回复加热速度对上淬Cu-Al-Mn合金的形状记忆效应的影响

摘要

采用光学显微镜、透射电子显微镜和电阻率测量技术，研究回复加热速度对上淬后Cu-8.8Al-10.27Mn合金的形状记忆效应的影响。结果表明：材料形状回复率随回复加热速度的减小而减小。当回复加热速度为20°C/min时，形状回复率可达75%；而当回复加热速度为1°C/min时，其形状回复率仅为8%。原位金相观察表明：材料的形状记忆效应是由马氏体逆转变后的残余孪晶形变马氏体的稳定性引起的。电阻率分析结果表明：残余孪晶形变马氏体的稳定性与其界面处空位与位错在慢速加热时形成的复合缺陷相关。而复合缺陷的形成会阻碍孪晶形变马氏体的逆转变。%The effect of recovery heating rate on shape memory effect of the up-quenched Cu-8.88Al-10.27Mn (mass fraction, %) alloy was investigated by optical microscopy, electron transmission microscopy (TEM) and electrical resistivity measurement. It is found that the shape recovery rate decreases as the heating rate decreases. It can reach 75% when the heating rate is 20°C/min, while it is only 8% when the heating rate is 1°C/min. In situ microstructure observation indicates that the dependence of shape memory effect on recovery heating rate is caused by the stabilization of twinned martensite induced by deformation. The analysis of electrical resistivity shows that the stabilization of twinned martensite may be ascribed to formation of compound defects of vacancies and dislocations at the boundaries of twinned martensite during the slow heating. The compound defects prevent the reverse transformation of twinned martensite.