真空固溶及时效处理后NiTi合金的两步逆相变

The two-step reverse martensitic transformation of NiTi alloy after vacuum solution and aging

利用真空炉对NiTi形状记忆合金进行了固溶处理，并对固溶处理及时效后合金的相变行为及力学性能进行了研究。结果表明，时效处理及预应变后合金丝的DSC曲线上均有两个逆马氏体相变峰，并随着预应变的增加，两个逆马氏体相变温度均升高。预应变后的合金丝在自由加热过程中能够输出两段回复应变，分别对应于两步逆马氏体相变。

A NiTi alloy is solution-treated in a vacuum furnace of 6.7 ×10^3pa at 950℃ for lh and then aged at 500℃ for 0.5h. After heat-treatment, the transformation behaviors and mechanical properties are investigated. The results show that there are two-step reverse martensitic transformations in both of the aged and prestrained NiTi alloys. Also the two-step reverse martensitic transformation peaks increase with the increasing of prestrain. A two-stage recovery strain in a predeformed martensitic NiTi alloy wire is obtained during free heating.