New approaches to jerky flow

Serrated flow in Al-Mg alloys was investigated by examining the statistical distributions of the stress drops and through a dynamical analysis of the discontinuous stress vs. time curves. At high strain rates and low temperatures the behavior appears to be characterized by power law statistical distributions and avalanch-like dynamics, while in the domain of low strain rates and high temperatures, peaked distributions are associated with chaotic dynamics. These results are discussed in relation to two models for the Portevin - Le Chatelier effect. A relation is tentatively established between the observed dynamical behavior, the types of Portevin - Le Chatelier bands (propagating or non propagating) and the strength of the spatial coupling between neighbouring volume elements of the specimen.