Microstructure and properties of dissimilar metals TIG welding-brazing joint of aluminum alloy to stainless steel using Al-Si flux-cored wire

Dissimilar metals of aluminum alloy to stainless steel by non-coated TIG welding-brazing was investigated using Al-Si flux-cored wire. The joint was characterized in order to determine the phases and the brittle intermetallic compound (IMC) in the interfacial layer by OM, SEM, EDS and XRD, and the effect of the flux was analyzed during the process and the mechanical properties were also tested. The results show that the flux of the wire can improve the wettability and spreadability of Al-Si filler metal on the surface of the steel and the wetting angle is less than 30°. The non-complete volatilizing of the flux causes mass of voids in the welded beam. The interfacial layer in steel side comprises [Al, Fe, Si] phase and Fe₄Al₁₃, and the welded beam comprises α-Al matrix, "Chinese script" α-phase (Fe₂SiAl₈) and needle-plate mixed phase (β-phase FeSiAl₅ and Al-Si eutectic phases). During the shearing test, the fracture occurs at the interfacial layer in steel side and the shear strength is only 55 MPa. The fracture surface comprises [Al, Fe, Si] phase, Fe₄Al₁₃ and little of Fe₂Si and Al₅Cr phases.