4 alloy with highglass-forming ability was synthesized by melt spinning. The supercooled liquid region before crystallization reaches about 65.7 K. The crystallized structure consists of α-Fe, Fe3B, FeB, Fe3P and Fe3C phases. The Febased amorphous alloy exhibits good magnetic properties with a high saturation magnetization and a low saturated magnetostriction. The crystallization leads to an obvious decrease in the soft magnetic properties.

  17. Isothermal grain growth of reactive spray formed 7075 alloys in semi-solid state

    Institute of Scientific and Technical Information of China (English)

    Huimin Liu; Hua Cui; Bin Yang; Jishan Zhang

    2004-01-01

    The grain growth behavior in reactive spray formed 7075+2.91vol%TiC Al alloy was studied and compared with that of spray formed 7075 Al alloy at semi-solid state. The effects of in-situ TiC particles on the microstructure of spray formed 7075 Al alloy were also investigated. The specimens were heat-treated isothermally at various temperatures between the solidus and liquidus of 7075 Al alloy for times in the range of 10-60 min, then quenched in water. The microstructure of reheated specimens was characterized using scanning electron microscopy and optical microscopy. The grain size was measured using a mean linear intercept method.Results show that the in-situ TiC particles can effectively retard grain growth and refine the grain at a limited size. The grain growth exponent in Arrhenius equation increases from 2 to 3, which indicates that the in-situ TiC particles have the significant pinning effect on grain coarsening in the semi-solid state.

  18. Abnormal Grain Growth Suppression in Aluminum Alloys

    Science.gov (United States)

    Hales, Stephen J. (Inventor); Claytor, Harold Dale (Inventor); Alexa, Joel A. (Inventor)

    2015-01-01

    The present invention provides a process for suppressing abnormal grain growth in friction stir welded aluminum alloys by inserting an intermediate annealing treatment ("IAT") after the welding step on the article. The IAT may be followed by a solution heat treatment (SHT) on the article under effectively high solution heat treatment conditions. In at least some embodiments, a deformation step is conducted on the article under effective spin-forming deformation conditions or under effective superplastic deformation conditions. The invention further provides a welded article having suppressed abnormal grain growth, prepared by the process above. Preferably the article is characterized with greater than about 90% reduction in area fraction abnormal grain growth in any friction-stir-welded nugget.

  19. Unified constitutive modelling for two-phase lamellar titanium alloys at hot forming conditions

    Directory of Open Access Journals (Sweden)

    Yang Lei

    2016-01-01

    Full Text Available In this paper, a set of mechanism based unified viscoplastic constitutive equations have been established for two-phase titanium alloys with initial lamellar microstructure, which models the softening mechanisms of the alloys in hot forming conditions. The dislocation density, rotation and globularization of lamellar α-phase and their effects on flow behaviour can also be modelled. The values of material constants in the equation set have been calibrated, according to stress-strain curves and globularization fractions of lamellar α-phase obtained from compression tests at a range of temperatures and strain rates, using a genetic algorithm (GA based optimisation method. Based on the determined constitutive equations, flow stress and globularization evolution of Ti-17 and TA15 alloys at different temperatures and strain rates were predicted. Good agreements between the experimental and computed results were obtained.

  20. Soft-ferromagnetic bulk glassy alloys with large magnetostriction and high glass-forming ability

    Directory of Open Access Journals (Sweden)

    Jiawei Li

    2011-12-01

    Full Text Available The effect of Dy addition on the glass-forming ability (GFA, magnetostriction as well as soft-magnetic properties and fracture strength in FeDyBSiNb glassy alloys was investigated. In addition to the increase of supercooled liquid region from 55 to 100 K, the addition of Dy is effective in approaching alloy to an eutectic point and increasing the saturation magnetostrction (λs. Accordingly, bulk glassy alloy (BGA rods with diameters up to 4 mm were produced, which exhibit a large λs as high as 65×10-6. Besides, the BGA system exhibits superhigh fracture strength of 4000 MPa, combined with good soft-magnetic properties.

  1. Analysis of melting and solidification behaviour of glass-forming alloys by synchrotron radiation

    Energy Technology Data Exchange (ETDEWEB)

    Baser, T.A.; Baricco, M. [Dipartimento di Chimica, Universita di Torino (Italy); NIS, Torino (Italy); Bostrom, M. [The European Synchrotron Radiation Facility, (ESRF), Grenoble (France); Stoica, M. [Leibniz-Institut fuer Festkorper- und Werkstoffforschung Dresden (Germany); Yavari, A.R. [Laboratorie de Thermodynamique et Physico-chimie Metallurgique (LTPCM-UMR 5614), Institut National Polytechnique de Grenoble, CNRS (France)

    2007-06-15

    This paper aims to study the melting and solidification behaviour of Fe48Cr15Mo14Y2C15B6 and Cu50Zr50 glass-forming alloys by in-situ synchrotron X-ray diffraction from data obtained at the European Synchrotron Radiation Facility (ESRF). Melting and solidification behaviour for both alloys were measured by high temperature differential scanning calorimetry (HTDSC). The phase identification was performed by Rietveld refinement of diffraction patterns collected as a function of temperature. The phase mixture on melting and solidification has been clarified, confirming that in-situ X-ray diffraction by synchrotron radiation is a powerful technique for the study of phase transformations in alloys. (Abstract Copyright [2007], Wiley Periodicals, Inc.)

  2. Microstructure characteristics of laser forming repaired Ti60 alloy

    Institute of Scientific and Technical Information of China (English)

    Yanhong Liu; Jing Chen; Qiang Zhang; Lei Xue; Xin Lin; Weidong Huang

    2011-01-01

    The microstructure characteristics of laser forming repaired(LFR) Ti60(Ti-5.6A1-4.8Sn-2Zr-1Mo-O.35Si0.3Nb) as-deposited and annealed samples are analyzed.The microstructure of as-deposited repaired zone (RZ) consists of epitaxial columnar prior β grains,in which fine woven a laths and β-phase between a laths exist.The heat-affected zone(HAZ) experiences a continuous microstructural transition from duplex microstructure of the base metal zone(BMZ) to the microstructure of RZ.The presence of silicide precipitates is observed in both RZ and BMZ in an annealed sample by transmission electron microscopy.They are identified as(Ti,Zr)6Si3 distributed mainly at the α/β interface with the size of 100-300 nm.The fine a2 precipitates are detected in BMZ by electron diffraction; there was no a2 detected in RZ.

  3. FEM Analysis of Spring-backs in Age Forming of Aluminum Alloy Plates

    Institute of Scientific and Technical Information of China (English)

    Huang Lin; Wan Min; Chi Cailou; Ji Xiusheng

    2007-01-01

    The age forming technology, characterized by huge spring-backs, has been developed to manufacture large integral wing-skin panel parts, which necessitates devising a method of predicting spring-backs. A 7B04-T7451 aluminum alloy creep test in tension is accomplished at 155 ℃, and the creep curves are obtained. The material constants of the mechanism-based creep constitutive equations are determined through experiments. The age forming process and the spring-backs of 7B04 aluminum alloy plates are analyzed using the commercial finite element software ABAQUS. The effects of plate thickness and formingtime on spring-backs are researched. The spring-backs decrease with the increase of plate thickness and forming time. The test results verify the reliability of the finite element method (FEM) analysis.

  4. Correlation between liquid structure and glass forming ability in glassy Ag-based binary alloys

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The atomic structures of liquid Ag-based binary alloys have been investigated in the solidification process by means of X-ray diffraction. The results of liquid structure show that there is a break point in the mean nearest neighbor distance r1 and the coordination number Nmin for glass-forming liquid, while the correlation radius rc and the coordination number Nmin display a monotone variational trend above the break point. It means glass-forming liquids have a steady changing in structure above liquidus and more inhomogeneous state at liquidus. We conclude that there is a strong correlation between liquid structure and glass forming ability in Ag-based binary alloys.

  5. Nanostructure and corrosion behaviors of nanotube formed Ti-Zr alloy

    Institute of Scientific and Technical Information of China (English)

    Won-Gi KIM; Han-Cheol CHOE

    2009-01-01

    In order to investigate the nanostructures and corrosion behaviors of Ti-Zr alloys, nanotube formed Ti-Zr(10%, 20%, 30% and 40% in mass fraction) alloys were prepared by arc melting and the condition of controlling nanostructure was at 1 000 ℃ for 24 h in argon atmosphere; formation of nanotubes was conducted by anodizing a Ti-Zr alloy in H3PO4 electrolyte with a small amount of fluoride ions at room temperature. The corrosion properties of specimens were examined through potentiodynamic test (potential range of -1 500-2 000 mV) in 0.9% NaCl solution by using potentiostat. Microstructures of the alloys were observed by optical microscope(OM), field emission scanning electron microscope(FE-SEM) and X-ray diffractometer(XRD). Diameter of nanotube does not depend on Zr content, but interspace of nanotube predominantly depends on Zr content, which confirms that ZrO2 oxides play a role to increase the interspace of nanotube formed on the surface.

  6. CROSS-ROLL FLOW FORMING OF ODS ALLOY HEAT EXCHANGER TUBES FOR HOOP CREEP ENHANCEMENT

    Energy Technology Data Exchange (ETDEWEB)

    Bimal K. Kad

    2004-08-31

    Mechanically alloyed oxide dispersion strengthened (ODS) Fe-Cr-Al alloy thin walled tubes and sheets, produced via powder processing and consolidation methodologies, are promising materials for eventual use at temperatures up to 1200 C in the power generation industry, far above the temperature capabilities of conventional alloys. Target end-uses range from gas turbine combustor liners to high aspect ratio (L/D) heat exchanger tubes. Grain boundary creep processes at service temperatures, particularly those acting in the hoop direction, are the dominant failure mechanisms for such components. The processed microstructure of ODS alloys consists of high aspect ratio grains aligned parallel to the tube axis, a result of dominant axial metal flow which aligns the dispersoid particles and other impurities in the longitudinal direction. The dispersion distribution is unaltered on a micro scale by recrystallization thermal treatments, but the high aspect ratio grain shape typically obtained limits transverse grain spacing and consequently the hoop creep response. Improving hoop creep in ODS-alloy components will require understanding and manipulating the factors that control the recrystallization behavior, and represents a critical materials design and development challenge that must be overcome in order to fully exploit the potential of ODS alloys. The objectives of this program are to (1) increase creep-strength at temperature in ODS-alloy tube and liner components by 100% via, (2) preferential cross-roll flow forming and grain/particle fibering in the critical hoop direction. Recent studies in cross-rolled ODS-alloy sheets (produced from flattened tubes) indicate that transverse creep is significantly enhanced via controlled transverse grain fibering, and similar improvements are expected for cross-rolled tubes. The research program outlined here is iterative in nature and is intended to systematically (i) prescribe extrusion consolidation methodologies via detailed

  7. CROSS-ROLL FLOW FORMING OF ODS ALLOY HEAT EXCHANGER TUBES FOR HOOP CREEP ENHANCEMENT

    Energy Technology Data Exchange (ETDEWEB)

    Bimal K. Kad

    2004-03-31

    Mechanically alloyed oxide dispersion strengthened (ODS) Fe-Cr-Al alloy thin walled tubes and sheets, produced via powder processing and consolidation methodologies, are promising materials for eventual use at temperatures up to 1200 C in the power generation industry, far above the temperature capabilities of conventional alloys. Target end-uses range from gas turbine combustor liners to high aspect ratio (L/D) heat exchanger tubes. Grain boundary creep processes at service temperatures, particularly those acting in the hoop direction, are the dominant failure mechanisms for such components. The processed microstructure of ODS alloys consists of high aspect ratio grains aligned parallel to the tube axis, a result of dominant axial metal flow which aligns the dispersoid particles and other impurities in the longitudinal direction. The dispersion distribution is unaltered on a micro scale by recrystallization thermal treatments, but the high aspect ratio grain shape typically obtained limits transverse grain spacing and consequently the hoop creep response. Improving hoop creep in ODS-alloy components will require understanding and manipulating the factors that control the recrystallization behavior, and represents a critical materials design and development challenge that must be overcome in order to fully exploit the potential of ODS alloys. The objectives of this program are to (1) increase creep-strength at temperature in ODS-alloy tube and liner components by 100% via, (2) preferential cross-roll flow forming and grain/particle fibering in the critical hoop direction. Recent studies in cross-rolled ODS-alloy sheets (produced from flattened tubes) indicate that transverse creep is significantly enhanced via controlled transverse grain fibering, and similar improvements are expected for cross-rolled tubes. The research program outlined here is iterative in nature and is intended to systematically (1) prescribe extrusion consolidation methodologies via detailed

  8. CROSS-ROLL FLOW FORMING OF ODS ALLOY HEAT EXCHANGER TUBES FOR HOOP CREEP ENHANCEMENT

    Energy Technology Data Exchange (ETDEWEB)

    Bimal K. Kad

    2004-05-31

    Mechanically alloyed oxide dispersion strengthened (ODS) Fe-Cr-Al alloy thin walled tubes and sheets, produced via powder processing and consolidation methodologies, are promising materials for eventual use at temperatures up to 1200 C in the power generation industry, far above the temperature capabilities of conventional alloys. Target end-uses range from gas turbine combustor liners to high aspect ratio (L/D) heat exchanger tubes. Grain boundary creep processes at service temperatures, particularly those acting in the hoop direction, are the dominant failure mechanisms for such components. The processed microstructure of ODS alloys consists of high aspect ratio grains aligned parallel to the tube axis, a result of dominant axial metal flow which aligns the dispersoid particles and other impurities in the longitudinal direction. The dispersion distribution is unaltered on a micro scale by recrystallization thermal treatments, but the high aspect ratio grain shape typically obtained limits transverse grain spacing and consequently the hoop creep response. Improving hoop creep in ODS-alloy components will require understanding and manipulating the factors that control the recrystallization behavior, and represents a critical materials design and development challenge that must be overcome in order to fully exploit the potential of ODS alloys. The objectives of this program are to (1) increase creep-strength at temperature in ODS-alloy tube and liner components by 100% via, (2) preferential cross-roll flow forming and grain/particle fibering in the critical hoop direction. Recent studies in cross-rolled ODS-alloy sheets (produced from flattened tubes) indicate that transverse creep is significantly enhanced via controlled transverse grain fibering, and similar improvements are expected for cross-rolled tubes. The research program outlined here is iterative in nature and is intended to systematically (1) prescribe extrusion consolidation methodologies via detailed

  9. CROSS-ROLL FLOW FORMING OF ODS ALLOY HEAT EXCHANGER TUBES FOR HOOP CREEP ENHANCEMENT

    Energy Technology Data Exchange (ETDEWEB)

    Bimal K. Kad

    2004-11-30

    Mechanically alloyed oxide dispersion strengthened (ODS) Fe-Cr-Al alloy thin walled tubes and sheets, produced via powder processing and consolidation methodologies, are promising materials for eventual use at temperatures up to 1200 C in the power generation industry, far above the temperature capabilities of conventional alloys. Target end-uses range from gas turbine combustor liners to high aspect ratio (L/D) heat exchanger tubes. Grain boundary creep processes at service temperatures, particularly those acting in the hoop direction, are the dominant failure mechanisms for such components. The processed microstructure of ODS alloys consists of high aspect ratio grains aligned parallel to the tube axis, a result of dominant axial metal flow which aligns the dispersoid particles and other impurities in the longitudinal direction. The dispersion distribution is unaltered on a micro scale by recrystallization thermal treatments, but the high aspect ratio grain shape typically obtained limits transverse grain spacing and consequently the hoop creep response. Improving hoop creep in ODS-alloy components will require understanding and manipulating the factors that control the recrystallization behavior, and represents a critical materials design and development challenge that must be overcome in order to fully exploit the potential of ODS alloys. The objectives of this program are to (1) increase creep-strength at temperature in ODS-alloy tube and liner components by 100% via, (2) preferential cross-roll flow forming and grain/particle fibering in the critical hoop direction. Recent studies in cross-rolled ODS-alloy sheets (produced from flattened tubes) indicate that transverse creep is significantly enhanced via controlled transverse grain fibering, and similar improvements are expected for cross-rolled tubes. The research program outlined here is iterative in nature and is intended to systematically (i) prescribe extrusion consolidation methodologies via detailed

  10. CROSS-ROLL FLOW FORMING OF ODS ALLOY HEAT EXCHANGER TUBES FOR HOOP CREEP ENHANCEMENT

    Energy Technology Data Exchange (ETDEWEB)

    Bimal K. Kad

    2005-02-28

    Mechanically alloyed oxide dispersion strengthened (ODS) Fe-Cr-Al alloy thin walled tubes and sheets, produced via powder processing and consolidation methodologies, are promising materials for eventual use at temperatures up to 1200 C in the power generation industry, far above the temperature capabilities of conventional alloys. Target end-uses range from gas turbine combustor liners to high aspect ratio (L/D) heat exchanger tubes. Grain boundary creep processes at service temperatures, particularly those acting in the hoop direction, are the dominant failure mechanisms for such components. The processed microstructure of ODS alloys consists of high aspect ratio grains aligned parallel to the tube axis, a result of dominant axial metal flow which aligns the dispersoid particles and other impurities in the longitudinal direction. The dispersion distribution is unaltered on a micro scale by recrystallization thermal treatments, but the high aspect ratio grain shape typically obtained limits transverse grain spacing and consequently the hoop creep response. Improving hoop creep in ODS-alloy components will require understanding and manipulating the factors that control the recrystallization behavior, and represents a critical materials design and development challenge that must be overcome in order to fully exploit the potential of ODS alloys. The objectives of this program are to (1) increase creep-strength at temperature in ODS-alloy tube and liner components by 100% via, (2) preferential cross-roll flow forming and grain/particle fibering in the critical hoop direction. Recent studies in cross-rolled ODS-alloy sheets (produced from flattened tubes) indicate that transverse creep is significantly enhanced via controlled transverse grain fibering, and similar improvements are expected for cross-rolled tubes. The research program outlined here is iterative in nature and is intended to systematically (i) prescribe extrusion consolidation methodologies via detailed

  11. Bioactive titanate layers formed on titanium and its alloys by simple chemical and heat treatments.

    Science.gov (United States)

    Kokubo, Tadashi; Yamaguchi, Seiji

    2015-01-01

    To reveal general principles for obtaining bone-bonding bioactive metallic titanium, Ti metal was heat-treated after exposure to a solution with different pH. The material formed an apatite layer at its surface in simulated body fluid when heat-treated after exposure to a strong acid or alkali solution, because it formed a positively charged titanium oxide and negatively charged sodium titanate film on its surface, respectively. Such treated these Ti metals tightly bonded to living bone. Porous Ti metal heat-treated after exposure to an acidic solution exhibited not only osteoconductive, but also osteoinductive behavior. Porous Ti metal exposed to an alkaline solution also exhibits osteoconductivity as well as osteoinductivity, if it was subsequently subjected to acid and heat treatments. These acid and heat treatments were not effective for most Ti-based alloys. However, even those alloys exhibited apatite formation when they were subjected to acid and heat treatment after a NaOH treatment, since the alloying elements were removed from the surface by the latter. The NaOH and heat treatments were also not effective for Ti-Zr-Nb-Ta alloys. These alloys displayed apatite formation when subjected to CaCl2 treatment after NaOH treatment, forming Ca-deficient calcium titanate at their surfaces after subsequent heat and hot water treatments. The bioactive Ti metal subjected to NaOH and heat treatments has been clinically used as an artificial hip joint material in Japan since 2007. A porous Ti metal subjected to NaOH, HCl and heat treatments has successfully undergone clinical trials as a spinal fusion device.

  12. Effect of scandium addition on the microstructure, mechanical and wear properties of the spray formed hypereutectic aluminum–silicon alloys

    Energy Technology Data Exchange (ETDEWEB)

    Raghukiran, Nadimpalli; Kumar, Ravi, E-mail: nvrk@iitm.ac.in

    2015-08-12

    Hypereutectic Al–x%Si–0.8Sc alloys (x=13, 16, 19 and 22 wt%) were produced by spray forming. The microstructures of all the alloys exhibited very fine silicon phase with average size of about 5–10 µm irrespective of the silicon content of the alloy. Transmission electron microscopy revealed the presence of a nano-scale scandium rich phase, identified as AlSi{sub 2}Sc{sub 2} (V-phase) uniformly distributed in the alloy. The presence of V-phase resulted in higher matrix hardness (1.34 GPa) in contrast to 1.04 GPa observed in the case of binary Al–Si alloys by nanoindentation. Isothermal heat treatment at 375 °C revealed insignificant coarsening of silicon phase in both binary and ternary alloys. The Al–x%Si–0.8Sc alloys exhibited higher flow stress and tensile strength in contrast to their binary alloy counterparts which was attributed to the bi-modal size distribution of the strengthening phases in the form of nano-scale V-phase and sub-micron to 10 µm size silicon particles. The pin-on-disk wear tests exhibited appreciable improvement in the wear performance of the relatively low-silicon content ternary alloys over their binary counterparts while the high-silicon content binary and ternary alloys exhibited no much difference in the wear performance.

  13. Influence of forming velocity on the uniformity of microstructure of semisolid die forging 7075 alloy

    Directory of Open Access Journals (Sweden)

    Jianbo TAN

    2016-12-01

    Full Text Available Liquid phase segregation frequently occurs in the process of semi solid die forging, which makes the parts appear "weak point" or "weak region", and usually, the "weak point" or "weak area" is the reason of crack and service condition failure. In order to analyze the influence factors of the liquid phase segregation of the semi solid die forging, DEFORM-3D is used for the numerical simulation of semi-solid die forging forming process of 7075 aluminum alloy, to study the influence rule of forming velocity on the forming process of cup part. Based on the simulation results, the rheological die forging forming of 7075 aluminum alloythe part is conducted to research the influence of forming velocity on the uniformity of microstructure by means of press machine and cup mould. The simulation and experimental results show that as the filling velocity is faster, the forming process is more unstable; under the condition of head temperature of 400 ℃, the forming pressure of 50 MPa, and the alloy temperature 628 ℃, as the forming velocity increases, the liquid phase segregation degree of cup part increases, and the microstructure is far from uniformity. The segregation degree is up to 18.2% as the forming velocity is 5 mm/s.

  14. Electrochemical characterization of oxide formed on chromium containing mild steel alloys in LiOH medium

    Energy Technology Data Exchange (ETDEWEB)

    Subramanian, Veena, E-mail: veenasn1974@gmail.com; Chandran, Sinu; Subramanian, H.; Chandramohan, P.; Bera, S.; Rangarajan, S., E-mail: sranga@igcar.gov.in; Narasimhan, S.V.

    2014-06-01

    Flow accelerated corrosion leads to wall thinning of outlet-feeder pipes in the primary heat transport system of pressurized heavy water reactors and can even necessitate enmasse feeder replacement. Replacement of carbon steel 106-grade-B (CS) with chromium containing carbon steel reduces the risk of this failure. This paper discusses the role of small additions of chromium in modifying the properties of the oxide film. CS and chromium containing mild steels viz., A333, 2.25Cr–1Mo and modified 9Cr–1Mo alloy were exposed to primary heat transport (PHT) system chemistry conditions. The oxide films formed were characterized by electrochemical and surface characterization techniques. Mott–Schottky analysis showed donor type of defects. The densities of defects in the oxides of chromium containing alloys were 3–15 times less than that in CS. In presence of ∼200 ppb of dissolved oxygen, the oxides formed were hematite with two orders of magnitude smaller concentration of defects as compared to that formed under reducing conditions. These results suggest that the presence of chromium lowers the defect density of the oxide film and thus ensures a reduced corrosion rate. - Graphical abstract: Display Omitted - Highlights: • High temperature oxides formed on Cr containing mild steels are less defective. • Defect densities of oxides decrease with increase in Cr content in the alloy. • O{sub 2} in solution greatly influences the nature and defect chemistry of oxides.

  15. Investigation of Intermetallic Compound Formed from Rapid Solidification of Al-Ti-RE Alloy

    Institute of Scientific and Technical Information of China (English)

    杨明珊; 王振飞

    2004-01-01

    Al-Ti alloy containing rare earth elements can produce fine,uniform dispersion intermetallic phase through rapid solidification(RS)technology.RS Al-Ti-RE alloy can be designed for applications at elevated-temperature since the intermetallic compound has good thermal stability.A transmission electron microscopy investigation shows the intermetallic phase has a diamond cubic structure(a=1.47736 nm),with space group Fd3m.The chemical stoichiometry is Al20Ti2La.The particle is formed from the melting directly,prior to other phases,and the nucleus is formed from icosahedrons composed with twenty tetrahedrons.Twin crystal structure plays an important role in the nucleation stage.

  16. A set of microstructure-based constitutive equations in hot forming of a titanium alloy

    Institute of Scientific and Technical Information of China (English)

    Xiaoli Li; Miaoquan Li

    2006-01-01

    A physical model of microstructure evolution including dislocation density rate and grain growth rate was established based on the deformation mechanism for the hot forming of a class of two-phase titanium alloys. Further, a set of mechanism-based constitutive equations were proposed, in which the microstructure variables such as grain size and dislocation density were taken as internal state variables for characterizing the current material state. In the set of constitutive equations, the contributions of different mechanisms and individual phase to the deformation behavior were analyzed. The present equations have been applied to describe a correlation of the flow stress with the microstructure evolution of the TC6 alloy in hot forming.

  17. An Investigation into the Effect of Aging on the Forming Limit Diagram of 6063 Aluminum Alloy

    Science.gov (United States)

    Hosseini, S. M.; Hosseimpour, S. J.; Nourouzi, S.; Gorji, A. H.

    2011-01-01

    In this study, the effect of ageing on the forming limit diagram of a commercially available 6063 aluminum alloy has been investigated. For this purpose, initially the specimens have been aged at 200° C and at various times. The hardness tests have been carried out and the hardness-aging time curve has been obtained for this alloy. Moreover, the mechanical properties were determined by tensile test. Then, the forming limit diagrams have been achieved by using the out-of-plane formability test method at four different conditions containing: annealed, under-aged, peak-aged, and over-aged. The results indicate that in comparing with the annealed condition the FLD0 decreases significantly from the under-aged condition to the peak-aged condition and increases slightly from the peak-aged condition to the over-aged condition.

  18. Wear resistance of TiN(Ti2N)/Ti composite layer formed on C17200 alloy by plasma surface Ti-alloying and nitriding

    Science.gov (United States)

    Liu, L.; Shen, H. H.; Liu, X. Z.; Guo, Q.; Meng, T. X.; Wang, Z. X.; Yang, H. J.; Liu, X. P.

    2016-12-01

    The duplex treatment of plasma Ti-alloying and plasma nitriding was applied on the surface of C17200 alloy to improve its wear resistance. C17200 substrate was alloyed with Ti using double glow plasma alloying to form a Ti-alloyed layer in its surface, and then treated by plasma nitriding to make a TiN(Ti2N) alloying layer based on the Ti-alloyed surface. The microstructure and formation mechanism were studied by using GDOES, XRD and SEM. The hardness, tribological property and electrical conductivity of C17200 alloy after plasma alloying and nitriding were investigated by mean of micro-hardness tester, friction and wear testers as well as impedance analyzers. Modulus of elasticity and the adhesive strength of TiN(Ti2N)/Ti composite layer were evaluated by nano-indenter and scratch tester. The result shows that a TiN(Ti2N)-Ti-Be-Cu composite layer with a thickness of 27 μm is formed in the C17200 surface and is mainly composed of TiN, Ti2N, Cu(Ti) solid solution, etc. The composite alloying surface consists of the hard TiN(Ti2N)-rich layer on the top surface and Ti-Cu-Be diffusion layer, showing a strong adhesive strength with the C17200 substrate and a little decrease in the modulus of elasticity. A certain amount of Cu and Be together with TiN/Ti2N exists in the outmost, resulting in a better combination of wear resistance and conductive performance.

  19. New Zr-based glass-forming alloys containing Gd and Sm

    Directory of Open Access Journals (Sweden)

    Luis César Rodríguez Aliaga

    2012-10-01

    Full Text Available The effect of minor additions of Gd and Sm on the glass-forming ability (GFA of Cu-Zr-Al alloys is investigated here. The rationale for these additions is the fact that the atomic size distribution can increase GFA by changing the topology of the alloy as a function of cluster stability, which is tied to the electronegativity and ionic and covalent nature of alloys. Ingots with nominal compositions of Cu40Zr49Al10.5Gd0.5, Cu40Zr49Al10.5Sm0.5 and Cu39Zr50Al9Gd2 were prepared by arc-melting and rapidly quenched ribbons were produced by the melt-spinning technique. Bulk samples with a thickness of up to 10 mm were also produced by casting, using a wedge-shaped copper mold. The samples were characterized by differential scanning calorimetry, X-ray diffractometry and scanning electron microscopy. The three compositions showed a fully amorphous structure in the ribbons and a predominantly homogeneous amorphous structure with a thickness of up to 10 mm, although some gadolinium oxide crystals as well as samarium compounds were found to be scattered in the amorphous matrix in 5-mm-thick samples. The amorphous phases in the alloys showed high thermal stability with a supercooled liquid region (ΔTx of about 70 K.

  20. Cross-Roll Flow Forming of ODS Alloy Heat Exchanger Tubes For Hoop Creep Enhancement

    Energy Technology Data Exchange (ETDEWEB)

    Bimal Kad

    2007-09-30

    Mechanically alloyed oxide dispersion strengthened (ODS) Fe-Cr-Al alloy thin walled tubes and sheets, produced via powder processing and consolidation methodologies are promising materials for eventual use at temperatures up to 1200 C in the power generation industry, far above the temperature capabilities of conventional alloys. Target end-uses range from gas turbine combustor liners to high aspect ratio (L/D) heat exchanger tubes. Grain boundary creep processes at service temperatures, particularly those acting in the hoop direction, are the dominant failure mechanisms for such components. The processed microstructure of ODS alloys consists of high aspect ratio grains aligned parallel to the tube axis, a result of dominant axial metal flow which aligns the dispersoid particles and other impurities in the longitudinal direction. The dispersion distribution is unaltered on a micro scale by recrystallization thermal treatments, but the high aspect ratio grain shape typically obtained limits transverse grain spacing and consequently the hoop creep response. Improving hoop creep in ODS-alloy components will require understanding and manipulating the factors that control the recrystallization behavior, and represents a critical materials design and development challenge that must be overcome in order to fully exploit the potential of ODS alloys. The objectives of this program were to (1) increase creep-strength at temperature in ODS-alloy tube and liner components by 100% via, (2) preferential cross-roll flow forming and grain/particle fibering in the critical hoop direction. The research program outlined was iterative and intended to systematically (i) examine and identify post-extrusion forming methodologies to create hoop strengthened tubes, to be (ii) evaluated at 'in-service' loads at service temperatures and environments. Our report outlines the significant hoop creep enhancements possible via secondary cross-rolling and/or flow-forming operations. Each

  1. Textures formed in a CoCrMo alloy by selective laser melting

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Xin, E-mail: zhouxin12@mails.tsinghua.edu.cn [School of Materials Science and Engineering, Tsinghua University, 100084 Beijing (China); Science and Technology on Plasma Dynamics Lab, Xi’an, 710038 (China); Li, Kailun [Imperial College, South Kensington Campus, SW7 2AZ London (United Kingdom); Zhang, Dandan; Liu, Xihe; Ma, Jing; Liu, Wei [School of Materials Science and Engineering, Tsinghua University, 100084 Beijing (China); Shen, Zhijian [School of Materials Science and Engineering, Tsinghua University, 100084 Beijing (China); Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University, S-106 91 Stockholm (Sweden)

    2015-05-15

    Highlights: • Unique crystal textures were formed by selective laser melting of a CoCrMo alloy. • Along the building direction, long columnar grains were discovered. • Columnar grain orientations were a concurrence of 〈0 0 1〉 and 〈0 1 1〉. • A (0 1 1)〈1 0 0〉 texture was limited to the top surface. • A 〈0 0 1〉 fiber texture existed in the whole solid bulk. - Abstract: Unique crystal textures formed by selective laser melting of a CoCrMo alloy were characterized by electron backscattered diffraction. Preferred crystallographic orientations were found for individual grains in the solid alloy microstructure. Along the building or radial grain growth direction in the rapidly cooling melt pool the formed columnar grains were not purely 〈0 0 1〉 or 〈1 1 1〉, as reported before, but a concurrence of 〈0 0 1〉 and 〈0 1 1〉. Along the scanning direction, a (0 1 1)〈1 0 0〉 texture was limited to the outmost surface whereas in the solid bulk the preferred orientation was a 〈0 0 1〉 fiber texture.

  2. Enhancement of Formability of AA5052 Alloy Sheets by Electrohydraulic Forming Process

    Science.gov (United States)

    Ahmed, Meraj; Kumar, D. Ravi; Nabi, M.

    2017-01-01

    Formability of lightweight materials like Al and Mg alloys is a major concern for their application in automobiles. Forming limit diagram (FLD) and strain distribution are extremely useful in the assessment of overall formability of sheet metals. At very high strain rates, the deformation behavior of Al alloys and the safe forming window could be different from quasi-static conventional forming. In this paper, formability of Al 5052 alloy sheets of 0.5 mm thickness has been assessed in electrohydraulic forming (EHF) in terms of FLD and strain distribution and compared with formability in conventional forming by punch-stretching experiments. EHF is a high strain rate forming process which utilizes energy released from a capacitor bank to generate shockwaves in a fluid medium. Experiments have been conducted at different energy levels to identify the highest safe strains in different modes of deformation. From the experimental results, it has been observed that the limit strains increased by nearly 45-50% in all the three regions of the FLD (tension-tension, plane strain and tension compression). Unlike in the case of conventional forming, no clear necking due to strain localization has been observed prior to failure due to very high strain rates of the order of 103/s. The strain distribution has been found to be more uniform in the case of EHF with a single strain peak at the pole. Absence of friction in EHF also leads to higher degree of biaxiality leading to higher limit strains in biaxial tension. In the case of EHF, the effective strain and hardness are maximum at the pole and their variation correlated well with the findings from the strain distribution analysis. In all modes of deformation, the features of fractured surface in EHF appeared different from a normal ductile failure.

  3. Numerical simulation and its application of rheological forming of titanium alloy vane disk

    Institute of Scientific and Technical Information of China (English)

    YU Min; LUO Ying-she; PENG Xiang-hua; QIN Yin-hui

    2006-01-01

    The hot rheological forming method was proposed to form the second titanium alloy vane disk. The hot rheological forming process of the TC11 titanium vane disk under a certain temperature and different strain rates was investigated by using the bulk forming software of DEFORM 3D. A series of results including temperature field,equivalent strain distribution,load-stroke curve and rheology procedure were obtained by this finite element method. The rheological forming characteristics were well realized and the forming parameters were determined. The results and analysis show that with decreasing strain rate,the metal flow more equably and the filling of the vane shape is also better. Moreover,the mechanical properties and microstructures of the products produced by this new technique are improved evidently compared with that produced by traditional method.

  4. Semi-solid forming of Al and Mg alloys for transportation applications

    Energy Technology Data Exchange (ETDEWEB)

    Shehata, M. [Canada Centre for Mineral and Energy Technology, Ottawa, ON (Canada). Materials Technology Lab

    2001-07-01

    This Power Point presentation outlined the process of semi-solid forming of aluminium and magnesium alloys for transportation applications with particular reference to its advantages and applications. The presentation also referred to the Canadian Lightweight Materials Research Initiative (CLiMRI) Project which is aimed at optimizing semi-solid processing of aluminium and magnesium alloys in the following four areas: (1) production of thixotropic feed stock suitable for semi-solid forming, (2) optimizing heating of feed stock using an energy efficient high frequency induction heating, (3) optimizing semi-solid die casting, forging and extrusion, and (4) modeling. Materials characterisation was also part of the project. Semi-solid forming methods include thixocasting, thixoforging, thixomolding and rheocasting or slurry on demand. The general advantages of semi-solid forming methods over conventional forming methods for the die casting and forging processes were described. In the die-casting process, semi-solid forming methods require a low cast temperature of 580 degrees C. They require less heat removal, less cycle time, and produce only a small amount of shrinkage. They also result in enhanced mechanical properties. Typical automotive applications are for engine mounts, hydraulic cylinders, air-conditioner scrolls, wheels and other structural parts such as bearings and knuckles. 14 figs.

  5. Adherent Al2O3 scales formed on undoped NiCrAl alloys

    Science.gov (United States)

    Smialek, James L.

    1987-01-01

    Changes in the spalling behavior of Al2O3 scales formed on an undoped NiCrAl alloy are described. Two samples of Ni-15Cr-13Al (wt pct), one a control and the other sanded, were subjected to 25 oxidation cycles. It is observed that adherent scales formed on the sanded sample; however, the control sample had speckled, spalled scales. The data reveal that the adherent scales are caused by repeated removal of surface layers after each oxidation cycle. It is determined that interfacial segregation of sulfur influences spallation and sulfur removal increases bonding. The effect of moisture on scale adhesions is investigated.

  6. Cross-Roll Flow Forming of ODS Alloy Heat Exchanger Tubes For Hoop Creep Enhancement

    Energy Technology Data Exchange (ETDEWEB)

    Bimal K. Kad

    2006-09-30

    Mechanically alloyed oxide dispersion strengthened (ODS) Fe-Cr-Al alloy thin walled tubes and sheets, produced via powder processing and consolidation methodologies, are promising materials for eventual use at temperatures up to 1200 C in the power generation industry, far above the temperature capabilities of conventional alloys. Target end-uses range from gas turbine combustor liners to high aspect ratio (L/D) heat exchanger tubes. Grain boundary creep processes at service temperatures, particularly those acting in the hoop direction, are the dominant failure mechanisms for such components. The processed microstructure of ODS alloys consists of high aspect ratio grains aligned parallel to the tube axis, a result of dominant axial metal flow which aligns the dispersoid particles and other impurities in the longitudinal direction. The dispersion distribution is unaltered on a micro scale by recrystallization thermal treatments, but the high aspect ratio grain shape typically obtained limits transverse grain spacing and consequently the hoop creep response. Improving hoop creep in ODS-alloy components will require understanding and manipulating the factors that control the recrystallization behavior, and represents a critical materials design and development challenge that must be overcome in order to fully exploit the potential of ODS alloys. The objectives of this program are to (1) increase creep-strength at temperature in ODS-alloy tube and liner components by 100% via, (2) preferential cross-roll flow forming and grain/particle fibering in the critical hoop direction. The research program outlined here is iterative in nature and is intended to systematically (a) examine and identify post-extrusion forming methodologies to create hoop strengthened tubes, which will be (b) evaluated at ''in-service'' loads at service temperatures and environments. In this 12th quarter of performance, program activities are concluded for Task 2 and continuing

  7. Microstructure and high temperature mechanical properties of laser rapidly formed Ti-6Al-4V alloy

    Institute of Scientific and Technical Information of China (English)

    XUE Lei; CHEN Jing; LIN Xin; LU Xiao-wei; WANG Wei; HUANG Wei-dong

    2006-01-01

    Several tensile samples were prepared using laser rapid forming (LRF) with Ti-6Al-4V alloy as powder material, and the samples were annealed. The microstructure and high temperature mechanical properties of laser formed Ti-6Al-4V alloy through annealing treatment were investigated. The short-term and long-term tensile tests at 350 ℃ were performed. The results show that the microstructure of LRF samples consists of the large columnar prior β grains which grow epitaxially from the substrate along the deposition direction. There are Widmanst-tten α laths in prior β grains, but α laths in annealed microstructure are coarser, and their aspect ratio is lower than that in as-deposited microstructure. In addition, the prior β grain boundary is also coarsened and broken off through the annealing treatment. The high temperature mechanical properties of the annealed LRF samples exceed those of casting alloy significantly, especially the stress-rupture lifetime reaches 661.7 h even while the test stress increases from initial value of 490 MPa to the final stress of 800 MPa gradually.

  8. Biodegradation behavior of micro-arc oxidized AZ31 magnesium alloys formed in two different electrolytes

    Energy Technology Data Exchange (ETDEWEB)

    Seyfoori, A. [School of Metallurgical Engineering, Iran University of Science and Technology, Tehran (Iran, Islamic Republic of); Mirdamadi, Sh., E-mail: Mirdamadi@iust.ac.ir [School of Metallurgical Engineering, Iran University of Science and Technology, Tehran (Iran, Islamic Republic of); Khavandi, A.; Raufi, Z. Seyed [School of Metallurgical Engineering, Iran University of Science and Technology, Tehran (Iran, Islamic Republic of)

    2012-11-15

    Highlights: Black-Right-Pointing-Pointer Phosphate coating has lesser degradation rate than silicate coating in r-SBF solution. Black-Right-Pointing-Pointer Farringtonite phase is chemically more stable than forsterite phase in SBF solution. Black-Right-Pointing-Pointer Apatite forming ability of forsterite containing coating is better than farringtonite containing film. Black-Right-Pointing-Pointer The hydrophilisity nature of silicate film on magnesium alloy with respect to its roughness, is greater than phosphate film. - Abstract: Degradation behavior of coated magnesium alloys is among most prominent factors for their biomedical applications. In this study, bio-corrosion behavior of micro-arc oxidized magnesium AZ31 alloys formed in silicate and phosphate baths was investigated in r-SBF medium. For this purpose polarization behavior and open circuit profile of the coated samples were achieved by electrochemical and immersion tests, respectively. Moreover, the morphology and composition of the coatings were evaluated before and after immersion test using scanning electron microscopy, X-ray diffraction and energy dispersive spectroscopy. The results showed that the phosphate film had better corrosion resistance and greater thickness than silicate film and, in turn, the lesser degradability in SBF solution, so that Ca{sup 2+} and PO{sub 4}{sup 3-} containing compounds were more abundant on silicate film than phosphate film. Moreover phosphate film had greater surface roughness and lesser hydrophilic nature.

  9. Ni and Cr addition to alloy waste forms to reduce radionuclide environmental releases

    Energy Technology Data Exchange (ETDEWEB)

    Olson, L. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

    2016-10-11

    Reference alloy waste forms (RAW) were fabricated and underwent hybrid corrosion/immersion testing to parameterize the ANL analytical oxidative-dissolution model to enable the calculation of fractional release rates and to determine the effectiveness of Ni and Cr trim additions in reducing release rates of radionuclide surrogates. Figure 1 shows the prototypical multiphase microstructure of the alloys with each phase type contributing about equally to the exposed surface area. The waste forms tested at SRNL were variations of the RAW-6 formulation that uses HT9 as the main alloy component, and are meant to enable evaluation of the impact of Ni and Cr trim additions on the release rates of actinides and Tc-99. The test solutions were deaerated alkaline and acidic brines, ranging in pH 3 to pH 10, representing potential repositories with those conditions. The testing approach consisted of 4 major steps; 1) bare surface corrosion measurements at pH values of 3, 5, 8, and 10, 2) hybrid potentiostatic hold/exposure measurements at pH 3, 3) measurement of radionuclide concentrations and relations to anodic current from potentiostatic holds, and 4) identification of corroding phases using SEM/EDS of electrodes.

  10. Corner forming of AZ61A magnesium alloy tube within warm hydroforming

    Institute of Scientific and Technical Information of China (English)

    HU Lan; HAN Cong; HE Zhu-bin; TANG Ze-jun; LIU Gang; YUAN Shi-jian

    2009-01-01

    The corners with small radii on cross sections are crucial for forming hydroformed components with polygonal sections. In this paper, warm hydroforming experiments of AZ61 A magnesium alloy tubes were carried out to study the forming regularity of round corners by using a demonstration part with square sections.Effects of temperature on radius forming, thinning ratio distribution and microstructure were revealed and a component with relative outer corner radius of 3.0 was obtained by warm hydroforming at 240℃. The minimum thickness of the formed square section was located in the transition position between the corner and the straight wall. The thinning ratio of the round corner increased with the increase of forming temperature. Formability of the magnesium tube was improved by raising temperature under the effect of dynamic recrystallization at 240℃.

  11. Interatomic potential for the compound-forming Li–Pb liquid alloy

    Energy Technology Data Exchange (ETDEWEB)

    Fraile, Alberto, E-mail: albertofrailegarcia@gmail.com [Instituto de Fusión Nuclear, ETSI Industriales, Universidad Politécnica de Madrid, Jose Gutierrez Abascal 2, 28006 Madrid (Spain); Cuesta-López, Santiago, E-mail: scuesta@ubu.es [Universidad de Burgos, Parque Científico I+D+I, Plaza Misael Bañuelos s/n, 09002 Burgos (Spain); Caro, Alfredo; Schwen, Daniel [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Manuel Perlado, J. [Instituto de Fusión Nuclear, ETSI Industriales, Universidad Politécnica de Madrid, Jose Gutierrez Abascal 2, 28006 Madrid (Spain)

    2014-05-01

    Atomistic simulations of liquid alloys face the challenge of correctly modeling basic thermodynamic properties. In this work we present an interatomic potential for this system, as well as a study of physical properties of Li–Pb alloys. Despite the complexity due to Li–Pb being a compound forming system where charge transfer is expected, we show here how the empirical EAM formalism is able to satisfactorily describe several physical properties in a wide range of Li concentration. Application of our potential to Li–Pb eutectic allows us to correctly predict many physical properties observed experimentally and calculated with ab initio techniques, providing in this way a potential suitable for future studies in the context of tritium breeder blanket designs in Fusion technology.

