The Physical Origin of Diffusion Induced Grain Boundary Migration Explored by Atomistic Simulations

Abstract

Diffusion-induced grain boundary motion (DIGM) is the phenomenon of normal grain boundary migration caused by the lateral diffusion of solutes along it. Despite its technological importance and the fact that DIGM has been firstly observed and studied since 1970, the physical origin of DIGM still remains largely hypothetical. In this work, a comprehensive approach by combining two atomistic simulation techniques, i.e., the synthetic driving force method and the interface random walk method is developed to quantify the driving forces that operate during DIGM. It is found that the driving force that initiates DIGM is quantitatively consistent with that arising from coherency strain energy, which proves that a major driving force of DIGM originates from unbalanced coherency strain energy across the boundary due to the non-uniform distribution of solute atoms. The simulation results also show that segregation plays an important role in promoting DIGM once GB is in close contact with the solute atoms. All observations made during the simulations are supported by the atomic configurations and graphical analysis at different stages of the process. It is hoped that this study sheds some light and provides a clearer picture of DIGM after more than a decade’s stagnation in this field.