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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 ,诱发双程形状记忆效应
The effects of heat treatment process, deformation amount and deformation temperature on the two-way shape memory effect and microstructure of NiTi alloy were investigated by bending test and transmission electron microscope analysis. The results show that after annealing at different temperatures, the reversible strain of two-way reversible strain increases with the increase of annealing temperature. When the annealing temperature exceeds 550 ℃, the temperature continues to rise and the reversible strain of two-way reversal does not change. At the same annealing temperature, the two-way reversible strain increases with the increase of bending deformation, reaches the maximum value when εt = 12%, εt increases further, and the two-way reversible strain decreases. When the bending deformation is the same, the bending temperature increases and the reversible strain εt decreases. When the deformation temperature exceeds Mσs, the two-way memory effect no longer appears. Dislocations formed by the reorientation of martensite can produce an effective internal stress field and induce a two-way shape memory effect