Investigation of the electroplastic effect using nanoindentation

TL;DR

This study introduces a novel nanoindentation setup to investigate the electroplastic effect in metallic-intermetallic composites, revealing dislocation de-pinning as a key mechanism influenced by electric current pulses.

Contribution

The paper presents a new experimental approach to study electroplastic effects at the nanoscale, linking micro- and macroscopic behaviors and identifying dislocation de-pinning as a dominant process.

Findings

Current pulses cause displacement shifts and stress drops.

Higher current intensity and loading rate increase effects.

Dislocation de-pinning dominates over thermal effects.

Abstract

A promising approach to deform metallic-intermetallic composite materials is the application of electric current pulses during the deformation process to achieve a lower yield strength and enhanced elongation to fracture. This is known as the electroplastic effect. We developed a novel setup to study the electroplastic effect during nanoindentation on individual phases and well-defined interfaces. Using a eutectic Al- Al2Cu alloy as a model material, we compare the electroplastic nanoindentation results to macroscopic electroplastic compression tests. The results of the micro- and macroscopic investigations reveal current induced displacement shifts and stress drops, respectively, with the first displacement shift / stress drop being higher than the subsequent ones. A higher current intensity, higher loading rate and larger pulsing interval all cause increased displacement shifts. This observation, in conjunction with the fact that the first displacement shift is highest, strongly indicates that de-pinning of dislocations from obstacles dominates the mechanical response, rather than solely thermal effects.