Deformation mechanisms and dynamic recrystallization of AZ31 Mg alloy with different initial textures during hot tension

Abstract

Deformation mechanisms and dynamic recrystallization (DRX) of AZ31 Mg alloy during tension at a temperature of 300°C and strain rate of 5×10−4s−1 were investigated by using three tension specimens with different initial textures. It is shown that initial texture has a great influence on the twinning behavior of the AZ31. A lot of {10−12} extension twins were observed in ND specimen, and only a small amount of {10−12} extension twins were observed in ND45 specimen, while no twin was observed in RD specimen. The initial texture also affects DRX. If the c-axis is parallel to the tensile axis (TA), as seen in ND specimen, extensive DRX process was observed, and a highest volume fraction of DRX together with a smallest grain size was formed after 45% tension strain before fracture. When the c-axis is inclining 45° or perpendicular to the TA, as seen in ND45 or RD specimen, DRX occurred at a slow rate resulting with a low volume fraction of DRX compared to ND specimen. In all samples, the texture of unrecrystallized grains with the orientation of the as-received ND45 specimen rotates to that of the as-received RD specimen, while the texture of unrecrystallized grains with the orientation of the as-received RD specimen evolves into a basal fiber texture with 〈10−10〉 parallel to the TA. It is believed that the effect of initial texture on DRX of ND specimen is caused by the activation of 〈c+a〉 slip since cross-slip and climb are easier to take place than for other slip systems during tension resulting in the formation of high angle boundaries. As a consequence, the grains, which deformed by slipping, not by {10−12} extension twinning, would not survive during tension due to DRX. The evolutions of microstructures and textures of the three tensile samples were discussed based on their deformation mechanisms and DRX behavior.