Flow localization during severe plastic deformation of AZ81 magnesium alloy: Micro-shear banding phenomenon

The present study deals with the flow localization and its effects on the deformation mechanism as well as texture characteristics of AZ81 magnesium alloy during severe plastic deformation. Towards this purpose, a set of accumulative back extrusion (ABE) was conducted at temperatures ranging from 300 °C to 450 °C. The results indicate that the severe imposed strain tends to be localized in the form of micro-shear band due to the intrinsic anisotropic plasticity of the alloy. This banding evolves from the mechanical twinning which has a great contribution in accommodation of severe plastic strain during initial stages of ABE-processing. In addition, the micro-shear banding provides paths by which the extensive operation of slip systems and high dislocation density promote the initiation of dynamic recrystallization and dynamic precipitation of γ particles. The microshear banding has also resulted in the deviation from the strong fiber basal texture at higher deformation temperature. This is mainly attributed to the reorientation of basal planes parallel to the shear plane and widening of the bands via progression of the recrystallization inside the micro-shear bands.