Effect of Rotary Swaging on Microstructure, Texture, and Mechanical Properties of a Mg-Al-Zn Alloy

The effect of rotary swaging on the microstructure, texture, and mechanical properties of the magnesium alloy Mg-4.4Al-0.9Zn-0.4Mn is studied. Repetitive processing, conducted at progressively dropped deformation temperature (from 400 down to 200 degrees C), leads to an increase in the cumulative strain epsilon. Rotary swaging of the alloy is shown to lead to microstructure fragmentation due to intensive twinning on various crystallographic planes. A high density of twins observed at the final stage of deformation, at epsilon = 2.77, leads to a decrease in the distance between boundaries (including both twins and grain boundaries) to approximate to 3 mu m. With decreasing temperature, 0.2-mu m-wide secondary deformation twins form within the primary twins with a width in the range of 1.5-2.5 mu m. The texture analysis shows that, upon deformation, the number of orientations increases as does their scatter. Rotary swaging at 350 degrees C to epsilon = 2.77 gives rise to an increase of both strength and tensile ductility of the alloy. The high strength characteristics are achieved due to the formation of a subgrain structure and profuse twinning. The increased tensile ductility is associated with the activation of prismatic slip in addition to developed basal slip.