Microstructure and mechanical behaviour of CMT-welded Mg/Al dissimilar joint using Inconel 625 as filler metal

Mg/Al dissimilar lap joint was produced by modified cold metal transfer process using Ni-based alloy wire Inconel 625 as filler metal. The characteristics of microstructure and mechanical behaviour of the joint were investigated. Microstructural analysis shows that the weld interface near Mg substrate consists of six types of areas: Mg2Al3-based area, Mg17Al12-based area, Al solid solution-based area, fusion zone-based area, Mg + Mg17Al12 eutectic area, and mixed area. With the characteristic of quasi-cleavage fracture, the tensile-shear load of the lap joint reached to 1.28 kN. The failure occurred primarily at the Mg2Al3-based area within the weld interface near Mg substrate. However, the harmful effect of the Mg2Al3 intermetallics on the strength of welded joint is limited.