The Experts below are selected from a list of 201 Experts worldwide ranked by ideXlab platform
Guanghua Chen - One of the best experts on this subject based on the ideXlab platform.
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solid solution Alloys of alcocrfenitix with excellent room temperature mechanical properties
Applied Physics Letters, 2007Co-Authors: Yongjian Zhou, Yong Zhang, Yijiao Wang, Guanghua ChenAbstract:Alloys with composition of AlCoCrFeNiTix (x: molar ratio; x=0,0.5,1,1.5) were designed by using the strategy of equiatomic ratio and High entropy of mixing. The alloy system is composed mainly of body centered cubic solid solution and possesses excellent room-temperature compressive mechanical properties. Particularly for AlCoCrFeNiTi0.5 alloy, the yield stress, fracture Strength, and plastic strain are as High as 2.26GPa, 3.14GPa, and 23.3%, respectively, which are superior to most of the High-Strength Alloys such as bulk metallic glasses.
Yongjian Zhou - One of the best experts on this subject based on the ideXlab platform.
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solid solution Alloys of alcocrfenitix with excellent room temperature mechanical properties
Applied Physics Letters, 2007Co-Authors: Yongjian Zhou, Yong Zhang, Yijiao Wang, Guanghua ChenAbstract:Alloys with composition of AlCoCrFeNiTix (x: molar ratio; x=0,0.5,1,1.5) were designed by using the strategy of equiatomic ratio and High entropy of mixing. The alloy system is composed mainly of body centered cubic solid solution and possesses excellent room-temperature compressive mechanical properties. Particularly for AlCoCrFeNiTi0.5 alloy, the yield stress, fracture Strength, and plastic strain are as High as 2.26GPa, 3.14GPa, and 23.3%, respectively, which are superior to most of the High-Strength Alloys such as bulk metallic glasses.
Osamu Umezawa - One of the best experts on this subject based on the ideXlab platform.
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Critical experiments and analyses at cryogenic temperature to promote a better understanding of mechanical properties in High-Strength Alloys
2014Co-Authors: Osamu Umezawa, Kotobu NagaiAbstract:Mechanical test at cryogenic temperature shows the advantages on characterization of deformation and cracking behavior in Alloys from the viewpoint of microstructure. Microstructural crack initiation in High-cycle fatigue is clearly detected at the specimen interior. The High-Strength Alloys also show Higher strain rate dependence on tensile deformation and low temperature creep deformation under thermal activation process. Not only microstructural analyses using noble techniques but also modeling works on the subsurface crack generation and tensile deformation are focused.
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Subjects on Fatigue Crack Generation in High Strength Alloys for Long-Life Design
Materials Science Forum, 2011Co-Authors: Osamu Umezawa, Satoshi MorookaAbstract:The very localized deformation processes have been found to be decisive for subsurface fatigue crack generation at the lower stress level such as the elastic incompatibility at boundaries where only a very small fraction of plastically deformed grains was detected. The material design and its microstructure modification to achieve Higher fatigue resistance in long-life range are needed for the High Strength Alloys, which is one of the ways developing an ecomaterial. Novel systems have employed to clarify the substance crack generation and growth mechanisms of High Strength Alloys. The initial crack size Highly depends on the maximum cyclic stress range, which implies a threshold of stress intensity range controlling mechanism. Heterogeneous microplasticity due to planar slip and restricted system is considered to play an important role on making the subsurface crack. Then, it should be progressed in the understanding of damage stage in High-cycle fatigue fracture process.
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Deformation structure and subsurface fatigue crack generation in austenitic steels at low temperature
Metallurgical and Materials Transactions A, 1998Co-Authors: Osamu Umezawa, Kotobu NagaiAbstract:In order to progress in the understanding of fatigue crack generation for High-Strength Alloys, the subsurface fatigue crack initiation sites were characterized and the deformation structure was investigated for the solution-treated 24Cr-15Ni-4Mn-0.3N and 32Mn-7Cr-0.1N austenitic steels. High-cycle fatigue tests of those steels were carried out at 4, 77, and 293 K. Subsurface crack initiation was detected in the lower-peak stress and/or in the longer-life range at the three temperatures. The subsurface crack initiation sites were intergranularly formed. The localized deformation and/or strain concentration by dislocation arrays of the (111)–〈110〉 system assisted intergranular cracking due to incompatibility at grain boundaries. Dislocation movements were restricted to their slip planes. Even at the lower stress level, dislocations had generated in more than one slip system and piled up to a grain boundary. The peak cyclic stress was lowered with the increasing size of the subsurface crack initiation site. The dependence of the subsurface crack size on the peak cyclic stress was discussed.
