Effect of annealing and initial temperature on mechanical response of a Ni–Ti–Cr shape-memory alloy
Effect of annealing and initial temperature on mechanical response of a Ni–Ti–Cr shape-memory alloy
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DOI：
10.1016/j.msea.2006.05.155
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发表时间：
2006-09
期刊：
影响因子：
6.4
通讯作者：
J. Choi;S. Nemat-Nasser
中科院分区：
文献类型：
--
作者：
J. Choi;S. Nemat-Nasser
在Instron液压试验机上，研究了在10−3/S应变速率下，热处理条件和初始温度对Ni-Ti-Cr三元形状记忆合金压缩响应的影响。退火温度和时间对从奥氏体相变到应力诱发马氏体相的正向相变和反向相变有很大影响。应力诱发马氏体的转变应力和屈服应力随退火温度的升高而增大。当退火温度为573K时，转变应力达到最大值，在673K时，屈服应力达到最大值。此后，两种应力均随退火温度的进一步升高而减小。最小析出物的转变应力最大。另外，随退火温度的降低，冷却和加热时的相变由单步向多步转变。应力诱发马氏体形变的转变应力随初始温度的升高而增加，在8.5 Mpa/K左右，产生最大转变应力和屈服应力的最佳热处理条件为573K/60min。
The effect of the annealing conditions and the initial temperature on the compressive response of a ternary Ni–Ti–Cr shape-memory alloy is investigated at a strain rate of 10−3/s, using an Instron hydraulic testing machine. The annealing temperature and duration considerably influence the forward, from austenite to the stress-induced martensite, and the reverse phase transformation. The transition stress and the yield stress of the resulting stress-induced martensite increase with the increasing annealing temperature. The transition stress reaches its maximum value for an annealing temperature of 573K, and the yield stress for 673K. Thereafter, both stresses decrease with further increase in the annealing temperature. The highest transition stress is attained for the smallest precipitates. In addition, the phase transformation upon cooling and heating changes from a single-step to a multiple-step with the decreasing annealing temperature. The transition stress for the stress-induced martensite formation increases with increasing initial temperature at a rate of about 8.5MPa/K. The optimum annealing condition that produces the highest transition and yield stresses without an accompanying residual strain is 573K for 60min.