Strain rate dependence of deformation mechanisms in a Ni-Ti-Cr shape-memory alloy
Strain rate dependence of deformation mechanisms in a Ni-Ti-Cr shape-memory alloy
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DOI：
10.1016/j.actamat.2004.10.001
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发表时间：
2005-01-01
期刊：
影响因子：
9.4
通讯作者：
Choi, JY
中科院分区：
文献类型：
--
作者：
Nemat-Nasser, S;Choi, JY
利用Instron液压试验机和CEAM/UCSD改进的分离式Hopkinson杆系统，研究了Ni-Ti-Cr形状记忆合金在不同初始温度、宽应变率范围内的压缩响应。该合金在一定的初始温度和应变速率范围内具有超弹性，应变小于5%。应力诱发马氏体相变的转变应力、马氏体的屈服应力和母体奥氏体的屈服应力均表现出应变率敏感性，且均随应变速率的增加而单调增加。在很宽的应变速率范围内，转变应力小于母体奥氏体的屈服应力(小于产生的马氏体的屈服应力)，但一旦超过临界应变速率，它最终会超过这个屈服应力。当应变速率低于临界值时，非弹性变形开始于应力诱发马氏体形变，随后马氏体塑性屈服；而当应变速率高于临界值时，非弹性变形直接源于母体奥氏体位错诱发塑性变形，其奥氏体相变极小(如果有的话)。在超弹性温度范围内，应变速率显著影响该形状记忆合金的超弹性和屈服行为。(C)2004年Acta Materialia Inc.由爱思唯尔有限公司出版。保留所有权利。
The compressive response of a Ni-Ti-Cr shape-memory alloy is investigated at various initial temperatures, over a wide range of strain rates, using an Instron hydraulic testing machine and one of the CEAM/UCSD's modified split Hopkinson bar systems. The alloy is superelastic over a range of initial temperatures and strain rates, for strains less than about 5%. The transition stress for the stress-induced martensite formation, the yield stress of the resulting martensites, and the yield stress of the parent austenite show strain-rate sensitivity, all increasing monotonically with the increasing strain rate. The transition stress is less than the yield stress of the parent austenite (which is less than the yield stress of the resulting martensite) over a wide range of strain rates, but it eventually exceeds this yield stress once a critical strain rate is exceeded. Inelastic deformation at strain rates below the critical level begins by stress-induced martensite formation and continues by subsequent plastic yielding of the martensites, whereas at strain rates above the critical, inelasticity directly stems from the dislocation-induced plastic deformation of the parent austenite with minimal (if any) austenite-to-martensite phase transformation. The strain rate significantly affects the superelastic and yielding behavior of this shape-memory alloy within the superelastic temperature range. (C) 2004 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.