Effects of Texture and Alloying Elements on Stretch Formability of Mg Alloy Sheets

Abstract

A study has been made on the effects of texture and alloying elements on stretch formability of Mg alloys. AZ31, AT31, and ZX11 alloys having different textures have been subjected to uniaxial tensile loading and bi-axial stretch forming tests, and their microstructures and textures before and after deformation have been analyzed. It shows that the deformation of AT31 alloy is mainly controlled by the activation of prismatic slip besides the basal slip. On the other hand, there is a significantly high activity of tension twinning in ZX11 alloy regardless of tensile loading directions, resulting in the smallest Lankford values in ZX11 alloy among three alloys, followed by AT31 and AZ31 alloys. Nevertheless, the results of Erichsen cup tests in these alloys show the different behaviors such that AT31 alloy has the best stretch formability, followed by ZX11 and AZ31 alloys. It has been shown that the excellent stretch formability of AT31 alloy comes from an increased activity of prismatic slip and its characteristic texture counterbalanced by broadened distribution of basal poles along the transverse direction and split basal poles along the rolling direction. Although ZX11 alloy shows an increased activity of tension twinning during stretch forming, its orthotropic texture would lead to significant anisotropic deformation at a late stage of stretch forming, resulting in a premature failure.