Barrier effect of grain boundaries on the avalanche propagation of polycrystalline plasticity

TL;DR

This study uses molecular dynamics simulations to explore how grain boundaries in polycrystals influence the propagation of plastic deformation avalanches, revealing both blocking and penetrating behaviors.

Contribution

It introduces a probabilistic model to quantify the barrier effect of grain boundaries on avalanche propagation at the atomic scale.

Findings

Stress-drop distributions follow power-law decay with grain size.

Some avalanches are confined by grain boundaries, others penetrate through.

Blocking probability varies with grain boundary characteristics.

Abstract

To investigate the barrier effect of grain boundaries on the propagation of avalanche-like plasticity at the atomic-scale, we perform three-dimensional molecular dynamics simulations by using simplified polycrystal models including symmetric-tilt grain boundaries. The cut-offs of stress-drop distributions following power-law distributions decrease as the size of the crystal grains decreases. We show that some deformation avalanches are confined by grain boundaries; on the other hand, unignorable avalanches penetrate all the grain boundaries included in the models. The blocking probability that one grain boundary hinders this system-spanning avalanche is evaluated by using an elemental probabilistic model.