Role of electroplated interlayer in continuous drive friction welding of AA6061 to AISI 304 dissimilar metals

Aluminium austenitic stainless steel joints find application in cryogenic engines, spacecrafts and automobiles. This dissimilar material combination is unweldable by conventional fusion welding due to a tendency for brittle intermetallic formation. Solid state welding processes such as friction welding are reported to be employed in such situations. This paper deals with continuous drive friction welding of AA6061 Al alloy to AISI 304 austenitic stainless steel. Direct welding of this combination resulted in brittle joints with 0° bend angle due to the formation of Fe₂Al₅. To alleviate this problem welding was carried out by incorporating Cu, Ni and Ag as diffusion barrier interlayers. The interlayer was incorporated by electroplating. Welds with Cu and Ni interlayer were also brittle due to the presence of CuAl₂ and NiAl₃. Ag acted as an effective diffusion barrier for Fe avoiding the formation of Fe₂Al₅. Therefore welds with Ag interlayer were stronger and ductile and could be bent to an angle of 100°.