Isotropic superplastic flow in textured magnesium alloy

A textured Mg-9Al-1Zn alloy rod exhibited highly isotropic flow along the longitudinal and transverse directions during superplastic deformation, indicating that crystallographic orientation had a negligible effect on flow stress. Although there was an overall weakening of the initial basal texture during deformation due to grain boundary sliding, the texture changes differed between tensile and compressive deformation along the longitudinal direction. This indicates that dislocation slip plays an important role in superplastic deformation. Macroscopic specimen shape anisotropy, on the other hand, would be expected to appear under the preferential activation of basal slip during compression along the transverse direction, but was not observed experimentally. These results imply that dislocation slip acts primarily as an accommodation mechanism for local stress concentration produced by grain boundary sliding.