Metallurgy and mechanical performance of AZ31 magnesium alloy friction spot welds

Microstructural features were studied along the cross-section of AZ31 magnesium alloy friction spot welded joints made using different combinations of welding parameters. Static lap shear testing was performed to evaluate the mechanical properties of the welded joints, and the resulting fracture mechanisms and crack propagation paths were fully examined. Failure load is optimized when the welding procedure is performed with the combination of parameters that maximizes the material mixing, the size of fully metallurgical bonding and simultaneously minimizes the vertical displacement of hook region. The welds demonstrate three failure modes during lap shear testing: through the weld and non-circumferential pull-out modes, in which crack propagation crosses the recrystallized zone, and circumferential pull-out mode, around this zone.