  12. Glass forming ability of Zr-and Fe-based alloys at quenching from melts

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The master alloy ingots(MAI)with the nominal composition Zr52.5 Ti5Cu17.9 Ni14.6Al10 and Fe61Co7Zr10Mo5W2B15(at%)were prepared by arc-melting in Ti-gettered Ar atmosphere.The Zr-based buttons of 6 mm and 9 mm in diameter were fully amorphous,but those of 13 mm in diameter experienced crystallization.The glass forming ability(GFA)of Fe-based alloys was relatively lower,and the buttons obtained were fully crystallized.The microhardness of the Zr-based buttons was about 500(Hv),and the Fe-based rod obtained by injection technique exhibited a high Vickers hardness of 1329.In addition,an amorphous-crystalline transition layers were observed in both the buttons and the rods.

  13. Study of a New Chromium-Free Conversion Coating Formed on ZnAl Alloy

    Institute of Scientific and Technical Information of China (English)

    LONG Jin-ming; GUO Zhong-cheng; HAN Xia-yun; YANG Ning

    2004-01-01

    A new chromium-free conversion film was obtained on surface of a ZnAl alloy by chemical conversion process.Influence of the additives in treating solution containing cerium salt on the corrosion protection of the conversion film formed on zinc alloy was investigated. Corrosion tests and electrochemical measurements in sodium chloride solution were performed. The microstructure and composition of the coatings were examined by means of SEM, EDS and XRD. It was found that the corrosion protection capabilities of the conversion film are markedly increased with the cerium nitride plus additives (hydrogen fluoride acid and an organic inhibitor) treating process. The modified conversion film is an organic/inorganic composite coating and is much more corrosion resistant than the conventional chromate conversion coating and the single cerium conversion coating.

  14. Study of a New Chromium-Free Conversion Coating Formed on ZnAl Alloy

    Institute of Scientific and Technical Information of China (English)

    LONGJin-ming; GUOZhong-cheng; HANXia-yun; YANGNing

    2004-01-01

    A new chromium-free conversion film was obtained on surface of a ZnA1 alloy by chemical conversion process. Influence of the additives in treating solution containing cerium salt on the corrosion protection of the conversion film formed on zinc alloy was investigated. Corrosion tests and electrochemical measurements in sodium chloride solution were performed. The microstructure and composition of the coatings were examined by means of SEM, EDS and XRD. It was found that the corrosion protection capabilities of the conversion film are markedly increased with the cerium nitride plus additives (hydrogen fluoride acid and an organic inhibitor) treating process. The modified conversion film is an organic/inorganic composite coating and is much more corrosion resistant than the conventional chromate conversion coating and the single cerium conversion coating.

  15. Newtonian Viscous Flow and Superplasticity in Fine Grained Metallic Alloys

    Science.gov (United States)

    1993-01-31

    Propriedas Mecanicas de Materiales Laminados Mg-9%Li de Pequeno Tamano de Grano", 7th National Conference on Metallurgical Science and Technology...34in Proceedings of Sampe Symposium, Reno, Nevada, (1984). 8 7. 0. A. Ruano and 0. D. Sherby, "Caracterizaci6n Y obtenci6n de materiales superpllsticos

  16. CROSS-ROLL FLOW FORMING OF ODS ALLOY HEAT EXCHANGER TUBES FOR HOOP CREEP ENHANCEMENT

    Energy Technology Data Exchange (ETDEWEB)

    Bimal K. Kad

    2005-06-27

    Mechanically alloyed oxide dispersion strengthened (ODS) Fe-Cr-Al alloy thin walled tubes and sheets, produced via powder processing and consolidation methodologies, are promising materials for eventual use at temperatures up to 1200 C in the power generation industry, far above the temperature capabilities of conventional alloys. Target end-uses range from gas turbine combustor liners to high aspect ratio (L/D) heat exchanger tubes. Grain boundary creep processes at service temperatures, particularly those acting in the hoop direction, are the dominant failure mechanisms for such components. The processed microstructure of ODS alloys consists of high aspect ratio grains aligned parallel to the tube axis, a result of dominant axial metal flow which aligns the dispersoid particles and other impurities in the longitudinal direction. The dispersion distribution is unaltered on a micro scale by recrystallization thermal treatments, but the high aspect ratio grain shape typically obtained limits transverse grain spacing and consequently the hoop creep response. Improving hoop creep in ODS-alloy components will require understanding and manipulating the factors that control the recrystallization behavior, and represents a critical materials design and development challenge that must be overcome in order to fully exploit the potential of ODS alloys. The objectives of this program are to (1) increase creep-strength at temperature in ODS-alloy tube and liner components by 100% via, (2) preferential cross-roll flow forming and grain/particle fibering in the critical hoop direction. Recent studies in cross-rolled ODS-alloy sheets (produced from flattened tubes) indicate that transverse creep is significantly enhanced via controlled transverse grain fibering, and similar improvements are expected for cross-rolled tubes. The research program outlined here is iterative in nature and is intended to systematically (i) prescribe extrusion consolidation methodologies via detailed

  17. Cross-Roll Flow Forming of ODS Alloy Heat Exchanger Tubes For Hoop Creep Enhancement

    Energy Technology Data Exchange (ETDEWEB)

    Bimal K. Kad

    2005-11-23

    Mechanically alloyed oxide dispersion strengthened (ODS) Fe-Cr-Al alloy thin walled tubes and sheets, produced via powder processing and consolidation methodologies, are promising materials for eventual use at temperatures up to 1200 C in the power generation industry, far above the temperature capabilities of conventional alloys. Target end-uses range from gas turbine combustor liners to high aspect ratio (L/D) heat exchanger tubes. Grain boundary creep processes at service temperatures, particularly those acting in the hoop direction, are the dominant failure mechanisms for such components. The processed microstructure of ODS alloys consists of high aspect ratio grains aligned parallel to the tube axis, a result of dominant axial metal flow which aligns the dispersoid particles and other impurities in the longitudinal direction. The dispersion distribution is unaltered on a micro scale by recrystallization thermal treatments, but the high aspect ratio grain shape typically obtained limits transverse grain spacing and consequently the hoop creep response. Improving hoop creep in ODS-alloy components will require understanding and manipulating the factors that control the recrystallization behavior, and represents a critical materials design and development challenge that must be overcome in order to fully exploit the potential of ODS alloys. The objectives of this program are to (1) increase creep-strength at temperature in ODS-alloy tube and liner components by 100% via, (2) preferential cross-roll flow forming and grain/particle fibering in the critical hoop direction. Recent studies in crossrolled ODS-alloy sheets (produced from flattened tubes) indicate that transverse creep is significantly enhanced via controlled transverse grain fibering, and similar improvements are expected for cross-rolled tubes. The research program outlined here is iterative in nature and is intended to systematically (1) examine and identify post-extrusion forming methodologies to

  18. Modeling microstructural evolution and the mechanical response of superplastic materials

    Energy Technology Data Exchange (ETDEWEB)

    Lesuer, D.R.; Syn, C.K.; Cadwell, K.L.; Preuss, C.S.

    1993-01-11

    A model has been developed that accounts for grain growth during, superplastic flow and its subsequent influence on stress-strain-strain rate behavior. These studies are experimentally based and have involved two different types of superplastic materials -- a quasi-single phase metal (Coronze 638) and a microduplex metal (ultrahigh-carbon steel - UHCS). In both materials the kinetics of strain-enhanced grain growth have been studied as a function of strain, strain rate and temperature. An equation for the rate of grain growth has been developed that incorporates the influence of temperature. The evolution of the grain size distribution during superplastic deformation has also been investigated. Our model integrates grain growth laws derived from these studies with two mechanism based, rate dependent constitutive laws to predict the stress-strainstrain rate behavior of materials during superplastic deformation. The influence of crain size distribution and its evolution with strain and strain rate on the stress-strain-strain rate behavior has been represented through the use of distributed parameters. The model can capture the stress-strain-strain rate behavior over a wide range of strains and strain rates with a single set of parameters. Many subtle features of the mechanical response of these materials can be adequately predicted.

  19. Effect of blank holder pressure on viscous pressure forming aluminum alloy ladder parts

    Institute of Scientific and Technical Information of China (English)

    王忠金; 王新云; 王仲仁

    2002-01-01

    Viscous pressure forming (VPF), is suitable for forming difficult-to-form sheet metal parts. An investigation in the effect of blank holder pressure (BHP) on VPF aluminum alloy ladder parts was conducted. Based on experimental and numerical simulation results of the effect of BHP on dimensional accuracy, wall-thickness reduction, forming pressure, material flow and defects (such as wrinkling and fracture) of specimens, the effect patterns of BHP load path on VPF ladder parts were explained. The limits of BHP corresponding to specimens with no defect and with wrinkling or fracture defect were determined. In the limits of formable BHP, the variable load path of BHP was beneficial to drawing blank into the die and decreasing wall-thickness reduction of specimens. The experimental results show that the ladder parts of good surface fineness and high dimensional accuracy can be obtained by variable load paths of BHP.

  20. Evaluation of Vitreous and Devitrifying Enamels as Hot Forming Lubricants for Aluminum AA5083 Alloy

    Science.gov (United States)

    Riahi, A. R.; Morales, A. T.; Alpas, A. T.

    2008-06-01

    The adhesion of aluminum to tool surfaces during the hot forming of sheet aluminum alloys presents challenging tribological problems. Graphite and boron nitride are commonly used as aluminum adhesion mitigating solid lubricants for hot forming processes, but lubricant breakdown in high-stress areas, such as corners and bends, remains an issue compromising the quality of the formed parts as well as the tool life. Low-melting temperature enamels may provide an affordable and easy to apply alternative. In this study, vitreous (amorphous glass) and devitrifying (two phase crystalline glass) layers were deposited on the surface of sheet aluminum samples with a sedimentation technique. Enamel lubrication was effective in preventing aluminum transfer to the steel counterface. Hence, the prospect exists for the use of these enamels as aluminum workpiece lubricants in hot forming operations.

  1. Equilibrium electrochemical synthesis diagrams of systems, forming homogeneous alloys and compounds

    Directory of Open Access Journals (Sweden)

    Kaptay G.

    2003-01-01

    Full Text Available In the present paper thermodynamic limitations will be derived and summarized in the form of Equilibrium Electrochemical Synthesis (EES diagrams, in order to predict the composition of the equilibrium phase, synthesized by galvanostatic co-deposition of components on inert electrodes. As a thermodynamic parameter, a difference of deposition potentials of pure components ( ∆E on inert cathodes is used (this parameter is a function of melt composition and temperature. Generally, the EES diagram predicts the equilibrium composition of the alloy as function temperature and ∆E. However, for systems with homogeneous alloy formation the composition- ∆E diagrams, drawn at a fixed temperature are more informative. As examples EES diagrams are constructed for the liquid Mg-Nd alloy, for some A(III-B(V (where A = Al, Ga, In and B = As, Sb, Si-C and for the Al-Ti system. For the Al-rich part of the Al-Ti system, also a semi-schematic non-equilibrium ES diagram is constructed. Based on these diagrams, the synthesis conditions of various phases has been discussed.

  2. The glass-forming ability of model metal-metalloid alloys

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Kai; Liu, Yanhui; Schroers, Jan [Department of Mechanical Engineering and Materials Science, Yale University, New Haven, Connecticut 06520 (United States); Center for Research on Interface Structures and Phenomena, Yale University, New Haven, Connecticut 06520 (United States); Shattuck, Mark D. [Department of Physics and Benjamin Levich Institute, The City College of the City University of New York, New York, New York 10031 (United States); Department of Mechanical Engineering and Materials Science, Yale University, New Haven, Connecticut 06520 (United States); O’Hern, Corey S. [Department of Mechanical Engineering and Materials Science, Yale University, New Haven, Connecticut 06520 (United States); Center for Research on Interface Structures and Phenomena, Yale University, New Haven, Connecticut 06520 (United States); Department of Physics, Yale University, New Haven, Connecticut 06520 (United States); Department of Applied Physics, Yale University, New Haven, Connecticut 06520 (United States)

    2015-03-14

    Bulk metallic glasses (BMGs) are amorphous alloys with desirable mechanical properties and processing capabilities. To date, the design of new BMGs has largely employed empirical rules and trial-and-error experimental approaches. Ab initio computational methods are currently prohibitively slow to be practically used in searching the vast space of possible atomic combinations for bulk glass formers. Here, we perform molecular dynamics simulations of a coarse-grained, anisotropic potential, which mimics interatomic covalent bonding, to measure the critical cooling rates for metal-metalloid alloys as a function of the atomic size ratio σ{sub S}/σ{sub L} and number fraction x{sub S} of the metalloid species. We show that the regime in the space of σ{sub S}/σ{sub L} and x{sub S} where well-mixed, optimal glass formers occur for patchy and LJ particle mixtures, coincides with that for experimentally observed metal-metalloid glass formers. Thus, our simple computational model provides the capability to perform combinatorial searches to identify novel glass-forming alloys.

  3. The glass-forming ability of model metal-metalloid alloys

    Science.gov (United States)

    Zhang, Kai; Liu, Yanhui; Schroers, Jan; Shattuck, Mark D.; O'Hern, Corey S.

    2015-03-01

    Bulk metallic glasses (BMGs) are amorphous alloys with desirable mechanical properties and processing capabilities. To date, the design of new BMGs has largely employed empirical rules and trial-and-error experimental approaches. Ab initio computational methods are currently prohibitively slow to be practically used in searching the vast space of possible atomic combinations for bulk glass formers. Here, we perform molecular dynamics simulations of a coarse-grained, anisotropic potential, which mimics interatomic covalent bonding, to measure the critical cooling rates for metal-metalloid alloys as a function of the atomic size ratio σS/σL and number fraction xS of the metalloid species. We show that the regime in the space of σS/σL and xS where well-mixed, optimal glass formers occur for patchy and LJ particle mixtures, coincides with that for experimentally observed metal-metalloid glass formers. Thus, our simple computational model provides the capability to perform combinatorial searches to identify novel glass-forming alloys.

  4. Ceramic coatings of LA141 alloy formed by plasma electrolytic oxidation for corrosion protection.

    Science.gov (United States)

    Li, Zhijun; Yuan, Yi; Sun, Pengpeng; Jing, Xiaoyan

    2011-09-01

    Superlight Mg-Li alloy is a promising structural materials in aerospace, automobile, and electronics because of its excellent properties such as low density, high ductility, superior strength-to-weight ratio, and good damping ability. The fabrication of compact plasma electrolytic oxidation coatings with excellent corrosion resistance is valuable for the widespread application of Mg-Li alloy. Here we present a ceramic coating on the surface of Mg-14Li-1Al (LA141) alloy for corrosion protection via plasma electrolytic oxidation (PEO) in an alkaline silicate electrolyte with tungstate as an additive. X-ray photoelectron spectroscopy and thin film-X-ray diffraction analysis of coatings show that the surface coating is mainly comprised of Mg(2)SiO(4), MgO and WO(3). Scanning electron microscopy observations have revealed that the dense and compact coating formed in the presence of tungstate has less structural imperfections in comparison to the control one fabricated without use of tungstate. The effect of oxidation time on the morphology and phase composition of coatings is also examined in detail.

  5. Some TEM observations of Al2O3 scales formed on NiCrAl alloys

    Science.gov (United States)

    Smialek, J.; Gibala, R.

    1979-01-01

    The microstructural development of Al2O3 scales on NiCrAl alloys has been examined by transmission electron microscopy. Voids have been observed within grains in scales formed on a pure NiCrAl alloy. Both voids and oxide grains grew measurably with oxidation time at 1100 C. The size and amount of porosity decreased towards the oxide-metal growth interface. It was postulated that the voids resulted from an excess number of oxygen vacancies near the oxide-metal interface. Short-circuit diffusion paths were discussed in reference to current growth stress models for oxide scales. Transient oxidations of pure, Y-doped, and Zr-doped NiCrAl was also examined. Oriented alpha-(Al,Cr)2O3 and Ni(Al,Cr)2O4 scales often coexisted in layered structures on all three alloys. Close-packed oxygen planes and directions in the corundum and spinel layers were parallel. The close relationships between oxide layers provided a gradual transition from initial transient scales to steady state Al2O3 growth.

  6. Atomic dynamics in Zr-based glass forming alloys near the liquidus temperature

    Science.gov (United States)

    Basuki, Sri Wahyuni; Yang, Fan; Gill, Elisabeth; Rätzke, Klaus; Meyer, Andreas; Faupel, Franz

    2017-01-01

    We report simultaneous radiotracer diffusion experiments of Co-57 and of Zr-95 in binary Z r64N i36 , Z r36N i64 , and ternary Z r60N i25A l15 alloys above but near the liquidus temperature (Tl). In contrast to the multicomponent Z r46.75T i8.25C u7.5N i10B e27.5 (Vit4), where a significant component decoupling at the Tl is observed, the ratio between Zr and Co self-diffusion coefficients is smaller than two in the alloys with fewer components. The difference in the degree of decoupling compared to Vit4 can be explained in terms of different Tl's. Moreover, owing to the high accuracy of the simultaneous tracer diffusion technique, we are able to resolve a small but notable composition dependence of the ratio DCo/DZr , which decreases with increasing Zr content for all glass forming alloys reported here. In contrast to a hard sphere (HS)-like mixture, where decoupling is controlled only by atomic sizes, this indicates a coupling of the Co/Ni and Zr diffusion, due to the strong chemical affinity between the diffusing components. Our results are in very good agreement with recent simulations in Z r64N i36 based on mode coupling theory (MCT).

  7. Correlation Between Superheated Liquid Fragility And Onset Temperature Of Crystallization For Al-Based Amorphous Alloys

    Directory of Open Access Journals (Sweden)

    Guo J.

    2015-06-01

    Full Text Available Amorphous alloys or metallic glasses have attracted significant interest in the materials science and engineering communities due to their unique physical, mechanical, and chemical properties. The viscous flow of amorphous alloys exhibiting high strain rate sensitivity and homogeneous deformation is considered to be an important characteristic in thermoplastic forming processes performed within the supercooled liquid region because it allows superplastic-like deformation behavior. Here, the correlation between the superheated liquid fragility, and the onset temperature of crystallization for Al-based alloys, is investigated. The activation energy for viscous flow of the liquid is also investigated. There is a negative correlation between the parameter of superheated liquid fragility and the onset temperature of crystallization in the same Al-based alloy system. The activation energy decreases as the onset temperature of crystallization increases. This indicates that the stability of a superheated liquid can affect the thermal stability of the amorphous alloy. It also means that a liquid with a large superheated liquid fragility, when rapidly solidified, forms an amorphous alloy with a low thermal stability.

  8. Microscopic insight into the origin of enhanced glass-forming ability of metallic melts on micro-alloying

    Energy Technology Data Exchange (ETDEWEB)

    Chen, C. J.; Chathoth, S. M., E-mail: smavilac@cityu.edu.hk [Department of Physics and Materials Science, City University of Hong Kong, Kowloon Tong, Hong Kong (China); Podlesnyak, A. [Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States); Mamontov, E. [Chemical and Engineering Materials Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States); Wang, W. H. [Institute of Physics, Chinese Academy of Science, Beijing 100190 (China)

    2015-09-28

    Extensive efforts have been made to develop metallic-glasses with large casting diameter. Such efforts were hindered by the poor understanding of glass formation mechanisms and the origin of the glass-forming ability (GFA) in metallic glass-forming systems. In this work, we have investigated relaxation dynamics of a model bulk glass-forming alloy system that shows the enhanced at first and then diminished GFA on increasing the percentage of micro-alloying. The micro-alloying did not have any significant impact on the thermodynamic properties. The GFA increasing on micro-alloying in this system cannot be explained by the present theoretical knowledge. Our results indicate that atomic caging is the primary factor that influences the GFA. The composition dependence of the atomic caging time or residence time is found to be well correlated with GFA of the system.

  9. Cross-Roll Flow Forming of ODS Alloy Heat Exchanger Tubes for Hoop Creep Enhancement

    Energy Technology Data Exchange (ETDEWEB)

    Bimal K. Kad

    2006-04-10

    Mechanically alloyed oxide dispersion strengthened (ODS) Fe-Cr-Al alloy thin walled tubes and sheets, produced via powder processing and consolidation methodologies, are promising materials for eventual use at temperatures up to 1200 C in the power generation industry, far above the temperature capabilities of conventional alloys. Target end-uses range from gas turbine combustor liners to high aspect ratio (L/D) heat exchanger tubes. Grain boundary creep processes at service temperatures, particularly those acting in the hoop direction, are the dominant failure mechanisms for such components. The processed microstructure of ODS alloys consists of high aspect ratio grains aligned parallel to the tube axis, a result of dominant axial metal flow which aligns the dispersoid particles and other impurities in the longitudinal direction. The dispersion distribution is unaltered on a micro scale by recrystallization thermal treatments, but the high aspect ratio grain shape typically obtained limits transverse grain spacing and consequently the hoop creep response. Improving hoop creep in ODS-alloy components will require understanding and manipulating the factors that control the recrystallization behavior, and represents a critical materials design and development challenge that must be overcome in order to fully exploit the potential of ODS alloys. The objectives of this program are to (1) increase creep-strength at temperature in ODS-alloy tube and liner components by 100% via, (2) preferential cross-roll flow forming and grain/particle fibering in the critical hoop direction. The research program outlined here is iterative in nature and is intended to systematically (1) examine and identify post-extrusion forming methodologies to create hoop strengthened tubes, which will be (2) evaluated at ''in-service'' loads at service temperatures and environments. This research program is being conducted in collaboration with the DOE's Oak Ridge National

  10. Semiconducting behavior of the anodically passive films formed on AZ31B alloy

    OpenAIRE

    A. Fattah-alhosseini; M. Sabaghi Joni

    2014-01-01

    This work includes determination of the semiconductor character and estimation of the dopant levels in the passive film formed on AZ31B alloy in 0.01 M NaOH, as well as the estimation of the passive film thickness as a function of the film formation potential. Mott–Schottky analysis revealed that the passive films displayed n-type semiconductive characteristics, where the oxygen vacancies and interstitials preponderated. Based on the Mott–Schottky analysis, it was shown that the calculated do...

  11. Novel Bioactive Titanate Layers Formed on Ti Metal and Its Alloys by Chemical Treatments

    Directory of Open Access Journals (Sweden)

    Tadashi Kokubo

    2009-12-01

    Full Text Available Sodium titanate formed on Ti metal by NaOH and heat treatments induces apatite formation on its surface in a body environment and bonds to living bone. These treatments have been applied to porous Ti metal in artificial hip joints, and have been used clinically in Japan since 2007. Calcium titanate formed on Ti-15Zr-4Nb-4Ta alloy by NaOH, CaCl2, heat, and water treatments induces apatite formation on its surface in a body environment. Titanium oxide formed on porous Ti metal by NaOH, HCl, and heat treatments exhibits osteoinductivity as well as osteoconductivity. This is now under clinical tests for application to a spinal fusion device.

  12. Benchmark 3 - Springback of an Al-Mg alloy in warm forming conditions

    Science.gov (United States)

    Manach, Pierre-Yves; Coër, Jérémy; Jégata Hervé Laurent, Anthony; Yoon, Jeong Whan

    2016-08-01

    Accurate prediction of springback is a long-standing challenge in the field of warm forming of aluminium sheets. The objective of this benchmark is to predict the effect of temperature on the springback process through the use of the split-ring test [1] with an Al-Mg alloy. This test consists in determining the residual stress state by measuring the opening of a ring cut from the sidewall of a formed cylindrical cup. Cylindrical cups are drawn with a heated die and blank-holder at temperatures of 20, 150 and 240°C. The force-displacement response during the forming process, the thickness and the earing profiles of the cup as well as the ring opening and the temperature of the blank are used to evaluate numerical predictions submitted by the benchmark participants. Problem description, material properties, and simulation reports with experimental data are summarized.

  13. Processing and Composition Effects on the Fracture Behavior of Spray-Formed 7XXX Series Al Alloys

    Science.gov (United States)

    Sharma, M. M.; Ziemian, C. W.; Eden, T. J.

    2010-12-01

    The fracture properties of high-strength spray-formed Al alloys were investigated, with consideration of the effects of elemental additions such as zinc, manganese, and chromium and the influence of the addition of SiC particulate. Fracture resistance values between 13.6 and 25.6 MPa (m)1/2 were obtained for the monolithic alloys in the T6 and T7 conditions, respectively. The alloys with SiC particulate compared well and achieved fracture resistance values between 18.7 and 25.6 MPa (m)1/2. The spray-formed materials exhibited a loss in fracture resistance ( K I) compared to ingot metallurgy 7075 alloys but had an improved performance compared to high-solute powder metallurgy alloys of similar composition. Characterization of the fracture surfaces indicated a predominantly intergranular decohesion, possibly facilitated by the presence of incoherent particles at the grain boundary regions and by the large strength differential between the matrix and precipitate zone. It is believed that at the slip band-grain boundary intersection, particularly in the presence of large dispersoids and/or inclusions, microvoid nucleation would be significantly enhanced. Differences in fracture surfaces between the alloys in the T6 and T7 condition were observed and are attributed to inhomogeneous slip distribution, which results in strain localization at grain boundaries. The best overall combination of fracture resistance properties were obtained for alloys with minimum amounts of chromium and manganese additions.

  14. Glass Forming Ability and Magnetic Property of Fe74Al4Sn2(PSiB)20 Amorphous Alloy

    Institute of Scientific and Technical Information of China (English)

    CHEN Fei-fei; ZHOU Shao-xiong

    2004-01-01

    Amorphous ribbons of Fe74Al4Sn2(PSiB)20 alloy have been synthesized by melt spinning and axial design method. The thermal properties of the amorphous ribbons have been measured by differential scanning calorimeter (DSC). The DSC results show that the Fe74Al4Sn2P12Si4B4 amorphous alloy has relatively wider supercooled liquid region with a temperature interval of 40.38 K (ΔTx=Tx-Tg). The alloys with a higher phosphorous content in the metalloid element composition triangle of Fe74Al4Sn2(PSiB)20 have high glass forming ability. The amorphous alloys also show good magnetic properties in which Fe74Al4Sn2P6.67Si6.67B6.67 alloy has a large maximum permeability (μm), Fe78Al4Sn2P3Si3B10 alloy exhibits a high square ratio (Br/B10) and Fe74Al4Sn2P4Si12B4 shows a low core loss (P0.5/1.3T). High glass forming ability and good magnetic properties make Fe74Al4Sn2(PSiB)20 amorphous alloys valuable in future research.

  15. Forming a perfect cubic texture in thin copper-yttrium alloy strips during cold rolling and annealing

    Science.gov (United States)

    Schastlivtsev, V. M.; Rodionov, D. P.; Khlebnikova, Yu. V.; Akshentsev, Yu. N.; Egorova, L. Yu.; Suaridze, T. R.

    2016-03-01

    The structure of strips produced from the Cu-1 wt % Y binary alloy using cold deformation by rolling to the degree of deformation of 99%, followed by recrystallization annealing, as well as the process of texture formation in these strips, is studied. The possibility of forming a perfect cubic texture in a thin strip made of a binary yttrium-modified copper-based alloy has been shown in principle, which opens the prospect of the use of this alloy to produce substrates for strip high-temperature superconductors of the second generation. The optimum conditions of annealing have been determined, which make it possible to form a perfect biaxial texture in the Cu-1 wt % Y alloy with a content of cubic grains {001} ± 10° on the surface of the textured strip of over 95%.

  16. Impedance and XPS study of benzotriazole films formed on copper, copper-zinc alloys and zinc in chloride solution

    Energy Technology Data Exchange (ETDEWEB)

    Kosec, Tadeja; Merl, Darja Kek [Jozef Stefan Institute, Department of Physical and Organic Chemistry, Jamova 39, 1000 Ljubljana (Slovenia); Milosev, Ingrid [Jozef Stefan Institute, Department of Physical and Organic Chemistry, Jamova 39, 1000 Ljubljana (Slovenia); Orthopaedic Hospital Valdoltra, Jadranska c. 31, 6280 Ankaran (Slovenia)], E-mail: ingrid.milosev@ijs.si

    2008-07-15

    The formation of protective layers on copper, zinc and copper-zinc (Cu-10Zn and Cu-40Zn) alloys at open circuit potential in aerated, near neutral 0.5 M NaCl solution containing benzotriazole was studied using electrochemical impedance spectroscopy (EIS) and X-ray photoelectron spectroscopy (XPS). Benzotriazole (BTAH), generally known as an inhibitor of copper corrosion, also proved to be an efficient inhibitor for copper-zinc alloys and zinc metal. The surface layers formed on alloys in BTAH-inhibited solution comprised both polymer and oxide components, namely Cu(I)BTA and Zn(II)BTA polymers and Cu{sub 2}O and ZnO oxides, as proved by the in-depth profiling of the layers formed. A tentative structural model describing the improved corrosion resistance of Cu, Cu-xZn alloys and Zn in BTAH containing chloride solution is proposed.

  17. Glass-forming ability analysis of selected Fe-based bulk amorphous alloys

    Directory of Open Access Journals (Sweden)

    R. Nowosielski

    2010-09-01

    Full Text Available Purpose: The paper mainly aims to present the structure and thermal stability of selected Fe-based bulk metallic glasses: Fe72B20Si4Nb4 and Fe43Co14Ni14B20Si5Nb4.Design/methodology/approach: The investigated samples were cast in form of the rods by the pressure die casting method. The structure analysis of the studied materials in as-cast state was carried out using XRD and TEM methods. The thermal stability associated with glass transition temperature (Tg, onset (Tx and peak (Tp crystallization temperature was examined by differential scanning calorimetry (DSC. Several parameters have been used to determine the glass-forming ability of studied alloys. The parameters of GFA included reduced glass transition temperature (Trg, supercooled liquid region (ΔTx, the stability (S and (Kgl parameter.Findings: The XRD and TEM investigations revealed that the studied as-cast metallic glasses were fully amorphous. Changes of the onset and peak crystallization temperature and the glass transition temperature as a function of glassy samples thickness were stated. The good glass-forming ability (GFA enabled casting of the Fe72B20Si4Nb4 and Fe43Co14Ni14B20Si5Nb4 glassy rods.Practical implications: The obtained examination results confirm the utility of applied investigation methods in the thermal stability analysis of examined bulk amorphous alloys. It is evident that parameters Trg, ΔTx, Kgl, S could be used to determine glass-forming ability of studied bulk metallic glasses.Originality/value: The success of fabrication of studied Fe-based bulk metallic glasses in form of rods with diameter up to 3 mm is important for the future progress in research of this group of materials.

  18. Selection of compositions with high glass forming ability in the Ni-Nb-B alloy system

    Directory of Open Access Journals (Sweden)

    Marcio Andreato Batista Mendes

    2012-10-01

    Full Text Available A combination of an extension of the topological instability "λ criterion" and the "average electronegativity" has been recently reported in the literature to predict compositions with high glass-forming ability (GFA. In the present work, both criteria have been applied to select the Ni61.0Nb36.0B3 alloy with a high glass-forming ability. Ingots were prepared by arc-melting and were used to produce ribbons processed by the melt-spinning technique further characterized by differential scanning calorimetry (DSC, X-ray diffraction (XRD and scanning electron microscopy (SEM. The Ni61.0Nb36.0B3 alloy revealed a complete amorphization and supercooled liquid region ΔTx = 68 K. In addition, wedge-shaped samples were prepared using copper mold casting in order to determine the critical thickness for amorphous formation. Scanning electron microscopy (SEM revealed that fully amorphous samples could be obtained, reaching up to ~800 µm in thickness.

  19. Material modelling and its application to creep-age forming of aluminium alloy 7B04

    Directory of Open Access Journals (Sweden)

    Lam Aaron C.L.

    2015-01-01

    Full Text Available Creep-ageing behaviour of aluminium alloy 7B04-T651 at 115 °C under a range of tensile stress levels has been experimentally investigated and numerically modelled for creep-age forming (CAF applications. Creep strain, yield strength evolution and precipitate growth of creep-aged specimens were investigated. The alloy was modelled using a set of unified constitutive equations, which captures its creep deformation and takes into account yield strength contributions from three creep-age hardening mechanisms. Applications of the present work are demonstrated by implementing the determined material model into a commercial finite element analysis solver to analyse CAF operations carried out in a novel flexible CAF tool. Stress relaxation, yield strength, precipitate size and springback were predicted for the creep-age formed plates. The predicted springback were further quantified and compared with experimental measurements and a good agreement of 2.5% deviation was achieved. This material model now enables further investigations of 7B04 under various CAF scenarios to be conducted inexpensively via computational modelling.

  20. Plasma Surface Cu Alloyed Layer as a Lubricant on Stainless Steel Sheet:Wear Characteristics and On-job Performance in Incremental Forming

    Institute of Scientific and Technical Information of China (English)

    WU Hongyan; WEI Hongyu; Ghulam Hussain; TAO Kemei; Asif Iqbal; RAO Weifeng

    2016-01-01

    To solve the problems of poor forming and easy adhesion of the stainless steel, Cu alloyed layer on the stainless steels was prepared by the double glow plasma surface alloying technique. The experimental results indicated that the supersaturated copper dispersedly precipitated in grain interior and crystal boundaries and formed the vermicular structure. The tribological tests indicated that the friction coefifcient of the Cu alloyed layer was lower than that of the stainless steels. The wear rate of stainless steel in the presence of Cu alloyed layer was approximately 2-fold lower than that in the absence of the alloyed layer. The results of the incremental forming indicated that the ploughing phenomenon was not observed on the stainless steel in the presence of Cu alloyed layer during the incremental forming, while the stainless steel presented the deep ploughing. Therefore, Cu alloyed layer on stainless steel exhibited excellent self-lubrication and forming properties.

  1. Semiconducting behavior of the anodically passive films formed on AZ31B alloy

    Directory of Open Access Journals (Sweden)

    A. Fattah-alhosseini

    2014-12-01

    Full Text Available This work includes determination of the semiconductor character and estimation of the dopant levels in the passive film formed on AZ31B alloy in 0.01 M NaOH, as well as the estimation of the passive film thickness as a function of the film formation potential. Mott–Schottky analysis revealed that the passive films displayed n-type semiconductive characteristics, where the oxygen vacancies and interstitials preponderated. Based on the Mott–Schottky analysis, it was shown that the calculated donor density increases linearly with increasing the formation potential. Also, the electrochemical impedance spectroscopy (EIS results indicated that the thickness of the passive film was decreased linearly with increasing the formation potential. The results showed that decreasing the formation potential offer better conditions for forming the passive films with higher protection behavior, due to the growth of a much thicker and less defective films.

  2. Molecular dynamics study of the ternary Cu50Ti25Zr25 bulk glass forming alloy

    Directory of Open Access Journals (Sweden)

    Celtek M.

    2011-05-01

    Full Text Available The structure and thermodynamic properties of a ternary Cu50Ti25Zr25 metallic glass forming alloy in solid-liquid to glass phases were studied using molecular dynamics (MD method based on tight-binding (TB potentials. An atomic description of the melting, glass formation and crystallization process has been analyzed using different heating and cooling rates. The computed Glass Forming Ability (GFA parameters are in good agreement with experimental data. The structure analysis of the Cu50Ti25Zr25 based on molecular dynamics simulation will be also presented and compared with available MD results. We have also discussed the crystallization transition with two different interatomic potentials used in this work

  3. Influence of carbon content on superplastic behavior in Ti- and B-added Cr-Mo steels

    Energy Technology Data Exchange (ETDEWEB)

    Aramaki, M.; Higashida, K.; Onodera, R. [Kyushu Univ., Fukuoka (Japan). Dept. of Materials Science and Engineering

    1999-05-01

    Superplasticity has been investigated in various ferrous alloys and steels. However, in these materials, especially in hypoeutectoid steels below the A{sub 1} temperature, the relationship between the content of carbon and elongation to failure is not obvious. In the present investigation, the influence of carbon content on superplastic behavior is studied using carbon steels based on Cr-Mo steel. In order to obtain the fine grain structure, a small amount of Ti and B were added and the content of carbon was controlled to be in the range from 0.24 to 0.83 pct. The largest value of elongation to failure was 644 pct, which was obtained for a specimen containing 0.58 pct carbon. The temperature and strain rate at which the maximum value was obtained were 710 C and 5 {times} 10{sup {minus}4} s{sup {minus}1}, respectively. Of all the specimens, this specimen had the minimum grain size. Moreover, the area fraction of carbide took the maximum value at the temperature where the largest elongation value was obtained. These results show that the addition of carbon has an effect on grain refinement by the formation of carbide, but excess amounts of carbon (>0.6 pct) bring about premature failure because of the resulting coarse microstructure and larger carbides.

  4. Superplastic Formed Aluminum Airframe Structures. Volume 1. Executive Summary

    Science.gov (United States)

    1987-07-01

    only ten pieces. All of the substructure was combined into one waffled pan (four formers and three intercostals . The final assembly was rivet bonded... articulated by an actua- tor attached to the left hand forward corner (Figure 2). The design is complicated by a cooling air outlet vent located in... intercost - als are of two-piece construction. This is to assure proper fit between the deck and skin. Shear clips are required at each frame and

  5. Fundamental alloy design of oxide ceramics and their composites

    Energy Technology Data Exchange (ETDEWEB)

    Chen, I.W.

    1992-01-01

    The main research was on microstructural development of oxide ceramics. Projects were completed and the publications given. Abstracts are given on: Reactive CeO[sub 2]powders by homogeneous precipitation, SiC whisker-reinforced lithium aluminosilicate composite, solute drag on grain boundary in ionic solids (space charge effect), in-situ alumina/aluminate platelet composites, exaggerated texture and grain growth of superplastic silicon nitride (SiAlON), hot extrusion of ceramics, control of grain boundary pinning in Al[sub 2]O[sub 3]/ZrO[sub 2] composites with Ce[sup 3+]/Ce[sup 4+] doping, superplastic forming of ceramic composites, computer simulation of final stage sintering (model, kinetics, microstructure, effect of initial pore size), development of superplastic structural ceramics, and superplastic flow of two-phase ceramics containing rigid inclusions (zirconia/mullite composites). A proposed research program is outlined: materials, solute drag, densification and coarsening, and grain boundary electrical behavior.

  6. Nanocrystallization kinetics and glass forming ability of the Fe65Nb10B25 metallic alloy

    Science.gov (United States)

    Torrens-Serra, J.; Rodríguez-Viejo, J.; Clavaguera-Mora, M. T.

    2007-12-01

    The crystallization kinetics of glassy Fe65Nb10B25 melt-spun ribbons is studied by differential scanning calorimetry in the mode of continuous heating and isothermal annealing and by x-ray diffraction and transmission electron microscopy. Continuous heat treatments of the ribbons show the presence of multiple exothermic peaks before melting. The low-temperature peak corresponds to the precipitation of nanoscale Fe23B6 -type crystalline metastable phase, and further annealing leads to its transformation into the metastable Fe3B phase and subsequent formation of bcc-Fe , Fe2B , and FeNbB stable crystalline phases. The nucleation frequency and the growth rate are determined at selected temperatures from the analysis of the microstructures that emerge during the Fe23B6 -type nanocrystallization. The master curve method is used to obtain the apparent activation energy and the Avrami exponent at the nanocrystallization onset. The nanocrystallization kinetics is explained in the framework of the Kolmogorov-Johnson-Mehl-Avrami theory. The rejection of insoluble alloy atoms during primary crystallization, the formation of diffusion layers around the crystals, and the decrease in the nucleation frequency caused by alloy enrichment of the residual disordered matrix is modeled through a soft impingement factor. Estimated values for the interfacial energy that provide a satisfactory agreement between experiments and modeling are derived considering that homogeneous nucleation frequency and interface-controlled grain growth are dominant at the onset of the nanocrystallization. Consequently, the time-temperature-transformation diagram is also drawn and the critical cooling rate estimated for this glass forming alloy.

  7. Characterisation of fresh surface films formed on molten Mg-Nd alloy protected by different atmospheres

    Science.gov (United States)

    Mirak, A. R.; Davidson, C. J.; Taylor, J. A.

    2014-05-01

    This study examines the early stages of surface oxidation of liquid Mg-3 wt%Nd under UPH argon, dry air, and air mixed with protective fluorine-bearing gases. Each of the gases were introduced as bubbles into solidifying castings. The chemistry and structure of the protective film inside the trapped bubbles were characterized by SEM and EDX analyses. Results show that due to Nd added to Mg alloy under dry air, a dense and wrinkled surface film that contains MgO and Nd2O3 are formed. Under fluorine-bearing gas mixtures, a dense and coherent surface film was found to be a mixed fluoride and oxide. For SF6, the film thickness was 50-100 nm thick while for HFC-R134a it was 35-45 nm. Needle shaped phases distributed in the Mg matrix and flake-like phases segregated on the inner bubble surface in proximity to the interdendritic regions of the alloy were both identified as Nd rich compounds. These were present under all gas conditions. The results obtained lead to a conclusion that HFC-R134a is capable of providing the most effective melt protection. The integrity and protective capability of the early surface film formation on the liquid Mg-Nd alloy was found to be significantly improved compared to pure Mg under identical gas conditions due to formation of a dense and compact MgO/Nd2O3 layer, regardless of whether fluorine species were also present.

  8. Preliminary Study on Some Properties of Co-Cr Dental Alloy Formed by Selective Laser Melting Technique

    Institute of Scientific and Technical Information of China (English)

    ZHANG Biao; HUANG Qirong; GAO Yang; LUO Peng; ZHAO Chuang

    2012-01-01

    The surface condition,some properties and ion releasing behavior of cobalt-chromium (Co-Cr)dental alloy formed by selective laser melting (SLM) technique were investigated.Before porcelain fused firing,the surface condition of the Co-Cr alloy was observed using a scanning electron microscope (SEM),and then the density and hardness were examined.After porcelain fused firing,the interface of porcelain and alloy was observed,and then the metal-ion release of the samples was tested.SLM technique provides Co-Cr alloy higher hardness than casting method.After degassing-oxidation procedure and porcelain fused firing,the interface of the alloy and porcelain showed excellent combination.Co ion was more than Cr ion released from SLM Co-Cr alloy,the amounts of Co and Cr ions were safe according to ISO security criterion.Considering the properties before and after porcelain fused sintering process,SLM technique is suitable for dental Co-Cr alloy restoration.

  9. Localization model description of diffusion and structural relaxation in glass-forming Cu-Zr alloys

    Science.gov (United States)

    Douglas, Jack F.; Pazmino Betancourt, Beatriz A.; Tong, Xuhang; Zhang, Hao

    2016-05-01

    We test the localization model (LM) prediction of a parameter-free relationship between the α-structural relaxation time τ α and the Debye-Waller factor    for a series of simulated glass-forming Cu-Zr metallic liquids having a range of alloy compositions. After validating this relationship between the picosecond (‘fast’) and long-time relaxation dynamics over the full range of temperatures and alloy compositions investigated in our simulations, we show that it is also possible to estimate the self-diffusion coefficients of the individual atomic species (D Cu, D Zr) and the average diffusion coefficient D using the LM, in conjunction with the empirical fractional Stokes-Einstein (FSE) relation linking these diffusion coefficients to τ α . We further observe that the fragility and extent of decoupling between D and τ α strongly correlate with    at the onset temperature of glass-formation T A where particle caging and the breakdown of Arrhenius relaxation first emerge.

  10. Study on the early surface films formed on Mg-Y molten alloy in different atmospheres

    Directory of Open Access Journals (Sweden)

    A.R. Mirak

    2015-09-01

    Full Text Available In the present study, the non-isothermal early stages of surface oxidation of liquid Mg-1%Y alloy during casting were studied under UPH argon, dry air, and air mixed with protective fluorine-bearing gases. The chemistry and morphology of the surface films were characterized by SEM and EDX analyses. The results indicate a layer of smooth and tightly coherent oxidation film composed of MgO and Y2O3 formed on the molten Mg-Y alloy surface with 40–60 nm thickness under dry air. A dendritic/cellular microstructure is clearly visible with Y-rich second phases gathered in surface of the melt and precipitated along the grain/cell boundaries under all gas conditions. Under fluorine-bearing gas mixtures, the surface film was a mixed oxide and fluoride and more even; a flat and folded morphology can be seen under SF6 with oxide as dominated phase and under 1, 1, 1, 2-tetra-fluoroethane, a smooth and compact surface film uniformly covering the inner surface of the bubble with equal oxide and fluoride thickness, which results in a film without any major defects. MgF2 phase appears to be the key characteristic of a good protective film.

