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利用长距离显微镜(ＱＲＭＳ)对经过精细抛光的试样表面进行观察．原位研究了ＴｉＮｉ形状记忆合金中应力诱发马氏体相变(ＳＩＭＴ)和逆相变对疲劳行为的影响．包括对应力－应变响应和疲劳裂纹萌生和裂纹扩展规律的影响、并与普通金属的疲劳行为进行了对比．结果表明:ＴｉＮｉ形状记忆合金中可逆的应力诱发马氏体相变有利于改善疲劳性能、然而也正是反复发生的ＳＩＭＴ引起的滑移导致了疲劳裂纹的萌生．此外．在实验中还观察到若干反常的疲劳行为．如恒△Ｋ加载时裂纹扩展速率对裂纹长度的依赖性、裂纹扩展时的分叉以及疲劳试样表面出现的大量二次裂纹等现象．
The surface of the finely polished specimen was observed using a long range microscope (QRMS). The effect of stress-induced martensitic transformation (SIMT) and reverse phase transformation on fatigue behavior in TiNi shape memory alloys was investigated in situ. Including the effects of stress-strain response and fatigue crack initiation and crack propagation, and compared with the fatigue behavior of common metals. The results show that the reversible stress-induced martensitic transformation in TiNi shape memory alloys can improve the fatigue properties, however, it is exactly the repeated SIMT-induced slip that leads to the initiation of fatigue cracks. In addition. Several abnormal fatigue behaviors were also observed in the experiment. For example, the dependence of the crack propagation rate on the crack length at constant ΔK loading, the bifurcation during the crack propagation, and the large number of secondary cracks on the surface of the fatigue specimen were observed.