On the characteristics of Portevin-Le Chatelier bands in aluminum alloy 5182 under stress-controlled and strain-controlled tensile testing

Plastic instabilities associated with the Portevin-Le Chatelier (PLC) effect are investigated in an At-based alloy of the 5000 series, in a wide range of temperatures and loading rates. The domains of occurrence of the PLC effect are explored and compared for constant stress rate and constant strain rate tensile testing. In both cases, experimental results shock that the PLC domains are bounded towards high temperatures and loading rates. The critical strain for the onset Of repeated yielding increases with increasing loading rate at low temperatures and high loading rates (normal behaviour), while it decreases at high temperatures and low loading rates (inverse behaviour), with different types of serration associated with the normal and the inverse behaviour, A simple model is proposed to explain this relation between the PLC type and the behaviour of the critical strain. Moreover, the specimen surface finish is found to have a significant influence on the stress-strain curves and the band propagation velocities. Finally, the experimentally observed PLC domain is shown to be in good agreement with a physical model of the dynamic strain ageing associated with the PLC effect. (C) 2002 Elsevier Science B.V. All rights reserved.