【摘要】 制备了三种名义成分分别为Ni₅₀Ti₅₀、Ni₄₉Ti₄₉Fe2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,Ni₅₀Ti₅₀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。更多还原

【Abstract】 Three different NiTi-based alloys, whose nominal compositions were Ni₅₀Ti₅₀, Ni₄₉Ti₄₉Fe₂, Ni₄₅Ti_51.8Fe_3.2（mole fraction, %）, respectively, were used in the current research to understand the influence of Fe addition on phase transformation behavior in NiTi shape memory alloy（SMA）. The microstructure and phase transformation behavior of the alloys were investigated by optical microscopy（OM）, transmission electron microscopy（TEM）, X-ray diffraction（XRD） and differential scanning calorimetry（DSC） analysis. The results show that the matrix of the Ni₅₀Ti₅₀ alloy consists of both B19′（martensite） phase and B2（austenite） phase. Moreover, the substructures of twins could be observed in the B19′ phase. However, the ternary alloys of NiTiFe exhibit B2 phase in the microstructures. Such microstructures were also characterized by large presence of Ti₂Ni precipitates dispersed homogenously in the matrix of the two kinds of alloys. The addition of Fe to the NiTi SMA results in the decrease in phase transformation temperatures in the ternary alloys. Based on mechanism analysis, it can be concluded that this phenomenon is primarily attributed to atom relaxation of the distorted lattice induced by Ni-antisite defects and Fe substitutions during phase transformation, which enables stabilization of B2 phase during phase transformation.更多还原