循环应力作用下TiNi形状记忆合金应力诱发相变行为演变的原位研究

利用马氏体相变有相变潜热释放的性质,通过精确测量TiNi形状记忆合金在不同变形条件下试样温度的变化波形,结合应力应变响应研究了循环应力作用下TiNi形状记忆合金相变行为的演变过程,对循环应力造成形状记忆合金超弹性退化的原因进行了探讨.结果表明:试样的温度变化比普通金属材料高许多,可以用温度法来研究马氏体相变在变形过程中的变化;在应力控制的循环应力作用下,试样内应力诱发马氏体相变量随着循环周次的增加而不断减小,每一周内应力诱发马氏体相变行为也在不断演化,发生应力诱发马氏体相变的临界应力不断减小,而由马氏体弹性变形所携带的应力增加.

In situ study of evolution of stress-induced martensitic transformation in TiNi shape memory alloy during cyclic deformation

The stress-induced martensitic transformation (SIMT) behavior and its change in TiNi shape memory alloys (SMAs) were investigated through accurately monitoring the fatigue specimen temperature change, along with the study of the stress-strain response. The effect of cyclic loading on the degradation of super elasticity (SE) was discussed. The results show that the temperature change of TiNi SMAs is much higher than that of common metallic materials due to SIMT. Therefore, it is reasonable to study the SIMT behavior by accurately monitoring the specimen temperature change. With increasing loading cycles, the amount of SIMT decreases under stress control. SIMT can take place at lower stress, and the stress is carried by elastic deformation of SMAs, instead of by SIMT.