Interrupted Tensile Tests to Reveal the Non-Uniform Tensile Deformation of AZ31 Magnesium Alloy Welding Joint Processed by Friction Stir Welding

Interrupted tensile tests were conducted on FSWed AZ31 Mg alloy to reveal the non-uniform tensile deformation and underlying deformation mechanisms along welding joint. During tensile test, plastic deformation is inhomogeneous along tensile sample. Tensile deformation concentrates at the welding joint, especially at the intermediate zone between NZ and TMAZ. Depending on texture variation, different deformation mechanisms are concluded to be responsible for such inhomogeneous deformation. The activation stress of each deformation mechanism changes gradually from advancing side to retreating side. { 1012} Twinning, prismatic slip and basal slip are the dominating deformation mechanisms in TMAZ, NZ and their intermediate zones, respectively. Thus, inhomogeneous deformation was found along the center line of welding joint, and producing different working hardening. It is verified through micro-hardness distribution along the center line where the intermediate zone has the highest micro-hardness improvement. The results presented in this study give a clear exposition on deformation mechanisms induced inhomogeneous deformation in Mg alloy welding joint.