Effect of initial texture on dynamic recrystallization and deformation mechanisms in AZ31 Mg alloy extruded at 573 K

Abstract

AZ31 magnesium alloy with two different forms of initial textures were extruded at 573K to investigate the effect of initial texture on dynamic recrystallization (DRX) and deformation mechanisms. It reveals that the initial texture significantly affected twinning behavior. Hardly any twins were found in the extruded and annealed (EA) rod while {10−12} extension twins were observed to be very active in the rolled and annealed (RA) rod. DRX in the RA rod was retarded compared with that in the EA rod. The delay of DRX in the RA rods was attributed to the different deformation mechanisms occurring before DRX initiation. For the EA rod, dislocation slip was considered as the main deformation mechanism at the initial stage of extrusion which resulted in a faster increasing of the stored energy within the grains and consequently DRX was initiated. For the RA rod, {10−12} extension twin was a dominant deformation mechanism at the initial stage of extrusion before DRX initiated which resulted in an extrusion texture with the basal planes parallel to the extrusion direction (ED). Because of the profuse twinning, the stored energy caused by dislocation motion was relatively small in the RA rod, which was considered as the main reason of the delay of DRX in the RA rod. However, although the initial texture had great influence on DRX and deformation mechanisms during extrusion it had no significant effect on final fully DRX extrusion microstructure. DRX is a texture weakening process during extrusion. A weak fiber texture with the basal planes parallel to ED but without any specific crystallographic direction parallel to ED was obtained in the fully DRX extrusion microstructure.