The Portevin–Le Chatelier (PLC) effect and shear band formation in an AA5754 alloy

A non-contact strain measurement technique, based on digital image correlation (DIC) analysis, has been utilized in order to observe Portevin–Le Chatelier (PLC) band behaviour during tensile deformation of AA5754 sheet and subsequently to measure the level of incremental plastic strain carried within the bands. In addition, PLC banding was studied as a function of prior deformation under positive strain rate sensitivity conditions (i.e., at low temperature). Small prestrains (of the order of the Lüders strain) do not affect subsequent room-temperature deformation. However, prestrains of 0.1 or higher change the nature of the PLC bands that form at room temperature. Finally, careful experiments were performed involving low-temperature prestrains sufficient to cause immediate necking when deformation was continued at room temperature. These suggest that shear localization is independent of existing PLC bands.