Comparative study on the weldability of AZ31 magnesium alloy using different GTAW currents

This study investigates the impact of alternating current (AC) and pulsed current (PC) on gas tungsten arc welding (GTAW) of AZ31 Mg alloy sheets. Welding was performed using AC (85, 125 A) and PC (130–90 P, 140–100 P) conditions. Results indicated that the welding current mode influences grain morphology and mechanical performance. High-heat input (125 A, 140–100 P) led to grain coarsening; however, the 130–90 P condition resulted in refined equiaxed grains, reducing the average grain size by ∼35–40%. The 125 A joint achieved the highest tensile strength (225 MPa), while the 130–90 P joint provided nearly equivalent strength at a reduced heat input compared with the 125 A condition. The hardness profiles indicated that the base-metal consistently demonstrated greater hardness compared to the heat-affected zone. The weld metal exhibited the lowest hardness values, indicating the influence of thermal softening and microstructural recovery in the welded regions. The findings suggest that optimised pulsed current GTAW achieves a balance between mechanical performance and microstructural control while requiring a reduced heat input for AZ31 Mg alloy welds.