Microstructure characteristics and mechanical property of aluminum alloy/stainless steel lap joints fabricated by MIG welding–brazing process

Lap joints of aluminum alloy 2B50 and stainless steel 1Cr18Ni9Ti were welded by MIG welding–brazing method with 4043 Al–Si filler metal. The effect of aluminizing coating and galvanized zinc coating on fusion metal spreadability were studied. The aluminized coating had limited effect to promote weld surface appearance and obvious micro-cracks were found between the compound layer and the steel side. The fracture in tensile tests occurred at the interfacial layer of the weld with a low tensile strength about 60 MPa. Joints between aluminum alloy and galvanized steel had good surface appearances and the intermetallic compound in fusion zone region close to joint interface was Al4.5FeSi. The thickness of the intermetallic compound layer varied from about 5 μm to 15 μm depending on the heat input and the highest tensile strength of lap joint could reached 193.6 MPa when the heat input is 0.846 KJ/cm.