TiNiCu形状记忆合金热机械训练诱发双向记忆效应的DSC曲线特征

Characterization of DSC curves of the two-way shape memory effect induced by thermo-mechanical training in TiNiCu alloy

利用示差扫描量热法(DSC)研究了TiNiCu双向记忆弹簧训练过程中热机械训练及退火对合金相变特征的影响。结果表明,训练前升温时,DSC曲线表现出的吸热峰由多个小峰组成,随着训练次数的增加,峰的个数减少,具有稳定双向记忆效应的试样中,升温时只出现一个锐利的峰。这是因为在训练过程中引入特定取向的位错,产生一定的应力场,使得马氏体变体的取向比较一致,相变点基本相同所致。由于位错的引入,引起相变点As和Af下降。训练不同次数的样品400℃退火后,由多个小峰组成的吸热峰合并为一个峰,这是由退火导致热机械训练诱发特定取向的位错恢复引起的。

Transformation characters of TiNiCu two-way shape memory (TWSM) spring were investigated by differential scanning calorimetry DSC measurement during thermo-mechanical training. The results show that before training the profile of endothermic peaks are composed of several small peaks. With training the amount of the small peaks decreases. After the stabilized TWSME induced into the TiNiCu alloy, there was only one sharp peak appear. This because that the dislocations structures create an anisotropic stress field, which guides the orientation of martensite variants very similar. And the dislocations also lead to the decrease of As and Af. Annealing induced the small peaks merge into one peak which resulted from the annihilation of the dislocation introduced by thermo-mechanical training.