STATISTICAL BEHAVIOR AND STRAIN LOCALIZATION PATTERNS IN THE PORTEVIN-LE CHATELIER EFFECT

Statistics of the stress drops associated with the Portevin-Le Chateli er effect in an Al-Mg alloy were studied both experimentally and theor etically. II was shown that the character of the statistics changes fr om a peaked distribution of the stress drop magnitudes to a monotonica lly decreasing one as the imposed strain rate or the temperature are i ncreased. A discrete mode: based on a micromechanically founded local constitutive equation combined with spatial coupling between the eleme nts of the system was shown to reproduce the observed statistical beha viour. The mechanism of spatial coupling is connected with elastic str esses due to local plastic incompatibilities. The model was Further ap plied to simulate spatial deformation patterns including propagative d eformation bands. The systematics of the bands reported in the literat ure as well as the observed dependence of the band velocity on the imp osed deformation rate were recovered. It was concluded that the model proposed provides an adequate description of both the statistics of st ress discontinuities and the spatial features of the Portevin-Le Chate lier effect. Copyright (C) 1996 Acta Metallurgica Inc.