Three types of Portevin-Le Chatelier effects: Experiment and modelling

By employing the dynamic digital speckle pattern interferometry (DSPI) technique, three types of Portevin-Le Chatelier (PLC) effects are investigated systematically, with emphasis on the temporal and spatial dynamic features. A new model based on the dynamic strain aging (DSA) mechanism is proposed, and three types of PLC effects at different applied strain rates are reproduced by it when the spatial coupling is included. The dynamic interaction between dislocation and diffusing solutes is also studied through the developed constitutive model. The results self-consistently exhibit three branches of the dislocation-solute interaction, two stable branches at low and high strain rate (or dislocation velocity), which correspond to the effective aging or unpinning of dislocation, respectively, and a metastable one at the intermediate strain rate, where negative strain rate sensitivities result from the dynamic strain aging. (c) 2006 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.