Effect of solute segregation on diffusion induced grain boundary migration studied by molecular dynamics simulations

摘要

Diffusion-induced grain boundary migration (DIGM) is the phenomenon of normal grain boundary (GB) migration caused by the lateral diffusion of solutes along it. Despite its technological importance and the fact that DIGM has been first observed and studied since 1970, many aspects of it are still not fully understood. In this study, molecular dynamics simulations are used to investigate the physical origin of DIGM with particular focus on the effects of solute-GB interactions. For this purpose, a few binary alloy systems are deliberately selected, e.g., Al-Ti, Al-Ni, and Ni-Cu, in which strong solute-GB interactions including both solute segregation and anti-segregation occur. The simulation results showed that strong solute segregation and anti-segregation can both influence DIGM, although past experimental and theoretical studies on DIGM mostly focused on systems with segregation. Furthermore, it is shown that the direction of GB migration strongly depends on the solute-GB interaction type, e.g., segregation or anti-segregation, which causes an attraction or repulsion between the GB and solute atoms, respectively. It is thus proved that solute-GB interactions, in general, play an important role in driving DIGM. Furthermore, by combining two atomistic simulation techniques, i.e., the synthetic driving force method and interface random walk method, we are able to quantify the driving forces for DIGM. All observations made during the simulations are supported by atomic configurations and graphical analysis. It is hoped that this study sheds some light on this research area after more than a decade's stagnation in this field.