Microstructure evolution in a lamellae Al-33%Cu eutectic alloy during equal channel angular pressing

Strain driven transformation of lamellae structure in an eutectic Al-33%Cu alloy into a homogeneous equiaxed micro-duplex structure was investigated in equal channel angular pressing (ECAP) at 400 degree C. Intensive strain during ECAP is accommodated by periodic bending, periodic shear banding, parallel shearing, and shear cutting of the lamellae in the eutectic. The transformation follows the stages of subdivision of colonies into smaller lamellae blocks, the separation of these lamellae blocks into isolated islands, and the contraction to disappear of these islands through the breaking down of the lamellae at near the lamellae block-equiaxed region boundaries. The kinetics of this strain driven microstructure transformation process, described by the dependence of relative lamellae area fraction on accumulated ECAP equivalent true strain, physiognomically resembles that of thermal activated transformation process described by JMAK model.