Development of the new method to investigate the phase transformations based on the computational scientific approachs.

(1)基于非线性演化方程的相分解计算机模拟(Miyazaki)：真实合金系统(如Al-Zn、Cu-Co、Fe-Mo、Fe-Al-Co、Fe-Cr和III-V化合物半导体等)相分解的时间演化。进行了实验研究。基于本研究发展的相场方法，模拟了这些合金体系的微观组织变化动力学。临界现象的计算分析(Mohri)，用原子簇变分和路径概率方法对相变点附近的有序-无序相变的磁化率和驰豫时间进行了数值研究。当转变类型为一级时，磁化率向调幅无序温度方向发散。众所周知，临界慢化将发生在二阶相变点。通过计算发现，即使是一阶相变也会发生类似的现象。转变点附近自由能的平坦化是产生上述现象的原因。(3)马氏体相变类橡胶行为的理论研究，成功地模拟了马氏体相变的类橡胶行为。从考虑孪晶边界运动的相场型演化方程出发，推导出应力应变场的本构方程。通过数值模拟对应力应变曲线及其频率依赖性进行了预测。

(1) Computer simulation of the phase decomposition based on the non-linear evolution equation (Miyazaki).The time evolution of the phase decomposition in the real alloy system (such as Al-Zn, Cu-Co, Fe-Mo, Fe-Al-Co, Fe-Cr and III-V compound semiconductor, etc.) was investigated experimentally. The dynamics of the microstructure changes for those alloy systems were simulated on the basis of the Phase-field Method developed by the present research. The morphological feature of the calculated microstructures were in good agreement with the experimental results.(2) Computational analysis of the critical phenomena (Mohri).The susceptibility and relaxation time for the order-disorder phase transition near the transition point were investigated by the Cluster Variation and Path Probability Method, numerically. The susceptibility diverged toward the spinodal disordering temperature when the transition type is first order. It is well known that the critical slowing down will occur at the second order phase transition point. We found that the similar phenomenon will take place even for the first order phase transition by our calculation. The flatness of the free energy at the vicinity of the transition point would be the origin for the phenomena above mentioned.(3) Theoretical investigation for the rubber-like behavior of Martensitic transformation (Ohta).The rubber-like behavior of Martensitic transformation was simulated, successfully. The constitutive equations for the stress and strain field were deduced from the phase field type evolution equations with considering the twin boundary motion. The stress-strain curve and its frequency dependence were predicted by the numerical simulation.