Dependence of rate on complex GB migration by ramped-ECO

TL;DR

This study uses molecular dynamics simulations with ramped energy driving forces to explore how the rate of driving force influences grain boundary migration, revealing complex behaviors like reverse shear coupling and transitions between migration modes.

Contribution

It introduces a novel approach using ramped-ECO driving force in MD simulations to analyze the dependence of GB migration on driving force rate and uncovers new migration behaviors.

Findings

Rate of driving force determines GB migration velocity

Reverse shear coupling observed at low rates in certain GBs

Transition points in shear coupling are linearly related to rate

Abstract

GB migration plays a central role in microstructural evolution. Many experiments and simulations have been conducted to clarify the relationships between GB velocity and various parameters to tailor GB networks. However, the complexity of GB migration has surpassed initial expectations. In this study, the ramped Energy Conserving Orientational (r-ECO) Driving Force (DF) in Molecular Dynamics (MD) simulations was utilized to investigate grain boundary (GB) motion for $\Sigma$3(110), $\Sigma$15(211), and $\Sigma$11(311). My findings indicate that the rate of the driving force determines the velocity of GB migration. Furthermore, a reverse shear coupling behavior during GB migration was observed when the rate was decreased in $\Sigma$15(211). In addition to the change in the direction of shear coupling, a linear relationship between the rate and the transition point during shear coupling migration was discovered. Specifically, a larger rate leads to a forward shift in the transition point. Moreover, GB transition from coupled to only normal migration states in the presence of dislocations nucleated in the GB was observed. These findings contribute to a deeper understanding of microstructural evolution and have implications for designing materials with enhanced properties.