Yield precursor dislocation avalanches in small crystals: the irreversibility transition

TL;DR

This study reveals that small crystalline metals exhibit a reversible-irreversible transition similar to other non-equilibrium systems, with yield precursor avalanches decaying under cyclic loading and diverging near failure stress.

Contribution

It demonstrates that small crystal deformation shares key features of RITs, including power law scaling of avalanches, linking crystal plasticity to broader non-equilibrium phenomena.

Findings

Yield precursor avalanches decay with cyclic loading.

Divergence of avalanche amplitude and decay time near failure.

Power law scaling consistent with RIT in other systems.

Abstract

The transition from elastic to plastic deformation in crystalline metals shares history dependence and scale-invariant avalanche signature with other non-equilibrium systems under external loading: dilute colloidal suspensions, plastically-deformed amorphous solids, granular materials, and dislocation-based simulations of crystals. These other systems exhibit transitions with clear analogies to work hardening and yield stress, with many typically undergoing purely elastic behavior only after 'training' through repeated cyclic loading; studies in these other systems show a power law scaling of the hysteresis loop extent and of the training time as the peak load approaches a so-called reversible-irreversible transition (RIT). We discover here that deformation of small crystals shares these key characteristics: yielding and hysteresis in uniaxial compression experiments of single-crystalline Cu nano- and micro-pillars decay under repeated cyclic loading. The amplitude and decay time of the yield precursor avalanches diverge as the peak stress approaches failure stress for each pillar, with a power law scaling virtually equivalent to RITs in other nonequilibrium systems.