单向拉伸镍钛合金带从奥氏体到马氏体的相变分析

Analysis of Phase Transformation From Austenite to Martensite in NiTi Alloy Strips Under Uniaxial Tension

单向拉伸镍钛合金带中从奥氏体到马氏体的相变已在实验中观测到,并被看作为局部变形进行了数值模拟.该文采用相变理论对其进行分析,考虑了两相界面处变形梯度的跳跃以及Maxwell关系,导出了相变的控制方程.相变分析归结为寻求载荷的最小值,使在该值下控制方程具有唯一的、物理上可以接受的实数解.控制方程被数值求解,证明了该唯一解确实存在.相变的Maxwell应力,马氏体相与奥氏体相内的应力与应变,以及相边界的倾角都可求出,并与实验所观测到的结果相吻合.

Phase transformation from austenite to martensite in NiTi alloy strips under uniaxial tension has been observed in experiments and has been numerically simulated as a localized deformation. This work presented an analysis of that using the theory of phase transfonnation. The jump of deformation gradient across interface between the two phases and the Maxwell relation were considered. Governing equations for the phase transformation were derived. The analysis was reduced to finding the minimum value of the loading at which the governing equations have a unique, real, physically acceptable solution. The equations were solved numerically and it is verified that the unique solution exists deftnitely. The Maxwell stress, the stresses and swains inside both austenite and martensite phases, and the transfomation-front orientation angle were determined that are in reasonably good agreement with experimental observations.