Fusion boundary microstructure evolution and mechanical properties of cold metal transfer welded dissimilar A5754 and A5083 joint

•Non-dendritic equiaxed fine zone (EQZ) is newly evolved and located between PMZ and weld metal zone (WMZ).•EQZ of A5083 side exhibits finer grains than A5754 side.•EQZ width is greater at the A5754 interface than the A5083 interface. Fusion boundary microstructure evolution and its effect on tensile properties of cold metal transfer (CMT) welded joint of dissimilar A5754 and A5083 is studied. Non-dendritic equiaxed fine zone (EQZ) is newly evolved and located between PMZ and weld metal zone (WMZ). The Si films are distributed as continuous layers at grain boundaries (GBs) of EQZ, these films are comparatively less and are distributed in a non-continuous manner at GBs of partially melted zone (PMZ). EQZ of A5083 side exhibits finer grains than A5754 side. The narrower EQZ width, finer grains at EQZ, finer dendrites at WMZ interface and larger distribution of secondary phase particles at PMZ and heat affected zone (HAZ) increase strength of A5083 side.