  11. Characterization of oxide films formed on magnesium alloys using bipolar pulse microarc oxidation in phosphate solutions

    Institute of Scientific and Technical Information of China (English)

    WANG Li-shi; CAI Qi-zhou; WEI Bo-kang; LIU Quan-xin

    2005-01-01

    The surface morphology and chemical composition of the oxide films formed on pure magnesium and AZ91D alloy in aqueous electrolytes which contained sodium hexafluorinealuminate(Na3 AlF6), potassium hydroxide (KOH), sodium hexametahposphate ((NaPO3)6), and triethanolamine were investigated by X-ray diffraction (XRD), scanning electron microscope(SEM) and energy dispersive spectroscopy(EDX). The results show that the input of the negative pulse has great influences on the quantity and the appearance of the microdischarges. Three types of pores can be distinguished on the surface of the oxide film and their size ranges are 0.5 - 1 μm, 1 -2μm and 4- 7 μm, respectively. A few microcracks are seen around the large pores. There exists a remarkable fluorideenriched zone of about 4 -6 μm for pure magnesium and 3 -5 μm for AZ91D alloy at the coating/substrate interface.

  12. Development of Cast Alumina-forming Austenitic Stainless Steel Alloys for use in High Temperature Process Environments

    Energy Technology Data Exchange (ETDEWEB)

    Muralidharan, Govindarajan [ORNL; Yamamoto, Yukinori [ORNL; Brady, Michael P [ORNL; Pint, Bruce A [ORNL; Pankiw, Roman [Duraloy Technologies Inc; Voke, Don [Duraloy Technologies Inc

    2015-01-01

    There is significant interest in the development of alumina-forming, creep resistant alloys for use in various industrial process environments. It is expected that these alloys can be fabricated into components for use in these environments through centrifugal casting and welding. Based on the successful earlier studies on the development of wrought versions of Alumina-Forming Austenitic (AFA) alloys, new alloy compositions have been developed for cast products. These alloys achieve good high-temperature oxidation resistance due to the formation of protective Al2O3 scales while multiple second-phase precipitation strengthening contributes to excellent creep resistance. This work will summarize the results on the development and properties of a centrifugally cast AFA alloy. This paper highlights the strength, oxidation resistance in air and water vapor containing environments, and creep properties in the as-cast condition over the temperature range of 750°C to 900°C in a centrifugally cast heat. Preliminary results for a laboratory cast AFA composition with good oxidation resistance at 1100°C are also presented.

  13. Glass-Forming Ability of an Iron-Based Alloy Enhanced by Co Addition and Evaluated by a New Criterion

    Institute of Scientific and Technical Information of China (English)

    CHEN Qing-Jun; SHEN Jun; FAN Hong-Bo; SUN Jian-Fei; HUANG Yong-Jiang; MCCARTNEY D. G.

    2005-01-01

    @@ A new Fe-based alloy that can be cast into a fully amorphous rod with a diameter of at least 16mm by the conventional copper-mould casting technique is obtained by partially replacing Fe with Co in a previously reported Fe-based bulk metallic glass. The preliminary thermodynamic analysis indicates that the Co-containing alloy has a significantly lower Gibbs free energy difference between the undercooled melt and the corresponding crystalline solid, compared to the Co-free alloy, reflecting the dramatic role of the Co addition in stabilizing the supercooled melt and facilitating glass formation in iron-based alloys. Here, a new criterion, derived from the classical nucleation and growth theory, is introduced to evaluate the glass-forming ability of Fe-based bulk metallic glasses.

  14. Effect of Aluminium Addition on Glass Forming Ability of Nd55-xAl10+xFe15Co20 (x=0, 5, 10) Alloys

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Nd55-xAl10+xCo20Fe15 (x=0, 5, 10) bulk glass-forming alloys with distinct glass transition in differential scanning calorimetry (DSC) traces were obtained by suction casting. The glass forming ability (GFA) of the alloys was investigated. It was found that the reduced glass transition temperature (Trg) and the parameter γ of the alloys increased with the increasing concentration of Al. The glass formation enthalpy of the alloys was calculated based on Miedema′s model, and it was suggested that the GFA of the alloys could be enhanced by the decrease of the glass formation enthalpy with Al additions.

  15. Superplastically foaming method to make closed pores inclusive porous ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Kishimoto, Akira; Hayashi, Hidetaka, E-mail: kishim-a@cc.okayama-u.ac.jp [Division of Molecular and Material Science, Graduate School of Natural Science and Technology, Okayama University Okayama (Japan)

    2011-04-15

    Porous ceramics incorporates pores to improve several properties including thermal insulation maintaining inherenet ceramic properties such as corrosion resistance and large mechanical strength. Conventional porous ceramics is usually fabricated through an insufficient sintering. Since the sintering accompanies the exclusion of pores, it must be terminated at the early stage to maintain the high porosity, leading to degraded strength and durability. Contrary to this, we have innovated superplastically foaming method to make ceramic foams only in the solid state. In this method, the previously inserted foam agent evaporates after the full densification of matrix at around the sintering temperature. Closed pores expand utilizing the superplastic deformation driven by the evolved gas pressure. The typical features of this superplastically foaming method are listed as follows, 1. The pores are introduced after sintering the solid polycrystal. 2. Only closed pores are introduced, improving the insulation of gas and sound in addition to heat. 3. The pore walls are fully densified expecting a large mechanical strength. 4. Compared with the melt foaming method, this method is practical because the fabrication temperature is far below the melting point and it does not need molds. 5. The size and the location pores can be controlled by the amount and position of the foam agent.

  16. Influence of superplastic deformation on the anisotropy of 03Kh26N6T steel

    Science.gov (United States)

    Fuad, M. F. Akhmed; Tsepin, M. A.; Lobach, A. A.

    1991-10-01

    The maximum difference in relative elongation parallel and transverse to the rolling direction at the optimum temperature of superplastic deformation does not completely characterize the anisotropy since it is caused by the increased sensitivity of superplastic deformation to transverse grain dimensions in these directions.

  17. A thermodynamic approach towards glass-forming ability of amorphous metallic alloys

    Indian Academy of Sciences (India)

    Sonal R Prajapati; Supriya Kasyap; Arun Pratap

    2015-12-01

    A quantitative measure of the stability of a glass as compared to its corresponding crystalline state can be obtained by calculating the thermodynamic parameters, such as the Gibbs free energy difference (), entropy difference () and the enthalpy difference () between the super-cooled liquid and the corresponding crystalline phase. is known as the driving force of crystallization. The driving force of crystallization () provides very important information about the glass-forming ability (GFA) of metallic glasses (MGs). Lesser the driving force of crystallization more is the GFA. The varies linearly with the critical size (). According to Battezzati and Garonne the parameter ( = (1−(/))/(1−( / ))) in the expression for should be a constant (i.e., 0.8), but its uniqueness is not observed for all MGs. The thermal stability of various alloy compositions is studied by their undercooled liquid region ( = − ). Large implies greater stability against crystallization of the amorphous structure. Other GFA parameters are also calculated and correlated with critical size ().

  18. Microstructures variation of spray formed Si-30%Al alloy during densification process

    Institute of Scientific and Technical Information of China (English)

    WEI Yan-guang; XIONG Bai-qing; ZHANG Yong-an; LIU Hong-wei; WANG Feng; ZHU Bao-hong

    2006-01-01

    Microstructure variation of spray-formed Si-30%Al alloy during densification process by hot pressing was studied. The results indicate that the microstructure of as-deposited preforms is fine and homogenous. The primary silicon phases distributing in aluminium matrix evenly are fine and irregular. Aluminium matrix is divided into two groups: supersaturated α-Al phase or α-Al phase and Al-Si pseudo-eutectic phase or Al-Si eutectic phase. During hot pressing, the primary silicon and the aluminium matrix realign as follows: the primary silicon fractures at a given compressive stress, the particles congregates in microzone with increasing stress, and the aluminium matrix flows and connects in harness. Al-Si pseudo-eutectic phase turns into Al-Si eutectic phase due to the diffusion of atoms during densification process.

  19. Glass forming ability and thermodynamic properties of Ti(Zr,Hf)NiCu shape memory alloys

    Science.gov (United States)

    Pasko, A.; Kolomytsev, V.; Babanly, M.; Sezonenko, A.; Ochin, P.; Portier, R.; Vermaut, Ph.

    2003-10-01

    Rapidly solidified amorphous and crystalline-amorphous ribbons have been produced from a number of quatemary Ti{50+z-x}(Zr,Hf){ x}Ni{50- z-y}Cu{ y} alloys where z =(-5, 0, 5). Structural states were checked by XRD, crystallization behaviour of amorphous phase and martensitic transformations in crystalline material were studied by DSC. The glass transition and crystallization temperatures have been measured at different heating rates, and the crystallization activation energy for each composition and heat event bas been calculated. Isothermal crystallization gives an alternative method of determining the activation energy according to the Arrhenius equation. Contradictory requirements for the conditions of martensitic transformation and good glass forming ability is discussed.

  20. The influence of Mg content and impurities in AA5083 alloy on the properties of flow formed tubes

    Directory of Open Access Journals (Sweden)

    Milutin Nikačević

    2013-12-01

    Full Text Available Microstructure and mechanical properties of flow formed thin-walled tubes of AA5083 alloy from two metallurgical heats are presented. The influence of the chemical composition and applied reduction on the surface features and residual macro stresses were also studied. The residual macro stresses were estimated by ring method. The heat with higher content of alloying elements and impurities (Mg, Mn, Fe, Si had higher strength of preforms as well as flow formed tubes. These tubes exhibit three times higher residual stresses, lower spinnability, and the large amount of the surface defects (microcracks. This behaviour is attributed to the inhomogeneous material flow during deformation and presence of impurities.

  1. Innovative forming and fabrication technologies : new opportunities.

    Energy Technology Data Exchange (ETDEWEB)

    Davis, B.; Hryn, J.; Energy Systems; Kingston Process Metallurgy, Inc.

    2008-01-31

    The advent of light metal alloys and advanced materials (polymer, composites, etc.) have brought the possibility of achieving important energy reductions into the full life cycle of these materials, especially in transportation applications. 1 These materials have gained acceptance in the aerospace industry but use of light metal alloys needs to gain wider acceptance in other commercial transportation areas. Among the main reasons for the relatively low use of these materials are the lack of manufacturability, insufficient mechanical properties, and increased material costs due to processing inefficiencies. Considering the enormous potential energy savings associated with the use of light metal alloys and advanced materials in transportation, there is a need to identify R&D opportunities in the fields of materials fabrication and forming aimed at developing materials with high specific mechanical properties combined with energy efficient processes and good manufacturability. This report presents a literature review of the most recent developments in the areas of fabrication and metal forming focusing principally on aluminum alloys. In the first section of the document, the different sheet manufacturing technologies including direct chill (DC) casting and rolling, spray forming, spray rolling, thin slab, and strip casting are reviewed. The second section of the document presents recent research on advanced forming processes. The various forming processes reviewed are: superplastic forming, electromagnetic forming, age forming, warm forming, hydroforming, and incremental forming. Optimization of conventional forming processes is also discussed. Potentially interesting light metal alloys for high structural efficiency including aluminum-scandium, aluminum-lithium, magnesium, titanium, and amorphous metal alloys are also reviewed. This section concludes with a discussion on alloy development for manufacturability. The third section of the document reviews the latest

  2. Material characterization and finite element simulations of aluminum alloy sheets during non-isothermal forming process

    Science.gov (United States)

    Zhang, Nan

    The utilization of more non-ferrous materials is one of the key factors to succeed out of the constantly increasing demand for lightweight vehicles in automotive sector. Aluminum-magnesium alloys have been identified as the most promising substitutions to the conventional steel without significant compromise in structural stiffness and strength. However, the conventional forming methods to deform the aluminum alloy sheets are either costly or insufficient in formability which limit the wide applications of aluminum alloy sheets. A recently proposed non-isothermal hot stamping approach, which is also referred as Hot Blank - Cold Die (HB-CD) stamping, aims at fitting the commercial grade aluminum alloy sheets, such as AA5XXX and AA7XXX, into high-volume and cost-effective production for automotive sector. In essence, HB-CD is a mutation of the conventional hot stamping approach for boron steel (22MnB5) which deforms the hot blank within the cold tool set. By elevating the operation temperature, the formability of aluminum alloy sheets can be significantly improved. Meanwhile, heating the blank only and deforming within the cold tool sets allow to reduce the energy and time consumed. This research work aims at conducting a comprehensive investigation of HB-CD with particular focuses on material characterization, constitutive modeling and coupled thermo-mechanical finite element simulations with validation. The material properties of AA5182-O, a popular commercial grade of aluminum alloy sheet in automotive sector, are obtained through isothermal tensile testing at temperatures from 25° to 300°, covering a quasi-static strain-rate range (0.001--0.1s-1). As the state-of-the-art non-contact strain measurement technique, digital image correlation (DIC) system is utilized to evaluate the stress-strain curves as well as to reveal the details of material deformation with full-field and multi-axis strain measurement. Material anisotropy is characterized by extracting the

  3. Pack Aluminide Coatings Formed at 650 ℃ for Enhancing Oxidation Resistance of Low Alloy Steels

    Institute of Scientific and Technical Information of China (English)

    Z. D. Xiang; S. R. Rose; P. K. Datta

    2004-01-01

    This study aims to investigate the feasibility of forming iron aluminide coatings on a commercial 9Cr-lMo (wt.%)alloy steel by pack cementation at 650 ℃ in an attempt to improve its high temperature oxidation resistance. Pack powders containing Al, Al2O3 and a series of halide salts were used to carry out the coating deposition experiments, which enabled identification of the most suitable activator for the pack aluminising process at the intended temperature. The effect of pack aluminium content on the growth kinetics and microstructure of the coatings was then studied by keeping deposition conditions and pack activator content constant while increasing the pack aluminium content from 1.4 wt.% to 6 wt.%. X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) techniques were used to analyse the phases and microstructures of the coatings formed and to determine depth profiles of coating elements in the coating layer. Oxidation resistance of the coating was studied at 650 ℃ in air by intermittent weight measurement at room temperature. It was observed that the coating could substantially enhance the oxidation resistance of the steel under these testing conditions, which was attributed to the capability of the iron aluminide phases to form alumina scale on the coating surface through preferential Al oxidation.

  4. Pack Aluminide Coatings Formed at 650℃ for Enhancing Oxidation Resistance of Low Alloy Steels

    Institute of Scientific and Technical Information of China (English)

    Z.D.Xiang; S.R.Rose; P.K.Datta

    2004-01-01

    This study aims to investigate the feasibility of forming iron aluminide coatings on a commercial 9Cr-1Mo (wt.%) alloy steel by pack cementation at 650℃ in an attempt to improve its high temperature oxidation resistance. Pack powders containing Al, Al2O3 and a series of halide salts were used to carry out the coating deposition experiments, which enabled identification of the most suitable activator for the pack aluminising process at the intended temperature. The effect of pack aluminium content on the growth kinetics and microstructure of the coatings was then studied by keeping deposition conditions and pack activator content constant while increasing the pack aluminium content from 1.4 wt.% to 6 wt.%. X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) techniques were used to analyse the phases and microstructures of the coatings formed and to determine depth profiles of coating elements in the coating layer. Oxidation resistance of the coating was studied at 650 ~C in air by intermittent weight measurement at room temperature. It was observed that the coating could substantially enhance the oxidation resistance of the steel under these testing conditions, which was attributed to the capability of the iron aluminide phases to form alumina scale on the coating surface through preferential A1 oxidation.

  5. Existing form and effect of zirconium in pure Mg, Mg-Yb, and Mg-Zn-Yb alloys

    Institute of Scientific and Technical Information of China (English)

    YU Wenbin; HE Hong; LI Chunmei; LI Qing; LIU Zhiyi; QIN Bing

    2009-01-01

    The existing form and grain refining effects of small zirconium addition in pure Mg, Mg-Yb and Mg-Zn binary alloys, and Mg-Zn-Yb ternary alloy (ZK60-Yb) were investigated. The results show that Zr element exists mainly in single and cluster particles of pure α-Zr or Zn-Zr compounds inside grains and at grain boundaries. Only the particles located in the interior of grains can act as the nucleus for α-Mg growth and effectively promote the formation of Fine equiaxed grains. The broken and dispersed Zr-rich particles produced during the hot extrusion process can form nebulous banded structure in which these free particles may act as obstacles to dislocation motion in wrought magnesium alloys.

  6. Forming of Hollow Shaft Forging From Titanium Alloy Ti6Al4V by Means of Rotary Compression

    Directory of Open Access Journals (Sweden)

    Tomczak J.

    2015-04-01

    Full Text Available This paper presents chosen results of theoretical-experimental works concerning forming of hollow shafts forgings from titanium alloys, which are applied in aviation industry. At the first stage of conducted analysis, the forging forming process was modeled by means of finite element method. Calculations were made using software Simufact Forming. On the basis of performed simulations optimal parameters of rotary compression process were determined. Next, experimental tests of forging forming in laboratory conditions were made. For the research needs, a forging aggregate, designed by the Authors, was used. Conducted research works confirmed the possibility of metal forming (by means of rotary compression of hollow shafts from hard workable titanium alloys. Numerous advantages of rotary compression process, make it attractive both for low series production (aircraft industry and for mass production (automotive industry.

  7. Wetting of WC by a Zr-base metallic glass-forming alloy

    Energy Technology Data Exchange (ETDEWEB)

    Shen, Ping, E-mail: shenping@jlu.edu.cn [Key Laboratory of Automobile Materials (Ministry of Education), Department of Materials Science and Engineering, Jilin University, Changchun 130025 (China); Zheng, Xiao-Hong [Key Laboratory of Automobile Materials (Ministry of Education), Department of Materials Science and Engineering, Jilin University, Changchun 130025 (China); Liu, Hui-Jie [State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology, Harbin 150001 (China); Jiang, Qi-Chuan [Key Laboratory of Automobile Materials (Ministry of Education), Department of Materials Science and Engineering, Jilin University, Changchun 130025 (China)

    2013-05-15

    Wetting of hot-pressed polycrystalline WC substrates by a Zr{sub 55}Cu{sub 30}Al{sub 10}Ni{sub 5} bulk metallic glass (BMG)-forming alloy was investigated at 1133–1253 K in a high vacuum using a modified sessile drop method. The alloy melt spread rapidly on the WC surface, reaching no more than 30° within 3 s, and then slowly (at T < 1213 K) or even remained steady (at T ≥ 1213 K) in the subsequent isothermal dwelling stage. The final equilibrium contact angles were between 11° and 20°, slightly increasing with rising temperature and thus presenting an appreciably anomalous temperature-dependent behavior. The reaction between WC and the Zr-base melt was moderate, slightly enhancing with increasing temperature, and yielded W, ZrC and W{sub 5}Zr{sub 3} at the interface. The wetting, in principle, was driven by the formation of a precursor film in front of the triple line as a result of the adsorption of active atoms (primarily Zr) rather than by the interfacial reaction. From the viewpoint of the wettability and reactivity, WC is a good reinforcement for the preparation of the Zr-base BMG matrix composites. - Highlights: ► WC shows good wettability and moderate reactivity with the Zr{sub 55}Cu{sub 30}Al{sub 10}Ni{sub 5} melt. ► The final wettability exhibits slightly anomalous dependence on temperature. ► The interfacial reaction yields ZrC, W and W{sub 5}Zr{sub 3} phases. ► The primary driving force for the wetting is the formation of the precursor film in front of the triple line.

  8. Material modelling for creep-age forming of aluminium alloy 7B04

    Directory of Open Access Journals (Sweden)

    Lam Aaron C.L.

    2015-01-01

    Full Text Available This paper presents a study on the creep-ageing behaviour of a peak-aged aluminium alloy 7B04 under different tensile loads at 115oC and subsequently modelling it for creep-age forming (CAF applications. Mechanical properties and microstructural evolutions of creep-aged specimens were investigated. The material was modelled using a set of unified constitutive equations, which not only captures the material's creep deformation but also takes into account yield strength contributions from solid solution hardening, age hardening and dislocation hardening during creep-ageing. A possible application of the present work is demonstrated by implementing the determined material model into a commercial finite element analysis solver via a user-defined subroutine for springback prediction of creep-age formed plates. A good agreement is observed between the simulated springback values and experimental results. This material model now enables further investigations of 7B04 under various CAF scenarios to be conducted inexpensively via computational modelling.

  9. Growth and Corrosion Characteristics of Plasma Electrolytic Oxidation Ceramic Films Formed on AZ31 Magnesium Alloy

    Institute of Scientific and Technical Information of China (English)

    王丽; 陈砺; 严宗诚; 王红林; 彭家志

    2009-01-01

    The growth characteristics of oxide ceramic films formed on AZ31 magnesium alloy with plasma electrolytic oxidation(PEO)technique in alkaline silicate solution Were investigated.The composition,slructure and morphology of the coatings were detected by energy dispersive X-ray spectroscope and scanning electron microscope.The amount of dissolved magnesium in the electrolytes during PEO process was measured by atomic absorption spectrometry.The results indicated that the growth process of PEO films had three stages when applied with constant voltage mode.In the first stage,the growth rate of PEO films was low,and concentrations of elements O.Mg and Si varied slightly.Atter sparking occurred(the second stage).the PEO films showed higher growth rate due to the high transfer rate of ionS and electrons,and the existoncc of plasma reactions.When the growth rate tended to maintain stable with time,the third stage happened.PEO films exhibited different uniform and pitting.corrosion characteristiCS in difierent reaction stages.The films formed at 300 V for 30 min performed best corrosion resistance and the phase of ceramic films was mainly composed of MgSiO3 and forsterite Mg2SiO4.

  10. Electrochemical and biological characterization of coatings formed on Ti-15Mo alloy by plasma electrolytic oxidation.

    Science.gov (United States)

    Kazek-Kęsik, Alicja; Krok-Borkowicz, Małgorzata; Pamuła, Elżbieta; Simka, Wojciech

    2014-10-01

    β-Type titanium alloys are considered the future materials for bone implants. To improve the bioactivity of Ti-15Mo, the surface was modified using the plasma electrolytic oxidation (PEO) process. Tricalcium phosphate (TCP, Ca3PO4), wollastonite (CaSiO3) and silica (SiO2) were selected as additives in the anodizing bath to enhance the bioactivity of the coatings formed during the PEO process. Electrochemical analysis of the samples was performed in Ringer's solution at 37°C. The open-circuit potential (EOCP) as a function of time, corrosion potential (ECORR), corrosion current density (jCORR) and polarization resistance (Rp) of the samples were determined. Surface modification improved the corrosion resistance of Ti-15Mo in Ringer's solution. In vitro studies with MG-63 osteoblast-like cells were performed for 1, 3 and 7 days. After 24h, the cells were well adhered on the entire surfaces, and their number increased with increasing culture time. The coatings formed in basic solution with wollastonite exhibited better biological performance compared with the as-ground sample.

  11. Advances in the Development of Processing - Microstructure Relations for Titanium Alloys (Postprint)

    Science.gov (United States)

    2016-05-06

    microstructure and composition on the superplastic flow behavior of α/β titanium alloys. Particular attention is given to models describing the refinement...titanium alloys, challenges in the rolling of foil of and gamma-TiAl alloys, and the effect of microstructure and composition on the superlastic flow...materials to billets, slabs , sheet etc. via upsetting, drawing/cogging, and rolling to produce semi-finished products such as billets, plate, and

  12. Studies of Nucleation and Growth, Specific Heat and Viscosity of Undercooled Melts of Quasicrystals and Polytetrahedral-Phase-Forming Alloys

    Science.gov (United States)

    Kelton, K. F.; Gangopadhyay, A. K.; Lee, G. W.; Hyers, R. W.; Rogers, J. R.; Robinson, M. B.; Rathz, T. J.; Krishnan, S.; Curreri, Peter A. (Technical Monitor)

    2002-01-01

    The local atomic structures of undercooled liquid metals are presumed to be icosahedral; this order is incompatible with translational periodicity, constituting a barrier to the nucleation of the crystal phase. The extended atomic structure of the icosahedral quasicrystal (i-phase) is similar to that presumed in the undercooled liquid. Therefore, a comparison of the maximum undercooling in alloys that form the i-phase with those that form crystal phases provides a probe of the liquid structure.

  13. The behaviour of entrainment defects formed in commercial purity Mg alloy cast under a cover gas of SF6

    Science.gov (United States)

    Li, T.; Griffiths, W. D.

    2016-03-01

    In the casting of light alloys, the oxidised film on the melt surface can be folded due to surface turbulence, thus forming entrainment defects that have a significant negative effect on the mechanical properties of castings. Previous researchers reported that the surface film of Mg alloys formed in an atmosphere containing SF6 had a complicated structure composed of MgO and MgF2. The work reported here aims to investigate the behaviour of entrainment defects formed in magnesium alloys protected by SF6-containing atmospheres. Tensile test bars of commercial purity Mg were cast in an unsealed environment under a cover gas of pure SF6. 34Scanning electron microscopy (SEM) of the fracture surface of the test bars indicated entrainment defects that consisted of symmetrical films containing MgO, but also sulphur and fluorine. The results of these examinations of the symmetrical films were used to infer the potential formation and development of entrainment defects in commercial purity Mg alloy.

  14. Composition and hardness of mullite coatings formed with direct current power supply on LY12 aluminum alloy surface

    Institute of Scientific and Technical Information of China (English)

    XIN Shi-gang; JIANG Zhao-hua; LI Yan-ping; ZHANG Ji-lin

    2005-01-01

    The surface modification of aluminum and its alloys using plasma technology is increasingly being investigated. Thick ceramic coatings with high hardness on aluminum alloys can be prepared successfully using a micro-plasma oxidation (MPO) technique. In this work, the composition, microstructure and elemental distribution of ceramic coatings formed by MPO on LY 12 aluminum alloy and its hardness are investigated using XRD, EPMA and microhardness instruments. The results show that the ceramic coatings consist of mullite, γ -Al2 O3 and a lot of amorphous matter. The content of silicon in the coatings increases from interface to the coatings, however, the content of aluminum decreases along this direction. The maximum hardness of ceramic coatings is up to 9. 2 GPa.

  15. Characterization of plasma electrolytic oxide formed onAZ91 Mg alloy in KMnO4 electrolyte

    Institute of Scientific and Technical Information of China (English)

    Duck-Young HWANG; Ki-Ryong SHIN; Bongyoung YOO; Dong-Heon LEE; Deok-Yong PARK; Dong-Hyuk SHIN

    2009-01-01

    The aim of this work is to investigate microstructure, corrosion resistance characteristics and nanohardness of the oxide layer on AZ91 Mg alloy by applying different voltage with KMnO4 contained solution. There are lots of closed pores that are filled with another oxide compound compared with the typical surface morphology with pore coated until 350 V of coating voltage. The thickness of oxide layer increases with increasing coating voltage. The oxide layer formed on AZ91 Mg alloy in electrolyte with potassium permanganate consists of MgO and Mn2O3. Corrosion potential of the oxide layer on AZ91 Mg alloy obtained at different plasma electrolytic oxidation(PEO) reaction stages increases with increasing coating voltage. The corrosion resistance of AZ91 Mg alloy depends on the existence of the manganese oxide in the oxide layer. The inner barrier layer composed of the MgO and Mn2O3 may serve as diffusion barrier to enhance the corrosion resistance and may partially explain the excellent anti-corrosion performance in corrosion test. Nanohardness values increase with increasing coating voltage. The increase in the nanohardness may be due to the effect of manganese oxide in the oxide layer on AZ91 Mg alloy coated from electrolyte containing KMnO4.

  16. Size-dependent structure and magnetocaloric properties of Fe-based glass-forming alloy powders

    Directory of Open Access Journals (Sweden)

    Qiang Luo

    2016-04-01

    Full Text Available We investigated the influence of particle size on the microstructure and magnetocaloric effect of Fe-based alloy powders (11 μm to 100 μm in diameter. The degree of structure order varies with the powder size. The 11 μm to 18 μm powders show the largest peak magnetic entropy change (MEC. Increasing the degree of structure order tends to decrease the maximum MEC. Nevertheless, enhancement of refrigerant capacity and MEC (above 70 K is achieved when the crystalline phase content is ∼50% (above 75 μm in the 75 μm to 100 μm powders. Exponent n of the field dependence of MEC increases with the decrease in powder size above 22.5 K. The size dependence of the structure and properties is associated with the fact that a larger particle has a slower cooling rate and takes a longer time to form medium-to-long range ordered structures.

  17. Non-contact sheet forming using lasers applied to a high strength aluminum alloy

    Directory of Open Access Journals (Sweden)

    Rafael Humberto Mota Siqueira

    2016-07-01

    Full Text Available Laser beam forming (LBF is a contactless mechanical process accomplished by the introduction of thermal stresses on the surface of a material using a laser in order to induce plastic deformation. In this work, LBF was performed on 1.6 mm thick sheets of a high strength aluminum alloy, AA6013-T4 class by using a defocused continuous Yb-fiber laser beam of 0.6 mm in diameter on the sheet top surface. The laser power and process speed were varied from 200 W to 2000 W and from 3 to 30 mm/s, respectively. For these experimental conditions, the bending angle of the sheet ranged from 0.1° to 2.5° per run. In the highest bending angle condition, 1000 W and 30 mm/s, the depth of remelted pool was 0.6 mm and the microstructure near the plate bottom surface remained unaltered. For the whole set of experimental conditions, the hardness remained constant at approximately 100 HV, which is similar to the base material. In order to verify the applicability of the method, some previously T-welded sheets were straightened. The method was efficient in correcting the distortion of the sheets with a bending angle up to 5°.

  18. Activation Energy for Superplastic Flow Above Critical Temperature of Die Steels

    Institute of Scientific and Technical Information of China (English)

    WEN Jiu-ba; ZHANG Ke-ke; CHEN Fu-xiao; YANG Yong-shun

    2006-01-01

    Some commercial cold working die steels GCr15 and CrWMn with ultra-fine grain size were chosen as tested materials to research the activation energy for superplastic flow at different temperatures and strain rates above critical temperature. Based on the Arrhenius equation, the activation energy for superplastic flow is evaluated. The activation energy at constant strain rate is estimated by the logσt vs 1/T relationship. The results show that the activation energy is usually small under the conditions of optimal flow. The characteristics of superplastic deformation of steels above the critical temperature were also analyzed.

  19. Morphological and Chemical Relationships in Nanotubes Formed by Anodizing of Ti6al4v Alloy

    Directory of Open Access Journals (Sweden)

    Kaczmarek- Pawelska A.

    2014-12-01

    Full Text Available The electrochemical formation of oxide nanotubes on the Ti6Al4V alloy has been so far difficult due to easy dissolution of vanadium reach β-phase of the two phase material. Due to the topographical heterogeneity of the anodic layer in nano and microscale at anodizing of the Ti6Al4V alloy we focused to establish the relationships between nanotube diameters on both phases of the alloy and fluorides concentration in electrolyte. We studied the effect of fluoride concentration (0.5-0.7 wt.% in 99% ethylene glycol on morphological parameters of nanotube layer on the Ti6Al4V alloy anodized at 20V for 20 min. Nanotubes with diameter ~40-50 nm ±5nm on the entire Ti6Al4V alloy surface in electrolyte containing 0.6% wt. NH4F were obtained. Microscale roughness studies revealed that nanotubular layer on α-phase is thicker than on β-phase. The annealing of nanotube layers at 600°C for 2h in air, nitrogen and argon, typically performed to improve their electrical properties, influenced chemical composition and morphology of nanotubes on the Ti6Al4V alloy. The vanadium oxides (VO2, V2O3, V2O5 were present in surface nanotube layer covering both phases of the alloy and the shape of nanotubes was preserved after annealing in nitrogen.

  20. Studies of Nucleation and Growth, Specific Heat and Viscosity of Undercooled Melts of Quasicrystals and Polytetrehedral-Phase-Forming Alloys

    Science.gov (United States)

    2003-01-01

    By investigating the properties of quasicrystals and quasicrystal-forming liquid alloys, we may determine the role of ordering of the liquid phase in the formation of quasicrystals, leading to a better fundamental understanding of both the quasicrystal and the liquid. A quasicrystal is solid characterized by a symmetric but non-periodic arrangement of atoms, usually in the form of an icosahedron (12 atoms, 20 triangular faces). It is theorized that the short-range order in liquids takes this same form. The degree of ordering depends on the temperature of the liquid, and affects many of the liquid s properties, including specific heat, viscosity, and electrical resistivity. The MSFC role in this project includes solidification studies, phase diagram determination, and thermophysical property measurements on the liquid quasicrystal-forming alloys, all by electrostatic levitation (ESL). The viscosity of liquid quasicrystal-forming alloys is measured by the oscillating drop method, both in the stable and undercooled liquid state. The specific heat of solid, undercooled liquid, and stable liquid are measured by the radiative cooling rate of the droplets.

  1. Softening phenomenon during compression test in nanograined aluminum alloys

    Energy Technology Data Exchange (ETDEWEB)

    Ko, S.H.; Jang, J.M.; Lee, W. [Korea Inst. of Industrial Technology, ChonAn (Korea)

    2005-07-01

    Al-Mg and Al-Mg-Cu alloys are known well to reveal superplasticity in tension at high temperatures. In this study, deformation behaviors of those alloys nanograined were investigated under compression test at room temperature. During plastic deformation softening phenomena occurred obviously in nanograined Al-1.5wt%Mg and Al-0.7wt%Mg-1.0wt%Cu alloys while slight strain hardening appeared in nanograined pure Al. These results suggest that the softening strongly depends on composition of alloys. The softening takes place over strain rate range from 10{sup -4} up to 10{sup -1}. (orig.)

  2. Oxidation-induced phase transformations and lifetime limits of chromia-forming nickel-base alloy 625

    Energy Technology Data Exchange (ETDEWEB)

    Chyrkin, Anton

    2011-12-05

    For its high creep resistance the commercial nickel-base alloy 625 relies on solid solution strengthening in combination with precipitation hardening by formation of δ-Ni{sub 3}Nb and (Ni,Mo,Si){sub 6}C precipitates during high-temperature service. In oxidizing environments the alloy forms a slow growing, continuous chromia layer on the material surface which protects the alloy against rapid oxidation attack. The growth of the chromia base oxide scale results during exposure at 900-1000 C in oxidation-induced chromium depletion in the subsurface zone of the alloy. Microstructural analyses of the cross-sectioned specimens revealed that this process results in formation of a wide subsurface zone in which the mentioned strengthening phases are dissolved, in spite of the fact that both phases do not contain substantial amounts of the scale-forming element chromium. The cross-sectional analyses revealed that, in parallel to the formation of a precipitate depleted zone, a thin, continuous layer of niobium-rich intermetallic precipitates formed in the immediate vicinity of the scale/alloy interface. The Subsurface Phase Enrichment (abbreviated as SPE) was shown to be the result of an uphill-diffusion of niobium, i.e. the element stabilizing the strengthening precipitates δ-Ni{sub 3}Nb, in the chromium activity gradient and is thus a natural consequence of the oxidation-induced chromium depletion beneath the chromia scale. The thermodynamic calculations carried out using the Thermo-Calc/DICTRA software packages revealed that in alloy 625 the chemical activity of niobium decreases with decreasing chromium content. As chromium is being continuously removed from the alloy as the result of the chromia scale growth, the zone of lowest Nb-activity is formed in the location with the lowest chromium concentration, i.e. the scale/alloy interface. This creates a driving force for Nb to diffuse towards the scale/alloy interface against its own concentration gradient, which is known

  3. Vacuum Plasma Spray Formed High Transition Temperature Shape Memory Alloys Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Smart materials control of aero-surfaces based on shape memory alloys (SMA) is seeing increased use for improving of future subsonic fixed wing aircraft aero-surface...

  4. Electrochemical Deposition of Si-Ca/P on Nanotube Formed Beta Ti Alloy by Cyclic Voltammetry Method.

    Science.gov (United States)

    Jeong, Yong-Hoon; Choe, Han-Cheol

    2015-08-01

    The purpose of this study was to investigate electrochemical deposition of Si-Ca/P on nanotube formed Ti-35Nb-10Zr alloy by cyclic voltammetry method. Electrochemical deposition of Si substituted Ca/P was performed by pulsing the applied potential on nanotube formed surface. The surface characteristics were observed by field-emission scanning electron microscopy, X-ray diffractometer, and potentiodynamic polarization test. The phase structure and surface morphologies of Si-Ca/P deposition were affected by deposition cycles. From the anodic polarization test, nanotube formed surface at 20 V showed the high corrosion resistance with lower value of Icorr, I300, and Ipass.

  5. Oxidation-induced phase transformations and lifetime limits of chromia-forming nickel-base alloy 625

    Energy Technology Data Exchange (ETDEWEB)

    Chyrkin, Anton

    2011-12-05

    For its high creep resistance the commercial nickel-base alloy 625 relies on solid solution strengthening in combination with precipitation hardening by formation of δ-Ni{sub 3}Nb and (Ni,Mo,Si){sub 6}C precipitates during high-temperature service. In oxidizing environments the alloy forms a slow growing, continuous chromia layer on the material surface which protects the alloy against rapid oxidation attack. The growth of the chromia base oxide scale results during exposure at 900-1000 C in oxidation-induced chromium depletion in the subsurface zone of the alloy. Microstructural analyses of the cross-sectioned specimens revealed that this process results in formation of a wide subsurface zone in which the mentioned strengthening phases are dissolved, in spite of the fact that both phases do not contain substantial amounts of the scale-forming element chromium. The cross-sectional analyses revealed that, in parallel to the formation of a precipitate depleted zone, a thin, continuous layer of niobium-rich intermetallic precipitates formed in the immediate vicinity of the scale/alloy interface. The Subsurface Phase Enrichment (abbreviated as SPE) was shown to be the result of an uphill-diffusion of niobium, i.e. the element stabilizing the strengthening precipitates δ-Ni{sub 3}Nb, in the chromium activity gradient and is thus a natural consequence of the oxidation-induced chromium depletion beneath the chromia scale. The thermodynamic calculations carried out using the Thermo-Calc/DICTRA software packages revealed that in alloy 625 the chemical activity of niobium decreases with decreasing chromium content. As chromium is being continuously removed from the alloy as the result of the chromia scale growth, the zone of lowest Nb-activity is formed in the location with the lowest chromium concentration, i.e. the scale/alloy interface. This creates a driving force for Nb to diffuse towards the scale/alloy interface against its own concentration gradient, which is known

  6. The Effect of Variable Blank-Holder Forces on the Formability of Aluminum Alloy Sheets during Sheet Metal Forming

    Institute of Scientific and Technical Information of China (English)

    Sun Chengzhi; Chen Guanlong; Lin Zhongqin

    2004-01-01

    In this paper, the effect of variable Blank-holder forces (VBHF) on the strain path during sheet metal forming has been investigated by numerical simulation and experiments. The formability of select aluminum alloy sheet was evaluated by theory prediction of forming limit curve based on the M-K method. The effect of different VBHF on the formability was presented. In order to verify the predictions of strain path, experiments are being carried out using a recently-built multi-points variable blank-holder forces hydraulic press. The results show that large side BHF with small comer BHF during rectangular box deep drawing can improve the formability of the selected aluminum alloy sheet

  7. Interionic pair potentials and partial structure factors of compound-forming quaternary NaSn liquid alloy: First principle approach

    Indian Academy of Sciences (India)

    Anil Thakur; P K Ahluwalia

    2007-10-01

    In this paper formulae for partial structure factors have been used to study partial structure factors of compound-forming quaternary liquid alloys by considering Hoshino's m-component hard-sphere mixture, which is based on Percus-Yevic equation of Hiroike. Formulae are applied to NaSn (Na, Sn, NaSn, Na3Sn) which is considered as a quaternary liquid mixture with the formation of two compounds simultaneously. We have compared the total structure factors for ternary and quaternary alloys with experimental total structure factors which are found to be in good agreement. This suggests that, for suitable stoichiometric composition, two compounds are formed simultaneously. The hard-sphere diameters needed have been calculated using Troullier and Martins ab-initio pseudopotentials.

  8. Modeling and Simulation of the Microstructure Evolution of the Gas-atomized Alloy Droplets during Spray Forming

    Institute of Scientific and Technical Information of China (English)

    Jiuzhou ZHAO; Dongming LIU; Hengqiang YE

    2003-01-01

    In order to understand the solidification process of an atomized droplet and predict the fraction solidification ofdroplets with flight distance during spray forming, a numerical model based on the population dynamics approach isdeveloped to describe the microstructure evolution under the common action of the nucleation and growth of grains.The model is coupled with droplets heat transfer controlling equations and solved for Al-4.5 wt pct Cu alloy. It isdemonstrated that the numerical results describe the solidification process well.

  9. Chemical short-range order domain in bulk amorphous alloy and the prediction of glass forming ability

    Institute of Scientific and Technical Information of China (English)

    HUI; Xidong(惠希东); YAO; Kefu(姚可夫); KOU; Hongchao(寇宏超); CHEN; Guoliang(陈国良)

    2003-01-01

    Short-range order domains of face central cubic Zr2Ni (F-Zr2Ni) and tetragonal Zr2Ni (T-Zr2Ni) type structure with a size about 1-3 nanometers were observed in bulk amorphous Zr52.5Cu17.9Ni14.6Al10Ti5 alloy by using HREM and nano-beam electron diffraction technique. A new thermodynamic model was formulated based on the concept of chemical short-range order (SCRO). The molar fractions of CSRO and thermodynamic properties in Ni-Zr, Cu-Zr, Al-Zr, Al-Ni, Zr-Ni-Al and Zr-Ni-Cu were calculated. According to the principle of maximum the optimum glass forming ability (GFA) compositions were predicted in binary and ternary alloys. These results were proved to be valid by the experimental data of crystallizing activation energy, ΔTx and XRD patterns. The TTT curves of Zr-Ni-Cu alloys calculated based on CSRO model shows that the lowest critical cooling rate GFA is in the order of 100 K/s, which is close to the practical cooling rate for the preparation of Zr-based BMG alloys.

  10. Microstructure and Deformation Behavior of Ti-10V-2Fe-3Al Alloy during Hot Forming Process

    Institute of Scientific and Technical Information of China (English)

    GUAN Renguo; ZHAO Zhanyong; Choi KS; Lee CS

    2015-01-01

    The microstructure evolution and formability of Ti-10V-2Fe-3Al alloy related to the initial microstructures and processing variables were investigated during hot forming process. The experimental results show that theα-phase growth is controlled by solute diffusion during the heat treatment processes. Four different microstructures were established by combinations of several heat treatments, and Ti-10V-2Fe-3Al alloy shows excellent formability both above and below theβ transus temperature. The alloy possesses low deformation resistance and active restoration mechanism during the deformation. A constitutive equation describing the hot deformation behavior of Ti-10V-2Fe-3Al alloy was obtained. Higher lfow stress was observed for the acicular morphology ofαphase in microstructures with large aspect ratios as compared with that of small aspect ratios. Due to the dynamic recovery in softβphase, and the dynamic recrystallization and breakage of acicularα-phase, lfow softening occurred signiifcantly during deformation. Dynamic recrystallization also occurred especially in the severely deformed regions of forged parts.

  11. Complete Maps for the Internal Oxidation of Ideal Ternary Alloys Forming Insoluble Oxides under High Oxidant Pressures

    Institute of Scientific and Technical Information of China (English)

    F.GESMUNDO; S.WANG; Y.NIU

    2009-01-01

    This paper presents an analysis of the conditions of stability of the different forms of internal oxidation of ideal ternary A-B-C alloys, where A is the most noble and C the most reactive component, forming insoluble oxide and exposed to high pressures of a single oxidant. The treatment, based on an extension to ternary alloys of Wagner's criterion for the transition from internal to external oxidation in binary alloys, allows to predict the existence of three different forms of internal oxidation. In fact, in addition to the most common kinds of internal attack, involving the coupled internal oxidation of B+C beneath external AO scales and the internal oxidation of C beneath external BO scales, a third mode, involving the internal oxidation of C beneath external scales composed of mixtures of AO+BO, becomes also possible under special conditions. A combination of the boundary conditions for the existence of these different types of internal oxidation allows to predict three different kinds of complete maps for the internal oxidation in these systems, one of which involves only two modes, while the other two involve all the three possible modes of internal oxidation.

  12. Microstructural evolution of aluminium/Al–Ni–Sm glass forming alloy laminates obtained by Controlled Accumulative Roll Bonding

    Energy Technology Data Exchange (ETDEWEB)

    Anghelus, Adrian, E-mail: anghelus.adrian@yahoo.com; Avettand-Fènoël, Marie-Noëlle, E-mail: marie-noelle.avettand-fenoel@univ-lille1.fr; Cordier, Catherine, E-mail: catherine.cordier@univ-lille1.fr; Taillard, Roland, E-mail: roland.taillard@univ-lille1.fr

    2015-05-15

    Highlights: • Elaboration of a UFG material by controlled ARB of Al/glass forming alloy multilayers. • Effect of the crystalline or amorphous nature of the reinforcement on the formability. • Investigation of the thermo-mechanical stability of the metallic glass. - Abstract: The current work deals with the early steps of the unprecedented elaboration of aluminium/Al based glass forming alloy laminates by only accumulative rolling at room temperature. The Al{sub 1−(x+y)}Ni{sub x}Sm{sub y} metallic glass forming alloy was introduced either in its original amorphous state or after total crystallization. This change of atomic structure, and therefore of both thermal and thermo-mechanical stability and mechanical behaviour, is shown to govern at once the processing parameters, the uniformity of the laminates microstructure and the bond strength at the matrix-reinforcement interfaces. The potential of the process so as to synthesize composite materials with a stable ultrafine structure is finally outlined.

