Effect of inhomogeneous deformation on anisotropy of AZ31 magnesium sheet

Inhomogeneous plastic deformation in AZ31 magnesium sheet has been studied during uniaxial tensile testing using digital image correlation and electron backscatter diffraction techniques. Large strain gradients develop on the sheet surface parallel and perpendicular to the loading direction while very little deformation occurs in the thickness direction. This lack of thinning leads to an abrupt fracture following the development of a premature but extensive diffuse neck but without any localized neck. The strain distribution on the sheet surface evolves nonlinearly with strain, impacting the measured plastic strain ratio, r-value. The results show that r-value should be measured at “points” rather than over the “gage length” in Mg alloys. Friction stir processing modifies the basal texture and thus significantly improves the forming limit for in-plane plane strain path.