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制备了三种名义成分分别为Ni_(50)Ti_(50)、Ni_(49)Ti_(49)Fe2和Ni45Ti51.8Fe3.2(摩尔分数,%)的不同NiTi基合金来揭示Fe的添加对NiTi形状记忆合金相变行为的影响。采用光学显微分析法、透射电子显微分析法、X射线衍射和差示扫描量热法对这些合金的组织和相变行为进行分析。结果表明,Ni_(50)Ti_(50)合金的基体由B19′马氏体相和B2奥氏体相组成。而且,在B19′相中可以观察到孪晶亚结构。然而,三元NiTi Fe合金的组织则为B2奥氏体相。这两种合金的基体中弥散分布着大量的Ti2Ni沉淀相。NiTi形状记忆合金中添加Fe后导致三元合金的相变温度下降。由机理分析可以得到如下结论:这一现象主要是由原子的弛豫引起的,弛豫会导致相变过程中B2相的稳定化。
Three different NiTi-based alloys with Ni 50 Ti 50, Ni 49 Ti 49 Fe 2 and Ni 45 Ti 51.8 Fe 3 0.2 (mole fraction,%) were prepared to reveal the effect of Fe addition on NiTi Effect of Phase Transformation Behavior of Shape Memory Alloy. The microstructure and phase transition behavior of these alloys were analyzed by optical microscopy, transmission electron microscopy, X-ray diffraction and differential scanning calorimetry. The results show that the matrix of Ni_ (50) Ti_ (50) alloy consists of B19 ’martensite and B2 austenite. Moreover, twinned substructures were observed in the B19 ’phase. However, the structure of the ternary NiTi Fe alloy is the B2 austenite phase. The matrix of these two alloys disperse a large number of precipitated phases of Ti2Ni. The addition of Fe to NiTi shape memory alloy leads to the decrease of the transformation temperature of the ternary alloy. From the mechanism analysis, it can be concluded that this phenomenon is mainly caused by the relaxation of the atoms, and the relaxation leads to the stabilization of the B2 phase during the phase transition.