Phase transformation and related thermo-mechanical behaviour. A molecular dynamics approach

Abstract
Melting and solidification processes axe simulated by molecular dynamics method to investigate the complicated phenomena associated with phase transformation, such as volume dilatation, change in stress, generation of latent heat and so on. To identify the fundamental thermo-physical characteristics, a crystal with fcc structure is heated uniformly without temperature distribution. In the following non-uniform heating, heat conduction and thermal stresses induced by the temperature gradient are simulated. As an application to an engineering process, melting and solidification processes on a thin film surface, which corresponds to data-writing and erasing processes in a phase-change-type optical disk, are carried out. Melting at a part of the surface causes the surface rippling around the molten area, and the subsequent rapid cooling reveals to generate an amorphous spot, while the region becomes crystal with moderate cooling. The amorphous structure is maintained at low temperature, which is metastable. If the spot is heated again, however, crystallization occurs and the amorphous spot is eliminated.