  13. Finite element analysis and experiment research on aluminum alloy ladder bowl with viscous pressure forming(VPF)

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The process parameters of aluminum alloy ladder bowl with viscous pressure forming and solid metal punch forming were numerically simulated by commercial finite element software DEFORM.The influence of blank holder pressure(BHP)on the formability of sheet metal was investigated.It was found that lower BHP does benefit to the distribution of thickness both with VPF and with solid punch forming.The forming force needed in VPF is bigger than that of with solid punch forming at the same stroke.The distribution of thickness with VPF is more uniform than that of with solid punch forming.Compared with solid punch forming,the damage values of workpiece at the top convex comer are lower by VPF.It was also shown that fracture tendency could be reduced with VPF,so that means the formability is improved.At the same time,aluminum alloy ladder bowl was manufactured with VPF.The results show that the simulation results are in agreement with the experimental data very well.

  14. Surface morphology of highly ordered nanotube formed and laser textured beta titanium alloys.

    Science.gov (United States)

    Kim, Jae-Un; Jeong, Yong-Hoon; Choe, Han-Cheol

    2013-03-01

    The aim of the present study is to produce and characterize a well-controlled surface texture on Ti-35Nb-xHf alloys to promote osseointegration. Ti-35Nb-xHf (x = 0, 3, 7 and 15 wt.%) alloys were prepared by arc melting and heat treated for 12 hr at 1000 degrees C in an argon atmosphere and then water quenching. For surface texturing, an amplified Ti: sapphire laser system was used for generating 184 femtosecond (FS, 10(-15) sec) laser pulses with the pulse energy over 30 mJ at a 1 kHz repetition rate with a central wavelength of 800 nm. The nanotube formation was achieved by anodizing a Ti-35Nb-xHf alloy in H3PO4 electrolytes containing 0.8 wt.% NaF at room temperature. The surface morphology of nano/micro structure will enhance osseointegration and cell adhesion.

  15. The Effect of Hydrogen Annealing on the Impurity Content of Alumina-Forming Alloys

    Science.gov (United States)

    Smialek, James L.

    2000-01-01

    Previously, the effect of hydrogen annealing on increasing the adhesion of Al2O3 scales had been related to the effective desulfurization that occurred during this process. The simultaneous reduction of other impurities has now been re-examined for up to 20 impurity elements in the case of five different alloys (NiCrAl, FeCrAl, PWA 1480, Rene'142, and Rene'N5). Hydrogen annealing produced measurable reductions in elemental concentration for B, C, Na, Mg, P, K, Sr, or Sn in varying degrees for at least one and up to three of these alloys. No single element was reduced by hydrogen annealing for all the alloys except sulfur. In many cases spalling occurred at low levels of these other impurities, while in other cases the scales were adherent at high levels of the impurities. No impurity besides sulfur was strongly correlated with adhesion.

  16. Microstructure evolution of laser solid forming of Ti-A1-V ternary system alloys from blended elemental powders

    Institute of Scientific and Technical Information of China (English)

    Hua Tan; Fengying Zhang; Jing Chen; Xin Lin; Weidong Huang

    2011-01-01

    @@ Morphology evolution of prior β grains of laser solid forming (LSF) Ti-xAl-yV (x ≤ 11,y ≤ 20) alloys from blended elemental powders is investigated.The formation mechanism of grain morphology is revealed by incorporating columnar to equiaxed transition (CET) mechanism during solidification.%Morphology evolution of prior β grains of laser solid forming (LSF) Ti-xAl-yV (x ≤ 11,y ≤ 20) alloys from blended elemental powders is investigated. The formation mechanism of grain morphology is revealed by incorporating columnar to equiaxed transition (CET) mechanism during solidification. The morphology of prior β grains of LSF Ti-6Al-yV changes from columnar to equiaxed grains with increasing element V content from 4 to 20 wt.-%. This agrees well with CET theoretical prediction. Likewise, the grain morphology of LSF Ti-xA1-2V from blended elemental powders changes from large columnar to small equiaxed with increasing A1 content from 2 to 11 wt.-%. The macro-morphologies of LSF Ti-8A1-2V and Ti-11A1-2V from blended elemental powders do not agree with CET predictions. This is caused by the increased disturbance effects of mixing enthalpy with increasing A1 content, generated in the alloying process of Ti, Al, and V in the molten pool.

  17. Effect of Melt Temperature on Surface Films Formed on Molten AZ91D Alloy Protected by Graphite Powder

    Science.gov (United States)

    Li, Weihong; Zhou, Jixue; Ma, Baichang; Wang, Jinwei; Wu, Jianhua; Yang, Yuansheng

    2017-08-01

    Graphite powder was adopted to prevent AZ91D alloy from oxidizing during melting and casting. The microstructure of the resultant surface films, formed at 933 K, 973 K, 1013 K, and 1053 K (660 °C, 700 °C, 740 °C, and 780 °C) for 30 minutes, was investigated by scanning electron microscopy, energy dispersive spectrometer, and X-ray diffraction, and the phase composition of the surface films was analyzed by the standard Gibbs free energy change of the reactions between the graphite powder, the alloy melt, and the ambient atmosphere. The effect and mechanism of melt temperature on the resultant surface films were also discussed. The results indicated that the surface films, of which the surface morphology comprised folds and wrinkles, were composed of a protective layer and MgF2 particles. The protective layer was contributive to the prevention of the molten alloy from oxidizing, and consisted of magnesium, oxygen, fluorine, carbon, and a small amount of aluminium existing in the form of MgO, MgF2, C, and MgAl2O4. The layer thickness was 200 to 900 nm. The melt temperature may affect the surface films through the increased interaction between the graphite powder, the melt, and the ambient atmosphere. The oxygen content and thickness of the protective layer decreased and then increased, while the height of the folds increased with melt temperature.

  18. Finite element analysis of stiffness and static dent resistance of aluminum alloy double-curved panel in viscous pressure forming

    Institute of Scientific and Technical Information of China (English)

    LI Yi; WANG Zhong-Jin

    2009-01-01

    The static dent resistance performance of the aluminum alloy double-curved panel formed using viscous pressure forming (VPF) was studied by finite element analysis, which mainly considers the forming process conditions. The whole simulation consisting of three stages, i.e., forming, spring-back and static dent resistance, was carried out continuously using the finite element code ANSYS. The influence of blank holder pressure (BHP) and the drawbead on the stiffness and the static dent resistance of the panels formed using VPF was analyzed. The results show that the adequate setting of the drawbead can increase the plastic deformation of the double-curved panel, which is beneficial to the initial stiffness and the static dent resistance. There is an optimum BHP range for the stiffness and the static dent resistance.

  19. Mechanical Characteristics of Welded Joints of Aluminum Alloy 6061 T6 Formed by Arc and Friction Stir Welding

    Science.gov (United States)

    Astarita, A.; Squillace, A.; Nele, L.

    2016-01-01

    Butt welds formed by arc welding in inert gas with nonconsumable electrode (tungsten inert gas (TIG) welding) and by friction stir welding (FSW) from aluminum alloy AA6061 T6 are studied. Comparative analysis of the structures and mechanical properties of the welded joints is performed using the results of optical and electron microscopy, tensile tests, tests for residual bending ductility, and measurements of microhardness. The changes in the microstructure in different zones and the degrees of degradation of the mechanical properties after the welding are determined. It is shown that the size of the tool for the friction stir welding affects the properties of the welds. Quantitative results showing the relation between the microscopic behavior of the alloy and the welding-induced changes in the microstructure are obtained. Friction stir welding is shown to provide higher properties of the welds.

  20. Is Cu60Ti10Zr30 a bulk glass-forming alloy?

    DEFF Research Database (Denmark)

    Jiang, Jianzhong; Saida, J.; Kato, H.

    2003-01-01

    . Nanocrystals with a significant volume fraction are randomly distributed in the amorphous matrix. The copper element is enriched in nanocrystals while a slightly high zirconium content is found in the matrix. We classify that the Cu60Ti10Zr30 alloy prepared by both of the aforementioned methods...

  1. Thermo-mechanical Forming of Al–Mg–Si Alloys: Modeling and Experiments

    NARCIS (Netherlands)

    Kurukuri, S.; Boogaard, van den A.H.; Ghosh, M.; Miroux, A.; Barlat, F.; Moon, Y.H.; Lee, M.G.

    2010-01-01

    In an ongoing quest to realize lighter vehicles with improved fuel efficiency, deformation characteristics of the material AA 6016 is investigated. In the first part of this study, material behavior of Al–Mg–Si sheet alloy is investigated under different process (temperature and strain rate) and loa

  2. Microstructural features induced by spray forming of a ternary Pb–Sn–Sb alloy

    Indian Academy of Sciences (India)

    V C Srivastava; Anish Upadhyaya; S N Ojha

    2000-04-01

    An alloy containing Pb–12% Sn–12% Sb with small addition of copper and arsenic was spray deposited employing two different atomization gas pressure and nozzle to substrate distances. The temperature of the spray-deposit was measured during deposition at a distance of 2 and 10 mm above the substrate-deposit interface. Thermal profile data indicated small variation in temperature with time during deposition stage whereas during post deposition stage an exponential decrease in temperature was recorded. Second phase particle size along the thickness of the deposit varied from 4 to 8 m compared to 70 to 80 m size of these particles in the as cast alloy. Maximum porosity occurred in the section of the deposit near the contact surface of the substrate and also in its peripheral regions. X-ray diffraction analysis exhibited the formation of additional Cu2Sb phase in the spray-deposit and CuSn and Cu3.3Sb phases in atomized powders compared to that of the as cast alloy. The microstructural evolution during spray deposition of this alloy is discussed.

  3. Simultaneous dehydrogenation of organic compounds and hydrogen removal by hydride forming alloys

    NARCIS (Netherlands)

    Appelman, W.J.T.M.; Kuczynski, M.; Versteeg, G.F.

    1992-01-01

    The applicability of hydrogen-absorbing metals in dehydrogenation reactions was investigated. Based on thermodynamic considerations, operating ranges were defined within which an increase of the reactant conversion can he achieved owing to an in situ hydrogen removal by the alloy. Low plateau pressu

  4. Effect of microstructure refinement on low cycle fatigue behavior of Alloy 718

    Directory of Open Access Journals (Sweden)

    Mukhtarov Shamil

    2014-01-01

    Full Text Available Microstructure refinement down to d ∼ 0.1–1 μm is known to enhance processing properties of hard-to-deform materials and particularly can be used for facilitating superplastic forming or roll-forming. However refined microstructure can compromise service properties, particularly fatigue properties. In the present work, the fatigue behavior of the fine-grained Alloy 718 has been investigated. A number of fine-grained conditions with a grain size ∼0.1–1 μm were produced using multiple forging with a graduate decrease of the forging temperature. Part of the forged fine-grained conditions was also subjected to conventional solution annealing and ageing. In this case a small grain size was controlled by precipitates of the δ phase located on grain boundaries. Low cycle fatigue tests of the fine-grained conditions were carried out at room and elevated temperatures. The obtained properties are compared with those of the Alloy 718 in the coarse-grained conditions. The effect of the grain size on the fatigue strength of the fine-grained Alloy 718 is discussed in terms of the microstructure evolution and fracture mode.

  5. Preparation and corrosion resistance of a nanocomposite plasma electrolytic oxidation coating on Mg-1%Ca alloy formed in aluminate electrolyte containing titania nano-additives

    DEFF Research Database (Denmark)

    Daroonparvar, Mohammadreza; Yajid, M. A. M.; Yusof, N. M.

    2016-01-01

    Titania nanoparticles were utilized as suspension in alkaline aluminate electrolyte to form nanocomposite coatings on magnesium alloy containing 1 wt% calcium by plasma electrolytic oxidation process. Microhardness, wettability, potentiodynamic polarization, wettability, electrochemical impedance...

  6. Creep age forming of Al-Cu-Li alloy: Application to thick sheet forming of double curvature aircraft panel

    Directory of Open Access Journals (Sweden)

    Younes Wael

    2016-01-01

    Full Text Available Creep-age-forming of a thick Al-Cu-Li sheet is studied. An industrial stamping press is used to form a double curvature panel at a reduced scale. This forming, which includes several relaxation steps, is modelled using ABAQUS. A material model describing an elasto-viscoplastic behaviour with anisotropy effect has been identified and implemented in ABAQUS using Fortran subroutine. The numerical model is validated by comparing experiments and numerical results in terms of deformed shapes and an improved forming cycle is suggested.

  7. SUPERPLASTICITY AND DIFFUSION BONDING OF IN718 SUPERALLOY

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The superplasticity and diffusion bonding of IN718 superalloy were studied in this article. The strain rate sensitivity index m was obtained at different temperatures and various initial strain rates using the tensile speed mutation method; m reached its maximum value 0.53 at an initial strain rate of 1 ×10-4s-1 at 1253K. The diffusion bonding parameters, including the bonding temperature T,pressure p, and time t, affected the mechanism of joints. When the bonded specimen with 25μm thick nickel foil interlayer was tensile at room temperature, the shear fracture of the joints with nickel foil interlayer took place at the IN718 part. Microstructure study was carried out with the bonded samples. The microstructure shows an excellent bonding at the interfaces. The optimum parameters for the diffusion bonding are: T= 1273-1323K, p = 20-30MPa, t = 45-60min.

  8. Hot Superplastic Powder Forging for Transparent nanocrystalline Ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Cannon, W. Roger

    2006-05-22

    The program explored a completely new, economical method of manufacturing nanocrystalline ceramics, Hot Superplastic Powder Forging (HSPF). The goal of the work was the development of nanocrystalline/low porosity optically transparent zirconia/alumina. The high optical transparency should result from lack of grain boundary scattering since grains will be smaller than one tenth the wavelength of light and from elimination of porosity. An important technological potential for this process is manufacturing of envelopes for high-pressure sodium vapor lamps. The technique for fabricating monolithic nanocrystalline material does not begin with powder whose particle diameter is <100 nm as is commonly done. Instead it begins with powder whose particle diameter is on the order of 10-100 microns but contains nanocrystalline crystallites <<100 nm. Spherical particles are quenched from a melt and heat treated to achieve the desired microstructure. Under a moderate pressure within a die or a mold at temperatures of 1100C to 1300C densification is by plastic flow of superplastic particles. A nanocrystalline microstructure results, though some features are greater than 100nm. It was found, for instance, that in the fully dense Al2O3-ZrO2 eutectic specimens that a bicontinuous microstructure exists containing <100 nm ZrO2 particles in a matrix of Al2O3 grains extending over 1-2 microns. Crystallization, growth, phase development and creep during hot pressing and forging were studied for several compositions and so provided some details on development of polycrystalline microstructure from heating quenched ceramics.

  9. Preparation technology and anti-corrosion performances of black ceramic coatings formed by micro-arc oxidation on aluminum alloys

    Institute of Scientific and Technical Information of China (English)

    CHEN Ling; HAN Jing; YU Shengxue

    2006-01-01

    In order to prepare ornamental and anti-corrosive coating on aluminum alloys, preparation technology of black micro-arc ceramic coatings on Al alloys in silicate based electrolyte was studied.The influence of content of Na2WO4 and combination additive in solution on the performance of black ceramic coatings was studied; the anticorrosion performances of black ceramic coatings were evaluated through whole-immersion test and electrochemical method in 3.5% NaCl solution at different pH value; SEM and XRD were used to analyze the surface morphology and phase constitutes of the black ceramic coatings.Experimental results indicated that, without combination additives, with the increasing of Na2WO4 content in the electrolyte, ceramic coating became darker and thicker, but the color was not black; after adding combination additive, the coating turned to be black; the black ceramic coating was multi-hole form in surface.There was a small quantity of tungsten existing in the black ceramic coating beside α-Al2O3 phase and β-Al2O3 phase.And aluminum alloy with black ceramic coating exhibited excellent anti-corrosion property in acid, basic and neutral 3.5% NaCl solution.

  10. Heat-treated microstructure and mechanical properties of laser solid forming Ti-6Al-4V alloy

    Institute of Scientific and Technical Information of China (English)

    ZHANG Shuangyin; LIN Xin; CHEN Jing; HUANG Weidong

    2009-01-01

    The effects of heat treatment on the microstmcture and mechanical properties of laser solid forming (LSF) Ti-6Al-4V alloy were investigated. The influences of the temperature and time of solution treatment and aging treatment were analyzed. The results show that the microstructure of LSFed samples consists of Widmanstatten α laths and a little acicular in columnar prior β grains with an average grain width of 300 which grow epitaxially from the substmte along the deposition direction (Z). Solution treatment had an important effect on the width, aspect ratio, and volume fraction of primary and secondary α laths, and aging treatment mainly affects the aspect ratio and volume fraction of pri-mary α laths and the width and volume fraction of secondary α laths. Globular α phase was first observed in LSFed samples when the sam-ples were heat treated with solution treatment (950℃, 8 h/air cooling (AC)) or with solution treatment (950℃, 1 h/AC) and aging treatment (550℃, above 8 h/AC), respectively. The coarsening and globularization mechanisms of α phase in LSFed Ti-6Al-4V alloy during heat treatment were presented. To obtain good integrated mechanical properties for LSFed Ti-6Al-4V alloys, an optimized heat treatment regimen was suggested.

  11. Hydrogen diffusivity in oxide layers formed in Zr alloy in air or steam

    Science.gov (United States)

    Kato, Taro; Takagi, Ikuji; Sakamoto, Kan; Aomi, Masaki

    2017-10-01

    The effect of the oxidation conditions on hydrogen diffusion in oxide layers in Zr alloy was experimentally studied. Samples of GNF-Ziron (high-iron Zircaloy-2-type alloy) sheets were oxidized in air or steam and then exposed to deuterium plasma to charge them with deuterium. Deuterium depth profiles in each sample were observed by nuclear reaction analysis during plasma exposure, and the deuterium diffusion coefficient D was estimated. The results showed that the D values of the steam-oxidized samples were high, whereas that of a steam-oxidized sample that was subsequently heated in vacuum was as low as those of air-oxidized samples. The difference in D was not attributed to the structure but is probably due to the presence of OH groups absorbed during steam oxidation.

  12. Structure and properties of ceramic coatings formed on aluminum alloys by microarc oxidation

    Institute of Scientific and Technical Information of China (English)

    LIU Wan-hui; BAO Ai-lian; LIU Rong-xiang; WU Wan-liang

    2006-01-01

    The thick and hard ceramic coatings were deposited on 2024 Al alloy by microarc oxidation in the electrolytic solution.Microstructure, phase composition and wear resistance of the oxide coatings were investigated by SEM, XRD and friction and wear tester. The microhardness and thickness of the oxide coatings were measured. The results show that the ceramic coating is mainly composed of α-Al2O3 and γ-Al2O3. During oxidation, the temperature in the microarc discharge channel is very high to make the local coating molten. From the surface to interior of the coating, microhardness increases gradually. The microhardness of the ceramic coating is HV1 800, and the microarc oxidation coatings greatly improve the antiwear properties of aluminum alloys.

  13. Molecular dynamics study of structure and glass forming ability of Zr70Pd30 alloy

    Science.gov (United States)

    Celtek, Murat; Sengul, Sedat; Domekeli, Unal; Canan, Cem

    2016-03-01

    In this study, the temperature effects on the structural evolution of the Zr70Pd30 binary alloy in the glassy and liquid states were studied using the molecular dynamics simulations based on the many-body type tight-binding potential. We considered the following properties in detail: the temperature dependence of the volume, the partial and total pair distribution functions and the simulated glass transition temperature. The effects of the cooling rates on the glass transition temperature were examined. The Wendt-Abraham parameter was calculated to determine the glass transition temperature of Zr70Pd30 glassy alloy. The pair analysis technique of Honeycutt-Andersen was applied to define local atomic arrangements produced from molecular dynamics simulations. The results show that the icosahedral ordering in glassy state has been composed during quenching period, and the simulated glass transition temperature and the total pair distribution functions are in good agreement with the experimental data.

  14. The relationship between viscosity and glass forming ability of Al-(Ni)-Yb alloy systems

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The dynamic viscosity of Al-Yb and Al-Ni-Yb superheated melts was measured using a torsional oscillation viscometer. The results show that the temperature dependence of viscosity fits the Arrhenius law well and the fitting factors are calculated. The amorphous ribbons of these alloys were produced by the melt spinning technique and the thermal properties were characterized by using a differential scanning calorimetry (DSC). E (the activation energy for viscous flow), which reflects the change rate of viscosity, has a good negative relation with the GFA in both Al-Yb and Al-Ni-Yb systems. However, there is no direct relation between liquidus viscosity (ηL) and GFA. The superheated fragility M can predict GFA in Al-Yb or Al-Ni-Yb alloy system.

  15. Fundamental alloy design of oxide ceramics and their composites. [Annual] report, May 1, 1990--August 31, 1992

    Energy Technology Data Exchange (ETDEWEB)

    Chen, I.W.

    1992-12-31

    The main research was on microstructural development of oxide ceramics. Projects were completed and the publications given. Abstracts are given on: Reactive CeO{sub 2}powders by homogeneous precipitation, SiC whisker-reinforced lithium aluminosilicate composite, solute drag on grain boundary in ionic solids (space charge effect), in-situ alumina/aluminate platelet composites, exaggerated texture and grain growth of superplastic silicon nitride (SiAlON), hot extrusion of ceramics, control of grain boundary pinning in Al{sub 2}O{sub 3}/ZrO{sub 2} composites with Ce{sup 3+}/Ce{sup 4+} doping, superplastic forming of ceramic composites, computer simulation of final stage sintering (model, kinetics, microstructure, effect of initial pore size), development of superplastic structural ceramics, and superplastic flow of two-phase ceramics containing rigid inclusions (zirconia/mullite composites). A proposed research program is outlined: materials, solute drag, densification and coarsening, and grain boundary electrical behavior.

  16. Oxide Scales Formed on NiTi and NiPtTi Shape Memory Alloys

    Science.gov (United States)

    Smialek, James L.; Garg, Anita; Rogers, Richard B.; Noebe, Ronald D.

    2011-01-01

    Ni-49Ti and Ni-30Pt-50Ti (at.%) shape memory alloys were oxidized isothermally in air over the temperature range of 500 to 900 C. The microstructure, composition, and phase content of the scales were studied by SEM, EDS, XRD, and metallography. Extensive plan view SEM/EDS identified various features of intact or spalled scale surfaces. The outer surface of the scale was a relatively pure TiO2 rutile structure, typified by a distinct highly striated and faceted crystal morphology. Crystal size increased significantly with temperature. Spalled regions exhibited some porosity and less distinct features. More detailed information was obtained by correlation of SEM/EDS studies of 700 C/100 hr cross-sections with XRD analyses of serial or taper-polishing of plan surfaces. Overall, multiple layers exhibited graded mixtures of NiO, TiO2, NiTiO3, Ni(Ti) or Pt(Ni,Ti) metal dispersoids, Ni3Ti or Pt3Ti depletion zones, and substrate, in that order. The NiTi alloy contained a 3 at.% Fe impurity that appeared in embedded localized Fe-Ti-rich oxides, while the NiPtTi alloy contained a 2 v/o dispersion of TiC that appeared in lower layers. The oxidation kinetics of both alloys (in a previous report) indicated parabolic growth and an activation energy (250 kJ/mole) near those reported in other Ti and NiTi studies. This is generally consistent with TiO2 existing as the primary scale constituent, as described here.

  17. Co-based soft magnetic bulk glassy alloys optimized for glass-forming ability and plasticity

    Indian Academy of Sciences (India)

    LI LI; HUAIJUN SUN; YUNZHANG FANG; JIANLONG ZHENG

    2016-06-01

    Co-based bulk glassy alloys (BGAs) have become more and more important because of their nearly zero magnetostriction and high giant magneto-impedance effect. Here, we report the improvement of glass-formingability (GFA), soft-magnetic properties and plasticity by a small addition of Mo atoms in CoFeBSiNbMo BGAs.(Co$_{0.6}$Fe$_{0.4}$)$_{69}$B$_{20.8}$Si$_{5.2}$Nb$_{5−x}$Mo$_{x}$ ferromagnetic BGA cylindrical glassy rods were fabricated successfully with adiameter of 5 mm by conventional copper mould casting method. It reveals that the substitution of a small amount of Mo for Nb makes the composition to approach a eutectic point and effectively enhances the GFA of alloy. Inaddition to high GFA and superhigh strength, the compressive test shows that the Mo addition can improve the plasticity for the obtained BGAs. The combination of high GFA, excellent soft-magnetic properties and good plasticitydemonstrated in our alloys is promising for the future applications as functional materials.

  18. Effect of Zr Addition on Glass-Forming Ability and Magnetic Properties of Fe-Nd-Al-B Alloys Prepared by Suction Casting

    Institute of Scientific and Technical Information of China (English)

    BAI Qin; XU Hui; TAN Xiao-Hua; MENG Tao

    2009-01-01

    The microstructure and magnetic behaviors of the Fe--Nd-AI-B alloys prepared by suction casting with zirconium addition are investigated. With the small amount of zirconium addition, the magnetic properties of the alloys change from hard magnetic property to soft magnetic property. The proper addition of Zr (6%) not only improves the glass forming ability, but also suppresses the crystallization. From the scanning electron microscopy of the [(Fe0.53Nd0.37Al0.10)0.96B0.04]94Zr6 alloy and the local average elemental compositions determined using energy dispersive spectroscopy analysis, the amorphous phase with a composition of Fe47Nd38Al12Zr3 in the alloy can be observed. The bulk amorphous Fe47Nd38Al12Zr3 alloy is prepared by suction casting exhibiting good glassforming ability and soft magnetic behavior.

  19. Microstructural Features and Mechanical Properties Induced by the Spray Forming and Cold Rolling of the Cu-13.5 wt pct Sn Alloy

    Institute of Scientific and Technical Information of China (English)

    Xiaofeng WANG; Jiuzhou ZHAO; Jie HE; Jiangtao WANG

    2008-01-01

    Copper alloys with high strength and high conductivity are an important functional material with full of potential applications. In the present investigation, a bronze with higher tin content (Cu-13.5 wt pct Sn)was prepared successfully by spray forming, the feasibility of cold rolling this alloy was investigated, and the cold rolling characteristics of this alloy have also been discussed. The results indicate that the spray-formed Cu-13.5 wt pct Sn alloy, compared with the as-cast ingot, shows a quite fine and homogeneous single-phase structure, and, therefore shows an excellent workability. It can be cold-rolled with nearly 15% reduction in the thickness per pass and the total reduction can reach 80%. The classical border between the wrought and cast alloys is shifted to considerably higher tin contents by spray forming. After proper thermo-mechanical treatment, spray-formed Cu-13.5 wt pct Sn alloy exhibits excellent comprehensive mechanical properties.Particularly, it shows a low elastic modulus (~88 GPa) and a high flow stress (over 800 MPa) after cold forming. This combination of properties is unique in the domain of metallic materials and could open new possibilities in spring technology field.

  20. An investigation of neutron irradiation test on superplastic zirconia-ceramic materials

    Energy Technology Data Exchange (ETDEWEB)

    Shibata, Taiju; Ishihara, Masahiro; Baba, Shinichi; Hayashi, Kimio [Japan Atomic Energy Research Inst., Oarai, Ibaraki (Japan). Oarai Research Establishment; Motohashi, Yoshinobu [Ibaraki Univ., Mito (Japan)

    2000-05-01

    A neutron irradiation test on superplastic ceramic materials at high temperature has been proposed as an innovative basic research on high-temperature engineering using the High Temperature Engineering Test Reactor (HTTR). For the effective execution of the test, we reviewed the superplastic deformation mechanism of ceramic materials and discussed neutron irradiation effects on the superplastic deformation process of stabilized Tetragonal Zirconia Polycrystal (TZP), which is a representative superplastic ceramic material. As a result, we pointed out that the decrease in the activation energy for superplastic deformation is expected by the radiation-enhanced diffusion. We selected a fast neutron fluence of 5x10{sup 20} n/cm{sup 2} and an irradiation temperature of about 600degC as test conditions for the first irradiation test on TZP and decided to perform a preliminary irradiation test by the Japan Materials Testing Reactor (JMTR). Moreover, we estimated the radioactivity of irradiated TZP and indicated that it is in the order of 10{sup 10} Bq/g (about 0.3 Ci/g) immediately after irradiation to a thermal neutron fluence of 3x10{sup 20} n/cm{sup 2} and that it decays to about 1/100 in a year. (author)

  1. Designing new biocompatible glass-forming Ti75-x Zr10 Nbx Si15 (x = 0, 15) alloys: corrosion, passivity, and apatite formation.

    Science.gov (United States)

    Abdi, Somayeh; Oswald, Steffen; Gostin, Petre Flaviu; Helth, Arne; Sort, Jordi; Baró, Maria Dolors; Calin, Mariana; Schultz, Ludwig; Eckert, Jürgen; Gebert, Annett

    2016-01-01

    Glass-forming Ti-based alloys are considered as potential new materials for implant applications. Ti75 Zr10 Si15 and Ti60 Zr10 Nb15 Si15 alloys (free of cytotoxic elements) can be produced as melt-spun ribbons with glassy matrix and embedded single β-type nanocrystals. The corrosion and passivation behavior of these alloys in their homogenized melt-spun states have been investigated in Ringer solution at 37°C in comparison to their cast multiphase crystalline counterparts and to cp-Ti and β-type Ti-40Nb. All tested materials showed very low corrosion rates as expressed in corrosion current densities icorr  corrosion properties, the Nb-containing nearly single-phase glassy alloy can compete with the β-type Ti-40Nb alloy. SBF tests confirmed the ability for formation of hydroxyapatite on the melt-spun alloy surfaces. All these properties recommend the new glass-forming alloys for application as wear- and corrosion-resistant coating materials for implants.

  2. Numerical modelling of microstructure forming process for Al-Al3Fe eutectic alloy

    Institute of Scientific and Technical Information of China (English)

    李荣德; 周振平

    2003-01-01

    A self-adjusting model was presented on the basis of the effect of temperature gradient on eutectic growth and a curved solid/liquid interface. Finite differential method was adopted to solve the model. The average lamellar spacing of the Al-Al3Fe eutectic alloy and the content fields ahead of the solidifying interface under different growth rates were calculated. Directional solidification experiments were carried out in order to prove the modification of the modeling. The experimental results are in relatively good agreement with the calculations.

  3. Martensitic transformation in nanostructured TiNi shape memory alloy formed via severe plastic deformation

    Energy Technology Data Exchange (ETDEWEB)

    Tsuchiya, K. [Department of Production Systems Engineering, Toyohashi University of Technology (Japan)]. E-mail: tsuchiya@pse.tut.ac.jp; Inuzuka, M. [Department of Production Systems Engineering, Toyohashi University of Technology (Japan); Tomus, D. [Department of Production Systems Engineering, Toyohashi University of Technology (Japan); Hosokawa, A. [Department of Production Systems Engineering, Toyohashi University of Technology (Japan); Nakayama, H. [Department of Mechanical Engineering, University of Washington (United States); Morii, K. [Research and Development Laboratory, Daido Steel, Co., Ltd. (Japan); Todaka, Y. [Department of Production Systems Engineering, Toyohashi University of Technology (Japan); Umemoto, M. [Department of Production Systems Engineering, Toyohashi University of Technology (Japan)

    2006-11-25

    Martensitic transformation and mechanical behavior was investigated on TiNi shape memory alloy subjected to severe plastic deformation by cold rolling. Transmission electron microscopy revealed the sample to be a mixture of nanocrystalline and amorphous material after 40% cold rolling. Diffrential scaning calorimetry measurements and X-ray diffractometry suggested that the martensitic transformation was suppressed when the thickness reduction was over 25%. The pseudoelastic stress-strain curves of nanocrystalline/amorphous TiNi are characterized by the absence of a stress-plateau and by small hysteresis.

  4. Thermoplastic Micro-Forming of Bulk Metallic Glasses: A Review

    Science.gov (United States)

    Li, Ning; Chen, Wen; Liu, Lin

    2016-04-01

    Bulk metallic glasses are a fascinating class of metallic alloys with an isotropic amorphous structure that is rapidly quenched from liquid melts. The absence of a crystalline micro-structure endows them with a portfolio of properties such as high strength, high elasticity, and excellent corrosion resistance. Whereas the limited plasticity and hence poor workability at ambient temperature impede the structural application of bulk metallic glasses, the unique superplasticity within the supercooled liquid region opens an alternative window of so-called thermoplastic forming, which allows precise and versatile net-shaping of complex geometries on length scales ranging from nanometers to centimeters that were previously unachievable with conventional crystalline metal processing. Thermoplastic forming not only breaks through the bottleneck of the manufacture of bulk metallic glasses at ambient temperature but also offers an alluring prospect in micro-engineering applications. This paper comprehensively reviews some pivotal aspects of bulk metallic glasses during thermoplastic micro-forming, including an in-depth understanding of the crystallization kinetics of bulk metallic glasses and the thermoplastic processing time window, the thermoplastic forming map that clarifies the relationship between the flow characteristics and the formability, the interfacial friction in micro-forming and novel forming methods to improve the formability, and the potential applications of the hot-embossed micro-patterns/components.

  5. Gibbs Free Energy and Activation Energy of ZrTiAlNiCuSn Bulk Glass Forming Alloys

    Institute of Scientific and Technical Information of China (English)

    Jianfei SUN; Jun SHEN; Zhenye ZHU; Gang WANG; Dawei XING; Yulai GAO; Bide ZHOU

    2004-01-01

    The Gibbs free energy differences between the supercooled liquid and the crystalline mixture for the (Zr52.5Ti5Al10- Ni14.6Cu17.9)(100-x)/100Snx ·(x=0, 1, 2, 3, 4 and 5) glass forming alloys are estimated by introducing the equation proposed by Thompson, Spaepen and Turnbull. It can be seen that the Gibbs free energy differences decrease first as the increases of Sn addition smaller than 3, then followed by a decrease due to the successive addition of Sn larger than 3, indicating that the thermal stabilities of these glass forming alloys increase first and then followed by a decrease owing to the excessive addition of Sn. Furthermore, the activation energy of Zr52.5Ti5Al10Ni14.6Cu17.9 and (Zr5 2.5Ti5 Al10 Ni14.6 Cu 17.9)0.97Sn3 was evaluated by Kissinger equation. It is noted that the Sn addition increases the activation energies for glass transition and crystallization, implying that the higher thermal stability can be obtained by appropriate addition of Sn.

  6. Modeling of precipitate-free zone formed upon homogenization in a multi-component alloy

    Energy Technology Data Exchange (ETDEWEB)

    Gandin, Ch.-A. [CEMEF UMR CNRS-ENSMP 7635, Ecole des Mines, BP207, 06904 Sophia Antipolis (France) and LSG2M UMR CNRS-INPL-UHP 7584, Ecole des Mines, Parc de Saurupt, 54042 Nancy (France)]. E-mail: charles-andre.gandin@ensmp.fr; Jacot, A. [LSMX, MX-G, Ecole Polytechnique Federale de Lausanne, 1015 Lausanne (Switzerland); CALCOM ESI SA, PSE, Ecole Polytechnique Federale de Lausanne, 1015 Lausanne (Switzerland)

    2007-04-15

    A comprehensive model is presented for the simulation of microstructure evolution during industrial solidification and homogenization processing of aluminum alloys. The model combines on the one hand microsegregation due to long-range diffusion during solidification and subsequent heat treatment with, on the other hand, precipitation in the primary Al phase. The thermodynamic data are directly obtained from a CALPHAD (CALculation of PHAse Diagrams) approach to thermodynamic equilibrium in multicomponent systems. The model is applied to the prediction of structure and segregation evolutions in a 3003 aluminum alloy for typical industrial solidification and homogenization sequences. It is shown that: (i) accounting for the nucleation undercooling of the eutectic/peritectic structures solidifying from the melt is essential to retrieval of the measured volume fractions of intergranular precipitates; (ii) calculations of intragranular precipitation are generally not applicable if long-range diffusion is neglected; (iii) the precipitate-free zone can be quantitatively predicted only based on the coupling between intergranular and intragranular precipitation calculations.

  7. Microstructure and property development in spray formed and extruded Al-Mg-Li-Zr alloys for aerospace and autosport applications

    Energy Technology Data Exchange (ETDEWEB)

    Mi, J.; Grant, P.S. [Department of Materials, Oxford University (United Kingdom); Nilsen, K.E.; Liotti, E. [BOAL UK Ltd. Loughborough (United Kingdom); Hogg, S.C.

    2010-07-15

    Low density Al-4Mg-1.3Li-0.4Zr and Al-6Mg-1.6Li-0.4Zr alloys were spray formed and the billets extruded under a range of conditions. The alloy compositions were selected to provide an attractive balance of tensile strength and elongation, without relying on complex post-processing and heat treatments - and are therefore suitable for complex cross section extrusions and free from quench distortion. The as-spray formed microstructures showed fine homogeneous, equiaxed grains with an average size of 10-15 {mu}m. Firstly, a laboratory scale extrusion was carried out to extrude 30 mm diameter billets into 7.5 mm diameter cross-section and to investigate the effects of temperature and ram speeds on microstructural development. The microstructure after extrusion at 400 C was partially dynamically recrystallised with a {proportional_to}0.5 area fraction of {proportional_to}1 {mu}m grains and the remainder were unrecrystallised elongated grains. Electron backscatter diffraction showed a mixed <111> + <100> double fibre texture. After peak age hardening at 150 C for 96 h, the Al-6Mg-1.6Li-0.4Zr alloy showed a 0.2% proof strength of 495 MPa, a tensile strength of 553 MPa and elongation to failure of 8.5%; Al-4Mg-1.3Li-0.4Zr showed a 0.2% proof strength of 392 MPa, a tensile strength of 476 MPa and an elongation of 10%. Subsequently, large-scale complex cross-section were extruded at {proportional_to}400 C. Due to the complexity of the cross-sections and the non-axisymetric deformation, the fibre texture was distorted to FCC rolled Copper and Brass orientations. After a dual-step age hardening treatment of 130 C for 8h followed by 160 C for 8h, the proof strength, ultimate strength and elongations were 340 MPa, 470 MPa and 16% respectively. The combination of relatively simple process steps, high strength and ductility/formability, and low distortion in complex sections demonstrated the strong potential for these low density alloys in aerospace and autosport applications

  8. Superplasticity and cooperative grain boundary sliding in nanocrystalline Ni{sub 3}Al

    Energy Technology Data Exchange (ETDEWEB)

    Mara, N.A. [Center for Integrated Nanotechnologies, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)], E-mail: namara@lanl.gov; Sergueeva, A.V.; Mara, T.D. [Materials Science Division, University of California, Davis, One Shields Avenue, Davis, CA 95616 (United States); McFadden, S.X. [Sandia Laboratories, Livermore, CA 94550 (United States); Mukherjee, A.K. [Materials Science Division, University of California, Davis, One Shields Avenue, Davis, CA 95616 (United States)

    2007-08-15

    Cooperative grain boundary sliding (CGBS) has been shown to account for the majority of macroscopic strain seen in microcrystalline metallic systems undergoing superplastic deformation. While CGBS has been observed on the surface of microcrystalline samples deforming superplastically through the shifting of diamond scribe lines, there have been few transmission electron microscopy results showing such occurrences in the bulk of the material, or the details behind the micromechanism of CGBS. In this work, nanocrystalline Ni{sub 3}Al produced via high-pressure torsion is deformed superplastically in the electron microscope. High-temperature ({approx}700 deg. C) in situ tensile testing shows the nature of CGBS at the nanoscale through direct observation of this phenomenon.

  9. Ultrasonic Nondestructive Testing of Superplastic Solid-State Welding Joint for Different Steels

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Based on quantitative microscopic examinations of welds and welding rate for different steels (40Cr and T10A) joint, which possess the ultra-fine microstructure after high frequency hardening (HFH) and salt-bath cyclic quenching (SCQ), the suitable defect grey scale threshold value was determined, and the welding rate of superplastic solid-state welding of different steels (40Cr and T10A steel) was systematically inspected and analyzed by means of self-made ultrasonic imaging inspection system. The experimental results showed that the superplastic solid-state weld of different steels can be inspected more accurately, reliably and quickly by this system, and the results were in good accordance with that of metallographic observation. The welding rate of superplastic welding is in linear relation with tensile strength of joint.

  10. Ultrasonic C-scanning imaging inspection of superplastic solid-state welded joint quality

    Institute of Scientific and Technical Information of China (English)

    张柯柯; 陈怀东; 杨蕴林; 薛锦

    2002-01-01

    Based on a large amount of dissection at welded interface and quantitative microscopic examination of welded rate, the suitable limit grey scale value was determined, and the welded rate of superplastic solid-state welding interface of heterogeneous steel was systematically studied by means of self-made ultrasonic C-scanning imaging inspection system. The experimental results show: the welded state of superplastic solid-state welding interface of heterogeneous steel can be conducted to be more accurately, reliably and quickly inspected by means of this system, and the ultrasonic testing results are good consistent with actual examination results of the interface defective distribution. Within the extent of the suitble welded rate,the welded rate in 40Cr/T10A superplastic welding process tested by this system is linear with its tensile strength of joint.

  11. Structural Origin of the Enhanced Glass-Forming Ability Induced by Microalloying Y in the ZrCuAl Alloy

    Directory of Open Access Journals (Sweden)

    Gu-Qing Guo

    2016-03-01

    Full Text Available In this work, the structural origin of the enhanced glass-forming ability induced by microalloying Y in a ZrCuAl multicomponent system is studied by performing synchrotron radiation experiments combined with simulations. It is revealed that the addition of Y leads to the optimization of local structures, including: (1 more Zr-centered and Y-centered icosahedral-like clusters occur in the microstructure; (2 the atomic packing efficiency inside clusters and the regularity of clusters are both enhanced. These structural optimizations help to stabilize the amorphous structure in the ZrCuAlY system, and lead to a high glass-forming ability (GFA. The present work provides an understanding of GFAs in multicomponent alloys and will shed light on the development of more metallic glasses with high GFAs.

  12. ANALYSIS OF RUBBER FORMING PROCESS OF FIRE BARRIER FROM TITANIUM CP2 ALLOY FOR AW 139 HELICOPTER

    Directory of Open Access Journals (Sweden)

    Mariusz Krakowski

    2015-05-01

    Full Text Available This paper presents conditions of forming products from titanium sheets by means of rubber stamping method. After introducing the issues connected with these elements manufacturing for aviation industry, considering standards and legal regulations, technological problems occurring during forming deep stiffening ribs. The results in the characteristic curvatures and distortion in the final products were generated in the process heterogeneous internal stress state. The Authors aimed at explaining and presenting of solutions limiting occurrence of chosen shape faults, which disqualify these products application in aviation industry. The proposed solutions significantly reduced the incidence of these unfavorable phenomena. The modified method of rubber stamping of firewall from titanium alloy CP-2 sheet was successfully implemented in manufacturing conditions of PZL Swidnik.

  13. A microstructural study of an Al-Cu-Mg-Zr alloy after hot forming

    Energy Technology Data Exchange (ETDEWEB)

    Cabibbo, M.; Evangelista, E.; Spigarelli, S. [Ancona Univ. (Italy). Dipt. di Meccanica

    2002-07-01

    The present study focuses on the influence of hot deformation on the microstructure of an Al-Cu-Mg-Zr alloy. Torsion tests were performed at temperatures between 300 and 500 C under strain rates ranging from 10{sup -3} to 5 s{sup -1}. The influence of hot deformation on microstructure was investigated by means of light and electron microscopy and X-ray diffraction (XRD) techniques. Grains were elongated and contained a large number of sub-grains few microns in width. Statistical measurements of subgrain distribution and size were performed by means of the intercept method. Energy-dispersive spectroscopy (EDS) analysis, on SEM, and selected area electron diffraction patterns (SAEDP) indexing, on TEM, allowed to identify the secondary-phase particles. A statistical evaluation of the size of hardening particles was carried out by TEM. (orig.)

  14. Ab initio contribution to the study of complexes formed during dilute FeCu alloys radiation

    CERN Document Server

    Becquart, C S

    2003-01-01

    Cu plays an important role in the embrittlement of pressure vessel steels under radiation and entities containing both Cu atoms and vacancies seem to appear as a consequence of displacement cascades. The characterisation of the stability as well as the migration of small Cu-vacancy complexes is thus necessary to understand and simulate the formation of these entities. For instance, cascade ageing studied by kinetic Monte Carlo or by rate theory models requires a good characterisation of such complexes which are parameters for these methods. We have investigated, by ab initio calculations based on the density functional theory, point defects and small defects in dilute FeCu alloys. The structure of small Cu clusters and Cu-vacancy complexes has been determined, as well as their formation and binding energies. Their relative stability is discussed. Vacancy migration energies in the presence of Cu atoms have been calculated and analysed. All the results are compared to the figures obtained with empirical interat...

