Work-softening behavior of the ultrafine-grained Al alloy processed by high-strain-rate, dissimilar-channel angular pressing

Abstract

Commercially pure Al alloy sheets were processed using high-strain-rate, dissimilar-channel angular pressing (DCAP) for as many as 100 passages through a channel with phi = 120 deg, to investigate the work hardening caused by a low strain level (epsilon < 2) and the work softening caused by an extremely high strain level (3 < epsilon < 58). The hardness of the alloy increased significantly by a factor of 2 at strains less than similar to2, while a gradual decrease in the hardness was observed at strains greater then similar to2. The work-hardening and the work-softening behaviors observed from the Al alloy were analyzed by correlating the measured properties with microstructural evolutions observed by transmission electron microscopy (TEM). A detailed micro structural-evolution sequence occurring at successive strain stages was also investigated based on TEM and electron backscattered diffraction (EBSD).