Dislocation Avalanches: Earthquakes on the Micron Scale

TL;DR

This study investigates dislocation avalanches in micron-scale materials, revealing their similarity to earthquakes through acoustic emission analysis, and introduces a novel experimental setup to correlate acoustic signals with dislocation motion.

Contribution

The paper presents a new experimental setup that detects acoustic emissions during dislocation slip, establishing a link between acoustic signals and local deformation events in micron-scale specimens.

Findings

Dislocation motion exhibits a scale-free size distribution similar to earthquakes.

Acoustic emission signals correlate with energy release during dislocation slip.

Plastic events show a two-level structure in acoustic signals.

Abstract

Compression experiments on micron-scale specimens and acoustic emission (AE) measurements on bulk samples revealed that the dislocation motion resembles a stick-slip process - a series of unpredictable local strain bursts with a scale-free size distribution. Here we present a unique experimental set-up, which detects weak AE waves of dislocation slip during the compression of Zn micropillars. Profound correlation is observed between the energies of deformation events and the emitted AE signals that, as we conclude, are induced by the collective dissipative motion of dislocations. The AE data also reveal a surprising two-level structure of plastic events, which otherwise appear as a single stress drop. Hence, our experiments and simulations unravel the missing relationship between the properties of acoustic signals and the corresponding local deformation events. We further show by statistical analyses that despite fundamental differences in deformation mechanism and involved length- and time-scales, dislocation avalanches and earthquakes are essentially alike.