  15. Cell interaction with modified nanotubes formed on titanium alloy Ti-6Al-4V.

    Science.gov (United States)

    Moravec, Hynek; Vandrovcova, Marta; Chotova, Katerina; Fojt, Jaroslav; Pruchova, Eva; Joska, Ludek; Bacakova, Lucie

    2016-08-01

    Nanotubes with diameters ranging from 40 to 60nm were prepared by electrochemical oxidation of the Ti-6Al-4V alloy in electrolyte containing ammonium sulphate and ammonium fluoride. The nanotubes were further modified with calcium and phosphate ions or were heat treated. Polished Ti-6Al-4V alloy served as a reference sample. The spreading of human osteoblast-like cells was similar on all nanotube samples but lower than on polished samples. The number of initially adhered cells was higher on non-modified nanotubes, but the final cell number was the highest on Ca-enriched nanotubes and the lowest on heat-treated nanotubes. However, these differences were relatively small and less pronounced than the differences in the concentration of specific molecular markers of cell adhesion and differentiation, estimated by their intensity of immunofluorescence staining. The concentration of vinculin, i.e. a protein of focal adhesion plaques, was the lowest on nanotubes modified with calcium. Collagen I, an early marker of osteogenic cell differentiation, was also the lowest on samples modified with calcium and was highest on polished samples. Alkaline phosphatase, a middle marker of osteogenic differentiation, was observed in lowest concentration on nanotubes modified with phosphorus and the highest on heat-treated samples. Osteocalcin concentrations, a late marker of osteogenic cell differentiation, were similar on all tested samples, although they tended to be the highest on heat-treated samples. Thus, osteogenic differentiation can be modulated by various additional treatments of nanotube coatings on Ti-6Al-4V implants.

  16. SUPERPLASTICITY OF A SiCw/2024 Al COMPOSITE MADE BY PRESSURE INFILTRATION

    Institute of Scientific and Technical Information of China (English)

    X.J. Xu; W. Wang; L. Cai

    2002-01-01

    The superplastic characteristics of the β-SiC whisker reinforced 2024 aluminum com-posite, fabricated by pressure infiltration and hot-rolling after extrusion, were inves-tigated. The composite has a fine grain size of about 1μm, and exhibits a maximumtensile elongation of 370% in the initial strain rate of 3.3× 10-3 s-1 at 788K. The su-perplastic deformation mechanism of the composite is thought to be grain boundary(interface) sliding accommodated by grain boundary diffusion of aluminum atom andan appropriate amount of liquid phase.

  17. HIGH STRAIN RATE SUPERPLASTICITY OF A AIN PARTICULATE REINFORCED 6061Al COMPOSITE

    Institute of Scientific and Technical Information of China (English)

    L.H. Han; J.T. Niu; D.M. Jiang; T. Imai

    2001-01-01

    The superplasticity of AlNp/6061Al composite, fabricated by powder metallurgy method and hot-rolled after extrusion, was investigated. The AlNp/6061Al composite exhibits an m-value of 0.49 and a maximum elongation of 438% in the strain rates ranging from 10-2-10°s-1 and at temperatures from 823K to 893K. Differential scanning calorimeter was used to ascertain the possibility of any partial melting in the vicinity of optimum superplastic temperature. These results suggested that liquid phase existed where maximum elongation was obtained.

  18. Investigation on Superplasticity in SiCp/2024 Cold Rolling Sheet after Heat Treatment

    Institute of Scientific and Technical Information of China (English)

    Bol(u) XIAO; Zongyi MA; Jing BI

    2003-01-01

    High strain rate superplastic deformation behavior of powder metallurgy (PM) processed 17 vol. pct SiCp/2024 Al composite sheet after heat treatment was investigated over a range of temperature from 753 to 833 K. At 813 K,a maximum elongation of 259% was discovered at a strain rate of 10-1 s-1. The activation energy was closed to that for lattice diffusion of Al and increased at temperature upon incipient melting temperature. The mechanism of superplastic deformation for present composites was attributed to lattice diffusion controlled grain boundary sliding.

  19. Self-organized double-wall oxide nanotube layers on glass-forming Ti-Zr-Si(-Nb) alloys.

    Science.gov (United States)

    Sopha, Hanna; Pohl, Darius; Damm, Christine; Hromadko, Ludek; Rellinghaus, Bernd; Gebert, Annett; Macak, Jan M

    2017-01-01

    In this work, we report for the first time on the use of melt spun glass-forming alloys - Ti75Zr10Si15 (TZS) and Ti60Zr10Si15Nb15 (TZSN) - as substrates for the growth of anodic oxide nanotube layers. Upon their anodization in ethylene glycol based electrolytes, highly ordered nanotube layers were achieved. In comparison to TiO2 nanotube layers grown on Ti foils, under the same conditions for reference, smaller diameter nanotubes (~116nm for TZS and ~90nm for TZSN) and shorter nanotubes (~11.5μm and ~6.5μm for TZS and TZSN, respectively) were obtained for both amorphous alloys. Furthermore, TEM and STEM studies, coupled with EDX analysis, revealed a double-wall structure of the as-grown amorphous oxide nanotubes with Ti species being enriched in the inner wall, and Si species in the outer wall, whereby Zr and Nb species were homogeneously distributed. Copyright © 2016 Elsevier B.V. All rights reserved.

  20. Effect of P addition on glass forming ability and soft magnetic properties of melt-spun FeSiBCuC alloy ribbons

    Science.gov (United States)

    Xu, J.; Yang, Y. Z.; Li, W.; Chen, X. C.; Xie, Z. W.

    2016-11-01

    The dependency of phosphorous content on the glass forming ability, thermal stability and soft magnetic properties of Fe83.4Si2B14-xPxCu0.5C0.1 (x=0,1,2,3,4) alloys was investigated. The experimental results showed that the substitution of B by P increased the glass forming ability in this alloy system. The Fe83.4Si2B10P4Cu0.5C0.1 alloy shows a fully amorphous character. Thermal stability of melt-spun ribbons increases and temperature interval between the first and second crystallization peaks enlarges with the increase of P content. And the saturation magnetic flux density (Bs) shows a slight increase with the increase of P content. The Fe83.4Si2B11P3Cu0.5C0.1 nanocrystalline alloy exhibits a high Bs about 200.6 emu/g. The Bs of fully amorphous alloy Fe83.4Si2B10P4Cu0.5C0.1 drops dramatically to 172.1 emu/g, which is lower than that of other nanocrystallines. Low material cost and excellent soft magnetic properties make the FeSiBPCuC alloys promise soft magnetic materials for industrial applications.

  1. Finemet nanocrystalline soft magnetic alloy: Investigation of glass forming ability, crystallization mechanism, production techniques, magnetic softness and the effect of replacing the main constituents by other elements

    Energy Technology Data Exchange (ETDEWEB)

    Gheiratmand, T.; Hosseini, H.R. Madaah, E-mail: madaah@sharif.ir

    2016-06-15

    Finemet soft magnetic alloy has been in the focus of interest in the last years due to its high saturation magnetization, high permeability and low core loss. The great quantity of papers has been devoted to the study of its structural and magnetic properties, confirms this claim. This paper reviews the different researches performed on Finemet up to now. The criteria that should be satisfied in order to have the high glass forming ability in an alloy and also the techniques applied for production of Finemet ribbons, powders and bulk samples have been explained. In addition, the mechanism of devitrification, nanocrystallization and magnetic softness in this applicable magnetic alloy has been discussed in detail. Finally, the effect of different elements substituted with the main constituents in Finemet has been summarized through the studies on the characterization and magnetic properties of different Finemet-type alloys. - Highlights: • The criteria for getting high glass forming ability in an alloy have been reviewed. • Techniques applied to make Finemet ribbons and bulk samples have been explained. • Mechanism of devitrification and nanocrystallization has been discussed in detail. • The mechanism of magnetic softness in this magnetic alloy has been demonstrated. • The effect of main elements substitution in Finemet has been summarized.

  2. Effect of Pre-aging on Stress Corrosion Cracking of Spray-formed 7075 Alloy in Retrogression and Re-aging

    Science.gov (United States)

    Su, Rui-ming; Qu, Ying-dong; You, Jun-hua; de Li, Rong-

    2015-11-01

    The effects of pre-aging in retrogression and re-aging (RRA) treatment on microstructure, mechanical properties, and stress corrosion cracking (SCC) behavior of spray-formed 7075 aluminum alloy were investigated by tensile test, slow strain rate test, and transmission electron microscope. The results show that the under aging (120 °C for 16 h) as the pre-aging in RRA treatment can vastly improve the mechanical properties and the SCC resistance of the alloy, compared with early aging (120 °C for 8 h), peak aging (120 °C for 24 h), and over aging (120 °C for 32 h) treatments, the ultimate tensile strength of the alloy is 782 MPa, which is higher than that for peak aging or conventional RRA treatment; and the SCC resistance of the alloy is also excellent after RRA with under aging as pre-aging.

  3. Effects of Mo additions on the glass-forming ability and magnetic properties of bulk amorphous Fe-C-Si-B-P-Mo alloys

    Institute of Scientific and Technical Information of China (English)

    YI; Seonghoon

    2010-01-01

    Glass formation, mechanical and magnetic properties of the Fe76-xC7.0Si3.3B5.0P8.7Mox (x=0, 1 at.%, 3 at.% and 5 at.%) alloys prepared using an industrial Fe-P master alloy have been studied. With the substitution of Mo for Fe, glass-forming ability (GFA) was significantly enhanced and fully amorphous rods with a diameter of up to 5 mm were produced in the alloy with 3% Mo. The Mo-containing amorphous alloys also exhibited high fracture strength of 3635–3881 MPa and excellent magnetic properties including a high saturation magnetization of 1.10–1.41 T, a high Curie temperature and a low coercive force. The unique combination of high GFA, high fracture strength and excellent magnetic properties make the newly developed bulk metallic glasses viable for practical engineering applications.

  4. Incremental forming of free surface with magnesium alloy AZ31 sheet at warm temperatures

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The formability of AZ31 sheet begins to increase drastically at 150 ℃. The incremental forming technique was thus applied to AZ31 sheet at 150 ℃ to utilize the formability to its fullest capacity at the lowest possible temperature for forming applications. A surface scanning technique was used followed by the tool path generation to incrementally form an egg surface. After thorough examination of various tool paths, the surface was most successfully produced by forming an intermediate shape followed by a series of tool paths. Flexible scale stickers were devised to improve the accuracy in the measurement of grid deformation.

  5. Examination of the Oxidation Protection of Zinc Coatings Formed on Copper Alloys and Steel Substrates

    Science.gov (United States)

    Papazoglou, M.; Chaliampalias, D.; Vourlias, G.; Pavlidou, E.; Stergioudis, G.; Skolianos, S.

    2010-01-01

    The exposure of metallic components at aggressive high temperature environments, usually limit their usage at similar application because they suffer from severe oxidation attack. Copper alloys are used in a wide range of high-quality indoor and outdoor applications, statue parts, art hardware, high strength and high thermal conductivity applications. On the other hand, steel is commonly used as mechanical part of industrial set outs or in the construction sector due to its high mechanical properties. The aim of the present work is the examination of the oxidation resistance of pack cementation zinc coatings deposited on copper, leaded brass and steel substrates at elevated temperature conditions. Furthermore, an effort made to make a long-term evaluation of the coated samples durability. The oxidation results showed that bare substrates appear to have undergone severe damage comparing with the coated ones. Furthermore, the mass gain of the uncoated samples was higher than this of the zinc covered ones. Particularly zinc coated brass was found to be more resistant to oxidation conditions in which it was exposed as it has the lower mass gain as compared to the bare substrates and zinc coated copper. Zinc coated steel was also proved to be more resistive than the uncoated steel.

  6. Studies of Nucleation, Growth, Specific Heat, and Viscosity of Undercooled Melts of Quasicrystals and Polytetrahedral-Phase-Forming Alloys

    Science.gov (United States)

    Kelton, K. F.; Croat, T. K.; Gangopadhyay, A.; Holland-Moritz, D.; Hyers, Robert W.; Rathz, Thomas J.; Robinson, Michael B.; Rogers, Jan R.

    2001-01-01

    Undercooling experiments and thermal physical property measurements of metallic alloys on the International Space Station (ISS) are planned. This recently-funded research focuses on fundamental issues of the formation and structure of highly-ordered non-crystallographic phases (quasicrystals) and related crystal phases (crystal approximants), and the connections between the atomic structures of these phases and those of liquids and glasses. It extends studies made previously by us of the composition dependence of crystal nucleation processes in silicate and metallic glasses, to the case of nucleation from the liquid phase. Motivating results from rf-levitation and drop-tube measurements of the undercooling of Ti/Zr-based liquids that form quasicrystals and crystal approximants are discussed. Preliminary measurements by electrostatic levitation (ESL) are presented.

  7. Effects of Microalloying on Glass Forming Ability and Thermodynamic Fragility of Cu-Pr-Based Amorphous Alloys

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The effects of microalloying of Ti and B on the glass formation of Cu60Pr30Ni10Al10-2xTixBx(x=0, 0.05%(atom fraction)) amorphous alloys was investigated using differential scanning calorimetry (DSC) and X-ray diffraction (XRD). XRD analysis showed that microalloying with 0.05% Ti and 0.05% B improved the glass forming ability (GFA). The smaller difference in the Gibbs free energy between the liquid and crystalline states at the glass transition temperature (ΔGl-x (Tg)) and the smaller thermodynamic fragility index (ΔSf/Tm, where ΔSf is the entropy of fusion, and Tm is the melting temperature) after microalloying correlated with the higher GFA.

  8. Structural State of a Weld Formed in Aluminum Alloy by Friction Stir Welding and Treated by Ultrasound

    Science.gov (United States)

    Klimenov, V. A.; Abzaev, Yu. A.; Potekaev, A. I.; Vlasov, V. A.; Klopotov, A. A.; Zaitsev, K. V.; Chumaevskii, A. V.; Porobova, S. A.; Grinkevich, L. S.; Tazin, I. D.; Tazin, D. I.

    2016-11-01

    The experimental data on structural state of an aluminum alloy, AlMg6, in the weld zone formed by friction stir welding are analyzed in order to evaluate the effect of its subsequent ultrasonic treatment. It is found that the crystal lattice transits into a low-stability state as a result of combined heat-induced and severe shear deformation. This transition is accompanied by considerable structural-phase changes that are manifested as an increased lattice parameter of the solid solution. This increase is caused by both high values of internal stresses and increased concentration of Mg atoms in the solid solution due to essential dissolution of the β-Al2Mg3 particles with the content of manganese higher than that in the matrix. This is accompanied by high-intensity diffusion and relaxation processes due to the low-stability state of crystal lattice (inhomogeneous stresses) in the weld zone.

  9. Three Dimensional FEM Simulation of Titanium Hollow Blade Forming Process

    NARCIS (Netherlands)

    Zhao Bing, [No Value; Li Zhiqiang, [No Value; Hou Hongliang, [No Value; Liao Jinhua, [No Value; Bai Bingzhe, [No Value

    2010-01-01

    With the introduction of high by-pass turbofan engines into both commercial and military aircraft industries, the fabrication of large size fan blade through superplastic forming/diffusion bonding (SPF/DB) has become a pivotal technique of turbine fan engine. There are three key steps to form a holl

  10. Crystalline Precipitate in a Bulk Glass Forming Zr-Based Alloy and Its Effect on Mechanical Properties

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Cylindrical and sheet samples of bulk metallic glass with a nominal composition of Zr52.5Ni14.6Al10Cu17.9Ti5 (at. pct) were prepared by melt injection casting. The crystalline precipitates formed during the casting were studied by metallographic observations and selected-area electron diffractions. The effect of crystalline precipitates on the mechanical properties were investigated by tensile and compressive tests at room temperature. Oxygen contents and the sample sizes (or cooling rates) strongly affect the formation of the crystalline precipitates. Overheating the alloy melt up to 200 K above its melting temperature can effectively prevent the formation of the crystalline precipitates to get fully glass samples with diameters up to 2 mm for cylinders and thickness up to 1 mm for sheets even the oxygen content is as higher as 0.08 wt pct.With increasing the sample sizes, the crystalline precipitates increase in volume fraction and size. The formation of the precipitates experienced two stages, i.e., initially nucleation and isotropic growth, and then anisotropic growth, finally forming faceted morphologies. Fully glassy Zr52.5Ni14.6Al10Cu17.9Ti5 alloy exhibits excellent tensile and compressive properties at room temperature. The presence of crystalline precipitates significantly decreases the tensile and compressive properties. With increasing the crystalline precipitates, the area of vein patterns on the fracture surface decreases, but the fracture steps increase, and the fracture mode changes from ductile to brittle resulting from the larger stress concentration caused by the larger sizes and faceted shapes of the crystalline precipitates.

  11. Dry metal forming of high alloy steel using laser generated aluminum bronze tools

    Directory of Open Access Journals (Sweden)

    Freiße Hannes

    2015-01-01

    Full Text Available Regarding the optimization of forming technology in economic and environmental aspects, avoiding lubricants is an approach to realize the vision of a new green technology. The resulting direct contact between the tool and the sheet in non-lubricated deep drawing causes higher stress and depends mainly on the material combination. The tribological system in dry sliding has to be assessed by means on the one hand of the resulting friction coefficient and on the other hand of the wear of the tool and sheet material. The potential to generate tailored tribological systems for dry metal forming could be shown within the investigations by using different material combinations and by applying different laser cladding process parameters. Furthermore, the feasibility of additive manufacturing of a deep drawing tool was demonstrated. The tool was successfully applied to form circular cups in a dry metal forming process.

  12. Forming Limits of Weld Metal in Aluminum Alloys and Advanced High-Strength Steels

    Energy Technology Data Exchange (ETDEWEB)

    Stephens, Elizabeth V.; Smith, Mark T.; Grant, Glenn J.; Davies, Richard W.

    2010-10-25

    This work characterizes the mechanical properties of DP600 laser welded TWBs (1 mm-1.5 mm) near and in the weld, as well as their limits of formability. The approach uses simple uniaxial experiments to measure the variability in the forming limits of the weld region, and uses a theoretical forming limit diagram calculation to establish a probabilistic distribution of weld region imperfection using an M-K method approach

  13. Forming limits under multi-index constraints in NC bending of aluminum alloy thin-walled tubes with large diameters

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    With increasing diameters of aluminum alloy thin-walled tubes (AATTs), the tube forming limits, i.e. the minimum bending factors, and their predictions under multi-index constraints including wrinkling, thinning and flattening have been being a key problem to be urgently solved for improving tube forming potential in numerical control (NC) bending processes of AATTs with large diameters. Thus in this paper, a search algorithm of the forming limits is put forward based on a 3D elastic-plastic finite element (FE) model and a wrinkling energy prediction model for the bending processes under axial compression loading (ACL) or not. This algorithm enables to be considered the effects of process parameter combinations including die, friction parameters on the multi-indices. Based on this algorithm, the forming limits of the different size tubes are obtained, and the roles of the process parameter combinations in enabling the limit bending processes are also revealed. The followings are found: the first, within the appropriate ranges of friction and clearances between the different dies and the tubes enabling the bending processes with smaller bending factors, the ACL enables the tube limit bending processes after a decrease of the mandrel ball thickness and diameters; then, without considering the effects of the tube geometry sizes on the tube constitutive equations, the forming limits will be decided by the limit thinning values for the tubes with diameters smaller than 80 mm, while the wrinkling for the tubes with diameters no less than 80 mm. The forming limits obtained from this algorithm are smaller than the analytical results, and reduced by 57.39%; the last, the roles of the process parameter combinations in enabling the limit bending processes are verified by experimental results.

  14. Influence of superplastic deformation on the anisotropy of 03Kh26N6T steel

    Energy Technology Data Exchange (ETDEWEB)

    Akhmed Faud, M.F.; Tsepin, M.A.; Lobach, A.A. [Tabbinskii Metallurgical Institute, Cario (Egypt)]|[Moscow Institute of Steel and Alloys (Russian Federation)] [and others

    1992-03-01

    The rules of change in anisotropy of 03Kh26N6T corrosion-resistant steel with a nonequiaxial fine-grained structure deformed under superplastic conditions were considered and an investigation was made of the change in anisotropy of the plastic properties in connection with the presence of original metallographic nonuniformity of the steel structure. 8 refs., 5 figs.

  15. Fatigue property of a bioabsorbable magnesium alloy with a hydroxyapatite coating formed by a chemical solution deposition.

    Science.gov (United States)

    Hiromoto, Sachiko; Tomozawa, Masanari; Maruyama, Norio

    2013-09-01

    A hydroxyapatite (HAp) coating was directly formed on an extruded AZ31 magnesium alloy by a single-step chemical solution deposition. The HAp coating consists of an outer porous HAp layer, an inner continuous HAp layer, and a thin intermediate MgO layer, and the inner HAp and MgO layers are composed of nanocrystals. Tensile and fatigue tests were performed on the HAp-coated AZ31 in air. The HAp coating microscopically showed neither crack nor detachment at 5% static elongation (1.5% residual strain). With further elongation under tensile stress, cracks were formed perpendicularly to the tensile direction, and fragments of the coating detached with a fracture inside the inner continuous HAp layer. The fatigue strengths at 10(7) cycles (fatigue limit) of HAp-coated and mechanically polished AZ31 were ca. 80 MPa and ca. 90 MPa, respectively. The slight decrease in the fatigue limit with the HAp coating is attributed to small pits with a depth of ca. 10 μm formed on the substrate during the HAp-coating treatment. The HAp coating remained on the specimen without cracks after 10(7) cycles at the fatigue limit, which provides ca. 3% cyclic elongation.

  16. Influence of coupling with calculation of phase diagrams on microsegregation forming simulation of Al-4.5%Cu alloy

    Institute of Scientific and Technical Information of China (English)

    LIU Yong-gang; CHEN Guang; SUN Guo-xiong

    2006-01-01

    The effect of coupling with calculation of phase diagrams on microsegregation forming simulation was investigated. The traditional simplified phase diagram and calculated phase diagram were introduced into the numerical models respectively and simulation on microsegregation forming of the Al-4.5%Cu alloy ingot was also presented. The simulation results were both compared with the experiment results. The results show that the calculated sencondary arm spacing with these two kinds of phase diagram are almost the same because relationship between the coarsening model and the information of phase diagram is not close. The calculated eutectic phase volume fractions of different locations in the ingot coupled with different phase diagrams are discrepant. The calculated volume fractions are consistent with the experiment results when calculated phase diagram couples, but are far from the experiment results and obviously inacceptable when traditional simplified phase diagram couples. So, coupling with accurate calculated phase diagrams is very significant for microsegregation forming simulation since much information of the phase diagram is used in the models and it can improve the precision of simulation results.

  17. Liquid -to-glass transition in bulk glass-forming Cu55-xZr45Agx alloys using molecular dynamic simulations

    Directory of Open Access Journals (Sweden)

    Celtek M.

    2011-05-01

    Full Text Available We report results from molecular dynamics (MD studies concerning the microscopic structure of the ternary, bulk metallic glass-forming Cu55-x Zr45Agx (x=0,10,20 alloys using tight-binding potentials. Understanding of the nature of Glass Forming Ability (GFA of studied alloys, GFA parameters, glass transition temperature (T-g, melting temperature (T-m, reduced glass transition temperature (T-g/T-m, the supercooled liquid region and other parameters were simulated and compared with experiments. The computed pair distribution functions reproduce well experimental x-ray data of Inoue and co-workers. Structure analysis of the Cu-Zr-Ag alloy based on MD simulation will be also presented

  18. Containerless processing of hypermonotectic and glass forming alloys using the Marshall Space Flight Center 100 meter drop tube facility

    Science.gov (United States)

    Andrews, J. B.

    1986-01-01

    Two separate projects were carried out to study alloys whose solidification structures can be strongly influenced by the presence of a container during melting and solidifications. One project involved containerless solidification of hypermonotectic Au35Rh65 alloys. This alloy exhibits liquid immiscibility over a temperature range. It has been suggested that containerless melting might be one solution to the problem of sedimentation in the dispersions of immiscible liquid phases. However, surface tension driven flows could also lead to accumulation of the minority liquid phase at the external surface of a containerlessly melted alloy. The research underway is a first step in determining the influence of containerless, microgravity processing on immiscible alloys. Nickel-niobium alloys were studied using the drop tube facility. One alloy in this system, a Ni60Nb40 alloy, is a good candidate for the formation of a bulk metallic glass. Amorphous alloys of this composition were produced using thin film and mechanical alloying techniques. However, theory indicates that if heterogeneous nucleation can be avoided, it should be possible to produce an amorphous structure in this system using a moderate cooling rate from the melt. The containerless melting and solidification capabilities of the drop tube faciltiy provide ideal conditions for a study of this type. To date, several Ni60Nb40 samples have been levitated, melted and cooled during 4.6 seconds of free fall in the 100 meter drop tube. Structures obtained are discussed.

  19. Nanometric Gouge in High-Speed Shearing Experiments: Superplasticity?

    Science.gov (United States)

    Green, H. W.; Lockner, D. A.; Bozhilov, K. N.; Maddon, A.; Beeler, N. M.; Reches, Z.

    2010-12-01

    rates by “superplasticity” (viscous flow dominated by grain-boundary sliding). The high-pressure gouge also coarsens rapidly after sliding stops if quench rate is too slow, presumably driven largely by the very fine grain size. We will use transmission electron microscopy to identify the gouge state (crystalline or amorphous) and whether the nanometric particles have been sintered into a nanocrystalline layer that could flow similarly to the high-pressure experiments (in which the gouge was created by different processes). If such a nanocrystalline layer exists, the large friction drop of this material may be due to “superplastic” flow similarly to the high-pressure experiments. The recrystallization of the gouge into a coarser-crystalline pavement after sliding stops but before temperature falls should take it out of the superplastic regime at high velocities because grain-boundary sliding is strongly grain-size dependent. Thus, refragmenting the coarsened gouge would be required to re-establish the very low apparent friction. We propose that development of such a superplastic gouge during propagation of earthquakes may yield very low apparent friction by dynamically producing this lubricating material.

  20. Corrosion behaviour of Al{sub 86.0}Co{sub 7.6}Ce{sub 6.4} glass forming alloy with different microstructures

    Energy Technology Data Exchange (ETDEWEB)

    Li, C.L., E-mail: lichunling@upc.edu.cn [Department of Materials Physics and Chemistry, College of Science, China University of Petroleum (East China), Qingdao 266580 (China); Wang, P.; Sun, S.Q. [Department of Materials Physics and Chemistry, College of Science, China University of Petroleum (East China), Qingdao 266580 (China); Voisey, K.T.; McCartney, D.G. [Materials, Mechanics and Structures Research Division, Faculty of Engineering, The University of Nottingham, Nottingham NG7 2RD (United Kingdom)

    2016-10-30

    Highlights: • Corrosion behaviour of Al-Co-Ce glass forming alloys is microstructure dependent. • Coarse-grain and microstructure refined crystalline alloys were locally corroded. • The superior corrosion resistance of EBSM treated alloy was limited by cracks. • Crack-free amorphous layer generated by LSM-EBSM showed uniform and slight corrosion. - Abstract: It has been extensively reported that Al-TM-RE amorphous alloy has excellent mechanical properties and corrosion resistance. In this paper, the corrosion behaviour of an Al{sub 86.0}Co{sub 7.6}Ce{sub 6.4} glass forming alloy with different microstructures is investigated through electrochemical experiments and microscopy. Results show the effect of microstructure. Laser and electron beam surface melting processes produce rapidly solidified microstructures with different extents of passivation compared to the as-cast alloy. An amorphous surface layer produced by these surface treatments had superior corrosion resistance compared with the crystalline alloy. As-cast and laser treated Al{sub 86.0}Co{sub 7.6}Ce{sub 6.4} suffered localised corrosion in the Al/Al{sub 11}Ce{sub 3} eutectic region whereas the amorphous material exhibited uniform corrosion. Compared with the electrochemical behaviour of AA2024 and Alclad 2024, the fully amorphous layer prepared by combined laser-electron beam treatment exhibited advantages such as the more negative corrosion potential, the higher pitting potential and the uniform corrosion mechanism, which indicates that this material is a potential anode candidate in the protection of AA2024.

  1. In situ observation of ultrasonic cavitation-induced fragmentation of the primary crystals formed in Al alloys.

    Science.gov (United States)

    Wang, Feng; Tzanakis, Iakovos; Eskin, Dmitry; Mi, Jiawei; Connolley, Thomas

    2017-11-01

    The cavitation-induced fragmentation of primary crystals formed in Al alloys were investigated for the first time by high-speed imaging using a novel experimental approach. Three representative primary crystal types, Al3Ti, Si and Al3V with different morphologies and mechanical properties were first extracted by deep etching of the corresponding Al alloys and then subjected to ultrasonic cavitation processing in distilled water. The dynamic interaction between the cavitation bubbles and primary crystals was imaged in situ and in real time. Based on the recorded image sequences, the fragmentation mechanisms of primary crystals were studied. It was found that there are three major mechanisms by which the primary crystals were fragmented by cavitation bubbles. The first one was a slow process via fatigue-type failure. A cyclic pressure exerted by stationary pulsating bubbles caused the propagation of a crack pre-existing in the primary crystal to a critical length which led to fragmentation. The second mechanism was a sudden process due to the collapse of bubbles in a passing cavitation cloud. The pressure produced upon the collapse of the cloud promoted rapid monotonic crack growth and fast fracture in the primary crystals. The third observed mechanism was normal bending fracture as a result of the high pressure arising from the collapse of a bubble cloud and the crack formation at the branch connection points of dendritic primary crystals. The fragmentation of dendrite branches due to the interaction between two freely moving dendritic primary crystals was also observed. A simplified fracture analysis of the observed phenomena was performed. The specific fragmentation mechanism for the primary crystals depended on their morphology and mechanical properties. Copyright © 2017 The Author(s). Published by Elsevier B.V. All rights reserved.

  2. Laser engineered surfaces from glass forming alloy powder precursors : Microstructure and wear

    NARCIS (Netherlands)

    Matthews, D. T. A.; Ocelik, V.; Branagan, D.; de Hosson, J. Th. M.

    2009-01-01

    Fe-based metallic glass forming powders have been deposited on mild steel substrates using high power laser cladding. Coatings microstructures have been analysed by scanning- and transmission-electron microscopy and at varying substrate dilutions, have been found to comprise a 100 to 500 nm interden

  3. Raising the Reliability of Forming Rolls by Alloying Their Core with Copper

    Science.gov (United States)

    Zhizhkina, N. A.

    2016-11-01

    The mechanical properties and the structure of forming rolls from cast irons of different compositions are studied. A novel iron including a copper additive that lowers its chilling and raises the homogeneity of the structure is suggested for the roll cores. The use of such iron should raise the reliability of the rolls in operation.

  4. Maintaining the mechanical strength of La-, Y-co-substituted zirconia porous ceramics through the superplastically foaming method

    Energy Technology Data Exchange (ETDEWEB)

    Kishimoto, Akira, E-mail: kishim-a@cc.okayama-u.ac.jp; Okada, Masanori; Teranishi, Takashi; Hayashi, Hidetaka

    2013-10-01

    The superplastically foaming method was adopted to make closed-pore inclusive zirconia-based ceramics. Lanthanum oxide was added to monoclinic or tetragonal yttria-stabilised zirconia to reduce the thermal conductivity of the matrix. Sintering and superplastic deformation led to a solid solution and transformation to the cubic phase. The resulting superplastically foamed porous ceramics having a porosity of 45% had only 40% of the thermal conductivity of the fully densified ceramics having the same composition. This value was comparable to that of conventionally fabricated porous ceramics with the same composition and porosity. The superplastically foamed ceramics had 60%, while conventionally fabricated ceramics had only 20%, of the mechanical strength of the fully dense ceramics.

  5. Antibacterial and bioactive calcium titanate layers formed on Ti metal and its alloys.

    Science.gov (United States)

    Kizuki, Takashi; Matsushita, Tomiharu; Kokubo, Tadashi

    2014-07-01

    An antibacterial and bioactive titanium (Ti)-based material was developed for use as a bone substitute under load-bearing conditions. As previously reported, Ti metal was successively subjected to NaOH, CaCl2, heat, and water treatments to form a calcium-deficient calcium titanate layer on its surface. When placed in a simulated body fluid (SBF), this bioactive Ti formed an apatite layer on its surface and tightly bonded to bones in the body. To address concerns regarding deep infection during orthopedic surgery, Ag(+) ions were incorporated on the surface of this bioactive Ti metal to impart antibacterial properties. Ti metal was first soaked in a 5 M NaOH solution to form a 1 μm-thick sodium hydrogen titanate layer on the surface and then in a 100 mM CaCl2 solution to form a calcium hydrogen titanate layer via replacement of the Na(+) ions with Ca(2+) ions. The Ti material was subsequently heated at 600 °C for 1 h to transform the calcium hydrogen titanate into calcium titanate. This heat-treated titanium metal was then soaked in 0.01-10 mM AgNO3 solutions at 80 °C for 24 h. As a result, 0.1-0.82 at.% Ag(+) ions and a small amount of H3O(+) ions were incorporated into the surface calcium titanate layers. The resultant products formed apatite on their surface in an SBF, released 0.35-3.24 ppm Ag(+) ion into the fetal bovine serum within 24 h, and exhibited a strong antibacterial effect against Staphylococcus aureus. These results suggest that the present Ti metals should exhibit strong antibacterial properties in the living body in addition to tightly bonding to the surrounding bone through the apatite layer that forms on their surfaces in the body.

  6. Reinforcement of 2124 Al alloy with low micron SiC and nano Al2O3 via solid-state forming

    CSIR Research Space (South Africa)

    Gxowa, Z

    2015-07-01

    Full Text Available A powder metallurgical process was used to fabricate Metal Matrix Composites (MMCs). A 2124 aluminium alloy was reinforced with 5 and 10 vol. % of Al2O3 (40-70nm) to form Metal Matrix Nano Composites (MMNCs) as well as 10 and 15 vol. % of SiC (1...

  7. Dry metal forming of high alloy steel using laser generated aluminum bronze tools

    OpenAIRE

    Freiße Hannes; Köhler Henry; Seefeld Thomas; Vollertsen Frank

    2015-01-01

    Regarding the optimization of forming technology in economic and environmental aspects, avoiding lubricants is an approach to realize the vision of a new green technology. The resulting direct contact between the tool and the sheet in non-lubricated deep drawing causes higher stress and depends mainly on the material combination. The tribological system in dry sliding has to be assessed by means on the one hand of the resulting friction coefficient and on the other hand of the wear of the too...

  8. Isothermal superplastic solid state bonding of 40Cr and Cr12MoV steels based on surface modification

    Institute of Scientific and Technical Information of China (English)

    Zhang Keke; Zhang Zhanling; Liu Shuai; Yue Yun; Ma Ning; Yang Yunlin

    2009-01-01

    Based on the feasibility of isothermal superplastic solid state bonding of 40Cr and Cr12MoV steels, the surfaces of both steels to be bonded were ultra-fined through high frequency hardening, then the superplastic solid state bonding were conducted, the microstructure and fracture surface of bonded joint were observed and analysed, and bonding mechanisms was researched. The experimental results show that with the sample surfaces of 40Cr and Cr12MoV steels after the high frequency hardening, under the prepressing stress of 56.6 MPa, initial strain rate of 1.5×10~(-2) min~(-1) and at the bonding temperature of 800-820℃, the superplastic solid state bonding can be carried out in about 3.5min, and the joint strength is up to that of 40Cr steel base metal and the radial expansion ratio of the joint does not exceed 6%. The superplastic solid state bonding parameter of both steels is within the ranges of the isothermal compressive superplastic deformation of Cr12MoV steel, and the deformation in Cr12MoV steel side near the interfacial zone of joint presents the characteristic of superplasticity. In bonding process, the atoms in two sides of joint interface have diffused each other.

  9. Vanadium Alloyed PVD CrAlN Coatings for Friction Reduction in Metal Forming Applications

    Directory of Open Access Journals (Sweden)

    K. Bobzin

    2012-06-01

    Full Text Available Hard coatings deposited on forming tools are used to improve the forming process and to increase tool life. The decrease of tool wear and reduction of friction are the main motivations for the development of self-lubricating coatings for forming applications at elevated temperatures. In the present study (Cr,Al,VN (Physical Vapour Deposition coatings with 5, 11 and 20 at % vanadium were deposited via a combination of HPPMS (High Power Pulse Magnetron Sputtering technology and direct current (DC Magnetron Sputter Ion Plating (MSIP PVD. The hardness and Young’s Modulus of the coatings were investigated by nanoidentation. Furthermore, high temperature Pin-on-Disk (PoD tribometer measurements against Ck15 (AISI 1015 were realized at different temperatures and compared with a (Cr,AlN reference hard coating. The samples were analyzed by means of SEM (Scanning Electron Microscopy and XRD (X-Ray Diffraction measurements after Pin-on-Disk (PoD tests. Moreover TEM (Transmission Electron Microscopy analyses were carried out after 4 h annealing at 800 °C in ambient air to investigate the diffusion of vanadium to the coating surface. The tribological results at 800 °C show no improvement of the friction coefficient for the pure (Cr,AlN coating and for the layer with 5 at % V. A time-dependent decrease of the friction coefficient was achieved for the coatings with 11 at % V (µ=0.4 and 20 at % V (µ=0.4 at 800 °C.

  10. Tool degradation during sheet metal forming of three stainless steel alloys

    DEFF Research Database (Denmark)

    Wadman, Boel; Nielsen, Peter Søe; Wiklund, Daniel

    2010-01-01

    To evaluate if changes in tool design and tool surface preparation are needed when low-Ni stainless steels are used instead of austenitic stainless steels, the effect on tool degradation in the form of galling was investigated with three different types of stainless steel. The resistance to tool...... degradation was analysed by the strip reduction test, simulating resistance to galling during ironing. It was shown that the surface condition of both the tools and the sheet metal was of importance to the galling resistance. Numerical simulations of the experimental tests were compared with the experimental...

  11. Microstructure evolution in a large-grained TiAl alloy

    Institute of Scientific and Technical Information of China (English)

    孙锋; 林栋樑

    2002-01-01

    Microstructure evolution during superplastic deformation of a large-grained TiA l alloys with near-γ microstructure was characterized by orientation imaging microscopy (OIM) and transmission electron microscopy (TEM). In OIM, significant grain refinement is observed at different strain levels with an increase in the density of low angle grain boundaries and high angle grain boundaries. A direct evidence of dynamic formation of grain boundaries with misorientation of 15 °~30° during deformation is found, which is a result of subboundary evolutio n. The formation of subboundaries by intersecting dislocations, and the evidence of dislocation glide in the interior of grains are revealed by TEM observations. A continuous recovery and recrystallization process similar to that in FeAl and Fe3Al is proposed as superplastic deformation mechanism in the large-grained TiAl alloy.

  12. Investigation of the inner corrosion layer formed in pulse electrodeposition coating on Mg-Sr alloy and corresponding degradation behavior.

    Science.gov (United States)

    Shangguan, Yongming; Wan, Peng; Tan, Lili; Fan, Xinmin; Qin, Ling; Yang, Ke

    2016-11-01

    Magnesium-based metals are considered as promising biodegradable orthopedic implant materials due to their potentials of enhancing bone healing and reconstruction, and in vivo absorbable characteristic without second operation for removal. However, the rapid corrosion has limited their clinical applications. Ca-P coating by electrodeposition has been supposed to be effective to control the degradation rate and enhance the bioactivity. In this work, a brushite coating was fabricated on the Mg-Sr alloy by pulse electrodeposition (PED) to evaluate its efficacy for orthopedic application. Interestingly, an inner corrosion layer was observed between the PED coating and the alloy substrate. Meanwhile the results of in vitro immersion and electrochemical tests showed that the corrosion resistance of the coated alloy was undermined in comparison with the uncoated alloy. It was deduced that the existence of this corrosion layer was attributed to the worse corrosion performance of the alloy. The mechanism on formation of the inner corrosion layer and its influence on consequent degradation were analyzed. It can be concluded that the electrodeposition coating should be not suitable for those magnesium alloys with poor corrosion resistance such as the Mg-Sr alloy. More importantly, it should be noted that the process of coating formation combined with the nature of substrate alloy is important to evaluate the efficacy of coating for biodegradable Mg-based implants application.

  13. Glass forming range of the Ti-Fe-Si amorphous alloys: An effective materials-design approach coupling CALPHAD and topological instability criterion

    Science.gov (United States)

    Zhao, Guo-Hua; Mao, Huahai; Louzguine-Luzgin, Dmitri V.

    2016-11-01

    A method of composition design for metallic glasses was proposed by using the Calculation of Phase Diagrams (CALPHAD) with the assistance of the topological instability criterion. This methodology was demonstrated in the quick and effective searching of glass-forming regions for Ti-Fe-Si and Ti-Zr-Fe-Si alloys containing no biologically toxic elements, e.g., Ni and Cu. In addition, the Ti-Fe-Si system may promote the glass formation owing to the existence of a deep eutectic at the Ti-rich corner. A self-consistent thermodynamic database was constructed based on the CALPHAD approach. The liquidus projection, isothermal sections, and the enthalpy of mixing were calculated by using the database. On the basis of these calculations coupling with the topological instability "lambda λ criterion," the potential glass-forming alloy compositions in a narrow region were suggested for experimental validation. Thereafter, the isothermal sections of the Ti-Zr-Fe-Si quaternary system were calculated at certain contents of Zr. The designed alloys were prepared by arc-melting and followed by melt-spinning to the ribbon shape. The experimental verifications matched reasonably well with the theoretical calculations. This work offers new insights for predicting glass-forming alloys based on thermodynamic arguments; it shall be of benefit for the exploration of new metallic glasses.

  14. Preparation and Characterization of Amorphous Layer on Aluminum Alloy Formed by Plasma Electrolytic Deposition (PED)

    Institute of Scientific and Technical Information of China (English)

    GUAN Yong-jun; XIA Yuan

    2004-01-01

    In this investigation, protective layers were formed on aluminum substrate by Plasma Electrolytic Deposition (PED) using sodium silicate solution. The relation between the thickness of the layer and process time were studied. XRD,SEM, EDS were used to study the layer's structure, composition and micrograph. The results show that the deposited layers are amorphous and contain mainly oxygen, silicon, and aluminum. The possible formation mechanism of amorphous [Al-Si-O] layer was proposed: During discharge periods, Al2O3 phase of the passive film and SiO32-near the substrate surface are sintered into xSiO2(1-x)Al2O3 and then transformed into amorphous [Al-Si-O] phase.

  15. Effect of the existing form of Cu element on the mechanical properties, bio-corrosion and antibacterial properties of Ti-Cu alloys for biomedical application.

    Science.gov (United States)

    Zhang, Erlin; Wang, Xiaoyan; Chen, Mian; Hou, Bing

    2016-12-01

    Ti-Cu alloys have exhibited strong antibacterial ability, but Ti-Cu alloys prepared by different processes showed different antibacterial ability. In order to reveal the controlling mechanism, Ti-Cu alloys with different existing forms of Cu element were prepared in this paper. The effects of the Cu existing form on the microstructure, mechanical, corrosion and antibacterial properties of Ti-Cu alloys have been systematically investigated. Results have shown that the as-cast Ti-Cu alloys showed a higher hardness and mechanical strength as well as a higher antibacterial rate (51-64%) but a relatively lower corrosion resistance than pure titanium. Treatment at 900°C/2h (T4) significantly increased the hardness and the strength, improved the corrosion resistance but had little effect on the antibacterial property. Treatment at 900°C/2h+400°C/12h (T6) increased further the hardness and the mechanical strength, improved the corrosion resistance and but also enhanced the antibacterial rate (>90%) significantly. It was demonstrated that the Cu element in solid solution state showed high strengthening ability but low antibacterial property while Cu element in Ti2Cu phase exhibited strong strengthening ability and strong antibacterial property. Ti2Cu phase played a key role in the antibacterial mechanism. The antibacterial ability of Ti-Cu alloy was strongly proportional to the Cu content and the surface area of Ti2Cu phase. High Cu content and fine Ti2Cu phase would contribute to a high strength and a strong antibacterial ability.

  16. Investigation of the structure/property relationship of spray-formed 7XXX series high-strength aluminum alloys and their metal matrix composites

    Science.gov (United States)

    Sharma-Judd, Malavika M.

