Laser brazing of Aluminum alloy and Galvannealed steel with Zn-Si filler metal

Abstract

Dissimilar metals of 6022 aluminum alloy and galvannealed steel were joined successfully by laser brazing with new zinc brazing filler metal which was added Si.Si addition in the filler metal has great effects in preventing the growth of the IMC layer such as Fe₂Al₅ and minimizing its thickness. The peel strength of the joint with ZnSi filler metal increased by 3.5 times from that of joint with ZnAl filler metal. Fracture occurred at aluminum HAZ for joint with ZnSi filler metal and at brazing interface for joint with ZnAl filler metal. From TEM observation and diffraction analysis of brazing interface with ZnSi filler metal, Fe₃Al₂Si₃ that had the same lattice spacing as α-Fe was observed. Thus, Fe₃Al₂Si₃ that formed on the surface of steel prevented the formation of brittle intermetallic compound like Fe₂Al₅.