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

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(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.