Grain-Boundary Kinetics: A Unified Approach

TL;DR

This paper introduces a unified disconnection-based framework for understanding and modeling grain boundary kinetics, linking microscopic defect behavior to macroscopic material properties in polycrystals.

Contribution

It presents a comprehensive, unifying approach to grain boundary kinetics using disconnection theory, integrating bicrystallography with defect dynamics.

Findings

Disconnections characterize GB behavior through bicrystallography.

GB kinetics can be modeled via disconnection nucleation, propagation, and reactions.

The framework links microscopic defect processes to microstructural evolution.

Abstract

Grain boundaries (GBs) are central defects for describing polycrystalline materials, and playing major role in a wide-range of physical properties of polycrystals. Control over GB kinetics provides effective means to tailor polycrystal properties through material processing. While many approaches describe different GB kinetic phenomena, this review provides a unifying concept for a wide range of GB kinetic behavior. Our approach rests on a disconnection description of GB kinetics. Disconnections are topological line defects constrained to crystalline interfaces with both step and dislocation character. These characteristics can be completely specified by GB bicrystallography and the macroscopic degrees of freedom of GBs. GB thermal fluctuations, GB migration and the ability of GBs to absorb/emit other defects from/into the delimiting grains can be modeled via the nucleation, propagation and reaction of disconnections in the GB. We review the fundamentals of bicrystallography and its relationship to disconnections and ultimately to the kinetic behavior of GBs. We then relate disconnection dynamics and GB kinetics to microstructural evolution. While this review of the GB kinetics literature is not exhaustive, we review much of the foundational literature and draw comparisons from a wide swath of the extant experimental, simulation, and theoretical GB kinetics literature.