NiTi合金相变过程中界面动力学的内耗研究

本文采用同时测量内耗、模量及电阻的方法,对NiTi合金变温过程中所发生的正、反马氏体相变及可逆I/C相变进行了系统的研究。结果表明,变温马氏体相变及I/C相变过程中内耗均为粘弹性型内耗,是相界面在克服粘滞性阻力而运动时引起的。从界面动力学出发,研究了相变过程中界面的运动动力学行为。由实验数据求得了马氏体相变过程中界面动力学关系的具体表达式为:V=V^*exp(—△G^*/△G—△G_R);相变过程内耗表达式为:Q^-1=(n²)/2·(μ△G^*)/((△G—△G_R)²)·(dF)/(dT)·T/ω;相变阻力△G_R约为10cal/mol的数量级。讨论了相变过程中的“软模”效应。马氏体相变过程中的模量“软化”来自声子模的软化和界面运动引起的附加模量亏损两个方面。 关键词：

AN INTERNAL FRICTION STUDY OF INTERFACE DYNAMICS IN THE PROCESS OF PHASE TRANSFORMATIONS OF NiTi ALLOY

The Martensitic (MP) and incommensurate/commensurate (I/C) phase transformations during the athermal process of NiTi alloy were studied by the measurements of internal friction, elastic modulus and electric resistance simultaneously. The IF behaviour in the processes of MP and I/C phase transformations are nearly the same and is associated with the motion of phase interface under the action of phase transformation driving force. Starting with the interface dynamics model, the interface dynamic behaviour of MP and I/C transformations were . studied. An explicit functional relationship of the interface dynamics in the process of marten-sitic transformation was obtained as V = V^* exp(-△G^*/△G - △G_R) and the expression for IF during the process of phase transformation as Q^-1 = (n²/2)×(μ△G^*/(△G-△G_R)²) dF/dT·T/ω. The transformation resistance froce △G_R is the order of 10 cal/mol. The "soft mode effect" during the transformation process was discussed, and it was shown that the softfening of pho-non mode and the modulus defect associated with interface motion coexist in the processes of martensitic and I/G phase transformations.