NiTi合金的显微组织和双程形状记忆效应

Microstructure and Two-way Shape Memory Effect in NiTi Alloy

通过弯曲试验和透射电镜分析系统研究了热处理工艺、形变量、形变温度对NiTi合金双程形状记忆效应和显微组织的影响。结果表明 ,冷轧变形试样经不同温度退火后 ,双程可逆应变量随退火温度的升高而增大 ,退火温度超过 550℃后 ,温度继续升高 ,双程可逆应变量基本不变。同一温度退火的试样 ,双程可逆应变量随弯曲形变量的增加而增加 ,至形变量εt=12 %时达到最大值 ,εt 进一步增加 ,双程可逆应变量呈下降趋势。弯曲形变量相同时 ,弯曲温度升高 ,双程可逆应变量εt 减小 ,形变温度超过Mσs 时基本不再呈现双程记忆效应。马氏体再取向形成的位错可以产生有效内应力场 。

The effect of heat treatment and bending deformation on the microstructure and two\|way shape memory effect (TWSME) in a Ti\|50 2Ni(at,%) alloy has been systematically investigated by means of bending test and transmission eletron microscopy (TEM) observations. The experimental results show that the two\|way shape memory strain in the NiTi alloy increases with and increase of annealing temperature. For the samples annealed at same temperature, the two\|way shape memory strain increases with increasing bending strain ( ε t ) as ε t is less that 12% and then decreases with ε t further increasing. The two\|way shape memory strain in the NiTi alloy decreases with an increase of bending temperature as the samples were bent to 8%. On the basis of above results, it is concluded that the dislocations induced in the martensite reorientation generate the effective internal stress for the TWSME.