Recrystallization texture during ECAP processing of ultrafine/nano grained magnesium alloy

Abstract

An ultrafine/nano grained AZ31 magnesium alloy was produced through four-pass ECAP processing. TEM microscopy indicated that recrystallized regions included nano grains of 75 nm. Pole figures showed that a fiber basal texture with two-pole peaks was developed after four passes, where a basal pole peak lies parallel to the extrusion direction (ED) and the other ~20° away from the transverse direction (TD) in the ED–TD plane and 70° from the normal direction (ND ) in the TD–ND plane. The texture of recrystallized grains at the vicinity of grain boundaries was addressed. To investigate the recrystallization texture, the orientation relationships for the recrystallized and parent grains were studied for the material deformed up to first and second passes. The EBSD results implied that the grains recrystallized at the grain boundaries during the first pass, almost follow the orientation of prior deformed grains, while during the second pass the grain boundary recrystallization adopted a texture different from the parent grains. It was rationalized that as the number of passes increased, the grains recrystallized at prior grain boundaries tend to take different orientation to that of deformed grains. The latter finding was discussed relying on the increased share of non-basal slips in evolution of finer grains developed during subsequent deformation passes.