Multiscale study of acoustic emission during smooth and jerky flow in an AlMg alloy

Abstract

The acoustic emission (AE) accompanying jerky flow in dilute alloys, the so-called Portevin–Le Chatelier effect, is usually considered to be composed of discrete bursts associated with the motion of large dislocation ensembles giving rise to stress serrations, which are superimposed on continuous AE generated during macroscopically smooth plastic flow. The data streaming technique which allows continuous AE recording is used to investigate the jerky flow of an AlMg alloy on different timescales. The apparent behavior, discrete or continuous, of AE is found to depend on the period of observation and the characteristic surveyed. However, it is proved that AE has a burst-like character during both stress serration and smooth flow. This behavior, revealed on timescales proper to the given strain rate, reflects the inherently intermittent, avalanche-like nature of collective dislocation dynamics, and unifies the concept generally applied to jerky flow with the similar approach to macroscopically uniform deformation flow, based on recent studies of AE during plastic deformation of pure materials.