Effects of Pre-Strain on the Evolution of Microstructure and Strain Hardening of Extruded Az31 Magnesium Alloy

Pre-compression 3% and pre-stretch 3% subsequent annealing at 200oC for 2h are conducted on AZ31 magnesium alloys, then inverse tensile and compressive deformation are carried out at room temperature, respectively. During inverse tension 3% deformation on 1st pre-compression samples, detwinning behavior happens; after 2nd pre-compression 3%, the volume fraction of {10-12} extension twins decreases comparing with 1st pre-compression. Due to the interaction of dislocation and induced twinning lamellas, strain hardening rate (θ) increases on 1st and 2nd pre-compression samples. {10-12} tensile twinning is restrained during inverse compressive deformation by pre-stretch process. Owing to the decreasing amount of twins, the texture strengthening in compressive deformation weakens. So the slop of stage III in strain hardening rate sustaining reduces after 1st pre-stretch 3% and 2nd pre-stretch 3% deformation during inverse compression deformation.