    2000-12-01

    The purpose of this investigation was to identify the structure/property relationship of spray formed 7XXX series alloys. High solute, ultra-high strength 7XXX series aluminum alloys with solute contents close to equilibrium solid solubility limits of the Al-Zn-Mg-Cu system have been produced by rapid solidification using spray deposition. The process yields massive preforms directly from the liquid state. Various elements, including chromium, manganese, silver, zirconium and scandium, were incorporated to produce a variety of microstructures and mechanical properties. SiC particulate was added to these same alloy compositions to produce metal matrix composites (MMCs). The resulting extruded products in the T6 and T7 conditions were evaluated and compared. Under peak-aged conditions in the unreinforced materials, strengths in excess of 860 MPa were achieved, with one alloy exceeding 900 MPa. Apart from the elongation to failure, the mechanical properties of the composite materials were equal to or superior to those of their unreinforced counterparts. The superior strength properties of the spray formed alloys were attributed to two major substructures with different scale; nanometer sized eta ' metastable precipitates and slightly larger, but finely distributed dispersoids. The large volume fraction of plate-like eta' precipitates (average size 58A, ranging up to 73 A in diameter) were identified as having a hexagonal structure with lattice parameters a = 0.488 nm and c = 1.376. The remarkable strengthening is predominantly attributed to precipitation hardening. The enhanced mechanical properties of the MMC materials are attributed to the increased dislocation density, and thus, a higher concentration of structural particles compared to the unreinforced materials. Higher gas-to-metal ratios of 4.45, as opposed to lower gas-to-metal ratios of 1.95 produced a refined grain structure with an evenly distributed second phase. In both unreinforced and MMC materials

  17. A Combinatorial Approach to the Investigation of Metal Systems that Form Both Bulk Metallic Glasses and High Entropy Alloys

    Science.gov (United States)

    Welk, Brian A.; Gibson, Mark A.; Fraser, Hamish L.

    2016-03-01

    In this work, compositionally graded specimens were deposited using the laser engineered net-shaping (LENS™) additive manufacturing technique to study the glass-forming ability of two bulk metallic glass (BMG) and high entropy alloy (HEA) composite systems. The first graded specimen varied from Zr57Ti5Al10Cu20Ni8 (BMG) to CoCrFeNiCu0.5 (HEA) and the second graded specimen varied from TiZrCuNb (BMG) to (TiZrCuNb)65Ni35 (HEA). After deposition, laser surface melting experiments were performed parallel to the gradient to remelt and rapidly solidify the specimen. Scanning electron microscopy and energy dispersive x-ray spectroscopy were used to determine the morphology and composition variations in the as-deposited and laser surface melted phases. Selected area diffraction of the melt pool regions confirmed an almost fully amorphous region in the first gradient and an amorphous matrix/crystalline dendrite composite structure in the second gradient.

  18. Effects of lanthanum ion-implantation on microstructure of oxide film formed on Co-Cr alloy

    Institute of Scientific and Technical Information of China (English)

    JIN Huiming; ZHOU Xiaowei; ZHANG Linnan

    2008-01-01

    Isothermal and cyclic oxidizing behavior of Co-40Cr alloy and its lanthanum ion-implanted samples were studied at 1000℃ in the air by thermal-gravimetric analysis (TGA). Scanning electronic microscopy (SEM) and transmission electronic microscopy (TEM) were used to examine the morphology and structure of oxide film after oxidation. Secondary ion mass spectrum (SIMS) method was used to examine the binding energy change of chromium caused by La-doping and its influence on the formation of Cr2O3 film. Laser Raman spectrum was used to examine the stress changes within the oxide film. It was found that lanthanum implantation remarkably reduced isothermal oxidizing rate of Co-40Cr and improved anti-cracking and anti-spalling properties of Cr2O3 oxide film. The reasons for the improvement were mainly that the implanted lanthanum reduced the grain size and internal stress of Cr2O3 oxide and increased high temperature plasticity of the oxide film. Lanthanum mainly existed on the outer surface of Cr2O3 oxide film in the form of fine La2O3 and LaCrO3 spinel particles.

  19. Prediction of forming limit curve (FLC) for Al-Li alloy 2198-T3 sheet using different yield functions

    Institute of Scientific and Technical Information of China (English)

    Li Xiaoqiang; Song Nan; Guo Guiqiang; Sun Zhonggang

    2013-01-01

    The Forming Limit Curve (FLC) of the third generation aluminum-lithium (Al-Li) alloy 2198-T3 is measured by conducting a hemispherical dome test with specimens of different widths. The theoretical prediction of the FLC of 2198-T3 is based on the M-K theory utilizing respectively the von Mises, Hill’48, Hosford and Barlat 89 yield functions, and the different predicted curves due to different yield functions are compared with the experimentally measured FLC of 2198-T3. The results show that though there are differences among the four predicted curves, yet they all agree well with the experimentally measured curve. In the area near the planar strain state, the predicted curves and experimentally measured curve are very close. The predicted curve based on the Hosford yield function is more accurate under the tension-compression strain states described in the left part of the FLC, while the accuracy is better for the predicted curve based on Hill’48 yield function under the tension-tension strain states shown in the right part.

  20. CRADA NFE-08-01456 Evaluation of Alumina-Forming Austenitic Stainless Steel Alloys in Industrial Gas Turbines

    Energy Technology Data Exchange (ETDEWEB)

    Brady, Michael P [ORNL; Pint, Bruce A [ORNL; Unocic, Kinga A [ORNL; Yamamoto, Yukinori [ORNL; Kumar, Deepak [ORNL; Lipschutz, Mark D. [Solar Turbines, Inc.

    2011-09-01

    Oak Ridge National Laboratory (ORNL) and Solar Turbines Incorporated (Solar) participated in an in-kind cost share cooperative research and development agreement (CRADA) effort under the auspices of the Energy Efficiency and Renewable Energy (EERE) Technology Maturation Program to explore the feasibility for use of developmental ORNL alumina-forming austenitic (AFA) stainless steels as a material of construction for industrial gas turbine recuperator components. ORNL manufactured lab scale foil of three different AFA alloy compositions and delivered them to Solar for creep properties evaluation. One AFA composition was selected for a commercial trial foil batch. Both lab scale and the commercial trial scale foils were evaluated for oxidation and creep behavior. The AFA foil exhibited a promising combination of properties and is of interest for future scale up activities for turbine recuperators. Some issues were identified in the processing parameters used for the first trial commercial batch. This understanding will be used to guide process optimization of future AFA foil material production.

  1. Critical Strain Rate of Uniform Deformation in Cross Section at Diffusion Dominated Superplastic Tensile Test%扩散控制超塑性拉伸断面均匀收缩的临界应变速率

    Institute of Scientific and Technical Information of China (English)

    张诗昌; 罗敏; 杨倩; 陈伟

    2012-01-01

    A parameter named λ was put forward and an equation was deduced to characterize the uniform deformation of superplastic tensile test under the conditions of difiusion dominated deformation. By solving the equation at λ=0, a critical strain rate εcn of uniform deformation was got ten. The results show that εcn is direct proportion to strain and diffusion coefficient and inversely proportion to the cross section area of undeformed specimens. The results of the tested A of AZ31 alloy under superplastic tensile show that A is becoming significant small and the cross section of the specimen tends to be uniform deformation when strain rate is near εcn.%引入了一个衡量超塑性拉伸断面收缩均匀性的特征参数λ,在假设变形以扩散为主的条件下,导出了λ的表达式.令λ=0时,得到断面均匀收缩的临界应变速率(.εcn).(.εcn)与扩散系数和应变量成正比,与试样原始截面积成反比.对AZ31镁合金超塑性拉伸特征参数λ值的测定结果表明;当应变速率越接近于临界应变速率,λ越小,试样越接近均匀变形.

  2. Influence of carbon content on superplastic behaviour in Ti and B doped Cr-Mo steels; Ti, B tenka kuromu moribudenko no chososei ni oyobosu tanso gan`yuryo no eikyo

    Energy Technology Data Exchange (ETDEWEB)

    Aramaki, M.; Nakai, O.; Onodera, R.; Higashida, K. [Kyushu University, Fukuoka (Japan). Faculty of Engineering

    1997-12-01

    Superplasticity has been investigated in various ferrous alloys and steels. However, in these materials, especially in the hypoeutectoid steel bellow A1 temperature, the relationship between the content of carbon and elongation to failure is not obvious. In the present investigation, the influence of carbon content on superplastic behaviour is studied using carbon steels based on Cr-Mo steel. In order to obtain the fine grain structure, a small amount of Ti and B were added and the content of carbon was controlled to be in the range of 0.24% to 0.83%. The largest value of elongation to failure was 644% which was obtained by the tensile test of the specimen containing 0.58% carbon. The temperature and strain rate at which the maximum value was obtained were 710degC and 5 times 10{sup -4}s{sup -1}, respectively. Of all the specimens, this. specimen had the minimum grain size. Moreover, the area fraction of carbide took the maximum value at the temperature where the largest elongation value was obtained. These results show that the addition of carbon has an effect on grain refinement by formation of carbide, but excess amounts of carbons (>0.6%) bring about premature failure because of coarse microstructure and larger carbide. 17 refs., 9 figs., 1 tab.

  3. Microstructural evolution and mechanical, and corrosion property evaluation of Cu-30Ni alloy formed by Direct Metal Deposition process

    Energy Technology Data Exchange (ETDEWEB)

    Bhattacharya, S., E-mail: sudipb@umich.edu [University of Michigan, 2350 Hayward Street, 2040 G.G. Brown Laboratories, Ann Arbor, MI 48109 (United States); Dinda, G.P.; Dasgupta, A.K. [Center for Advanced Technologies, Focus: HOPE, Detroit, MI 48238 (United States); Natu, H.; Dutta, B. [POM Group Inc., Auburn Hills, MI 48326 (United States); Mazumder, J. [University of Michigan, 2350 Hayward Street, 2040 G.G. Brown Laboratories, Ann Arbor, MI 48109 (United States); POM Group Inc., Auburn Hills, MI 48326 (United States)

    2011-06-02

    Research highlights: > Cu-30Ni alloy was successfully deposited with CO{sub 2} laser DMD system on C71500 substrate. > The microstructure consists of a single solid solution phase. > Columnar dendrites growing into equiaxed dendrites form layer microstructure. > Dendrite growth direction and angle relative to substrate was maintained in each layer. > Lattice parameter of solid solution phase is longer than reported lattice parameters. - Abstract: In the current investigation Cu-30Ni alloy was successfully laser deposited on a rolled C71500 plate substrate by Direct Metal Deposition technology. The microstructural investigation of the clad was performed using optical and scanning electron microscopy. The phase and crystal structure analysis was performed using X-ray diffraction technique and transmission electron microscopy. The microstructure consisted of columnar and equiaxed dendrites with face centered cubic crystal structure. The dendrites grew epitaxially from the substrate and layer and bead boundaries. Dendrites' growth direction <0 0 1> and growth angle 60{sup o} was maintained in each layer. The average primary dendritic arm spacing at the bottom part of the layers was about 7.5 {mu}m and average secondary dendritic arm spacing in the upper part of the layer varied between 2 {mu}m and 4.5 {mu}m. The lattice parameter of the identified phase was found to be longer than that reported in literature. The reported lattice parameters in literature are however from samples processed under equilibrium conditions. The microhardness of the clad was found to be less than the substrate but very consistent along the clad. Cu-30Ni clad specimen showed higher ultimate tensile strength but lower yield strength and percentage elongation as compared to the C71500 substrate. DMD Cu-30Ni clad/C71500 substrate specimen showed the worst mechanical properties. The corrosion resistance of the specimens was found to decrease in the order DMD Cu-30Ni clad, half-and-half DMD Cu

  4. Phase Transformation Behavior of Oxide Particles Formed in Mechanically Alloyed Fe-5Y{sub 2}O{sub 3} Powder

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Ga Eon; Choi, Jung-Sun; Noh, Sanghoon; Kang, Suk Hoon; Choi, Byoung Kwon; Kim, Tae Kyu [Korea Atomic Energy Research Institute, Deajeon (Korea, Republic of); Kim, Young Do [Hanyang University, Seoul (Korea, Republic of)

    2017-05-15

    The phase transformation behavior of the oxides formed in mechanically alloyed Fe-5Y{sub 2}O{sub 3} powder is investigated. Non-stoichiometric Y-rich and Fe-rich oxides with sizes of less than 300 nm are observed in the mechanically alloyed powder. The diffusion and redistribution reactions of the elements in these oxides during heating of the powder above 800 ℃ were observed, and these reactions result in the formation of a Y{sub 3}Fe{sub 5}O{sub 12} phase after heating at 1050 ℃. Thus, it is considered that the Y{sub 2}O{sub 3} powder and some Fe powder are formed from the non-stoichiometric Y-rich and Fe-rich oxides after the mechanical alloying process, and a considerable energy accumulated during the mechanical alloying process leads to a phase transformation of the Y-rich and Fe-rich oxides to Y{sub α}Fe{sub β}O{sub γ}-type phase during heating.

  5. Optimizing cathodic electrodeposition parameters of ceria coating to enhance the oxidation resistance of a Cr{sub 2}O{sub 3}-forming alloy

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Xu, E-mail: xuw388@mail.usask.ca; Fan, Fan; Szpunar, Jerzy A.

    2016-07-29

    Nano-ceria coating was deposited onto a chromium oxide forming alloy through galvanostatic cathodic electro-deposition method in cerium nitrate electrolyte. The electrochemical behavior and influence of main deposition parameters of current density, deposition time, and temperature were studied. It was seen that the crystal size decreased with increasing of current density while micro-cracks were also observed at higher current density. Slightly increasing of crystal size and smoothing of surface morphology were seen with increasing of deposition time. It was reported that the bath temperature has the most significant effect on crystal size and surface morphology of the deposit. Green rust as corrosion product was also observed with deposition temperatures higher than 35 °C. Optimized deposition parameters were used to produce homogeneous, continuous and green rust-free coatings which enhance the oxidation resistance of alloy 230. The electro-deposition process was found to be an accessible and efficient method to prepare nano-crystalline ceria coating. - Highlights: • Electrodeposition was used to make ceria coating on a chromium oxide forming alloy; • Deposition parameters of current density, time and temperature were investigated; • Crystal size and morphology of coating vary with changing of deposition parameters; • Coating prepared with optimized parameters reduced oxidation rate of alloy 230.

  6. The Effect of Normal Force on Tribocorrosion Behaviour of Ti-10Zr Alloy and Porous TiO2-ZrO2 Thin Film Electrochemical Formed

    Science.gov (United States)

    Dănăilă, E.; Benea, L.

    2017-06-01

    The tribocorrosion behaviour of Ti-10Zr alloy and porous TiO2-ZrO2 thin film electrochemical formed on Ti-10Zr alloy was evaluated in Fusayama-Mayer artificial saliva solution. Tribocorrosion experiments were performed using a unidirectional pin-on-disc experimental set-up which was mechanically and electrochemically instrumented, under various solicitation conditions. The effect of applied normal force on tribocorrosion performance of the tested materials was determined. Open circuit potential (OCP) measurements performed before, during and after sliding tests were applied in order to determine the tribocorrosion degradation. The applied normal force was found to greatly affect the potential during tribocorrosion experiments, an increase in the normal force inducing a decrease in potential accelerating the depassivation of the materials studied. The results show a decrease in friction coefficient with gradually increasing the normal load. It was proved that the porous TiO2-ZrO2 thin film electrochemical formed on Ti-10Zr alloy lead to an improvement of tribocorrosion resistance compared to non-anodized Ti-10Zr alloy intended for biomedical applications.

  7. Cathode Formed by Thermal Evaporation of Ba:Al Alloy and Estimations of Barrier Height in an Organic LED

    Institute of Scientific and Technical Information of China (English)

    DING Lei; ZHANG Fang-Hui

    2011-01-01

    @@ It is demonstrated that barium and aluminum alloy synthesized by melting in a glass tube under low vac- uum is applicable for organic laser emitting diodes (LEDs) as a thin film cathode.The alloy film obtained by the thermal evaporation of pre-synthesized alloy is used in a single-boat organic LED device with the struc- ture: indium tin oxide (ITO)/4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl(NPB)/tris-(8-hydroxyquinoline) aluminum(Alq) /barium:aluminum alloy.The experimental results show that devices with this alloy film cathode exhibit better current densityovoltage-luminance characteristics than those with a conventional pure AI cathode, and more weight of barium in aluminum leads to better performance of the devices.Characteristics of cur- rent density versus voltage for the electron-only devices are fitted by the Richardson-Schottky emission model, indicating that the electron injection barrier has a decrease of about 0.3 eV by this alloy cathode.%It is demonstrated that barium and aluminum alloy synthesized by melting in a glass tube under low vacuum is applicable for organic laser emitting diodes (LEDs) as a thin Rim cathode. The alloy Him obtained by the thermal evaporation of pre-synthesized alloy is used in a single-boat organic LED device with the structure: indium tin oxide (ITO)/4,4'-bis[N-(l-naphthyl)-N-phenylamino]biphenyl(NPB)/tris-(8-hydroxyquinoline) aluminum(Alq3)/barium:aluminum alloy. The experimental results show that devices with this alloy film cathode exhibit better current density-voltage-luminance characteristics than those with a conventional pure Al cathode, and more weight of barium in aluminum leads to better performance of the devices. Characteristics of current density versus voltage for the electron-only devices are fitted by the Richardson-Schottky emission model, indicating that the electron injection barrier has a decrease of about 0.3 eV by this alloy cathode.

  8. Finite element modelling of shot peening and peen forming processes and characterisation of peened AA2024-T351 aluminium alloy

    Science.gov (United States)

    Gariepy, Alexandre

    The main purpose of this thesis was to develop and validate finite element (FE) simulation tools for shot peening and peen forming. The specific aim was to achieve quantitatively accurate predictions for both processes and demonstrate the potential of reliable FE modelling for scientific investigation and industrial applications. First, an improved dynamic impact model that takes into account the stochastic nature of shot peening was proposed by carefully studying its dimensions, introducing a dispersion of shot sizes and significantly reducing its computational cost. In addition, cyclic mechanical testing was conducted to define a suitable material constitutive theory for aluminium alloy (AA) 2024-T3/T351 subjected to shot peening. By combining a realistic shot peening model with an appropriate material law, fairly good residual stress predictions were achieved for three different sets of shot peening parameters. Second, an experimental and numerical characterization of AA2024-T351 shot peened with parameters representative of fatigue life improvement applications was conducted. Multiple techniques, such as micro-indentation, residual stress determination and electron backscatter diffraction, were combined to gain a better understanding of the influence of shot peening on the material. The potential uses of finite element simulation to complement experimental data were also studied. The material heterogeneity arising from the random impact sequence was investigated and it was found that the impact modelling methodology could provide useful information on such heterogeneities. Third, a novel peen forming simulation methodology was introduced. The impact model provided the necessary input data as part of a multiscale approach. Numerically calculated unbalanced induced stress profiles were input into shell elements and the deformed shape after peen forming was computed as a springback analysis. In addition, a simple interpolation method was proposed to model the

  9. Development of Cutting Tool Through Superplastic Boronizing of Duplex Stainless Steel

    Science.gov (United States)

    Jauhari, Iswadi; Harun, Sunita; Jamlus, Siti Aida; Sabri, Mohd Faizul Mohd

    2017-03-01

    In this study, a cutting tool is developed from duplex stainless steel (DSS) using the superplastic boronizing technique. The feasibility of the development process is studied, and the cutting performances of the cutting tool are evaluated and compared with commercially available carbide and high-speed steel (HSS) tools. The superplastically boronized (SPB) cutting tool yielded a dense boronized layer of 50.5 µm with a surface hardness of 3956 HV. A coefficient of friction value of 0.62 is obtained, which is lower than 1.02 and 0.8 of the carbide and HSS tools. When tested on an aluminum 6061 surface under dry condition, the SPB cutting tool is also able to produce turning finishing below 0.4 µm, beyond the travel distance of 3000 m, which is comparable to the carbide tool, but produces much better results than HSS tool. Through superplastic boronizing of DSS, it is possible to produce a high-quality metal-based cutting tool that is comparable to the conventional carbide tool.

  10. SUPERPLASTICITY OF A WATER-QUENCHED AND TEMPERED 40Cr STEEL

    Institute of Scientific and Technical Information of China (English)

    X.J.Xu; G.L.Liu; L.J Shi; X.N.Cheng; L.Cai

    2004-01-01

    The superplastic deformation characteristics, of commercial 40Cr (i.e., 5140) steel that was water-quenched only 1 times and subsequent high-temperature tempered, were investigated.The results showed that the 40Cr steel has a fine grain of 10-15μm at room temperature,and exhibits a tensile elongation of 304%, a true flow stress of 89.3MPa and a strain rate sensitivity m-value of 0.227 at the initial strain rate of 1.0×10-3s-1and at the temperature of 750℃. The final fracture is caused by the development of neck. The experimental result of elongation is in good agreement with the theoretically predicated value according to the analytical expression ef = (1/f)mexp(nv+mε)-1(where ef, m, f, nv and e is respectively elongation, average strain rate sensitivity, initial geometric defect, average strain hardening sensitivity at constant deformation velocity and average true strain). The fracture surface is intergraular, and superplastic deformation induces an equiaxed and grown grain. Decreasing strain rate increases tensile elongation and strain rate sensitivity m-value. The primary superplastic deformation mechanism is thought to be atom-diffusion-controlled grain boundary sliding.

  11. Development of Cutting Tool Through Superplastic Boronizing of Duplex Stainless Steel

    Science.gov (United States)

    Jauhari, Iswadi; Harun, Sunita; Jamlus, Siti Aida; Sabri, Mohd Faizul Mohd

    2017-01-01

    In this study, a cutting tool is developed from duplex stainless steel (DSS) using the superplastic boronizing technique. The feasibility of the development process is studied, and the cutting performances of the cutting tool are evaluated and compared with commercially available carbide and high-speed steel (HSS) tools. The superplastically boronized (SPB) cutting tool yielded a dense boronized layer of 50.5 µm with a surface hardness of 3956 HV. A coefficient of friction value of 0.62 is obtained, which is lower than 1.02 and 0.8 of the carbide and HSS tools. When tested on an aluminum 6061 surface under dry condition, the SPB cutting tool is also able to produce turning finishing below 0.4 µm, beyond the travel distance of 3000 m, which is comparable to the carbide tool, but produces much better results than HSS tool. Through superplastic boronizing of DSS, it is possible to produce a high-quality metal-based cutting tool that is comparable to the conventional carbide tool.

  12. Mechanical analysis of temperature impact on stability during superplastic tensile deformation

    Institute of Scientific and Technical Information of China (English)

    SONG; Yuquan; GUAN; Zhiping; WANG; Minghui; SONG; Jiawang

    2006-01-01

    Based on state equation that stress is the function of strain, strain-rate and temperature, the paper establishes the differential constitutive equation used for analyzing load-stability and the variational constitutive equation used for analyzing geometry-stability during superplastic tensile deformation, which contain strain hardening index, strain-rate sensitivity index, temperature sensitivity index introducted for the first time and temperature undulation index introducted for the first time in the paper. And then, based on the universal condition of plastic elementary theory, the paper analyzes load-stability and geometry-stability under continuously rising temperature and under the non-uniform temperature along the axes of specimen respectively. The results prove the impact of continuously rising speed and non-uniform value of temperature on deformation stability is that the faster temperature rises and the more non-uniform temperature is, the smaller the corresponding uniform strain of load-stability and geometry-stability are; strain hardening index is the necessary condition of stability during superplastic tensile deformation, and geometry-instability will not happen when load-instability occurs, but happen when uniform deformation has lasted after load-instability; in the superplastic temperature field, constant temperature is not necessary condition of superplasticitiy, but during the deformation, the slower temperature rises and the more uniform temperature is, the more stable deformation is.

  13. Effect of thermal treatment on the bio-corrosion and mechanical properties of ultrafine-grained ZK60 magnesium alloy.

    Science.gov (United States)

    Choi, H Y; Kim, W J

    2015-11-01

    The combination of solid solution heat treatments and severe plastic deformation by high-ratio differential speed rolling (HRDSR) resulted in the formation of an ultrafine-grained microstructure with high thermal stability in a Mg-5Zn-0.5Zr (ZK60) alloy. When the precipitate particle distribution was uniform in the matrix, the internal stresses and dislocation density could be effectively removed without significant grain growth during the annealing treatment (after HRDSR), leading to enhancement of corrosion resistance. When the particle distribution was non-uniform, rapid grain growth occurred in local areas where the particle density was low during annealing, leading to development of a bimodal grain size distribution. The bimodal grain size distribution accelerated corrosion by forming a galvanic corrosion couple between the fine-grained and coarse-grained regions. The HRDSR-processed ZK60 alloy with high thermal stability exhibited high corrosion resistance, high strength and high ductility, and excellent superplasticity, which allow the fabrication of biodegradable magnesium devices with complicated designs that have a high mechanical integrity throughout the service life in the human body.

  14. Corrosion behaviour of Al86.0Co7.6Ce6.4 glass forming alloy with different microstructures

    Science.gov (United States)

    Li, C. L.; Wang, P.; Sun, S. Q.; Voisey, K. T.; McCartney, D. G.

    2016-10-01

    It has been extensively reported that Al-TM-RE amorphous alloy has excellent mechanical properties and corrosion resistance. In this paper, the corrosion behaviour of an Al86.0Co7.6Ce6.4 glass forming alloy with different microstructures is investigated through electrochemical experiments and microscopy. Results show the effect of microstructure. Laser and electron beam surface melting processes produce rapidly solidified microstructures with different extents of passivation compared to the as-cast alloy. An amorphous surface layer produced by these surface treatments had superior corrosion resistance compared with the crystalline alloy. As-cast and laser treated Al86.0Co7.6Ce6.4 suffered localised corrosion in the Al/Al11Ce3 eutectic region whereas the amorphous material exhibited uniform corrosion. Compared with the electrochemical behaviour of AA2024 and Alclad 2024, the fully amorphous layer prepared by combined laser-electron beam treatment exhibited advantages such as the more negative corrosion potential, the higher pitting potential and the uniform corrosion mechanism, which indicates that this material is a potential anode candidate in the protection of AA2024.

  15. Simultaneous aluminizing and chromizing of steels to form (Fe,Cr){sub 3}Al coatings and Ge-doped silicide coatings of Cr-Zr base alloys

    Energy Technology Data Exchange (ETDEWEB)

    Zheng, M.; He, Y.R.; Rapp, R.A. [Ohio State Univ., Columbus, OH (United States). Dept. of Materials Science and Engineering

    1997-12-01

    A halide-activated cementation pack involving elemental Al and Cr powders has been used to achieve surface compositions of approximately Fe{sub 3}Al plus several percent Cr for low alloy steels (T11, T2 and T22) and medium carbon steel (1045 steel). A two-step treatment at 925 C and 1150 C yields the codeposition and diffusion of aluminum and chromium to form dense and uniform ferrite coatings of about 400 {micro}m thickness, while preventing the formation of a blocking chromium carbide at the substrate surfaces. Upon cyclic oxidation in air at 700 C, the coated steel exhibits a negligible 0.085 mg/cm{sup 2} weight gain for 1900 one-hour cycles. Virtually no attack was observed on coated steels tested at ABB in simulated boiler atmospheres at 500 C for 500 hours. But coatings with a surface composition of only 8 wt% Al and 6 wt% Cr suffered some sulfidation attack in simulated boiler atmospheres at temperatures higher than 500 C for 1000 hours. Two developmental Cr-Zr based Laves phase alloys (CN129-2 and CN117(Z)) were silicide/germanide coated. The cross-sections of the Ge-doped silicide coatings closely mimicked the microstructure of the substrate alloys. Cyclic oxidation in air at 1100 C showed that the Ge-doped silicide coating greatly improved the oxidation resistance of the Cr-Zr based alloys.

  16. Porous TiO2-ZrO2 thin film formed by electrochemical technique to improve the biocompatibility of titanium alloy in physiological environment

    Science.gov (United States)

    Benea, L.; Dănăilă, E.; Ponthiaux, P.

    2017-02-01

    Porous Ti and Ti alloys have received increasing research interest for bone tissue engineering, especially for dental and orthopaedic implants because they provide cell ingrowths and vascularization, improving of adhesion and osseointegration. The tribocorrosion process is encountered in orthopaedic and dentistry applications, since it is known that the implants are often exposed to simultaneous chemical/electrochemical and mechanical stresses. The purpose of this study was to carry out a systematic investigation of the tribo-electrochemical performance of porous TiO2-ZrO2 thin film formed by anodization of Ti-10Zr alloy surface in an artificial saliva solution and to compare the resulted performance with that of the untreated Ti-10Zr alloy surface in order to be applied for biomedical use. The in situ electrochemical technique used for investigation of tribo-electrochemical degradation was the open circuit potential (OCP) measurement performed before, during and after sliding tests. The results presented herein show that controlled anodic oxidation method can significantly improve the tribocorrosion and friction performances of Ti-10Zr alloy surface intended for biomedical applications.

  17. Influence of potassium pyrophosphate in electrolyte on coated layer of AZ91 Mg alloy formed by plasma electrolytic oxidation

    Institute of Scientific and Technical Information of China (English)

    Jin-Young CHO; Duck-Young HWANG; Dong-Heon LEE; Bongyoung YOO; Dong-Hyuk SHIN

    2009-01-01

    The effect of potassium pyrophosphate in the electrolyte on plasma electrolytic oxidation (PEO) process for AZ91 Mg alloy was investigated. The morphologies and chemical compositions of the coating layer on the AZ91 Mg alloy were evaluated and corrosion resistance was also estimated by potentiodynamic polarization analysis. The coating layer on AZ91 Mg alloy coated from the Bath 2 containing 0.03 mol/L of potassium pyrophosphate for 360 s exhibited considerably dense structure and contained 11%-18% (mass fraction) of phosphorous. The higher content of phosphorous of coating layer coated from Bath 2 could be detected at the bottom of oxide layer, which strongly implied that the phosphorous ion might be concentrated at the barrier layer. Corrosion potential of coating layer of AZ91 Mg alloy increased and corrosion current density decreased with increasing the concentration of potassium pyrophosphate. The polarization resistance (Rp) of coating layer of AZ91 Mg alloy coated from Bath 2 was 4.65×107 Ω/cm2, which was higher than that (Rp=3.56×104 Ω/cm2) of the sample coated from electrolyte without potassium pyrophosphate. The coating layer coated from Bath 2 containing 0.03 mol/L potassium pyrophosphate exhibited the best corrosion resistance.

  18. Zr基大块非晶合金在过冷液相区超塑性成形的摩擦行为及机理研究%Study on the Friction Behavior and Mechanism of Zr-based Bulk Metallic Glass Superplastic Forming in the Supercooled Liquid Region

    Institute of Scientific and Technical Information of China (English)

    郑志镇; 成蛟; 王新云; 李建军

    2009-01-01

    The friction behavior of Zr_(55) Al_(10)Ni_5Cu_(30) bulk metallic glass in the supercooled liquid region was investigated. The influence of forming temperature and velocity on friction factor was established by double cup extrusion test. The calibration curves of friction factor were evaluated by FE simulation and Kawamura's constitutive equation was adopted. Constant parameters in the constitutive equation were acquired by fitting the data from compression test. The results indicate that the friction factor of bulk metallic glass forming in the supercooled liquid region is between 0. 2 and 0. 7. With the temperature rising, the friction factor decreases in general under a low forming velocity. However, the friction factor increases slightly and then decreases abruptly under a high forming velocity. In low temperature area of supercooled liquid region, the friction factor increases abruptly with increasing of the forming velocity. While in high temperature area of supercooled liquid region, the friction factor decreases slightly with increasing of the forming velocity. The friction mechanism of bulk metallic glass forming in supercooled liquid region was analyzed by modern tribology theory. Adhesion is the dominant factor contributing to the friction of bulk metallic glass.%采用双杯挤压方法研究了成形温度、应变速率等工艺参数对Zr_(55) Al_(10) Ni_5 Cu_(30)块体非晶合金在过冷液相区塑性成形时模具和零件之间的摩擦行为的影响.采用有限元模拟方法获得大块非晶合金双杯挤压的摩擦因数标定曲线,有限元模拟中非晶合金的变形采用Kawamura的本构模型,将高温压缩实验的数据拟合,获得本构模型中的参数,结果表明非晶合金在过冷液相区内变形的摩擦因数在0.2~0.7之间.当应变速率较低时,随着温度的升高,摩擦因数总体上降低;而当应变速率较高时,随着温度的升高,摩擦因数先略有上升,然后急剧下降.当温度较低

  19. Anti-corrosion film formed on HAl77-2 copper alloy surface by aliphatic polyamine in 3 wt.% NaCl solution

    Science.gov (United States)

    Yu, Yinzhe; Yang, Dong; Zhang, Daquan; Wang, Yizhen; Gao, Lixin

    2017-01-01

    The corrosion inhibition of a polyamine compound, N-(4-amino-2, 3-dimethylbutyl)-2, 3-dimethylbutane-1, 4-diamine (ADDD), was investigated for HAl77-2 copper alloy in 3 wt.% NaCl solution. Electrochemical measurements, scanning electron microscopy (SEM), atomic force microscope (AFM) and Fourier transform infrared spectroscopy (FT-IR) techniques were employed for this research. The results show that ADDD strongly suppresses the corrosion of HAl77-2 alloy. The inhibition efficiency of ADDD is 98.6% at 0.5 mM, which is better than benzotriazole (BTAH) at the same concentration. Polarization curves indicate that ADDD is an anodic type inhibitor. Surface analysis suggests that a protective film is formed via the interaction of ADDD and copper. FT-IR reveals that the inhibition mechanism of ADDD is dominated by chemisorption onto the copper alloy surface to form an inhibition film. Furthermore, quantum chemical calculation and molecular dynamics (MD) simulations methods show that ADDD adsorbs on HAl77-2 surface via amino group in its molecule.

  20. Metallurgical investigation of defects in super alloy 718 mill forms intended for aeroengine applications; Metallurgische Schadensanalyse an Halbzeugen aus der Superlegierung 718 fuer Triebwerksapplikationen

    Energy Technology Data Exchange (ETDEWEB)

    Gopala Krishna, V.; Srinivas, M. [Defence Metallurgical Research Lab., Hyderabad (India); Janakiram, G.D. [Utah State Univ., Logan, UT (United States); Murty, C.H.V.S.; Venugopal Reddy. A. [Regional Center for Military Airworthiness (Materials), Hyderabad (India)

    2008-10-15

    Super alloy 718 finds extensive utilization, particularly in aero engine industry, due to its excellent strength, low cycle fatigue and creep resistance. The alloy was manufactured using vacuum induction melting followed by vacuum arc remelting techniques. The electrodes, after thermo-mechanical processing to hot rolled square bar and flat forms, were ultrasonically inspected prior to machining of aeroengine compressor blades. During machining, crack-like defects were noticed. Visual / Stereo microscopic examination revealed that the defect was along the length of airfoil and was located at mid airfoil width. The defects were filled with dark gray colored debris. Fractographic examination of the crack facets revealed flaky gray region containing number of cracks and bright region with dimpled rupture features covered with debris. Analysis of the debris indicated the presence of oxygen in addition to the elements present in the material, suggesting that the debris is essentially an oxide. These features were correlated with processing histories and defect morphologies. (orig.)

  1. High-strain-rate superplasticity in oxide ceramics: a trial of microstructural design based on creep-cavitation mechanisms

    Institute of Scientific and Technical Information of China (English)

    Keijiro HIRAGA; Byung-Nam KIM; Koji MORITA; Hidehiro YOSHIDA; Yoshio SAKKA; Masaaki TABUCHI

    2011-01-01

    From existing knowledge about high-temperature cavitation mechanisms, necessary conditions were discussed for the suppression of cavitation failure during superplastic deformation in ceramic materials. The discussion, where special attention was placed on the relaxation of stress concentrations during grain-boundary sliding and cavity nucleation and growth, leaded to a conclusion that cavitation failure could be retarded by the simultaneous controlling of the initial grain size, the number of residual defects,diffusivity, dynamic grain growth and the homogeneity of microstructure. On the basis of this conclusion, high-strain-rate superplasticity (defined as superplasticity at a strain rate higher than 0.01 s-1) could be intentionally attained in some oxide ceramic materials. This was shown in tetragonal zirconia and composites consisting of zirconia, α-alumina and a spinel phase.

  2. Investigation by Differential Scanning Calorimetry of Microstructure in a Superplastic Al-Mg-Zr Alloy.

    Science.gov (United States)

    1987-06-01

    this, described in detail by Askeland [Ref. 5:p. 2813 are: 1) Solution treatment 2) Quenching 3) Aging. Dispersion strengthening is accomplished...Prentice-Hall, 1984. 4. Dieter, G.E., Mechanical Metallurgy, McGraw-Hill, 1976. 5. Askeland , D.R., The Science and Engineering of Materials, Brooks/Cole

  3. Analysis of Grain Refinement and Superplasticity in Aluminum-Magnesium Alloys.

    Science.gov (United States)

    1987-12-01

    have appeared in recent years and a number of monographs have been published (Mukherjee, 1975; Gittus , 1975; Edington, 1976; Alden, 1977; Taplin, et al... Gittus , J., Creep Viscoelzsticity and Creep Fracture in Solids, p. 509, Applied Sci- ence Publishers, Ltd., London, 1975. Griffith, P., and Hammond, C

  4. Studies of Nucleation and Growth, Specific Heat and Viscosity of Undercooled Melts of Quasicrystal and Polytetrahedral-Phase Forming Alloys

    Science.gov (United States)

    Kelton, K. F.; Gangopadhyay, Anup K.; Lee, G. W.; Hyers, Robert W.; Rathz, T. J.; Robinson, Michael B.; Rogers, Jan R.

    2003-01-01

    From extensive ground based work on the phase diagram and undercooling studies of Ti-Zr-Ni alloys, have clearly identified the composition of three different phases with progressively increasing polytetrahedral order such as, (Ti/Zr), the C14 Laves phase, and the i-phase, that nucleate directly from the undercooled liquid. The reduced undercooling decreases progressively with increasing polytetrahedral order in the solid, supporting Frank s hypothesis. A new facility for direct measurements of the structures and phase transitions in undercooled liquids (BESL) was developed and has provided direct proof of the primary nucleation of a metastable icosahedral phase in some Ti-Zr-Ni alloys. The first measurements of specific heat and viscosity in the undercooled liquid of this alloy system have been completed. Other than the importance of thermo-physical properties for modeling nucleation and growth processes in these materials, these studies have also revealed some interesting new results (such as a maximum of C(sup q, sub p) in the undercooled state). These ground-based results have clearly established the necessary background and the need for conducting benchmark nucleation experiments at the ISS on this alloy system.

  5. Influence of multi-step heat treatments in creep age forming of 7075 aluminum alloy: Optimization for springback, strength and exfoliation corrosion

    Energy Technology Data Exchange (ETDEWEB)

    Arabi Jeshvaghani, R.; Zohdi, H. [Department of Materials Engineering, Tarbiat Modares University, P.O. Box 14115-143, Tehran (Iran, Islamic Republic of); Shahverdi, H.R., E-mail: shahverdi@modares.ac.ir [Department of Materials Engineering, Tarbiat Modares University, P.O. Box 14115-143, Tehran (Iran, Islamic Republic of); Bozorg, M. [Department of Materials Engineering, Tarbiat Modares University, P.O. Box 14115-143, Tehran (Iran, Islamic Republic of); Hadavi, S.M.M. [School of Materials Science and Engineering, MA University of Technology, P.O. Box 16765-3197, Tehran (Iran, Islamic Republic of)

    2012-11-15

    Multi-step heat treatments comprise of high temperature forming (150 Degree-Sign C/24 h plus 190 Degree-Sign C for several minutes) and subsequent low temperature forming (120 Degree-Sign C for 24 h) is developed in creep age forming of 7075 aluminum alloy to decrease springback and exfoliation corrosion susceptibility without reduction in tensile properties. The results show that the multi-step heat treatment gives the low springback and the best combination of exfoliation corrosion resistance and tensile strength. The lower springback is attributed to the dislocation recovery and more stress relaxation at higher temperature. Transmission electron microscopy observations show that corrosion resistance is improved due to the enlargement in the size and the inter-particle distance of the grain boundaries precipitates. Furthermore, the achievement of the high strength is related to the uniform distribution of ultrafine {eta} Prime precipitates within grains. - Highlights: Black-Right-Pointing-Pointer Creep age forming developed for manufacturing of aircraft wing panels by aluminum alloy. Black-Right-Pointing-Pointer A good combination of properties with minimal springback is required in this component. Black-Right-Pointing-Pointer This requirement can be improved through the appropriate heat treatments. Black-Right-Pointing-Pointer Multi-step cycles developed in creep age forming of AA7075 for improving of springback and properties. Black-Right-Pointing-Pointer Results indicate simultaneous enhancing the properties and shape accuracy (lower springback).

  6. Optimum synthesis conditions of nanometric Fe50Ni50 alloy formed by chemical reduction in aqueous solution

    Indian Academy of Sciences (India)

    Marwa A Mohamed; Azza H El-Maghraby; Mona M Abd El-Latif; Hassan A Farag

    2013-10-01

    In the present article, various nanometric Fe50Ni50 alloys were synthesized by chemical reduction of the corresponding metal ions, with hydrazine in an aqueous solution. Process variables of reaction temperature, pH of the hydrazine solution and concentration of metal ions were varied in order to determine the optimum synthesis conditions regarding quality, productivity and cost. It is found that pH of hydrazine solution, at low concentration of metal ions, is the most crucial variable affecting the reaction rate, average crystallite and particle sizes of the synthesized nanometric Fe50Ni50 alloy, followed by the total concentration of metal ions. Thus, increase of pH of hydrazine solution acts as an efficient stabilizer in reducing the particle size. On the contrary, at high concentration of metal ions, the structural characteristics of the nanometric Fe50Ni50 alloy are almost insensitive to reaction temperature and pH of hydrazine solution, but the reduction rate is remarkably sensitive to reaction temperature. Based on these results, it is decided that a reaction temperature of 80 °C, pH of the hydrazine solution of 12.5 and concentration of metal ions of 0.6 M represent the optimum synthesis conditions. The role of pH of hydrazine solution in reducing the alloy’s average particle size as well as efficient stabilizer confirms tremendous effect of synthesis conditions on the alloy structure and therefore, the importance of this study for industrial production of nanometric Fe50Ni50 alloy.

  7. A technique to study the granular flow during superplastic deformation

    Energy Technology Data Exchange (ETDEWEB)

    Munoz-Andrade, J.D. [DCBI, Dept. de Materiales, Univ. Autonoma Metropolitana (Mexico); Universidad Central de Venezuela, Caracas. Facultad de Ingenieria; Mendoza-Allende, A.; Montemayor-Aldrete, J.A. [Universidad Autonoma de Puebla (Mexico). Dept. de Fisica; Torres-Villasenor, G. [Universidad Nacional Autonoma de Mexico, Mexico City (Mexico). Inst. de Investigaciones en Materiales

    1999-07-01

    A new technique for scanning electron microscopy (SEM), which provides a mesoscopic coordinate system inscribed on the surface of the center of a tension test specimen, and relates this system to another fixed at rest in laboratory it is developed. Such technique allows to establish in a repeatable way any angle relative to any axis of any coordinate system, or distances between grains, or to measure local or global true deformation in parallel or perpendicular direction relatives to the tension axis. This technique was applied to give some results on a Zn-20.2% Al-1.8% Cu Alloy tension test specimen with 412 {mu}m length. (orig.)

  8. Super-plasticity of Zr64.80Cu14.85Ni10.35Al10 bulk metallic glass at room temperature

    Institute of Scientific and Technical Information of China (English)

    TAO PingJun; YANG YuanZheng; BAI XiaoJun; XIE ZhiWei; CHEN XianCao; DONG ZhenJiang; Wen JianGuo

    2008-01-01

    Generally, bulk metallic glasses (BMGs) exhibit a very limited plastic deformation under a compression load at room temperature, often less than 2% before fracturing. In this letter, through an appropriate choice of BMGs' composition, an amorphous rod of Zr64.80Cu14.85Ni10.35Al10 with a diameter of 2 mm was prepared by using copper mold suction casting. X-ray diffraction and differential scanning calorimetry were utilized to determine its structure and thermal stability, and the uniaxial compression test was adopted to study its plastic deformation behavior at room temperature simultaneously. The results showed that the glass transition temperature and onset temperature of the exothermic reaction of the amorphous rod were 646 and 750 K, respectively, and its micro-hardness was 594.7 Hv. During com-pression, when the engineering strain and engineering stress arrived at 9.05% and 1732 MPa, respec-tively, i.e., the true strain and true stress reached 9.42% and 1560 MPa, respectively, the amorphous rod started to yield. After yielding, with the increase of load, the strain increased and the glass rod ulti-mately were compressed into flake-like form. Although the maximum engineering strain was larger than 70%, i.e., the maximum true strain exceeded by 120%, the amorphous specimen was not fractured, indicating that it has super-plasticity at room temperature. Through the appropriate choice of compo-sition and optimization of the technological process, flexible BMG with super-plasticity at room tem-perature could be produced.

