Flow softening behavior and microstructure evolution of aluminum alloy 6061 due to dynamic recovery

Abstract

Hot compression tests for Al–Mg–Si aluminum alloy were performed on Gleeble-1500 at the deformation temperatures of 300 ∼ 500 °C and strain rates of 0.01–10 s−1. It was found that the flow stress curves exhibit continuous flow softening after reaching the peak value. Microstructure observations indicate that dynamic recovery is the dominant restoration mechanism during the deformation. Continuous flow softening is considered to arise mainly due to thermal softening by deformation heating and microstructural softening by dynamic grain boundary migration. The effect of deformation heating on flow stresses was corrected with the measured instantaneous sample temperature. The dynamic grain boundary migration rate was calculated based on the measured grain thickness. A modified Laasraoui-Jonas model was developed through introducing the flow softening item induced by dynamic grain boundary migration. The predicted flow stresses overall agree well with the experimental data.