Micron-scale deformation: a coupled in-situ study of strain bursts and acoustic emission

TL;DR

This study investigates micron-scale plastic deformation by correlating stress drops and acoustic emissions during in-situ compression of micro-pillars, revealing dislocation avalanches as the cause of stochastic strain bursts.

Contribution

It introduces a precise fabrication method for micro-pillars and an in-situ testing setup that links acoustic emissions to dislocation activity during deformation.

Findings

Stress drops correlate with acoustic emissions.

Dislocation avalanches cause stochastic strain bursts.

Enhanced micro-pillar fabrication improves experimental control.

Abstract

Plastic deformation of micron-scale crystalline materials differ considerably from bulk ones, because it is characterized by random strain bursts. To obtain a detailed picture about this stochastic phenomenon, micron sized pillars have been fabricated and compressed in the chamber of a SEM. An improved FIB fabrication method is proposed to get non-tapered micro-pillars with a maximum control over their shape. The in-situ compression device developed allows high accuracy sample positioning and force/displacement measurements with high data sampling rate. The collective avalanche-like motion of dislocations appears as stress drops on the stress-strain curve. To confirm that these stress drops are directly related to dislocation activity, and not to some other effect, an acoustic emission transducer has been mounted under the sample to record emitted acoustic activity during strain-controlled compression tests of Al-5\% Mg micro-pillars. The correlation between the stress drops and the acoustic emission signals indicates that indeed dislocation avalanches are responsible for the stochastic character of the deformation process.