Microstructure and mechanical properties of cold metal transfer welded aluminium/nickel lap joints

Cold metal transfer (CMT) welding aluminium alloy to pure nickel using AlSi5 filler wire was investigated in this work. A characterisation of microstructure reveals that Al and Ni could be successfully jointed by the CMT welding process. From the Ni side to the Al side, the interfacial structure consisted of Ni substrate, Ni 3 Al–Ni 0·9 Al 1·1 –Ni 2 Al 3 intermetallic compound layer, NiAl 3 layer and Al–Si solid solution four parts. Moreover, the welding velocity had a significant influence on the interfacial morphology of the Ni/Al joints. Shear tensile testing shows that maximum shear strength of 42 MPa was obtained at a welding velocity of 15 mm s − 1 . Brittle fractures were observed in all of the lap joint specimens, with fractures located mainly at the NiAl and NiAl 3 intermetallic compound layer.