Plasticity-induced restructuring of a nanocrystalline grain boundary network

TL;DR

This study uses molecular dynamics simulations to investigate how plastic deformation causes restructuring of grain boundary networks in nanocrystalline aluminum, revealing increased special boundary fractions and network disruption, especially in smaller grains.

Contribution

The paper introduces new atomistic analysis tools to track and characterize grain boundary network evolution during deformation in nanocrystalline metals.

Findings

Plastic deformation increases special boundary fractions.

Grain boundary connectivity becomes more disrupted.

Smaller grains show more dramatic boundary evolution.

Abstract

The grain boundary-mediated mechanisms that control plastic deformation of nanocrystalline metals should cause evolution of the grain boundary network, since they directly alter misorientation relationships between crystals. Unfortunately, current experimental techniques are unable to track such evolution, due to limits on both spatial and temporal resolution. In this work, molecular dynamics simulations are used to study grain boundary restructuring in nanocrystalline Al during both monotonic tension and cyclic loading. This task is enabled by the creation of new analysis tools for atomistic datasets that allow for a complete characterization and tracking of microstructural descriptors of the grain boundary network. Quantitative measurements of grain boundary character distribution, triple junction type, grain boundary plane normal, and other interfacial network characteristics are extracted and analyzed. The results presented here show that nanocrystalline plasticity leads to an increase in special boundary fraction and disruption of two-dimensional boundary connectivity, with the most dramatic evolution occurring in the smallest grain sizes.