Effect of pre-existing {10(1)over-bar2} extension twins on mechanical properties, microstructure evolution and dynamic recrystallization of AZ31 Mg alloy during uniaxial compression

AZ31 Mg alloy plates were pre-compressed at room temperature along the transverse direction (TD) to introduce {10 (1) over bar2} extension twinning. Mechanical properties, microstructure evolution and dynamic recrystallization (DRX) mechanisms of twinned samples containing pre-existing twins during uniaxial compression were investigated and compared to those of as-received samples. The results indicated that compared to that of as-received sample compressed along the rolling direction (RD), the yield stress of twinned sample was dramatically increased at from room temperature to 200 degrees C. In contrast, when compressing along the normal direction (ND), the yield stress of twinned sample was greatly decreased at from room temperature to 200 degrees C. With the further increase of temperature, the as-received and twinned samples exhibited similar compression flow curves and obvious DRX had taken place. Continuous dynamic recrystallization (CDRX) was the main DRX mechanism in the as-received sample compressed along ND at 200 degrees C. Twin assisted DRX besides CDRX was also initiated in the as-received sample compressed along RD and in the twinned sample compressed along ND or RD at 200 degrees C. DRX mechanism was changed to discontinuous dynamic recrystallization (DDRX) in the as-received and twinned samples with the further increase of temperature.