  9. Nanoporous alumina formed by self-organized two-step anodization of Ni{sub 3}Al intermetallic alloy in citric acid

    Energy Technology Data Exchange (ETDEWEB)

    Stepniowski, Wojciech J., E-mail: wstepniowski@wat.edu.pl [Department of Advanced Materials and Technology, Faculty of New Technologies and Chemistry, Military University of Technology, Kaliskiego 2 Str., 00-908 Warszawa (Poland); Cieslak, Grzegorz; Norek, Malgorzata; Karczewski, Krzysztof; Michalska-Domanska, Marta; Zasada, Dariusz; Polkowski, Wojciech; Jozwik, Pawel; Bojar, Zbigniew [Department of Advanced Materials and Technology, Faculty of New Technologies and Chemistry, Military University of Technology, Kaliskiego 2 Str., 00-908 Warszawa (Poland)

    2013-01-01

    Highlights: Black-Right-Pointing-Pointer Anodic porous alumina was formed by Ni{sub 3}Al intermetallic alloy anodization. Black-Right-Pointing-Pointer The anodizations were conducted in 0.3 M citric acid. Black-Right-Pointing-Pointer Nanopores geometry depends on anodizing voltage. Black-Right-Pointing-Pointer No barrier layer was formed during anodization. - Abstract: Formation of the nanoporous alumina on the surface of Ni{sub 3}Al intermetallic alloy has been studied in details and compared with anodization of aluminum. Successful self-organized anodization of this alloy was performed in 0.3 M citric acid at voltages ranging from 2.0 to 12.0 V using a typical two-electrode cell. Current density records revealed different mechanism of the porous oxide growth when compared to the mechanism pertinent for the anodization of aluminum. Electrochemical impedance spectroscopy experiments confirmed the differences in anodic oxide growth. Surface and cross-sections of the Ni{sub 3}Al intermetallic alloy with anodic oxide were observed with field-emission scanning electron microscope and characterized with appropriate software. Nanoporous oxide growth rate was estimated from cross-sectional FE-SEM images. The lowest growth rate of 0.14 {mu}m/h was found for the anodization at 0 Degree-Sign C and 2.0 V. The highest one - 2.29 {mu}m/h - was noticed for 10.0 V and 30 Degree-Sign C. Pore diameter was ranging from 18.9 nm (2.0 V, 0 Degree-Sign C) to 32.0 nm (12.0 V, 0 Degree-Sign C). Interpore distance of the nanoporous alumina was ranging from 56.6 nm (2.0 V, 0 Degree-Sign C) to 177.9 nm (12.0 V, 30 Degree-Sign C). Pore density (number of pore occupying given area) was decreasing with anodizing voltage increase from 394.5 pores/{mu}m{sup 2} (2.0 V, 0 Degree-Sign C) to 94.9 pores/{mu}m{sup 2} (12.0 V, 0 Degree-Sign C). All the geometrical features of the anodic alumina formed by two-step self-organized anodization of Ni{sub 3}Al intermetallic alloy are depending on the

  10. Deformation behavior and mechanisms of Ti- 1023 alloy

    Institute of Scientific and Technical Information of China (English)

    BAO Ru-qiang; HUANG Xu; CAO Chun-xiao

    2006-01-01

    The deformation behavior and mechanisms of Ti-1023 alloy were studied in the temperature range of 650-900 ℃ and strain rate range of 0.001-10 s-1 by compression and tensile tests. The results show that in a limited strain rate range of 0.001-0.1 s-1,the kinetic rate equation is obeyed and a linear fit is obtained at all the temperatures. The apparent activation energy is 322 kJ/mol in the α-β region and 160 kJ/mol in the β region, respectively. Power dissipation maps of this alloy developed by using Gleeble test data show three domains in the tested range. Superplasticity, marked by abnormal elongation at 700 ℃, occurs in the temperature range of 650-750 ℃ and at strain rates below about 0.03 s-1 Large grain superplasticity takes place in the temperature range of 750-850℃ and strain rates range of 0.001-0.03 s-1. Dynamic recrystallization occurs in the temperature range of 850-900 ℃ and at strain rates below about 1 s-1. The instability maps of this alloy were also developed.

  11. Investigation of Abnormal Grain Growth in a Friction Stir Welded and Spin-Formed Al-Li Alloy 2195 Crew Module

    Science.gov (United States)

    Tayon, Wesley A.; Domack, Marcia S.; Hoffman, Eric K.; Hales, Stephen J.

    2013-01-01

    In order to improve manufacturing efficiency and reduce structural mass and costs in the production of launch vehicle structures, NASA is pursuing a wide-range of innovative, near-net shape manufacturing technologies. A technology that combines friction stir welding (FSW) and spin-forming has been applied to manufacture a single-piece crew module using Aluminum-Lithium (AL-Li) Alloy 2195. Plate size limitations for Al-Li alloy 2195 require that two plates be FSW together to produce a spin-forming blank of sufficient size to form the crew module. Subsequent forming of the FSW results in abnormal grain growth (AGG) within the weld region upon solution heat treatment (SHT), which detrimentally impacts strength, ductility, and fracture toughness. The current study seeks to identify microstructural factors that contribute to the development of AGG. Electron backscatter diffraction (EBSD) was used to correlate driving forces for AGG, such as stored energy, texture, and grain size distributions, with the propensity for AGG. Additionally, developmental annealing treatments prior to SHT are examined to reduce or eliminate the occurrence of AGG by promoting continuous, or uniform, grain growth

  12. Structure of the glass-forming metallic liquids by ab-initio and classical molecular dynamics, a case study: Quenching the Cu60Ti20Zr20 alloy

    Science.gov (United States)

    Amokrane, S.; Ayadim, A.; Levrel, L.

    2015-11-01

    We consider the question of the amorphization of metallic alloys by melt quenching, as predicted by molecular dynamics simulations with semi-empirical potentials. The parametrization of the potentials is discussed on the example of the ternary Cu-Ti-Zr transition metals alloy, using the ab-initio simulation as a reference. The pair structure in the amorphous state is computed from a potential of the Stillinger-Weber form. The transferability of the parameters during the quench is investigated using two parametrizations: from solid state data, as usual and from a new parametrization on the liquid structure. When the adjustment is made on the pair structure of the liquid, a satisfactory transferability is found between the pure components and their alloys. The liquid structure predicted in this way agrees well with experiment, in contrast with the one obtained using the adjustment on the solid. The final structure, after quenches down to the amorphous state, determined with the new set of parameters is shown to be very close to the ab-initio one, the latter being in excellent agreement with recent X-rays diffraction experiments. The corresponding critical temperature of the glass transition is estimated from the behavior of the heat capacity. Discussion on the consistency between the structures predicted using semi-empirical potentials and ab-initio simulation, and comparison of different experimental data underlines the question of the dependence of the final structure on the thermodynamic path followed to reach the amorphous state.

  13. Capacitive behaviour and electronic structure of passive films formed on nickel base alloy type Inconel 600; influence of Cr and Fe. Comportement capacitif et structure electronique des films passifs formes sur l'alliage a base de nickel du type Inconel 600 (75Ni-16Cr-8Fe); influence du chrome et du fer

    Energy Technology Data Exchange (ETDEWEB)

    Hakiki, N.E.; Da Cunha Belo, M. (Centre National de la Recherche Scientifique (CNRS), 94 - Vitry-sur-Seine (France). Centre d' Etudes de Chimie Metallurgique)

    1994-08-01

    The study of passive films formed on a nickel base alloy type Inconel 600 is performed by capacitance measurements (Mott-Schottky approach). This research is supported by the passivation study of the alloying elements Ni, Cr, Fe and high purity alloys Ni-Cr, Ni-Fe, Ni-Cr-Fe. The results obtained show that the capacitive behaviour of the Inconel 600 in the passive state is similar to that on a p-n heterojunction to which a barrier zone of nickel oxide is added. The individual or combined action of alloying elements on the development of this kind of electronic structure is discussed. (authors). 5 refs., 6 figs.

  14. Electrochemical and Spectroscopic Study of Benzotriazole Films Formed on Copper, Copper-zinc Alloys and Zinc in Chloride Solution

    OpenAIRE

    Milošev, I.; Kosec, T.

    2009-01-01

    The formation of protective layers on copper, zinc and copper-zinc (Cu-10Zn and Cu-40Zn) alloys at open circuit potential in aerated, near neutral 0.5 M NaCl solution containing benzotriazole (BTA) was studied using potentiodynamic measurements, electrochemical impedance spectroscopy (EIS) and X-ray photoelectron spectroscopy (XPS). The addition of benzotriazole affects the dissolution of the materials investigated. Benzotriazole, generally known as an inhibitor of copper corrosion, is als...

  15. Stress release phenomena in chromia scales formed on NiCr-30 alloys: Influence of metallurgical parameters

    Science.gov (United States)

    Guerain, M.; Goudeau, P.; Grosseau-Poussard, J. L.

    2011-11-01

    Stress release phenomena are studied for α-Cr2O3 thermal oxide films grown on NiCr-30 alloys. The influence of specific metallurgical parameters, such as cooling rate and initial surface roughness, is investigated thanks to Raman spectroscopy. Systematic correlations are established between the residual stress level in the scales and the damage rate resulting from a delamination process by buckling. Different buckling morphologies are characterized mainly according to the cooling rate range.

  16. Towards the problem of forming full strength welded joints on aluminum alloy sheets. Part II: AA7475

    Science.gov (United States)

    Kalashnikova, Tatiana; Tarasov, Sergey; Eliseev, Alexander; Fortuna, Anastasiya

    2016-11-01

    The microstructural evolution in welded joint zones obtained both by friction stir welding and ultrasonic- assisted friction stir welding on dispersion hardened 7475 aluminum alloy has been examined together with the analysis of mechanical strength and microhardness. It was established that ultrasonic-assisted friction stir provided leveled microhardness profiles across the weld zones as well as higher joint strength as compared to those of standard friction stir welding.

  17. Effects of TiN film coating on electrochemical behaviors ofnanotube formed Ti-xHf alloys

    Institute of Scientific and Technical Information of China (English)

    Kang LEE; Won-Gi KIM; Joo-Young CHO; Sang-Won EUN; Han-Cheol CHOE

    2009-01-01

    Ti-xHf (x=10%, 20%, 30% and 40%, mass fraction) alloys were prepared by arc melting, and the microstructure was controlled for 24 h at 1 000 ℃ in argon atmosphere. The formation of nanotube was conducted by anodizing on Ti-Hf alloys in 1.0 mol/L H3PO4 electrolytes with small amounts of NaF at room temperature. And then TiN coatings were coated by DC-sputtering on the anodized surface. Microstructures and nanotube morphology of the alloys were examined by field emission scanning electron microscopy(FE-SEM) and X-ray diffractometry(XRD). The corrosion properties of the specimens were examined through potentiodynamic test (potential range from -1 500 to 2 000 mV) in 0.9 % NaCl solution by potentiostat. The microstructure shows the acicular phase and α′ phase with Hf content. The amorphous oxide surface is transformed to crystalline anatase phase. TiN coated nanotube surface has a good corrosion resistance.

  18. Protection of zirconium by alumina- and chromia-forming iron alloys under high-temperature steam exposure

    Science.gov (United States)

    Terrani, Kurt A.; Parish, Chad M.; Shin, Dongwon; Pint, Bruce A.

    2013-07-01

    The viability of advanced oxidation-resistant Fe-base alloys to protect zirconium from rapid oxidation in high-temperature steam environments has been examined. Specimens were produced such that outer layers of FeCrAl ferritic alloy and Type 310 austenitic stainless steel were incorporated on the surface of zirconium metal slugs. The specimens were exposed to high-temperature 0.34 MPa steam at 1200 and 1300 °C. The primary degradation mechanism for the protective layer was interdiffusion with the zirconium, as opposed to high-temperature oxidation in steam. The FeCrAl layer experienced less degradation and protected the zirconium at 1300 °C for 8 h. Constituents of the Fe-base alloys rapidly diffused into the zirconium and resulted in the formation of various intermetallic layers at the interface and precipitates inside the bulk zirconium. The nature of this interaction for FeCrAl and 310SS has been characterized by use of microscopic techniques as well as computational thermodynamics. Finally, a reactor physics discussion on the applicability of these protective layers in light-water-reactor nuclear fuel structures is offered.

  19. Characterization of air-formed surface oxide film on a Co-Ni-Cr-Mo alloy (MP35N) and its change in Hanks' solution

    Energy Technology Data Exchange (ETDEWEB)

    Nagai, Akiko, E-mail: nag-bcr@tmd.ac.jp [Department of Inorganic Materials, Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University, 2-3-10 Kanda-surugadai, Chiyoda-ku, Tokyo 101-0062 (Japan); Tsutsumi, Yusuke [Department of Metals, Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University, 2-3-10 Kanda-surugadai, Chiyoda-ku, Tokyo 101-0062 (Japan); Suzuki, Yuta [Department of Inorganic Materials, Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University, 2-3-10 Kanda-surugadai, Chiyoda-ku, Tokyo 101-0062 (Japan); Faculty of Engineering, Tokai University, 4-1-1 Kitakaname, Hiratsuka, Kanagawa 259-1292 (Japan); Katayama, Keiichi [Faculty of Engineering, Tokai University, 4-1-1 Kitakaname, Hiratsuka, Kanagawa 259-1292 (Japan); Hanawa, Takao [Department of Metals, Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University, 2-3-10 Kanda-surugadai, Chiyoda-ku, Tokyo 101-0062 (Japan); Yamashita, Kimihiro [Department of Inorganic Materials, Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University, 2-3-10 Kanda-surugadai, Chiyoda-ku, Tokyo 101-0062 (Japan)

    2012-05-01

    The air-formed surface oxide films used for stents were characterized to determine their composition and chemical state on a Co-Ni-Cr-Mo alloy. The change of the films in Hanks' solution was used to estimate the reconstruction of the film in the human body. Angle-resolved X-ray photoelectron spectroscopy was used to characterize the composition of the film and substrate, as well as the film's thickness. The surface oxide film on the Co-Ni-Cr-Mo alloy (when mechanically polished) consists of oxide species of cobalt, nickel, chromium, and molybdenum, contains a large amount of OH{sup -}, and has a thickness of approximately 2.5 nm. Cations exist in the oxide as Co{sup 2+}, Ni{sup 2+}, Cr{sup 3+}, Mo{sup 4+}, Mo{sup 5+}, and Mo{sup 6+}. Chromium is enriched and cobalt and nickel are depleted in the oxide; however, nickel is enriched and cobalt is depleted in the substrate alloy just under the surface oxide film. Concentration of chromium was low and that of nickel was high at small take-off angles. This indicates that distribution of chromium is greater in the inner layer, but nickel is distributed more in the outer layer of the surface oxide film. During immersion in Hanks' solution, cobalt and nickel dissolved, and the film composition changed to mostly chromium oxide (Cr{sup 3+}), along with small amounts of cobalt, nickel, and molybdenum oxides, and calcium phosphate containing magnesium, potassium, and carbonate. After immersion in Hanks' solution, the thickness of the surface layer containing calcium phosphate increased to more than 4 nm, while the amount of OH{sup -} increased. The amount of cobalt and nickel in the surface oxide film and in the substrate alloy just below the oxide decreased during immersion.

  20. Microstructure and mechanical properties of multiphase layer formed during depositing Ti film followed by plasma nitriding on 2024 aluminum alloy

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, F.Y., E-mail: zfy19861010@163.com; Yan, M.F., E-mail: yanmufu@hit.edu.cn

    2014-05-01

    Highlights: • A novel duplex surface treatment on 2024 Al alloy was proposed. • A multiphase layer composed of TiN{sub 0.3}, Al{sub 3}Ti and Al{sub 18}Ti{sub 2}Mg{sub 3} was prepared on the surface of 2024 Al alloy. • The microstructures of TiN{sub 0.3}, Al{sub 3}Ti and Al{sub 18}Ti{sub 2}Mg{sub 3} were characterized by SEM and TEM. • The surface hardness of the multiphase layer reached to 590 HV{sub 0.01}, five times harder than 2024 Al alloy. • The wear resistance of 2024 Al alloy was improved significantly. - Abstract: In this study, a novel method was develop to fabricate an in situ multiphase layer on 2024 Al alloy to improve its surface mechanical properties. The method was divided into two steps, namely depositing pure Ti film on 2024 Al substrate by using magnetron sputtering, and plasma nitriding of Ti coated 2024 Al in a gas mixture comprising of 40% N{sub 2}–60% H{sub 2}. The microstructure and mechanical properties of the multiphase layer prepared at different nitriding time were investigated by using X-ray diffractometer (XRD), scanning electron microscopy (SEM), transmission electron microscope (TEM), microhardness tester and pin-on-disc tribometer. Results showed that multiphase layer with three sub-layers (i.e. the outmost TiN{sub 0.3} layer, the intermediate Al{sub 3}Ti layer and the inside Al{sub 18}Ti{sub 2}Mg{sub 3} layer) can be obtained. The thickness of the Al{sub 18}Ti{sub 2}Mg{sub 3} layer increased faster than TiN{sub 0.3} and Al{sub 3}Ti layer with increasing nitriding time. The hardness of the layer has reached about 593 HV, which is much higher than that of 2024 Al substrate. The wear rate of the coated samples decreased 53% for 4 h nitriding and 86% for 12 h nitriding, respectively, compared with that of the uncoated one. The analysis of worn surface indicated that the coated 2024 Al exhibited predominant abrasive wear, whereas the uncoated one showed severe adhesive wear.

  1. THREE-DIMENSIONAL VISU ALIZATION OF DEGENERATE FERRITE FORMED BELOW TTT-DIAGRAM BAY IN AN Fe-C-Mo ALLOY

    Institute of Scientific and Technical Information of China (English)

    K.M. Wu; M. Enomoto

    2003-01-01

    The evolution of degenerate ferrite in an Fe-0.28wt%C-3.0wt%Mo alloy isothermally reacted for 10ks at 20℃ below TTT diagram bay temperature have been revealed utilizing serial sectioning in conjunction with computer reconstruction and visualization.The degenerate ferrite is initially formed at prior austenite boundary and then grows toward grain interior rather than along the grain boundary. The degenerate morphology of ferrite may be attributed to repeated nucleation, growth and coalescence of adjacent ferrite crystals. The shape of individual ferrite crystals appears to be rod-like.

  2. Low Temperature Superplasticity of Ti-6Al-4V Processed by Warm Multidirectional Forging (Preprint)

    Science.gov (United States)

    2012-07-01

    using a JEOL JEM-2100FX transmission electron microscope (TEM) and a Quanta 600 field-emission-gun scanning-electron microscope (SEM). Results and...factor of three compared to the initial condition (Fig. 2b). A backscattered electron ( BSE ) image revealed the distribution of the  phase in the...a) BSE image of Ti-6Al-4V after annealing at Т=550С for 0.5 hour and (b) grain size as a function of soak time at 550C. Superplastic Behavior

  3. Microstructural evolution and magnetic properties of ultrafine solute-atom particles formed in a Cu75-Ni20-Fe5 alloy on isothermal annealing

    Science.gov (United States)

    Kim, Jun-Seop; Takeda, Mahoto; Bae, Dong-Sik

    2016-12-01

    Microstructural features strongly affect magnetism in nano-granular magnetic materials. In the present work we have investigated the relationship between the magnetic properties and the self-organized microstructure formed in a Cu75-Ni20-Fe5 alloy comprising ferromagnetic elements and copper atoms. High resolution transmission electron microscopy (HRTEM) observations showed that on isothermal annealing at 873 K, nano-scale solute (Fe,Ni)-rich clusters initially formed with a random distribution in the Cu-rich matrix. Superconducting quantum interference device (SQUID) measurements revealed that these ultrafine solute clusters exhibited super-spinglass and superparamagnetic states. On further isothermal annealing the precipitates evolved to cubic or rectangular ferromagnetic particles and aligned along the directions of the copper-rich matrix. Electron energy-band calculations based on the first-principle Korringa-Kohn-Rostocker (KKR) method were also implemented to investigate both the electronic structure and the magnetic properties of the alloy. Inputting compositions obtained experimentally by scanning transmission electron microscopy-electron dispersive X-ray spectroscopy (STEM-EDS) analysis, the KKR calculation confirmed that ferromagnetic precipitates (of moment 1.07μB per atom) formed after annealing for 2 × 104 min. Magneto-thermogravimetric (MTG) analysis determined with high sensitivity the Curie temperatures and magnetic susceptibility above room temperature of samples containing nano-scale ferromagnetic particles.

  4. Characteristics and corrosion studies of vanadate conversion coating formed on Mg-14 wt%Li-1 wt%Al-0.1 wt%Ce alloy

    Energy Technology Data Exchange (ETDEWEB)

    Ma Yibin [School of Chemical Engineering and Technology, Harbin Institute of Technology, Harbin 150001 (China); Li Ning, E-mail: lininghit@263.net [School of Chemical Engineering and Technology, Harbin Institute of Technology, Harbin 150001 (China); Li Deyu [School of Chemical Engineering and Technology, Harbin Institute of Technology, Harbin 150001 (China); Zhang Milin; Huang Xiaomei [Key Laboratory of Superlight Materials and Surface Technology, Ministry of Education, Harbin Engineering University, Harbin 150001 (China)

    2012-11-15

    Highlights: Black-Right-Pointing-Pointer Vanadate film forms on the surface of Mg-Li-Al-Ce alloy. Black-Right-Pointing-Pointer Vanadate coating improves the corrosion resistance. Black-Right-Pointing-Pointer Vanadate coating is composed of Mg(OH){sub 2}, Li{sub 2}O and V{sub 2}O{sub 5}. - Abstract: Mg-14Li-1Al-0.1Ce alloy is immersed in NH{sub 4}VO{sub 3} + K{sub 3}(Fe(CN){sub 6}) solutions with different NH{sub 4}VO{sub 3} and/or K{sub 3}(Fe(CN){sub 6}) concentrations, and different immersion time. The surface morphology and composition of the vanadate coating are then characterized by scanning electron microscopy with energy dispersion spectroscopy (SEM-EDS) and X-ray photoelectron spectroscopy (XPS), and the corrosion behavior of the conversion coating is studied by polarization technique and electrochemical impedance spectroscopy (EIS). The experimental results indicate that the vanadate film with better corrosion resistance forms on Mg-Li-Al-Ce surface after the sample is immersed in 30 g L{sup -1} NH{sub 4}VO{sub 3} + 3.75 g L{sup -1} K{sub 3}(Fe(CN){sub 6}) solution at 80 Degree-Sign C for 10 min. The coating consists of V{sub 2}O{sub 5}, Li{sub 2}O and Mg(OH){sub 2}.

  5. Coercivity of the Nd–Fe–B hot-deformed magnets diffusion-processed with low melting temperature glass forming alloys

    Energy Technology Data Exchange (ETDEWEB)

    Seelam, U.M.R. [Elements Strategy Initiative Center for Magnetic Materials (ESICMM), National Institute for Materials Science, 1-2-1 Sengen, Tsukuba 305-0047 (Japan); Liu, Lihua [Elements Strategy Initiative Center for Magnetic Materials (ESICMM), National Institute for Materials Science, 1-2-1 Sengen, Tsukuba 305-0047 (Japan); Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305-8571 (Japan); Akiya, T.; Sepehri-Amin, H.; Ohkubo, T. [Elements Strategy Initiative Center for Magnetic Materials (ESICMM), National Institute for Materials Science, 1-2-1 Sengen, Tsukuba 305-0047 (Japan); Sakuma, N.; Yano, M.; Kato, A. [Advanced Material Engineering Division, Toyota Motor Corporation, Susono 410-1193 (Japan); Hono, K., E-mail: kazuhiro.hono@nims.go.jp [Elements Strategy Initiative Center for Magnetic Materials (ESICMM), National Institute for Materials Science, 1-2-1 Sengen, Tsukuba 305-0047 (Japan); Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305-8571 (Japan)

    2016-08-15

    Nd- and Pr-based alloys with bulk glass forming ability and low melting temperatures, Nd{sub 60}Al{sub 10}Ni{sub 10}Cu{sub 20} and Pr{sub 60}Al{sub 10}Ni{sub 10}Cu{sub 20}, were used for grain boundary diffusion process to enhance the coercivity of hot-deformed magnets. The coercivity increment was proportional to the weight gain after the diffusion process. For the sample with 64% weight gain, the coercivity increased up to 2.8 T, which is the highest value for bulk Nd–Fe–B magnets that do not contain heavy rare-earth elements, Dy or Tb. Approximately half of the intergranular regions were amorphous and the remaining regions were crystalline. Magnetic isolation of the Nd{sub 2}Fe{sub 14}B grains by the Nd-rich amorphous/crystalline intergranular phases is attributed to the large coercivity enhancement. The coercivity does not change after the crystallization of the intergranular phase, indicating that the coercivity is not influenced by the strain at the interface with the crystalline intergranular phase. - Highlights: • Bulk-glass forming alloys were infiltrated into hot-deformed Nd–Fe–B magnets. • Very high coercivity of 2.8 T was attained without heavy rare-earth elements. • Approximately half of the inter-granular regions were amorphous. • Crystallization of amorphous intergranular phase does not change coercivity.

  6. Effects of benzotriazole on anodized film formed on AZ31B magnesium alloy in environmental-friendly electrolyte

    Energy Technology Data Exchange (ETDEWEB)

    Guo Xinghua [School of Chemical Engineering and Technology, Harbin Institute of Technology, Harbin (China); An Maozhong, E-mail: mzan@hit.edu.c [School of Chemical Engineering and Technology, Harbin Institute of Technology, Harbin (China); Yang Peixia; Li Haixian; Su Caina [School of Chemical Engineering and Technology, Harbin Institute of Technology, Harbin (China)

    2009-08-12

    An environmental-friendly electrolyte of silicate and borate, which contained an addition agent of 1H-benzotriazole (BTA) with low toxicity (LD50 of 965 mg/kg), was used to prepare an anodized film on AZ31B magnesium alloy under the constant current density of 1.5 A/dm{sup 2} at room temperature. Effects of BTA on the properties of the anodized film were studied by scanning electron microscopy (SEM), energy dispersion spectrometry (EDS), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), loss weight measurement, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS), respectively. The results demonstrated that anodized growth process, surface morphology, thickness, phase structure and corrosion resistance of the anodized film were strongly dependant on the BTA concentration, which might be attributed to the formation of an BTA adsorption layer on magnesium substrate surface. When the BTA concentration was 5 g/L in the electrolyte, a compact and thick anodized film could provide excellent corrosion resistance for AZ31B magnesium alloy.

  7. Investigation of rare earth sealing of porous micro-arc oxidation coating formed on AZ91D magnesium alloy

    Institute of Scientific and Technical Information of China (English)

    M.Laleh; Farzad Kargar; A.Sabour Rouhaghdam

    2012-01-01

    Magnesium and its alloys have been used in many industries,but they are reactive and require protection against aggressive environments.In this study,oxide coatings were applied on AZ91D magnesium alloy using micro-arc oxidation (MAO) process.Then,in order to seal the pores of the MAO coatings,the samples were immersed in cerium bath for different times.The surface morphologies and compositions of the coatings were analyzed by scanning electron microscopy (SEM) and X-ray energy dispersive spectroscopy (EDS),respectively.The corrosion behavior of the coatings was investigated with electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization tests in 3.5 wt.% NaCl solution.The amount of the porosity of the coating was measured by electrochemical method.It was found that the sealing treatments by immersion in cerium bath successfully sealed the pores of the MAO coatings.The results of the corrosion tests showed that the MAO coating which was sealed in Ce bath for 10 min enhanced the corrosion resistance of the substrate significantly.Furthermore,this coating had the lowest amount of the porosity among the coatings.

  8. Prediction of two-dimensional topological insulator by forming a surface alloy on Au/Si(111) substrate

    Science.gov (United States)

    Chuang, Feng-Chuan; Hsu, Chia-Hsiu; Chou, Hsin-Lei; Crisostomo, Christian P.; Huang, Zhi-Quan; Wu, Shih-Yu; Kuo, Chien-Cheng; Yeh, Wang-Chi V.; Lin, Hsin; Bansil, Arun

    2016-01-01

    Two-dimensional (2D) topological insulators (TIs), which can be integrated into the modern silicon industry, are highly desirable for spintronics applications. Here, using first-principles electronic structure calculations, we show that the Au/Si(111)-√{3 } substrate can provide a platform for hosting 2D TIs obtained through the formation of surface alloys with a honeycomb pattern of adsorbed atoms. We systematically examined elements from groups III to VI of the periodic table at 2/3 monolayer coverage on Au/Si(111)-√{3 }, and found that In, Tl, Ge, and Sn adsorbates result in topologically nontrivial phases with band gaps varying from 0 to 50 meV. Our scanning tunneling microscopy and low-energy electron diffraction experiments confirm the presence of the honeycomb pattern when Bi atoms are deposited on Au/Si(111)-√{3 }, in accord with our theoretical predictions. Our findings pave the way for using surface alloys as a potential route for obtaining viable 2D TI platforms.

  9. Application of powder metallurgy to an advanced-temperature nickel-base alloy, NASA-TRW 6-A

    Science.gov (United States)

    Freche, J. C.; Ashbrook, R. L.; Waters, W. J.

    1971-01-01

    Bar stock of the NASA-TRW 6-A alloy was made by prealloyed powder techniques and its properties evaluated over a range of temperatures. Room temperature ultimate tensile strength was 1894 MN/sq m (274 500 psi). The as-extruded powder product showed substantial improvements in strength over the cast alloy up to 649 C (1200 F) and superplasticity at 1093 C (2000 F). Both conventional and autoclave heat treatments were applied to the extruded powder product. The conventional heat treatment was effective in increasing rupture life at 649 and 704 C (1200 and 1300 F); the autoclave heat treatment, at 760 and 816 C (1400 and 1500 F).

  10. Deformation behaviour and microstructure development of magnesium AZ 31 alloy during hot and semi-hot deformation

    Energy Technology Data Exchange (ETDEWEB)

    Kawalla, R.; Stolnikov, A. [Institut fuer Metallformung, TU Bergakademie Freiberg, Bernhard-von-Cotta-Str. 4, 09596 Freiberg (Germany)

    2004-07-01

    Deformation properties and microstructure development between 20 and 450 C were investigated for Magnesium AZ31 alloy. It was found that this alloy softens preferably by dynamic recrystallisation. This process starts at suitable deformation conditions above 150 C. However, the temperature region above 250 C is more interesting for the production process the semi-finished products. The recrystallised grain size depends heavily on the deformation temperature. A grain size with a mean diameter smaller than 10 {mu}m can be created below 300 C. For further processing of Magnesium sheets, temperatures above 100 C are suitable, but temperatures above 300 C are responsible for superplasticity. (Abstract Copyright [2004], Wiley Periodicals, Inc.)

  11. Modeling and research of temperature distribution in surface layer of titanium alloy workpiece during AEDG and conventional grinding

    Science.gov (United States)

    Gołąbczak, M.; Gołąbczak, A.; Konstantynowicz, A.; Święcik, R.

    2016-11-01

    Titanium and its alloys are widely recognized as the hardly machinable materials, especially due to their relatively high hardness, low thermal conductivity and possible subcritical superplasticity. Then, a thorough control of the machining process parameters shall be maintained. In this paper, we have concentrated on the grinding of the Ti6Al4V titanium alloy using cBN (boron nitride) grinding wheel combined with the AEDG (abrasive electrodischarge grinding) process. The mathematical model we have dealt with has been based mainly on Jaeger model of the heat taking over between sliding bodies with substantial upgrades related to:estimation of the frictional heat generating based on friction forces distribution,

  12. Silicon-substituted hydroxyapatite coating with Si content on the nanotube-formed Ti–Nb–Zr alloy using electron beam-physical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Jeong, Yong-Hoon [Division of Restorative, Prosthetic and Primary Care Dentistry, College of Dentistry, The Ohio State University, 305 W. 12th Ave., Columbus, OH (United States); Department of Dental Materials, Research Center of Nano-Interface Activation for Biomaterials, and Research Center for Oral Disease Regulation of the Aged, School of Dentistry, Chosun University, Gwangju (Korea, Republic of); Choe, Han-Cheol, E-mail: hcchoe@chosun.ac.kr [Department of Dental Materials, Research Center of Nano-Interface Activation for Biomaterials, and Research Center for Oral Disease Regulation of the Aged, School of Dentistry, Chosun University, Gwangju (Korea, Republic of); Brantley, William A. [Division of Restorative, Prosthetic and Primary Care Dentistry, College of Dentistry, The Ohio State University, 305 W. 12th Ave., Columbus, OH (United States)

    2013-11-01

    The purpose of this study was to investigate the electrochemical characteristics of silicon-substituted hydroxyapatite coatings on the nanotube-formed Ti–35Nb–10Zr alloy. The silicon-substituted hydroxyapatite (Si–HA) coatings on the nanotube structure were deposited by electron beam-physical vapor deposition and anodization methods, and biodegradation properties were analyzed by potentiodynamic polarization and electrochemical impedance spectroscopy measurement. The surface characteristics were analyzed by field-emission scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-ray diffraction (XRD). The Si–HA layers were deposited with rough features having highly ordered nanotube structures on the titanium alloy substrate. The thickness of the Si–HA coating was less than that of the HA coating. The XRD results confirmed that the Si–HA coating on the nanotube structure consisted of TiO{sub 2} anatase, TiO{sub 2} rutile, hydroxyapatite, and calcium phosphate silicate. The Si–HA coating surface exhibited lower I{sub corr} than the HA coating, and the polarization resistance was increased by substitution of silicon in hydroxyapatite. - Highlights: • Silicon substituted hydroxyapatite (Si–HA) was coated on nanotubular titanium alloy. • The Si–HA coating thickness was less than single hydroxyapatite (HA) coating. • Si–HA coatings consisted of TiO{sub 2}, HA, and Ca{sub 5}(PO{sub 4}){sub 2}SiO{sub 4}. • Polarization resistance of the coating was increased by Si substitution in HA.

  13. The mixed-spin ternary-alloy in the form of ABpC1- p on the Bethe lattice

    Science.gov (United States)

    Albayrak, Erhan

    2011-04-01

    The ABpC1-p type of mixed ferromagnetic-ferrimagnetic ternary-alloy with A (spin-3/2), B (spin-1) and C (spin-5/2) ions was studied on the Bethe lattice with the odd numbered shells containing only A ions, while the even numbered shells either containing B or C ions randomly. The phase diagrams were obtained on the (R=|JAC|/JAB,kTc/JAB) and (p, kTc/JAB) planes for given values of p and R, respectively, with the coordination numbers z=3, 4, 5 and 6. The explicit dependence of the phase diagrams on z and each shell of the Bethe lattice having only one type of ion lead to some differences when compared with the previous works. The model presents one or two compensation temperatures for appropriate values of the system parameters.

  14. Electroless plating of low-resistivity Cu–Mn alloy thin films with self-forming capacity and enhanced thermal stability

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Sung-Te, E-mail: stchen@mail.hust.edu.tw [Department of Electronic Engineering, Hsiuping University of Science and Technology, Dali 412, Taichung, Taiwan (China); Chen, Giin-Shan [Department of Materials Science and Engineering, Feng Chia University, Seatwen 407, Taichung, Taiwan (China)

    2015-11-05

    Previous studies have typically used sputter deposition to fabricate Cu–Mn alloy thin films with concentrated solute additions which have exceeded several atomic percentages, and the electrical resistivity values of the resultant films from previous studies are relatively high, ranging from 2.5 to 3.5 μΩ-cm. Herein, we proposed a different approach by using electroless process to plate dilute Cu–Mn (0.1 at.%) alloy thin films on dielectric layers (SiO{sub 2}). Upon forming-gas annealing, the Mn incorporated into Cu–Mn films was segregated toward the SiO{sub 2} side, eventually converting itself into a few atomic layer thickness at the Cu/SiO{sub 2} interface, and forming films with a low level of resistivity the same as that of pure Cu films (2.0 μΩ-cm). The interfacial layer served as not only a diffusion barrier, but also an adhesion promoter that prevented the film’s agglomeration during annealing at elevated temperatures. The mechanism for the dual-function performance by the Mn addition was elucidated by interfacial bonding analysis, as well as dynamic (adhesive strength) and thermodynamic (surface-tension) measurements. - Highlights: • Electroless plating is proposed to grow dilute (0.1%) Cu–Mn films on SiO{sub 2} layers. • Adequate annealing results in a self-forming of MnO{sub x} at the Cu/SiO{sub 2} interface. • The role of interfacial MnO{sub x} as a barrier and adhesion promoter is demonstrated. • The treated dilute film has a low ρ level of pure Cu, in contrast to concentrated films. • Its potential as a single entity replacement of Cu interconnect is presented.

  15. 喷射成形硅铝合金镀覆工艺研究%Study of deposition technology on spray formed silicon-aluminum alloy

    Institute of Scientific and Technical Information of China (English)

    李忠宝; 付银辉; 李元朴

    2012-01-01

    The electroless nickel plating and gold electroplating processes on the surface of spray formed silicon-aluminum alloy (CE11) were studied. The variation of surface morphology and chemical composition on CE11 silicon-aluminum alloy during deposition were analyzed by scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS). The quality of deposit was tested by thermal shock, high-temperature baking, and welding tests. It was found that an electroless plated coating with good adhesion can be obtained on the surface of CE11 silicon-aluminum alloy when electroless nickel plating was carried out after roughening with a mixed solution of ammonium hydrogen fluoride and nitric acid, ultrasonic film removing, zinc immersion, and nickel pre-plating. The deposit after gold electroplating retains good adhesion after baking at 400 ℃, which meets the eutectic welding requirement of gold-germanium, gold-tin alloy, etc.%研究了喷射成形硅铝合金(CE11)材料表面化学镀镍和镀金工艺,使用电子显微镜(SEM)及能谱分析仪(EDS)分析了沉积过程中CE11硅铝合金表面形貌和沉积层化学成分,采用热震、高温烘烤、焊接试验等方法检测了硅铝合金样件的镀层质量.结果发现,CE11硅铝合金经氟化氢铵和硝酸混合溶液粗化、超声波去膜、浸锌、预镀镍后化学镀镍,可以获得结合力良好的化学镀层,镀金后能耐400℃烘烤而仍然保持很好的结合力,能够满足金锗、金锡等合金的共晶焊接使用要求.

  16. Influence of Lanthanum Ion-Implantation on Adhesive Property of Oxide Film Formed on Co-40Cr Alloy

    Institute of Scientific and Technical Information of China (English)

    JIN Hui-ming; ZHANG Lin-nan; LIU Xiao-jun

    2008-01-01

    The isothermal and cyclic oxidizing kinetics of Co-40Cr alloy and its lanthanum ion-implanted samples were studied at 1 000 ℃ in air by thermal gravimetric analysis (TGA). Scanning electron microscopy (SEM) was used to examine the Cr2O3 oxide film's morphology after oxidation. Secondary ion mass spectrum (SIMS) method was used to examine the binding energy change of chromium caused by La-doping and its influence on the formation of Cr2O3 film. Acoustic emission (AE) method was used in situ to monitor the cracking and spalling of oxide films during oxidizing and subsequent air-cooling stages. Laser Raman spectrum was used to examine the stress changes within oxide films. A theoretical model was proposed relating to the film fracture process and was used to analyze the AE spectrum both on time domain and AE-event number domain. It was found that lanthanum implantation remarkably reduced the isothermal oxidizing rate of Co-40Cr and improved the anti-cracking and anti-spalling properties of Cr2O3 oxide film. The reasons for the improvement were mainly that the implanted lanthanum reduced the grain size and internal stress of Cr2O3 oxide, increased the high temperature plasticity of oxide film, and remarkably reduced the number and size of Cr2O3/Co-40Cr interfacial defects.

  17. Effects of sodium tungstate on characteristics of microarc oxidation coatings formed on magnesium alloy in silicate-KOH electrolyte

    Institute of Scientific and Technical Information of China (English)

    DING Jun; LIANG Jun; HU Li-tian; HAO Jing-cheng; XUE Qun-ji

    2007-01-01

    Oxide coatings on AM60B magnesium alloy were prepared using the microarc oxidation(MAO) technique in silicate-KOH electrolyte with addition of 0-6.0 g/L Na2WO4. The MAO processes in base electrolyte with different concentrations of Na2WO4 were studied. The microstructure, compositions and mechanical tribological characteristics of the oxide coatings were also investigated by SEM, XRD, XPS, microhardness analysis and ball-on-disc friction testing, respectively. It is found that the addition of Na2WO4 into the base electrolyte has direct effect on the characteristics of voltage-time curves and breakdown voltage in MAO process. The number of micropores at top of the coating surface is increased by the addition of Na2WO4. The fraction of forsterite Mg2SiO4 in the oxide coating increases with increasing concentration of Na2WO4 in base electrolytes. Furthermore, the microhardness and wear resistance of oxide coatings are enhanced as well.

  18. The Influence of Various Additives on the Properties of Peo Coatings Formed on AZ31 mg Alloy

    Science.gov (United States)

    Rehman, Zeeshan Ur; Ahn, Byung-Hyun; Jeong, Yeong Seung; Song, Jung-Il; Koo, Bon-Heun

    2016-03-01

    In this work, plasma electrolytic oxidation (PEO) ceramic coatings were prepared on magnesium AZ31B alloy. Various electrolyte solutions including phosphate, aluminate and silicate as additives and NaOH + Na2SiF6 as constant agent were used to prepare the coatings. Influence of the additives on chemical composition and structure of the PEO coatings were examined by means of scanning electron microscope (SEM) and XRD. From structural analysis it was found that coatings prepared in the aluminate-based electrolyte have the best structural features. Microhardness and tribological characteristics of the PEO coatings were investigated using Vickers hardness test and pin-on-disc test. Microhardness for aluminate-based coating was found to be 1169.63HV while those for silicate-and phosphate-based coatings were 1093.42HV and 285.91HV, respectively. Wear rate of the aluminate-based coating was found to be lowest than all other coatings having a value of 2.78×10-3mg/Nm.

  19. Effects of cathodic voltages on structure and wear resistance of plasma electrolytic oxidation coatings formed on aluminium alloy

    Energy Technology Data Exchange (ETDEWEB)

    Li, Qingbiao [State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); School of Science, Lanzhou University of Technology, Lanzhou 730050 (China); Liang, Jun, E-mail: jliang@licp.cas.cn [State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); Liu, Baixing; Peng, Zhenjun [State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); Wang, Qing [School of Science, Lanzhou University of Technology, Lanzhou 730050 (China)

    2014-04-01

    Highlights: • The PEO coating growth rate increased with the cathodic voltage increasing. • Higher cathodic voltage resulted in more compact coating structure. • The compact structure led to low surface roughness and high wear resistance. - Abstract: Plasma electrolytic oxidation (PEO) coatings were prepared on aluminium alloy using pulsed bipolar power supply at constant anodic voltage and different cathodic voltages. The samples were prepared to attain the same coating thickness by adjusting the processing time. The scanning electron microscope (SEM), energy dispersive spectrometer (EDS), X-ray diffraction (XRD) and tribometer were employed to investigate the microstructure, element content, phase composition and wear resistance of the coatings respectively. It was found that the coating growth rate enhanced obviously and the coatings exhibited a more compact structure with thicker inner layer and lower surface roughness when the cathodic voltage increased. The coatings were mainly composed of crystalline γ-Al{sub 2}O{sub 3} and amorphous silicate oxides and their relative content changed with the cathodic voltage. The wear resistance of the coatings improved significantly with the increase of cathodic voltage.

  20. Effect of deformation temperature and strain rate on semi-solid deformation behavior of spray-formed Al-70 %Si alloys

    Institute of Scientific and Technical Information of China (English)

    ZHANG Di; YANG Bin; ZHANG Ji-shan; ZHANG Yong-an; XIONG Bai-qing

    2005-01-01

    Spray-formed Al-70%Si(mass fraction) alloys were deformed by compression in the semi-solid state.The effects of the deformation temperature, strain rate and the microstructure were studied. Two strain rates(1 s-1and 0.1 s-1) and six deformation temperatures (600 ℃, 720 ℃ , 780 ℃, 900 ℃, 1 000 ℃ and 1 100 ℃) were chosen. The stress-strain curve exhibits a peak at low strain and then decreases to a plateau before it starts to increase again as the strain increases. The stress required for deformation at lower strain rate and at higher deformation temperatures is less than those at higher strain rate and at lower deformation temperatures. Four mechanisms of semisolid deformation can be used to explain the different behaviors of the stress-strain curves under different conditions.

  1. Determination of sulfuric acid concentration for anti-cavitation characteristics of Al alloy by two step anodizing process to forming nano porous.

