Brazability of dissimilar metals tungsten inert gas butt welding–brazing between aluminum alloy and stainless steel with Al–Cu filler metal

Dissimilar metals tungsten inert gas butt welding–brazing between 5A06 aluminum alloy and SUS321 stainless steel was carried out using Al–Cu6 filler metal and non-corrosive flux. A thin intermetallic compound layer has formed in welded seam/steel interface and the average thickness of the whole layer is 3–5 μm, which is less than the limited value of 10 μm. The intermetallic compound layer consists of Fe4Al13 phase and at the bottom Sn deposits in the molten flux layer and diffuses into steel matrix to form the grain boundary filter layer, which is the weak zone of the butt joint. The average microhardness of the layer is 644.7 HV, compared with 104.5 HV in welded seam and 200 HV in steel matrix. The tensile strength of butt joint reaches 172.5 MPa and the crack initiates from the IMC layer at the bottom of the joint and derives into welded seam at the upper part of the joint. The present joint in this study has higher level than those with coated layer.