Effect of hot torsion deformation on microstructure in AZ31 magnesium alloy

Strength and ductility are desired characteristics in sheet materials for applications in the automobile industry. Such characteristics are developed during hot rolling of the as cast material to obtain sheet. Therefore, it is important to understand the evolution of microstructure during rolling. Because of the involvement of large strains in industrial sheet rolling, torsion deformation is a more suitable laboratory process to simulate the industrial rolling practice, compared to compressive or tensile deformation. In this work, an as cast AZ31 magnesium alloy was deformed in torsion under different thermomechanical conditions and the resultant microstructures were examined. At high temperatures, recrystallization through necklacing is the principal mechanism for microstructure evolution with nucleation of new grains at as cast grain boundaries. On the contrary, twinning contributes to the evolution of microstructure at low temperatures.