Multifractal analysis of the Portevin-Le Chatelier effect:: General approach and application to AlMg and AlMg/Al2O3 alloys

Recent studies of the Portevin-Le Chatelier (PLC) effect bear evidence that serrated deformation curves characteristic of unstable plastic flow may exhibit temporal features that reflect complex spatio-temporal patterns arising due to the collective nature of dislocation dynamics. We investigate the possibility of studying plastic instability within a general framework provided by multifractal analysis of deformation curves. The effect is studied on a classical Al-3%Mg alloy as a base material, as well as its composite modification produced by addition of Al2O3 dispersion particles. It is shown that using multifractal analysis, changes in the temporal structure of the deformation curves, which result from variation of the experimental conditions and/or addition of second-phase particles, can be quantified. Thus, this technique provides an additional tool for a comparison between experiment and theoretical models of the PLC effect on a quantitative basis. (c) 2005 Published by Elsevier Ltd on behalf of Acta Materialia Inc.