# A Continuum Multi-Disconnection-Mode Model for Grain Boundary Migration

## TL;DR

This paper develops a continuum model for grain boundary migration based on disconnection mechanisms, accounting for multiple modes and driving forces, and demonstrates its importance through numerical simulations.

## Contribution

It introduces a novel continuum two-dimensional model incorporating multiple disconnection modes and their interactions for grain boundary migration.

## Key findings

- Multiple disconnection modes influence GB migration behavior.
- Coupling and competition between modes are crucial for accurate modeling.
- Simulations reveal complex migration phenomena in polycrystalline structures.

## Abstract

We study the Grain Boundary (GB) migration based on the underlying disconnection structure and mechanism. Disconnections are line defects that lie solely within a GB and are characterized by both a Burgers vector and a step height, as set by the GB bicrystallography. Multiple disconnection modes can nucleate, as determined by their formation energy barriers and temperature, and move along the GB under different kinds of competing driving forces including shear stress and chemical potential jumps across the GBs. We present a continuum model in two dimensions for GB migration where the GB migrates via the thermally-activated nucleation and kinetically-driven motion of disconnections. We perform continuum numerical simulations for investigating the GB migration behavior in single and multi-mode disconnection limits in both a bicrystal (under two types of boundary conditions) and for a finite-length GB with pinned ends. The results clearly demonstrate the significance of including the coupling and competing between different disconnection modes and driving forces for describing the complex and diverse phenomena of GB migration within polycyrstalline microstructures.