Spatio-temporal features of the Portevin-Le Chatelier effect

We show that an extension of Ananthakrishna's (AK) model exhibits all the features of the Portevin-Le Chatelier (PLC) effect including the recently observed crossover from a low dimensional chaotic state at low and medium strain rates to a high dimensional power law state of stress drops at high strain rates. The model also displays three types of bands. The dislocation configurations are shown to be in the pinned stated in the chaotic regime (i.e., the region of type C and B bands) and at the edge of unpinning in the power law regime where propagating bands are seen.