Piobert-Luders plateau and Portevin-Le Chatelier effect in an Al-Mg alloy in simple shear

The jerky flow in an Al-Mg alloy is studied during simple shear tests at room temperature and various strain rates. Direct observations of the sample surface using digital image correlation allow the study of the type and the dynamics of bands associated to plastic instabilities as a function of shear strain and shear strain rate. The paper features that both Piobert-Luders and Portevin-Le Chatelier phenomena can be observed for a simple shear stress state at room temperature. The nucleation, growth and movement of the bands are described: it is shown that the kinematics of the bands is similar to those observed in tension but that the orientation of the bands varies with the shear strain. (C) 2012 Elsevier Ltd. All rights reserved.