Molecular Dynamics Simulation of the Influence of Lattice Defects on Bcc-Fcc Phase Transformation

摘要

Molecular dynamics simulations were carried out to study the influence of lattice defects on the structural phase transformation from bcc to fcc structures. The parameters in Morse-type potential function were adjusted so that both of bcc and fcc structures were stable at a wide range of temperature. For the obtained parameters, fcc structure was mostly superior to bcc structure at high temperatures, while both structures were stable at low temperature. Consequently, temperature-induced phase transformation from bcc to fcc was successfully simulated. The mechanism of the transformation was discussed compared with Bain's relation and revealed to show good agreement. Then, two types of lattice defects, scattered vacancies as point-defect model and aligned vacancies as a line-defect model, were introduced in the initial bcc structure, and the simulations were carried out. As a result, bcc structure tended more likely to transform to fcc structure as the rate of defects increased. The dynamic behavior during the phase transformation was also investigated using the snapshots of the configuration of atoms, and generation of apparent plastic deformation was observed. This result indicates the applicability of the present model to further investigation on the transformation plasticity and related phenomena.