    Science.gov (United States)

    Lee, Seung-Jun; Kim, Seong-Kweon; Jeong, Jae-Yong; Kim, Seong-Jong

    2014-12-01

    Al alloy is a highly active metal but forms a protective oxide film having high corrosion resistance in atmosphere environment. However, the oxide film is not suitable for practical use, since the thickness of the film is not uniform and it is severly altered with formation conditions. This study focused on developing an aluminum anodizing layer having hardness, corrosion resistance and abrasion resistance equivalent to a commercial grade protective layer. Aluminum anodizing layer was produced by two-step aluminum anodizing oxide (AAO) process with different sulfuric acid concentrations, and the cavitation characteristics of the anodized coating layer was investigated. In hardness measurement, the anodized coating layer produced with 15 vol.% of sulfuric acid condition had the highest value of hardness but exhibited poor cavitation resistance due to being more brittle than those with other conditions. The 10 vol.% of sulfuric acid condition was thus considered to be the optimum condition as it had the lowest weight loss and damage depth.

  2. Microstructural characteristics of oxide layers formed on Mg–9 wt%Al–1 wt%Zn alloy via two-step plasma electrolytic oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Kang Min [Department of Metallurgy and Materials Engineering, Hanyang University, Ansan 426-791 (Korea, Republic of); Ko, Young Gun, E-mail: younggun@ynu.ac.kr [School of Materials Science and Engineering, Yeungnam University, Gyeongsan 712-749 (Korea, Republic of); Shin, Dong Hyuk, E-mail: dhshin@hanyang.ac.kr [Department of Metallurgy and Materials Engineering, Hanyang University, Ansan 426-791 (Korea, Republic of)

    2014-12-05

    Graphical abstract: - Highlights: • The oxide layer on Mg alloy sample treated by two-step PEO coating was fabricated. • The breakdown voltage of sample via two-step PEO coating was observed to be ∼475 V. • Mg{sub 2}Zr{sub 5}O{sub 12} and ZrO{sub 2} were synthesized in the oxide layer via two-step PEO coating. - Abstract: A study investigated the formation and microstructural features of the oxide layer formed on Mg–9 wt%Al–1 wt%Zn alloy coated by two-step plasma electrolytic oxidation (PEO) where an acid electrolyte with K{sub 2}ZrF{sub 6} was used for the second PEO coating after the initial coating was done in an alkaline electrolyte. The microstructure, chemical compositions, and constituent compounds of the oxide layers were observed using scanning electron microscopy, electron probe micro-analyzer, and X-ray diffraction, respectively. The microstructural observations showed that the micropores caused by plasma discharge were formed in the oxide layers which were comprised of three different parts, namely, inner, intermediate, and outer layers from the substrate to the surface of the sample. The outer layer contained the highest concentration of Zr element whose amount decreased toward the substrate whereas the concentration of Mg element increased in the order of outer, intermediate, and inner layers. This finding suggested that the outer oxide layer was mainly comprised of ZrO{sub 2} compound while both ZrO{sub 2} and Mg{sub 2}Zr{sub 5}O{sub 12} compounds existed together as the main compounds in the intermediate oxide layer.

  3. Microstructure of Al2O3 scales formed on NiCrAl alloys. Ph.D. Thesis - Case Western Reserve Univ.

    Science.gov (United States)

    Smialek, J. L.

    1981-01-01

    The structure of transient scales formed on pure and Y or Zr-doped Ni-15Cr-13Al alloys oxidized for 0.1 hr at 1100 C was studied by the use of transmission electron microscopy. Crystallographically oriented scales were found on all three alloys, but especially for the Zr-doped NiCrAl. The oriented scales consisted of alpha-(Al,Cr)2O3, Ni(Al,Cr)2O4 and gamma-Al2O3. They were often found in intimate contact with each other such that the close-packed planes and directions of one oxide phase were aligned with those of another. The prominent structural features of the oriented scales were approximately equal to micrometer subgrains; voids, antiphase domain boundaries and aligned precipitates were also prevalent. Randomly oriented alpha-Al2O3 was also found and was the only oxide ever observed at the immediate oxide metal interface. These approximately 0.15 micrometer grains were populated by intragranular voids which decreased in size and number towards the oxide metal interface. A sequence of oxidation was proposed in which the composition of the growing scale changed from oriented oxides rich in Ni and Cr to oriented oxides rich in Al. At the same time the structure changed from cubic spinels to hexagonal corundums with apparent precipitates of one phase in the matrix of the other. Eventually randomly oriented pure alpha-Al2O3 formed as the stable oxide with an abrupt transition: there was no gradual loss of orientation, no gradual compositional change or no gradual decrease in precipitate density.

  4. Superplastic Solid-Phase Welding of 40 Cr-T10A Steel

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The microstructure of 40Cr and T10A steel sample and its surface to be welded is ultra-fined through salt-bath cyclic quenching and high frequency hardening, then the surface is cleaned. Under non-vacuum and no shielded gas, the welding parameter of isothermal superplastic solidphase welding and the effect of surface microstructure prior to pressure welding on the quality of joint are studied. At the temperature of 730~750°C and at initial strain rate of (2~4) × 10-4 s-1,the strength of the joint is up to or close to that of 40Cr base metal in 3~5 min pressure welding.

  5. Synthesis and Enhanced Superplasticity of the Zirconia-dispersed Alumina Nanocomposite

    Institute of Scientific and Technical Information of China (English)

    Guoqing CHEN; Kaifeng ZHANG; Wenbo HAN; Junting LUO

    2005-01-01

    A series of alumina-zirconia composites with various grain sizes were prepared from the nano-sized powders with different agglomerations. Microstructural analysis of the sintered compacts indicates that the as-sintered material is a typical intra/inter granular nanocomposite with uniform distribution of the zirconia grains in the alumina matrix.Superplastic deep drawing test under different conditions demonstrates that dense Al2O3/ZrO2 samples with average grain size of 230 nm can be elongated to a dome height of at least 12 mm at the punch rate of 0.6 mm.min-1at 1400℃. Further drawing tests show that for the composites with larger grain size, such elongation cannot be achieved at such a strain rate.

  6. Structure analysis of CoPt alloy film with metastable ordered phases of L11 and Bh formed on Ru(0001 underlayer

    Directory of Open Access Journals (Sweden)

    Ohtake Mitsuru

    2014-07-01

    Full Text Available CoPt alloy films of 40 nm thickness are prepared on MgO(111 substrates with and without Ru(0001 underlayer at 300 °C by radio-frequency magnetron sputtering. CoPt films with the close-packed plane parallel to the substrate surface grow epitaxially on the Ru underlayer as well as on the MgO substrate. Flat surfaces with the arithmetical mean roughness value of 0.2 nm are realized for both films. The crystal structure is determined by considering the atomic stacking sequence of close-packed plane and the order degree. The film formed on MgO substrate consists of an fcc-based L11 ordered crystal, whereas the film grown on Ru underlayer involves an hcp-based Bh ordered crystal in addition to the L11 ordered crystal. The order degrees of films formed on MgO substrate and Ru underlayer are 0.30 and 0.34, respectively. The L11 crystal consists of two variants whose stacking sequences of close-packed plane are ABCABC… and ACBACB…, while the Bh crystal is a single-crystal with the stacking sequence of ABAB… Formation of Bh crystal is promoted on the Ru underlayer. The film formed on Ru underlayer shows a strong perpendicular magnetic anisotropy reflecting the magnetocrystalline anisotropies of L11 and Bh crystals.

  7. Effects of crystal boundary gliding and dislocation on superplastic deformation of SiCw/6061 Al composite

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    SiCw/6061Al composite was fabricated with squeeze casting method, hot extruded and superplastically tensile tested. At the temperature of 570  ℃and the strain rate of 2.0×10-3 s-1, an elongation of 280% was obtained. The change of grain shape, dislocation density and distribution was observed by TEM. The results show that during the superplastic deformation grain shape on the whole is unchanged, but the dislocation density and distribution vary quite a lot with the tensile action. Under the optimal straining conditions, dislocation mainly distributes along the grain boundary, which has an important effect on cooperative strain especially. When the strain magnitude is big enough, there appears stacking faults and twin crystals, which also has some effect on the cooperative strain.

  8. A study on microstructure and corrosion resistance of ZrO2-containing PEO coatings formed on AZ31 Mg alloy in phosphate-based electrolyte

    Science.gov (United States)

    Zhuang, J. J.; Guo, Y. Q.; Xiang, N.; Xiong, Y.; Hu, Q.; Song, R. G.

    2015-12-01

    ZrO2-containing ceramic coatings formed on the AZ31 Mg alloy were fabricated in an alkaline electrolyte containing sodium phosphate and potassium fluorozirconate (K2ZrF6) by plasma electrolytic oxidation (PEO). X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) techniques were used to study the phase structure and composition of the coatings. It is indicated that the coatings formed in the K2ZrF6-containing electrolyte were composed of MgO, MgF2 and t-ZrO2. Morphological investigation carried out by scanning electron microscopy (SEM) and stereoscopic microscopy, revealed that the uniformity of coatings increased and roughness of coatings decreased after the addition of K2ZrF6. Electrochemical investigation was achieved by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) test. The results showed that the PEO coating formed in K2ZrF6-containing electrolyte exhibited an improved corrosion resistance than that of the coating formed in K2ZrF6-free electrolyte. In addition, the polarization and EIS tests results both showed that the suitable concentration (2.5 g/l) of K2ZrF6 is of significant ability to improve the corrosion resistance of coatings. However, 5 g/l and 10 g/l K2ZrF6 has a negative effect on improving the corrosion resistance of PEO coatings compared with the coating formed in 2.5 g/l K2ZrF6-containing electrolyte.

  9. POWDER-GAS DISCHARGE, FORMED AT MELTING OF ALUMINIUM CASTING ALLOYS IN INDUCTION CRUCIBLE FURNACE IAT- 6

    Directory of Open Access Journals (Sweden)

    G. A. Rumjantseva

    2009-01-01

    Full Text Available The carried out analysis of powder-gas discharge shows that volumes and composition of the forming dust are determined by composition of recycled material, type of lubrication for machines under high pressure, quality of recycled material preparation and technology of refining processing.

  10. Observation On Void Formed In Oxide Scale Of Fe-Cr-Ni Alloy At 1073k In Dry And Humid Environments

    Directory of Open Access Journals (Sweden)

    Akbar Kaderi

    2012-01-01

    Full Text Available Void formation in oxide scale during high temperature oxidation is a common phenomenon. Over a long period of time voids will affect the mechanical property of scales by influencing the cracking and spalling. Voids formed in dry environment are different than that of formed in humid environment. With the presence of water vapor in humid environment the formation of void will increase, thus greater number of void compared to that in dry environment. Fe-Cr-Ni alloy samples were exposed isothermally at 1073 K in air (P_(O_2 = 0.21atm = 2.1×?10?^(5 Pa and  humid (air + steam environments. XRD analysis done to all samples confirms that Fe2O3, Fe3O4, NiCr2O4, FeCr2O4, Cr2O3 and NiO phases exist in the scale. EDX analysis done shows varying compositions of Fe,Cr,Ni and O in outer and inner oxide scale, oxide scale/metal interface and metal. Field emission scanning electron microscope (FE-SEM was used to investigate voids formed in the cross sections of the oxidized samples. Volume fraction of voids in the oxide scale was calculated in accordance to the cross sectional area fraction of voids in the scale. It shows that Fe-Cr-Ni alloy samples exposed in humid environment has as high as 71% more voids than that exposed in dry environment. It is concluded that the humid environment increased the number of void formed in the oxide scale, thus facilitates the exfoliation of protective scale during the high temperature oxidation. ABSTRAK: Pembentukan gelembung udara di dalam lapisan oksida ketika proses pengoksidaan di suhu tinggi merupakan satu fenomena biasa. Pada satu jangka masa yang panjang gelembung-gelembung ini akan memberi kesan kepada sifat mekanikal oksida dengan mempengaruhi pembentukan keretakan dan pengelupasan oksida. Gelembung udara yang terbentuk di dalam persekitaran kering berbeza daripada yang terbentuk di dalam persekitaran lembap. Dengan adanya wap air, pembentukan gelembung akan bertambah berbanding yang terbentuk di dalam

  11. Effect of some process parameters on geometric errors in twopoint incremental forming for Al-Cu-Mg Aluminum Alloy

    Science.gov (United States)

    Li, Xiaoqiang; Han, Kai; Yu, Honghan; Zhang, Yongsheng; Li, Dongsheng

    2016-08-01

    Two point incremental forming receives widespread study with its advantages of economy and flexibility in small batch products, such as aircraft parts. Aircraft parts, however, are rigorous in their shape errors. In this paper, one real airplane part is selected and formed with different process parameters to investigate the shape error level of part. Comparing the geometric errors caused by different process parameters, such as tool diameter, step size, feed rate and tool path, it is found that the geometric errors reduce as tool diameter increases. Meanwhile, the effect of step size is not linear. Influence law of feed rate is various with different other parameters. The bidirectional tool path, having opposite processing direction at adjacent layer, reduces the errors.

  12. Semi-solid Forming of a Damper Housing with Dendritic and Non-dendritic Al-Si-Mg Alloy

    Institute of Scientific and Technical Information of China (English)

    ChenCM; YangCC; ChaoCG

    2001-01-01

    A motorcycle component of damper housing was made by semi-solid forming process. This was used to investigate the effect of microstructures of feedstock on the formability of semisolid process. The soundness and microstructures of casting parts made by dendritic and non-dendritic feedstock were investigated. Separating of liquid phase was found in the casting produced by dendritic feedstock, which might result in defects of porosity, while uniform microstructures were found in the casting produced by no...

  13. Crystallization behavior of Ti61.67Zr17.15Ni14.80Cu6.38 glass-forming alloy

    Institute of Scientific and Technical Information of China (English)

    范金铎; 高逸群; 黎仕增

    2004-01-01

    Ti61.67 Zr17.15 Ni14.80 Cu6.38 (atom fraction,%) metallic glass has applications in brazing. Using the hammer-and-anvil technique, Ti61.67 Zr17.15 Ni14.80 Cu6.38 metallic glass was prepared. The crystallization behavior for this metallic glass was investigated by differential scanning calorimetry (DSC), X-ray diffractometry (XRD) and transmission electron microscopy(TEM). Th ere are three stages in DSC curves of crystallization. The reduced glass temperature Trg is 0.42. The kinetic parameters of crystallization were calculated by a set of equations of the maximum crystallization rate. The crystalline phase formed in the MSI(Metastable stage Ⅰ) is Zr2Cu, in the MSⅡ is α-Ti and in the MSⅢ is Ti2 Ni. This kind of alloy has lower glass forming ability, and the Ti61.67 Zr17. 15 Ni14. 80 Cu6.38 metallic glass has lower thermal stability.

  14. PIIID-formed (Ti, O)/Ti, (Ti, N)/Ti and (Ti, O, N)/Ti coatings on NiTi shape memory alloy for medical applications.

    Science.gov (United States)

    Sun, Tao; Wang, Lang-Ping; Wang, Min; Tong, Ho-Wang; Lu, William W

    2012-08-01

    (Ti, O)/Ti, (Ti, N)/Ti and (Ti, O, N)/Ti composite coatings were fabricated on NiTi shape memory alloy via plasma immersion ion implantation and deposition (PIIID). Surface morphology of samples was investigated using atomic force microscopy (AFM) and scanning electron microscopy (SEM). Cross-sectional morphology indicated that the PIIID-formed coatings were dense and uniform. X-ray diffraction (XRD) was used to characterize the phase composition of samples. X-ray photoelectron spectroscopy (XPS) results showed that the surface of coated NiTi SMA samples was Ni-free. Nanoindentation measurements and pin-on-disc tests were carried out to evaluate mechanical properties and wear resistance of coated NiTi SMA, respectively. For the in vitro biological assessment of the composite coatings in terms of cell morphology and cell viability, osteoblast-like SaOS-2 cells and breast cancer MCF-7 cells were cultured on NiTi SMA samples, respectively. SaOS-2 cells attached and spread better on coated NiTi SMA. Viability of MCF-7 cells showed that the PIIID-formed composite coatings were noncytotoxic and coated samples were more biocompatible than uncoated samples.

  15. Corrosion mechanisms for metal alloy waste forms: experiment and theory Level 4 Milestone M4FT-14LA0804024 Fuel Cycle Research & Development

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Xiang-Yang [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Taylor, Christopher D. [The Ohio State Univ., Columbus, OH (United States). Fontana Corrosion Center; Kim, Eunja [Univ. of Nevada, Las Vegas, NV (United States); Goff, George Scott [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Kolman, David Gary [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2014-07-31

    This document meets Level 4 Milestone: Corrosion mechanisms for metal alloy waste forms - experiment and theory. A multiphysics model is introduces that will provide the framework for the quantitative prediction of corrosion rates of metallic waste forms incorporating the fission product Tc. The model requires a knowledge of the properties of not only the metallic waste form, but also the passive oxide films that will be generated on the waste form, and the chemistry of the metal/oxide and oxide/environment interfaces. in collaboration with experimental work, the focus of this work is on obtaining these properties from fundamental atomistic models. herein we describe the overall multiphysics model, which is based on MacDonald's point-defect model for passivity. We then present the results of detailed electronic-structure calculations for the determination of the compatibility and properties of Tc when incorporated into intermetallic oxide phases. This work is relevant to the formation of multi-component oxides on metal surfaces that will incorporate Tc, and provide a kinetic barrier to corrosion (i.e. the release of Tc to the environment). Atomistic models that build upon the electronic structure calculations are then described using the modified embedded atom method to simulate metallic dissolution, and Buckingham potentials to perform classical molecular dynamics and statics simulations of the technetium (and, later, iron-technetium) oxide phases. Electrochemical methods were then applied to provide some benchmark information of the corrosion and electrochemical properties of Technetium metal. The results indicate that published information on Tc passivity is not complete and that further investigation is warranted.

  16. In-situ study of crystallization kinetics in ternary bulk metallic glass alloys with different glass forming abilities

    Science.gov (United States)

    Lan, Si; Wei, Xiaoya; Zhou, Jie; Lu, Zhaoping; Wu, Xuelian; Feygenson, Mikhail; Neuefeind, Jörg; Wang, Xun-Li

    2014-11-01

    In-situ transmission electron microcopy and time-resolved neutron diffraction were used to study crystallization kinetics of two ternary bulk metallic glasses during isothermal annealing in the supercooled liquid region. It is found that the crystallization of Zr56Cu36Al8, an average glass former, follows continuous nucleation and growth, while that of Zr46Cu46Al8, a better glass former, is characterized by site-saturated nucleation, followed by slow growth. Possible mechanisms for the observed differences and the relationship to the glass forming ability are discussed.

  17. In-situ study of crystallization kinetics in ternary bulk metallic glass alloys with different glass forming abilities

    Energy Technology Data Exchange (ETDEWEB)

    Lan, Si; Wei, Xiaoya; Wu, Xuelian; Wang, Xun-Li, E-mail: xlwang@cityu.edu.hk [Department of Physics and Materials Science, City University of Hong Kong, 83 Tat Chee Ave., Kowloon (Hong Kong); Zhou, Jie; Lu, Zhaoping [State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing (China); Feygenson, Mikhail; Neuefeind, Jörg [Chemical and Engineering Materials Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States)

    2014-11-17

    In-situ transmission electron microcopy and time-resolved neutron diffraction were used to study crystallization kinetics of two ternary bulk metallic glasses during isothermal annealing in the supercooled liquid region. It is found that the crystallization of Zr{sub 56}Cu{sub 36}Al{sub 8}, an average glass former, follows continuous nucleation and growth, while that of Zr{sub 46}Cu{sub 46}Al{sub 8}, a better glass former, is characterized by site-saturated nucleation, followed by slow growth. Possible mechanisms for the observed differences and the relationship to the glass forming ability are discussed.

  18. De-alloyed platinum nanoparticles

    Science.gov (United States)

    Strasser, Peter [Houston, TX; Koh, Shirlaine [Houston, TX; Mani, Prasanna [Houston, TX; Ratndeep, Srivastava [Houston, TX

    2011-08-09

    A method of producing de-alloyed nanoparticles. In an embodiment, the method comprises admixing metal precursors, freeze-drying, annealing, and de-alloying the nanoparticles in situ. Further, in an embodiment de-alloyed nanoparticle formed by the method, wherein the nanoparticle further comprises a core-shell arrangement. The nanoparticle is suitable for electrocatalytic processes and devices.

  19. Preparation and Characterization of Amorphous Layer on Aluminum Alloy Formed by Plasma Electrolytic Deposition (PED)

    Institute of Scientific and Technical Information of China (English)

    GUANYong-jun; XIAYuan

    2004-01-01

    In this investigation, protective layers were formed on aluminum substrate by Plasma Electrolytic Deposition (PED) using sodium silicate solution. The relation between the thickness of the layer and process time were studied. XRD, SEM, EDS were used to study the layer's structure, composition and micrograph. The results show that the deposited layers are amorphous and contain mainly oxygen, silicon, and aluminum. The possible formation mechanism of amorphous[Al-Si-O] layer was proposed: During discharge periods, Al2O3 phase of the passive film and SiO32- near the substrate surface are sintered into xSiO2(1-x)Al2O3 and then transformed into amorphous [Al-Si-O] phase.

  20. The effect of C atom concentration on the electronic properties of boron carbonitride alloy nanotube in zig-zag form

    Indian Academy of Sciences (India)

    H Milani Moghaddam

    2011-06-01

    Electronic properties of single-walled boron nitride nanotube in zig-zag form are numerically investigated by replacing B atoms with C atoms. Using a tight-binding Hamiltonian, the methods based on Green’s function theory, Landauer formalism and Dyson equation, the electronic density of states and electronic conductance in boron nitride nanotube and boron carbonitride nanotube are calculated. Our calculations indicate that in a boron nitride nanotube, the localized states associated with C impurities appear as the concentration of C atoms increases. The boron carbonitride nanotube thus behaves like a semiconductor. Also, by increasing the C atom concentration, the voltage in the first step on the – characteristics decreases, whereas the corresponding current increases.

  1. Superplasticity. Revision

    Science.gov (United States)

    1989-09-01

    NASA IAA Journal Article Issue 10 Structural materials for future aerospace developments. Materiales estructurales para los futuros desarrollos...aeroespaciale (AA)GARCIA POGGIO. JOSE A. (Congreso Nacional de Ingenieria Mecanica , 6th, Madrid. Spain. Dec. 15-18, 1987) Ingenieria Aeronautica y Astronautica

  2. Catalyst Alloys Processing

    Science.gov (United States)

    Tan, Xincai

    2014-10-01

    Catalysts are one of the key materials used for diamond formation at high pressures. Several such catalyst products have been developed and applied in China and around the world. The catalyst alloy most widely used in China is Ni70Mn25Co5 developed at Changsha Research Institute of Mining and Metallurgy. In this article, detailed techniques for manufacturing such a typical catalyst alloy will be reviewed. The characteristics of the alloy will be described. Detailed processing of the alloy will be presented, including remelting and casting, hot rolling, annealing, surface treatment, cold rolling, blanking, finishing, packaging, and waste treatment. An example use of the catalyst alloy will also be given. Industrial experience shows that for the catalyst alloy products, a vacuum induction remelt furnace can be used for remelting, a metal mold can be used for casting, hot and cold rolling can be used for forming, and acid pickling can be used for metal surface cleaning.

  3. Rare earth effect of yttrium on formation and property of Cr2O3 oxide film formed on Co-Cr binary alloy

    Institute of Scientific and Technical Information of China (English)

    JIN Huiming; FELIX A. Congrado; AROYAVE M. Hayara

    2006-01-01

    The isothermal oxidizing kinetics of Co-40Cr alloy and its yttrium ion-implanted samples were studied at 1000℃ in air by thermal-gravity analysis (TGA). Scanning electronic microscopy (SEM) was used to examine the Cr2O3 oxide film's morphology after oxidation. Secondary ion mass spectrum (SIMS) method was used to examine the binding energy change of chromium caused by Y-doping and its influence on formation of Cr2O3 film. Acoustic emission (AE) method was used in situ to monitor the cracking and spalling of oxide films formed on both samples during oxidizing and subsequent air-cooling stages. Theoretical model simulating the film fracture process was proposed to analyze the acoustic emission spectrum both on time domain and on AE-event number domain. It is found that yttrium ionimplantation can remarkably reduce the isothermal oxidizing rate of Co-40Cr and improve the anti-cracking and anti-spalling properties of Cr2O3 oxide film. Reasons for the improvement are mainly that the implanted yttrium can reduce the grain size of Cr2O3 oxide, increase the high temperature plasticity of oxide film, and remarkably reduce the number and size of Cr2O3/Co-40Cr interfacial defects.

  4. Effect of Al2O3 Micro-powder Additives on the Properties of Micro-arc Oxidation Coatings Formed on 6061 Aluminum Alloy

    Science.gov (United States)

    Wang, Ping; Wu, Ting; Xiao, You Tao; Pu, Jun; Guo, Xiao Yang; Huang, Jun; Xiang, Chun Lang

    2016-09-01

    Al2O3 micro-powder was suspended in the basis electrolyte to form micro-arc oxidation (MAO) coatings on 6061 aluminum alloy by MAO. During the stage of micro-arc oxidation, Al2O3 micro-powder with negative surface charge was melted by the micro-arc around the anode and incorporated into the MAO coatings. With the continuous addition of Al2O3 micro-powder, the oxidation voltages rose up firstly and then decreased. The surface and cross-sectional morphologies showed that the size of micropores decreased and the MAO coatings surface got loosened following the variation in Al2O3 micro-powder concentration. As a consequence of the changing coating structure, the corrosion resistance of the coatings decreased apparently. The micro-hardness of the coatings increased firstly and then decreased, opposite to the trend of the average friction coefficient. It revealed the minimum average friction coefficient of MAO coatings and maximum adhesion between the coatings and substrate when 2.0 g/L Al2O3 micro-powder was added into electrolyte. There were visible cracks and peelings on the coating surface merely at 4.0 g/L after thermal shock tests. The x-ray diffraction results indicated that the addition of Al2O3 micro-powder had less effect on the phase composition of MAO coatings.

  5. Characteristics of a multicomponent Nb-Ti-Al alloy via industrial-scale practice

    Energy Technology Data Exchange (ETDEWEB)

    Sikka, V.K. [Oak Ridge National Lab., TN (United States). Metals and Ceramics Div.; Loria, E.A. [Reference Metals Co., Inc., Bridgeville, PA (United States)

    1997-05-01

    Within the spectrum of advanced intermetallic materials, an alloy containing 44Nb-35Ti-6Al-5Cr-8V-1W-0.5Mo-0.3Hf (at. %) was investigated in the industrial-scale produced condition. The alloy was tensile tested in air from room temperature to 1,000 C and in vacuum at 750 and 850 C. Results of this study have shown that the alloy can be commercially produced and has adequate ductility for its secondary processing even at an oxygen level of 1,160 wppm. The alloy has room temperature ductility of 16% and superplastic elongation of 244% at 1,000 C. This alloy shows low intermediate temperature (600--850 C) ductility when tested in air. The vacuum testing revealed that the low ductility is associated within oxygen embrittlement phenomenon. It is expected that such an embrittlement can be taken care of by an oxidation resistant coating. The alloy also possesses superior strength to similar alloys in this class. Results of this investigation suggest a strong potential for consideration of this alloy to exceed the useful temperature range of nickel-base superalloys.

  6. Thermally assisted deformation of structural superplastics and nanostructured materials: A personal perspective

    Indian Academy of Sciences (India)

    K A Padmanabhan

    2003-02-01

    Optimal structural superplasticity and the deformation of nanostructured materials in the thermally activated region are regarded as being caused by the same physical process. In this analysis, grain/interphase boundary sliding controls the rate of deformation at the level of atomistics. Boundary sliding develops to a mesoscopic level by plane interface formation involving two or more boundaries and at this stage the rate controlling step is boundary migration. In other words, grain/interphase boundary sliding is viewed as a two-scale process. The non-zero, unbalanced shear stresses present at the grain/interphase boundaries ensure that near-random grain rotation is also a non-rate controlling concomitant of this mechanism. Expressions have been derived for the free energy of activation for the atomic scale rate controlling process, the threshold stress that should be crossed for the commencement of mesoscopic boundary sliding, the inverse Hall-Petch effect and the steady state rate equation connecting the strain rate to the independent variables of stress, temperature and grain size. Beyond the point of inflection in the log stress-log strain rate plot, climb controlled multiple dislocation motion within the grains becomes increasingly important and at sufficiently high stresses becomes rate controlling. The predictions have been validated experimentally.

  7. Superplastic behavior of silica nanowires obtained by direct patterning of silsesquioxane-based precursors

    Science.gov (United States)

    Yılmaz, Mustafa; Wollschläger, Nicole; Nasr Esfahani, Mohammad; Österle, Werner; Leblebici, Yusuf; Erdem Alaca, B.

    2017-03-01

    Silica nanowires spanning 10 μm-deep trenches are fabricated from different types of silsesquioxane-based precursors by direct e-beam patterning on silicon followed by release through deep reactive ion etching. Nanowire aspect ratios as large as 150 are achieved with a critical dimension of about 50 nm and nearly rectangular cross-sections. In situ bending tests are carried out inside a scanning electron microscope, where the etch depth of 10 μ {{m}} provides sufficient space for deformation. Silica NWs are indeed observed to exhibit superplastic behavior without fracture with deflections reaching the full etch depth, about two orders of magnitude larger than the nanowire thickness. A large-deformation elastic bending model is utilized for predicting the deviation from the elastic behavior. The results of forty different tests indicate a critical stress level of 0.1–0.4 GPa for the onset of plasticity. The study hints at the possibility of fabricating silica nanowires in a monolithic fashion through direct e-beam patterning of silsesquioxane-based resins. The fabrication technology is compatible with semiconductor manufacturing and provides silica nanowires with a very good structural integrity.

  8. AZ系列镁合金热模拟挤压过程中挤压力的研究%Extrusion Force of AZ Series Mg Alloy During Thermal Simulated Extrusion Forming

    Institute of Scientific and Technical Information of China (English)

    彭建; 周绸; 李权

    2011-01-01

    AZ 10, AZ31, AZ61 and AZ91 magnesium alloys were deformed with simulated extrusion system on Gleeble 1500D, which can determine the extrusion force during extrusion forming process. The microstructure of the alloys and the evolution of extrusion force were investigated. The results show that the extrusion force increases gradually with the increase of alloy element. Aimed at the same magnesium alloy, the deformed alloy with previous homogenization before extrusion has more extrusion force than that without homogenization, and dynamic recrystallization is a decisive factor in extrusion force during extrusion forming.%通过在Gleeble1500D热模拟试验机上对AZ10、AZ31、AZ61和AZ91镁合金进行模拟挤压,并对热模拟挤压成形过程中的挤压力进行测定,研究AZ系列镁合金热模拟挤压成形过程挤压力及其组织变化.研究结果表明,在AZ系列镁合金中,随着合金元素含量的增多,挤压力逐渐增大,并且同种镁合金在挤压前经均匀化退火处理后所需的挤压力比未经均匀化处理的合金所需挤压力大,动态再结晶是影响其挤压力大小的决定性因素.

  9. The relationship between the super plasticity of laser welding joint of titanium alloy and hydrogen treatment

    Science.gov (United States)

    Cao, Zean; Cheng, Donghai; Jiang, Xunyan; Hu, Dean; Chen, Yiping

    2017-06-01

    The superplastic deformation uniformity of laser welded joint of TC4 titanium alloy is improved by hydrogen treatment. The non-uniform deformation coefficient K was introduced to quantification ally characterize the non-uniform deformation. The results show when the content of hydrogen exceeds 0.29%, the super plasticity of the titanium alloy welded plate decreases with the increase of the hydrogen content. The decrease of the shrinkage of the base material is larger than that of the weld section with the increase of hydrogen content. The K can be used to describe the non-uniform deformation of the weld and the base material during the superplastic deformation of laser welded joint of the TC4. The K value increases with increaseing hydrogen content, increaseing deformation temperature and decreaseing strain rate. The K value reaches the maximum of 0.84 with hydrogen content of 1.299%, deformation temperature of 920 °C, strain rate of 10-4S-1.

  10. Basic Study on Selective Laser Melting Technique Formed to Dental Co-Cr Alloy%选择性激光熔融技术成形牙科钴铬合金性能的初步研究

    Institute of Scientific and Technical Information of China (English)

    李勇; 张飚; 黄奇容; 王萍; 赵创; 罗朋

    2012-01-01

    Objective: To investigate the surface condition and ion releasing behavior of cobalt-chromium (Co - Cr) dental alloy formed by selective laser melting (SLM) technique. Methods: Before porcelain fused sintering process, the surface condition was observed using a scanning electron microscope(SEM) , and then the density and hardness of the two alloys were examined. After porcelain fused firing, the interface of porcelain and alloy was observed. Results; SLM technique provide Co -Cr alloy higher hardness than traditional casting method, hwever the density of two alloys were same. After degassing-preoxidation procedure and porcelain fused firing, the interface of the two alloys with porcelain all showed excellent combination. Conclusions: Considering the properties before and after porcelain fused sintering process, SLM technique is suitable to form dental Co - Cr alloy.%目的:通过测试选择性激光熔融(selective laser melting,SLM)技术制作的牙科钴铬(Co- Cr)合金的部分机械性能、表面显微结构、瓷熔附后的界面情况,以期为该技术的应用提供基础资料.方法:使用SLM技术制作牙科钴铬合金样品,用扫描电镜观察样品的表面形貌和显微结构、测试样品的密度和硬度;将样品经过除气-预氧化处理,用扫描电镜观察样品表面氧化膜的形貌和显微结构;将经过除气-预氧化处理的样品进行瓷熔附,用扫描电镜观察样品金-瓷界面的显微结构.结果:SLM制作的钴铬合金的硬度明显高于铸造钴铬合金;经过除气-预氧化处理后的氧化膜细密均匀;两种方法制作的合金在瓷熔附处理后的金-瓷界面均没有发现明显裂纹.结论:SLM技术比传统铸造技术具有一定的优越性,技术细节有待深入研究.

  11. New amorphous alloy with high glass forming ability on the Cu-Zr-Al-Gd system; Desenvolvimento de nova liga com estrutura amorfa no sistema Cu-Zr-Al-Gd

    Energy Technology Data Exchange (ETDEWEB)

    Mazzer, E.M.; Aliaga, L.C.R.; Bolfarini, C.; Botta Filho, W.J.; Kiminami, C.S., E-mail: eric_mazzer@hotmail.co [Universidade Federal de Sao Carlos (DEMa/UFSCar), SP (Brazil). Dept. de Engenharia de Materiais

    2010-07-01

    The prediction of the Glass Forming Ability (GFA) in metallic alloys is usually performed by empirical or semi-empirical criteria in binary or ternary systems. For multi-component systems with more than three elements, the criteria or models become extremely complex making it impractical. In this paper we present the results on the GFA prediction of the Cu-Zr-Al-Gd alloys, where compositions had been selected for the synergy of the topological instability and electronegativity criteria which was increased by the average radio criterion for the quaternary system. Alloys were prepared and processed by arc-meting and die casting techniques. Characterization was made by x-ray diffraction (XRD), scanning electron microscopy (SEM) and differential scanning calorimetry (DSC) techniques. It was concluded that Cu{sub 39,2}Zr{sub 49}Al{sub 9}, {sub 80}Gd{sub 2} alloy presents high thermal stability expressed by great supercooled liquid region upper to 76 deg C. (author)

  12. Damping performance of Cu-Zn-Al shape memory alloys in engineering structures

    Institute of Scientific and Technical Information of China (English)

    司乃潮; 孙克庆; 孙少纯; 刘海霞

    2004-01-01

    The stress strain curves of two CuZnAl shape memory alloys which have the martensitic transformation temperatures of 50 ℃ and -10 ℃ respectively, were measured by using electronic material tester after treated by different heat-treatment conditions. The results show that the area enclosed by hysteresis loop of the CuZnAl shape memory alloy in martensitic state is much larger than that of the alloy in austenitic state with super-elasticity at room temperature. Therefore, the former has better vibration attenuation effect. After being oil-quenched, waterquenched, and step-quenched, the CuZnAl alloy takes on more stable shape memory effect, better super-plasticity and superelasticity (pseudoelasticity). A CuZnAl shape memory alloy damper was designed, produced and installed to a 2-layer frame structure. In addition, the vibration experiments were made by dynamic data collecting analysis meter. The velocity of vibration attenuation of frame structure with CuZnAl shape memory alloy damper is much faster than that without it. And with the help of CuZnAl shape memory alloy damper, the attenuation period reduces to 1/10 of the original.

  13. Ultrahigh temperature intermetallic alloys

    Energy Technology Data Exchange (ETDEWEB)

    Brady, M.P.; Zhu, J.H.; Liu, C.T.; Tortorelli, P.F.; Wright, J.L.; Carmichael, C.A.; Walker, L.R. [Oak Ridge National Lab., TN (United States). Metals and Ceramics Div.

    1997-12-01

    A new family of Cr-Cr{sub 2}X based alloys with fabricability, mechanical properties, and oxidation resistance superior to previously developed Cr-Cr{sub 2}Nb and Cr-Cr{sub 2}Zr based alloys has been identified. The new alloys can be arc-melted/cast without cracking, and exhibit excellent room temperature and high-temperature tensile strengths. Preliminary evaluation of oxidation behavior at 1100 C in air indicates that the new Cr-Cr{sub 2}X based alloys form an adherent chromia-based scale. Under similar conditions, Cr-Cr{sub 2}Nb and Cr-Cr{sub 2}Zr based alloys suffer from extensive scale spallation.

  14. Microstructure and Mechanical Performance of Cu-Sn-Ti-Based Active Braze Alloy Containing In Situ Formed Nano-Sized TiC Particles

    Science.gov (United States)

    Leinenbach, Christian; Transchel, Robert; Gorgievski, Klea; Kuster, Friedrich; Elsener, Hans Rudolf; Wegener, Konrad

    2015-05-01

    A Cu-Sn-Ti-based active brazing filler alloy was in situ reinforced with nanosized TiC particles by adding different amounts of a cellulose nitride-based binder. The TiC particles emanate from a reaction of the Ti within the filler alloy with the carbon from the binder that does not decompose completely during heating. The correlation between the microstructure and mechanical performance was studied. In addition, the effect of different binder amounts on the shear strength and cutting performance of brazed diamond grains was studied in shear tests and single grain cutting tests. The results clearly show that the mechanical performance of the brazed diamond grains can be improved by the formation of TiC particles. This is attributed to particle strengthening of the filler alloy matrix as well as to the decreasing grain size and more homogeneous distribution of the (Cu,Sn)3Ti5 phase with increasing amount of binder.

  15. M-Si-B合金非晶形成能力的CALPHAD模式评估%Evaluation of the amorphous-forming ability of M-Si-B ternary alloys using CALPHAD approach

    Institute of Scientific and Technical Information of China (English)

    长谷部光弘

    2005-01-01

    A thermodynamic study has been carried out on M-Si-B (M=Fe, Ni) ternary systems. A regular solution approximation based on the sublattice model was adopted to describe the Gibbs energy for the individual phases in the binary and ternary systems. Thermodynamic parameters for each phase were evaluated by using the experimental data. These parameters enabled us to obtain reproducible calculations of the isothermal and vertical section diagrams.The amorphous-forming ability of M-Si-B ternary alloys has been evaluated by introducing thermodynamic quantities obtained from the phase diagram calculations into Davies-Uhlmann kinetic formulations. For the computation, the timetemperature- transformation (TTT) diagram, which gives the time necessary for the formation of the detectable amount of crystal during transformation, was obtained at a finite temperature The critical cooling rate for amorphization could be defined as the minimum cooling speed that does not intersect the TTT curve and, hence, these critical cooling rates enable us to evaluate the glass-forming ability of M-Si-B ternary alloys. The driving force for the crystallization of the crystalline phase was derived, on the basis of the thermodynamic functions of each phase formulated by the present study. The calculated results showed good agreement with the experimental data on the compositional range of amorphization in these alloy systems.

  16. Grain size and texture changes of magnesium alloy AZ31 during multi-directional forging

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Grain size and texture changes of magnesium alloy AZ31 were studied in multidirectional forging(MDF) under decreasing temperature conditions. MDF was carried out up to large cumulative strains of 4.8 with changing the loading direction during decrease in temperature from pass to pass. MDF can accelerate the uniform development of fine-grained structures and increase the plastic workability at low temperatures. As a result, the MDFed alloy shows excellent higher strength as well as moderate ductility at room temperature even at the grain size below 1 μm. Superplastic flow takes place at 423 K and depends on the anisotropy of MDFed samples. The mechanisms of strain-induced free-grained structure development and of the plastic deformation were discussed in detail.

  17. Effects of friction stir processing on the microstructure and superplasticity of in situ nano-ZrB2/2024Al composite

    Institute of Scientific and Technical Information of China (English)

    Yutao Zhao; Xizhou Kai; Gang Chen; Weili Lin; Chunmei Wang

    2016-01-01

    In this study, in situ nano-ZrB2/2024Al composites fabricated from 2024Al–K2ZrF6–KBF4 system were processed by friction stir processing (FSP) to achieve superplasticity of the composites. And the effects of particle contents (1 wt%, 3 wt%, 5 wt%), matrix grain size (micron or sub-micron), strain rates (5 × 10¯3 s¯1, 1 × 10¯2 s¯1, 2 × 10¯2 s¯1) and deformation temperatures (400 K, 480 K, 600 K, 700 K, 750 K) on the superplasticity of the composites were investigated. After the friction stir processing, the coarse grains of the cast composites with matrix grain size of about 80–100 μm and nano-ZrB2 reinforcement size of 30–100 nm were crushed into small grains about 1 μm in size, and the uniformity of the nano-ZrB2 reinforcements was also improved. And under the same superplastic tensile testing condition at the temperature of 750 K and strain rate of 5 × 10¯3 s¯1, the FSP nano 3 wt%ZrB2/2024Al composite exhibited an superplastic elongation of 292.5%, while the elongation of the corresponding cast composite was only less than 100%. Meanwhile, the m values of the FSP composites were always higher than the cast composites, especially the FSP composites with 3 wt% particles has the m value of 0.5321 i.e., the FSP composites should had better superplastic properties than cast ones. Furthermore, the FSP composites had higher apparent deformation activation energy (Q) than that of the lattice diffusion of pure aluminium, indicating that the deformation mechanisms of the FSP composites should be grain boundary sliding mechanisms.

  18. RESEARCH OF GAS-FORMING ABILITY OF THE MATERIALS USED AT DEVELOPMENT OF DIVIDING COVERINGS FOR THE MOLDS OF CASTING OF ALUMINUM ALLOYS UNDER PRESSURE

    Directory of Open Access Journals (Sweden)

    A. M. Mihaltsov

    2012-01-01

    Full Text Available The methods of carrying out of experiments by determination of gas creating ability of different materials which are of interest from the point of view of molding of aluminum alloys under pressure are given and described, and the results of research are presented as well.

  19. Formation of carbide phases upon the mechanosynthesis of the (Fe0.93Cr0.07)75C25 alloy compared with other carbide-forming processes

    Science.gov (United States)

    Volkov, V. A.; Chulkina, A. A.; El'kin, I. A.; Elsukov, E. P.

    2016-02-01

    Methods of X-ray diffraction, differential thermal analysis, and measurements of the dynamic magnetic susceptibility have been used to investigate the sequence of phase transformations upon the mechanical alloying of a mixture of powders of the initial components of the composition (Fe0.93Cr.07)75C25. It has been shown that, at later stages of mechanical alloying, the phase composition is determined by the conditions of the dynamic equilibrium between the crystalline and amorphous phases. A change in the conditions of mechanical alloying leads to a shift in this equilibrium and to a change in the phase composition of the alloy. A comparison of carbide formation in the Fe-C system upon the mechanosynthesis, tempering of martensite, the saturation of iron with carbon from the gaseous medium, the quenching of the melt, and the sputtering deposition of films has been performed. Some general regularities have been established, from which it follows that an important role in phase formation upon the mechanosynthesis, just as in other abovementioned processes, is played by the thermally activated phenomena.

  20. Anti-corrosion and wear properties of plasma electrolytic oxidation coating formed on high Si content Al alloy by sectionalized oxidation mode

    Science.gov (United States)

    Dai, Libin; Li, Wenfang; Zhang, Guoge; Fu, Nianqing; Duan, Qi

    2017-01-01

    In this study, a uniform and less defective ceramic coating was prepared on high Si content aluminium alloys by a sectionalized plasma electrolytic oxidation (PEO) mode. The PEO process of Al-9 wt. % Si binary alloy was performed under constant current mode followed by constant voltage mode. The surface micrographs and chemical compositions of different samples were analysed by scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. Micro-hardness and reciprocal-sliding testers were used to measure the coatings hardness and tribological performance. It was found that the sectionalized PEO mode could produce hard and anti-friction passive oxide layers with smaller holes and fewer cracks on the Al-Si alloy, comparing with the single constant current mode. In addition, the results of polarization curves and electrochemical impedance spectroscopy (EIS) tests conducted in 3.5 wt. % NaCl solution revealed that the coatings obtained by sectionalized PEO mode had a higher corrosion resistance and provided better corrosion protection for Al-Si alloy.