The Universality Class of Nano-Crystal Plasticity: Self-Organization and Localization in Discrete Dislocation Dynamics

TL;DR

This paper investigates the universal behavior of nano-crystal plasticity through simulations, revealing how deformation dynamics depend on loading rates and dislocation interactions, bridging crystalline and amorphous systems.

Contribution

It introduces a two-dimensional discrete dislocation dynamics model that captures the rate-dependent avalanche behavior and localization phenomena in nanocrystalline deformation.

Findings

High loading rates lead to long-range correlated dislocation behavior.

Low rates cause plasticity localization and spatial avalanche integration.

Dislocation nucleation and rate effects control the system's statistical behavior.

Abstract

The universality class of the avalanche behavior in plastically deforming crystalline and amorphous systems has been commonly discussed, despite the fact that the microscopic defect character in each of these systems is different. In contrast to amorphous systems, crystalline flow stress increases dramatically at high strains and/or loading rates. We perform simulations of a two-dimensional discrete dislocation dynamics model that minimally captures the phenomenology of nanocrystalline deformation. In the context of this model, we demonstrate that a classic rate-dependence of dislocation plasticity at large rates (> 1000/s), fundamentally controls the system's statistical character as it competes with dislocation nucleation: At large rates, the behavior is statistically dominated by long-range correlations of "dragged" mobile dislocations. At small rates, plasticity localization dominates in small volumes and a spatial integration of avalanche behaviors takes place.