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Subsurface Crack Generation in High-cycle Fatigue for High Strength Alloys
ISIJ International, 1997Co-Authors: Osamu Umezawa, Kotobu NagaiAbstract:In order to progress in the understanding of fatigue fracture process for High Strength Alloys, the previous studies of the subsurface fatigue crack generation are reviewed. A change in crack initiation mechanism from specimen surface to specimen interior often introduces a plateau ("knee") followed by a rather sharp drop in the shape of S-N curve. Various subsurface crack origins are related with microstructural crackings and pre-existing defects. The subsurface initiation site is formed as a Stage I crack. A new explanation of microcrack growth is proposed for the subsurface crack generation process. The subsurface crack size is the most important parameter to determine how the crack becomes a fatal crack. The size Highly depends on the maximum cyclic stress range, which implies a ΔKth threshold controlling mechanism. The dislocation structures in High-cycle fatigue are fairly planar for both austenitic steel and titanium alloy.
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phenomenological aspects of fatigue life and fatigue crack initiation in High Strength Alloys at cryogenic temperature
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 1994Co-Authors: Osamu Umezawa, Keisuke IshikawaAbstract:Abstract Based on the SN (stress cycling) data of Ti6Al4V Alloys and High CrNi steels (JN1 and YUS170) at 4, 77 and 293 K, the fatigue Strength and crack initiation behavior in the long-life range were investigated in this study. Ti6Al4V rolled Alloys and YUS170 steel exhibited a good fatigue Strength in the long-life range at cryogenic temperatures. In Ti6Al4V forged Alloys and JN1 steel, however, there was a rather sharp drop in the fatigue Strength at 4 and 77 K between 106 and 107 cycles. Subsurface crack initiation occurred in the long-life range for each material, and the location of its site was determined. The size of the subsurface crack initiation site obviously increased for Ti6Al4V forged Alloys and JN1 steel as the number of cycles increased. We then proposed that the fatigue Strength in the long-life range for the present Alloys is related to the microcrack growth behavior in their microstructure.
Yong Zhang - One of the best experts on this subject based on the ideXlab platform.
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effect of component substitution on the microstructure and mechanical properties of mcocrfenitix m cu al solid solution Alloys
Rare Metals, 2008Co-Authors: Y J Zhou, Yong Zhang, Xuefei Wang, Yanli Wang, Guoliang ChenAbstract:Abstract MCoCrFeNiTix (M = Cu, Al; x : molar ratio, x = 0, 0.5) Alloys were prepared using the new alloy-design strategy of equal-atomic ratio and High entropy. By the component substitution of Al for Cu, the microstructure changes from the face-centered cubic solid solution of original CuCoCrFeNiTix Alloys to the body-centered cubic solid solution of AlCoCrFeNiTix Alloys. Compared with original CuCoCrFeNiTix Alloys, AlCoCrFeNiTix Alloys keep the similar good ductility and simultaneously possess a much Higher compressive Strength, which are even supe-rior to most of the reported High-Strength Alloys like bulk metallic glasses.
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solid solution Alloys of alcocrfenitix with excellent room temperature mechanical properties
Applied Physics Letters, 2007Co-Authors: Yongjian Zhou, Yong Zhang, Yijiao Wang, Guanghua ChenAbstract:Alloys with composition of AlCoCrFeNiTix (x: molar ratio; x=0,0.5,1,1.5) were designed by using the strategy of equiatomic ratio and High entropy of mixing. The alloy system is composed mainly of body centered cubic solid solution and possesses excellent room-temperature compressive mechanical properties. Particularly for AlCoCrFeNiTi0.5 alloy, the yield stress, fracture Strength, and plastic strain are as High as 2.26GPa, 3.14GPa, and 23.3%, respectively, which are superior to most of the High-Strength Alloys such as bulk metallic glasses.
Z.f. Zhang - One of the best experts on this subject based on the ideXlab platform.
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Intrinsic impact toughness of relatively High Strength Alloys
Acta Materialia, 2017Co-Authors: Q.q. Duan, P. Zhang, Z.j. Zhang, Z.f. ZhangAbstract:Abstract Although the Charpy impact test has been routine for decades to assess the ductile or brittle nature of materials, the impact toughness, which is strongly sample-thickness dependent, is not an intrinsic property. By re-examining the energy absorption during fracturing of relatively High Strength Alloys, here we find a remarkably good linear relation between the impact energies and the fracture surface areas of samples with different thickness, and the slope essentially renders the intrinsic impact toughness. The new findings, which also provide a scaling law to well predict the thickness effect on the traditional impact toughness, may have broad applications for precisely determining the ductile-to-brittle transition temperature of small-dimensional devices, selecting materials according to their toughness at the thickness in usage, and evaluating the intrinsic toughness of emerging High Strength materials with limited achievable size.