Observation and modelling of propagating Portevin-Le Chatelier deformation bands in Cu-15 at.% Al polycrystals

The nucleation and propagation of Portevin-Le ChaAtelier (PLC) deformation bands have been studied by means of a novel multizone laser scanning extensometer providing information on the local development of strain along the main part of the specimen, in addition to the conventional measurement of stress serrations. This permits us to distinguish clearly between the bands of types A, B a nd C, and to explore their ranges of existence at various temperatures, stresses and strain rates as well as transitions between them along the stress-strain curve. The laser extensometer provides independent data on the propagation velocity, concentrated strain and width of the bands. These experimental data are compared with a recent theoretical space-time analysis of propagating PLC bands, which combines explicitly a physical description of the kinetics of dynamic strain ageing and plastic deformation including the effect of long-range dislocation interactions. The model correctly predicts the above band parameters and their dependences on the deformation rate and specimen thickness.