预应变对Fe-Mn-Si记忆合金中应力诱发εM形态的影响

Effect of Pre-strain on Morphology of Stress Induced ε Martensite in an Fe-Mn-Si Shape Memory Alloy

利用拉伸试验方法测定了Fe-25%Mn-4.5%Si-1%Cr-2%Ni合金预应变对可恢复应变量的影响,并用X射线衍射分析方法考察了应力诱发ε马氏体(εM)体积分数随预应变量的变化关系。结果表明,当预应变大于5%而小于8%时,尽管应力诱发ε马氏体量仍然随预应变的增大而增多,而可恢复应变量却在预应变超过5%后随之迅速降低。利用透射电子显微镜对不同变形量试样中应力诱发εM形貌进行观察得知,预应变量由小及大,诱发出的εM形态变化很大,从而对记忆效应产生不同的影响。

The effect of pre-strain on shape recovery strain in an Fe-25 % Mn-4.5 % Si-1% Cr-2 % Ni shape memory alloy was investigated by tensile testing, and at the same time the relationship between the amount of stress induced ε martensite （εM） and pre-strain was determined by X-ray diffraction analysis. It was shown that the shape recovery strain decreases rapidly with increasing pre-strain when the deformation is above 5%, although the amount of stress induced εM still increases with increasing pre-strain in the range of 5% to 8%. Transmission electron microscope （TEM） observation on the stress induced εM in specimens of different pre-strain showed that morphology of εM changes greatly with different pre-strain, which would have great influence on the shape memory effect in the alloy.