形状记忆合金热疲劳前后的显微结构变化(英文)

Microstructure Change of TiNi Shape Memory Alloy during Thermal Fatigue

为了改进形状记忆合金的性能和延长形状记忆合金的寿命，跟踪和研究疲劳前后形状记忆合金的显微结构变化是十分重要的。通过比较ＴｉＮｉ 形状记忆合金疲劳前和疲劳后的显微结构变化，发现除了疲劳后的样品产生一些沉积物之外没有差别。本研究证明这些沉积物是１０２０ 纳米的ＴｉＮｉ３ 相颗粒。正是由于这些ＴｉＮｉ３ 相颗粒的存在，严重影响ＴｉＮｉ 形状记忆合金的性能，并可能进一步引起形状记忆合金的断裂。

In order to improve the performance and prolong the life of shape memory alloy materials (SMA), it is very important to trace and study the microstructure change during the fatigue of SMA. The microstructure features between samples before and after thermal fatigue (about 100,000 thermal cycles) of NiTi SMA film was examined and compared with each other by transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS). It was found that there is no difference in microstructure between the two kinds of samples except some precipitates appeared in the fatigue specimen. These precipitates which may be identified as TiNi 3 phase with a grain size of 10 20 nm may impede the transformation from martensite to austenite which is the working mechanism of SMA during thermal cycling. Therefore, these precipitates result in the serious decay of SMA performance and further fracture of the SMA material.