外加应力下Ni_2MnGa合金中马氏体孪晶变体再取向动力学的相场模拟

Phase-field simulation of reorientation kinetics of martensitic twin variants in Ni_2MnGa alloy under external stress

利用相场方法研究Ni2MnGa形状记忆合金中不同连续拉应力方向马氏体孪晶变体的再取向动力学。模拟结果表明:施加应力方向决定体系演化的最终结构和演化路径,沿[100]和[110]方向施加应力分别得到单变体和双变体,而沿[111]方向施加应力,体系依然保持为3种变体。计算了相应的与界面动力学因子和切变模量相关联的孪晶化应力,计算结果与实验结果接近。加载和卸载后2种变体和3种变体之间的组织转化具有可逆性。

The kinetics of reorientation of martensitic twin variants under the continuous tensile stress along different directions in Ni2MnGa shape memory alloys was investigated by phase-field method. The simulated results reveal that the final morphology and the pathway of microstructural evolution depend on the stress-applied direction. The single variant and two variants can be obtained when the external stress is applied along [100] and [110] directions, respectively, while three variants still exist when the stress is applied along [111] direction. The corresponding twinning stress related to interfacial dynamic factor and shear modulus was calculated, which is close to the experimental measurements. The structural evolution between two variants and three variants has good reversibility during loading and unloading.