Effect of processing temperature on microstructure of AZ61 magnesium alloy produced by compressive torsion processing

Abstract

A compressive torsion process, which is one of severe deformation processes, is applied to AZ61 magnesium alloy to control microstructure. This process is composed of relatively low compressive pressure and axial rotation, and can apply huge strain to a work piece without changing in shape during processing. Effect of processing temperature on grain refinement and texture change was investigated. The alloy with initial 10~200/im grains was refined under 10 μm by this process. The initial grains were refined smaller with lower process temperature, but the refinement was not enough at inner parts of a cylindrical specimen because of geometric strain gradient due to rotational loading. In the case of relatively higher temperature processing, though the refined grains became larger, the grain refinement were uniform all over the specimen even the geometric strain gradient. Axisymmetrical texture of (0002) crystal planes in the starting alloy was changed to the orientations parallel to the basal plane of a cylindrical specimen after this process.