Investigation of the electroplastic effect using nanoindentation

D Andre,T Burlet,F Körkemeyer,G Gerstein,J.S.K.-L Gibson,S Sandlöbes-Haut,S Korte-Kerzel

doi:10.1016/j.matdes.2019.108153

D Andre, T Burlet + Show 5 more

Open Access

https://doi.org/10.1016/j.matdes.2019.108153

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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. In this work, a novel setup to study the electroplastic effect during nanoindentation on individual phases and well-defined interfaces was developed. Using a eutectic Al-Al2Cu alloy as a model material, electroplastic nanoindentation results were directly compared with 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.

Highlights

The influence of electric current on the plastic deformation of metals, termed as the electroplastic effect (EPE), was first investigated by Troitskii and Likhtman [1]
The EP stress-strain curves further reveal that the stress drop induced by the first electric current pulse amounts to more than two times the stress drops induced by the following electric current pulses
We have developed a new nanoindentation setup to apply electric current pulses during nanoindentation

Summary

Introduction

The influence of electric current on the plastic deformation of metals, termed as the electroplastic effect (EPE), was first investigated by Troitskii and Likhtman [1]. Work by Troitskii et al [1, 11] and later by Conrad et al [5, 12] considered the effect of the ‘electron wind’, i.e. the drift of conduction electrons upon application of an electric potential, in assisting dislocations to overcome lattice obstacles. The ‘electron wind’ theory has since been widely applied and is able to predict key features of the EPE in a variety of materials and loading conditions [12]. Molotskii [13] proposed the de-pinning of dislocations from paramagnetic obstacles by the magnetic field induced by the electric current as an alternative mechanism for the EPE in metals. The effects of an electric current applied separately to any deformation or heating process has been shown to differ from those where an electric current is applied in combination with deformation [17]

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