Ni4Ti3沉淀相对NiTi形状记忆合金相变行为的影响

采用第二近邻修正型嵌入原子势的分子动力学方法，建立了共格沉淀相与半共格沉淀相块状/柱状模型，模拟了温度诱发相变和应力诱发相变，分析了Ni₄Ti₃沉淀相对Ni Ti形状记忆合金相变行为的影响．结果表明，Ni₄Ti₃沉淀相本征应变诱发的弹性应力场对相变中马氏体变体类型、形核位置、分布等有重要影响.在温度诱发相变时，共格沉淀相促进部分马氏体变体的形核生长，能显著提高Ni Ti超弹性形状记忆合金的马氏体相变开始温度;在应力诱发相变时，Ni₄Ti₃沉淀相使马氏体早于无沉淀相区域形核，导致了相变应力降低、抑制了马氏体解孪，减小了应力-应变曲线的滞回环.

Effect of Ni4Ti3 precipitates on phase transformation behavior of NiTi superelastic shape memory alloy

The temperature-induced phase transformation and stress-induced phase transformation of coherent precipitated phase and semi-coherent precipitated phase block/pillar model were simulated by molecular dynamics method with second nearest neighbor correction embedded atom potential. The effect of Ni4Ti3 precipitates on the phase transformation behavior of NiTi shape memory alloy was analyzed. The results show that the elastic stress field induced by the intrinsic strain of Ni4Ti3 precipitated phase has an important effect on the type, nucleation location and distribution of martensitic variants during the phase transformation. During the temperature-induced phase transformation, the coherent precipitated phase promotes the nucleation and growth of some martensitic variants, which can significantly increase the martensitic transformation starting temperature of NiTi shape memory alloy. During the stress-induced phase transformation, the Ni4Ti3 precipitated phase makes the martensite nucleate earlier than the non-precipitated phase region, resulting in a decrease in the phase transformation stress, inhibiting the martensite detwinning, and reducing the hysteresis loop of the stress-strain curve.