热-机械循环处理对FeMnSiCrNi 合金 记忆效应的影响

采用电子拉伸试验机考察了不同预变形量热-机械循环处理对FeMnSiCrNi合金形状记忆效应的影响,并利用光学及透射电子显微分析方法研究了经热-机械循环处理后母相γ及应力诱发ε马氏体的组织变化.结果表明:在预变形量为4%、5%、和6%的情况下,经2次循环训练后具有最高的应变恢复率;适当的热-机械循环处理能促进母相γ中形成大量按一定取向分布的晶体缺陷,为择优取向ε马氏体的成长打开通道,显著降低ε马氏体的几何尺寸,提高其逆相变的晶体学可逆性;若热-机械循环次数过多,母相γ中会形成位错缠结,阻碍γ→ε相变过程中层错扩展,从而不利于形状记忆效应.

Effect of thermal-mechanical cycling treatment on the shape memory effect in an FeMnSiCrNi alloy

The influence of thermal-mechanical cycling treatment on the shape memory effect in FeMnSiCrNi alloy was investigated using an electronic tensile tester,and the microstructural variation of parent phase γ and the stress induced ε martensite after thermal-mechanical cycling treatment were investigated by optical and transmission electronic microscopy.The results show that with pre-strain of 4%,5% and 6%,the FeMnSiCrNi samples exhibit the maximum recovery ratio when subjected two treatment cycles.A lot of crystal defects orientated on some directions are introduced to the parent phase γ through thermal-mechanical cycle treatment,which is helpful for the growth of stress induced ε martensite of preferential orientations.At the same time,the thermal-mechanical cycle treatment results in the significant decrease of the average size of stress induced ε martensite,which can improve the crystallographic reversibility of ε martensite during the reverse transformation process.However,excessive treatment cycles may lead to tangled dislocations,which can hinder the extension of fault defects during stress induced γ→ε transformation,and thus decrease the shape memory effect in the FeMnSiCrNi alloy.