On the critical character of plasticity in metallic single crystals

TL;DR

This study provides experimental evidence that dislocation avalanches in metallic single crystals exhibit self-organized criticality, characterized by power-law distributions and avalanche interactions, supporting a universal SOC framework for crystalline plasticity.

Contribution

It is the first to experimentally demonstrate SOC behavior in metallic single crystals, extending previous ice crystal findings to metals.

Findings

Dislocation avalanches follow power-law energy distributions.

Slip and twinning events show similar statistical behavior.

Evidence of avalanche interactions and clustering supports SOC theory.

Abstract

Previous acoustic emission (AE) experiments on ice single crystals, as well as numerical simulations, called for the possible occurrence of self-organized criticality (SOC) in collective dislocation dynamics during plastic deformation. Here, we report AE experiments on hcp metallic single crystals. Dislocation avalanches in relation with slip and twinning are identified with the only sources of AE. Both types of processes exhibit a strong intermittent character. The AE waveforms of slip and twinning events seem to be different, but from the point of view of the AE event energy distributions, no distinction is possible. The distributions always follow a power law, even when multi-slip and forest hardening occur. The power law exponent is in perfect agreement with those previously found in ice single crystals. Along with observed time clustering and interactions between avalanches, these results are new and strong arguments in favour of a general, SOC-type, framework for crystalline plasticity.