热机械循环对Ti_(49.8)Ni_(50.2)形状记忆合金相变行为的影响

Effects of Thermo-Mechanical Cycling on Transformation Behavior of Ti_(49.8)Ni_(50.2) Shape Memory Alloy

研究了热机械循环对Ti49.8Ni50.2形状记忆合金的回复应变RS、应力诱发马氏体的临界应力σM以及马氏体相变温度Ms和Mf的影响。实验结果表明:Ti49.8Ni50.2在热机械循环冷却过程中始终发生应力诱发B2→B19′马氏体相变。RS在第一次和第二次循环中分别获得最大值和最小值,随着循环的继续进行又逐渐增加。RS在达到第二个极大值后又开始逐步减小。σM随着循环次数增加而迅速下降。Ms和Mf在前10次循环中无明显变化,随着循环的继续进而升高。循环500次后,RS,σM以及Ms和Mf均达到稳定状态。循环引入的位错结构被认为是造成以上变化的主要原因。

Effects of thermo-mechanical cycling on recovery strain （ RS ）, critical stress for inducing martensites （aM） and martensitic transformation temperatures （M, and Mr） of Ti49.8Ni50.2 shape memory alloy were studied. The results showed that stress-induced B2→B 19＇ transformation happened during cooling upon thermo-mechanical cycling. RS of the allay specimens reached maximum and minimum respectively inthe first and second cycle, and increased to another peak value then decreased in the further cycling. With the increasing number of cycles, σM decreased, while M. and Mf did not obviously change in the first 10 cycles. RS, σM, M. and Mf all reached steady values after 500 cycles. It was believed that dislocation structure developed during thermo-mechanical cycling was responsible for these changes.