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您的检索式：作者名="J.Wadsworth"
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| 1 | CONTROLLING HIGHTEMPERATURE DEFORMATION BY VARYING MICROSTRUCTURE IN A Ti47Al2Cr2Nb ALLOY显示文摘A Ti 47Al 2Cr 2Nb alloy was made by powder extrusion methods. By varying extrusion temperature, different microstructures were produced. At an extrusion temperature of 1 400 ℃ (above α transus), a uniform, fully lamellar structure was observed. In contrast, when powders were extruded at 1 150 ℃, an inhomogeneous microstructure consisting of γ,α 2 and metastable β phases was obtained. It was demonstrated that, while alloy extruded at 1 400 ℃ exhibited an excellent creep resistance, alloy with the same composition extruded at 1 150 ℃ exhibited superplasticity. The good creep resistance was resulted from the presence of fine lamellae which restrict dislocation slip within γ grains. These fine lamellae also promote the nucleation of deformation twins which impede dislocation glide along the interfaces ( γ/γ and γ/α 2) and, thus, reduces creep rate. In the case of low temperature extrusion, an elongation value of over 300% was obtained at a strain rate of 2×10 -5 s -1 and at a temperature as low as 800 ℃, which is close to the ductile to brittle transition temperature. This is in contrast to the prior major observations of superplastic behaviors in TiAl in which typical temperatures of 1 000 ℃ have usually been required for superplasticity. It was proposed that the occurrence of superplasticity at 800 ℃ is caused by the presence of a B2 phase which, during superplastic deformation (grain boundary sliding), accommodates sliding strains to reduce the propensity for cavitation at grain triple junctions and, thus, delays the fracture process. | T.G.Nieh and J.Wadsworth Lawrence Livermore National Laboratory, L-369, P.O.Box 808, Livermore, CA 94550, U.S.A. | 1999 | 中国有色金属学会会刊:英文版1999，9，S1： | 5 |
| 2 | 金属基复合材料中高应变速率超塑性的流变学观点显示文摘超塑成形是实用而有效的制造技术。然而,超塑性变形速率低,典型速率为10-5~10-3S-1,是其存在的主要问题之一。最近的一些研究表明,以非常高的应变速率(大于10-1S-1,最高达102S-1)也能出现超塑性。一特定实例是应变速率为lS-1时,抗拉伸长率超过1250%。迄今,由本文作者发现的这种高应变速率超塑性(HSRS)现象,在某些材料中已有报导,这类材料包括金属合金。 | T.G.Nieh J.Wadsworth 章四琪 | 1993 | 铝加工1993，0，4： | 0 |
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