Decomposition of general grain boundaries

TL;DR

This paper introduces the concept of grain boundary decomposition, a new kinetic behavior where a grain boundary splits into two, demonstrated through molecular dynamics simulations and confirmed with experimental data, expanding understanding of microstructure evolution.

Contribution

It presents the novel concept of grain boundary decomposition driven by differential forces, supported by simulations and experimental observations, highlighting its potential universality in microstructure dynamics.

Findings

Discovered reversible GB decomposition in nickel Σ7 boundaries.

Confirmed decomposition-like process in high-energy diffraction microscopy data.

Identified GB decomposition as a new kinetic behavior in microstructure evolution.

Abstract

As a central part of microstructure evolution, grain boundary (GB) migration is believed to be both monolithic and unidirectional. But here, we introduce the concept of GB decomposition: one GB separates into two new GBs by exerting differential Peach-Koehler forces on its disconnections. Molecular dynamics simulation is used to reveal the disconnection mechanisms and direction-dependent motion behaviors associated with the reversible decomposition of a nickel {\Sigma}7 general GB. We also observed a decomposition-like process in a high-energy diffraction microscopy (HEDM) dataset of high purity nickel polycrystal (Science 2021, 374, 189-193), and performed HEDM-data-based simulations to confirm it. The decomposition should be considered as a new GB kinetic behavior, based on its particularity and potential universality.