Disruptive Atomic Jumps Induce Grain Boundary Stagnation

TL;DR

This study reveals that atomic-scale disruptive jumps at grain boundaries can cause stagnation in grain growth, with implications for understanding non-Arrhenius behavior and the effects of temperature and size.

Contribution

It introduces a displacement vector analysis method to detect subtle disruptive atomic jumps responsible for grain boundary stagnation.

Findings

Disruptive atomic jumps can cause entire grain boundary stagnation.

High temperature and driving forces activate disruptive jumps.

A size-dependent transition in thermal behavior of grain boundaries.

Abstract

Grain growth in polycrystalline materials can be impeded by grain boundary (GB) stagnation. Using atomistic simulations, we observed that during GB migration, the disruptive jumps of a few GB atoms can disturb the original ordered collective movement of GB atoms, leading to the stagnation of the entire GB. These disruptive atomic jumps can be activated by both high driving forces and high temperatures, with even jumps of a few atoms capable of causing the stagnation of an entire GB. This mechanism also explains the non-Arrhenius behavior observed in some GBs. Additionally, a large model size could increase the rate of disruptive atomic jumps, and a clear transition in thermal behavior is observed with the increase of the GB size in GBs exhibiting clear thermally activated stagnation. Our further investigation shows that the disruptive atoms involved in these jumps do not differ from other GB atoms in terms of atomic energy, volume, density, local entropy, or Voronoi tessellation, and no "jam transition" was observed in the energy barrier spectra. This fact makes those disruptive jumps challenging to detect. To address this issue, we propose a displacement vector analysis method that effectively identifies these subtle disruptive jumps.