Revealing the Effect of Dynamic Structural Evolution on Triple Junction Deformation Mechanism: Molecular Dynamics Simulations and an Energetic Model

Abstract

Triple junction (TJ) migration is a plastic deformation mechanism in polycrystalline metals mediated by the interplay between neighboring grain boundaries (GBs). Compared with GB migration, the dynamic change of TJ structure during migration and its impact on subsequent TJ behavior is often overlooked. In this study, we explore the effect of dynamic TJ structure evolution on TJ deformation mechanism in a face-centered cubic metal Au model using molecular dynamics simulations. Our analysis reveals that the dislocation accumulation at TJ due to inconsistent disconnection nucleation from neighboring GBs can influence the stick-slip behavior of TJ migration. With the dynamic change of TJ structure, the velocity of TJ migration is gradually reduced, leading to a transition from TJ migration to dislocation emission from TJ. We have developed an energetic model to evaluate the critical stresses required for TJ migration and dislocation emission, providing an explanation of the competition between TJ migration and dislocation emission. Our findings deepen the understanding of TJ-governed plastic deformation mechanisms in polycrystalline materials.