Novel sacrificing-sheet linear friction welding method to fabricate sound dissimilar joint between steel and aluminum alloy

Abstract

In this study, a novel joining method, called sacrificing-sheet linear friction welding (SSLFW), was developed and utilised to join SS400 structural carbon steel and A7075 aluminum alloy. SSLFW involves placing a centre sheet between the two side materials to be joined. The centre sheet is subjected to linear oscillating motion while side materials are pressed against it. The thermomechanical effect from each side leads to the expulsion of centre sheet from joining interface, enabling direct joining between the side materials. Furthermore, intermetallic compounds (IMCs) layer thickness at dissimilar joint interface was minimised with increase in welding pressure accompanied by increased forging speed. Consequently, joints produced at forging speeds of 40 and 50 mm/s show the highest joint strength of 425 MPa, exhibiting a joint efficiency of 88% with respect to base metal strength of SS400 steel. Furthermore, following post-weld artificial aging treatment, the joint strength was enhanced to $\sim$ 448 MPa, improving the joint efficiency to 93%.