Thermal analyses and simulations of the type A and type B Portevin-Le Chatelier effects in an Al-Mg alloy

The process of plastic deformation is associated with a transformation of mechanical energy to heat energy. In this study, the type A and type B Portevin-Le Chatelier (PLC) effects were investigated by infrared thermography. The formation, propagation, and morphology of individual PLC bands were observed and characteristic parameters of the bands were measured. In particular, temperature increments originating from elastic shrinkage outside a deformation band were observed for the type B PLC effect, and this shrinkage was confirmed by a computation of the strain rate and plastic deformation within the band. Thus, we suggest a new criterion for distinguishing between the type A and type B PLC effects by the existence of elastic shrinkage outside deformation bands. A phenomenological model is described in detail, taking into account the effect of temperature changes, competition between mobile dislocations and solute atoms, and the influence of elastic deformation. The model has been used in numerical simulations of stress strain curves and temperature changes associated with the PLC effect. It is shown that the numerical results are able to reproduce most of the experimentally observed phenomena with reasonable accuracy. (C) 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.