Shear banding phenomenon during severe plastic deformation of an AZ31 magnesium alloy

Abstract

Severe plastic deformation was applied on a wrought AZ31 magnesium alloy by a new method called accumulative back extrusion (ABE). Instabilities of plastic flow in the form of localized shear bands were experimentally observed during ABE processing of the AZ31 alloy. The obtained microstructures show the appearance of shear bands in ABE processed specimens, the extent of which was observed to be decreased by increasing the temperature. The restricted flow (due to the deformation geometry) was discussed as the main cause of the latter behavior. A noticeable grain refinement was observed inside the shear bands which was attributed to the occurrence of continuous dynamic recrystallization inside the bands. To analyze the homogeneity of mechanical properties, the microhardness variations from the deformed bulk to the shear bands were measured and interpreted. The role of shear banding in grain refinement with no harmful effect on material soundness was explained.