Comparative study of laser swelding-brazing of aluminum alloy to galvanized steel butted joints using five different filler wires

Abstract

The purpose of this paper is to provide the gist for the selection of filler wire during the laser welding-brazing of Al to steel. A comprehensive comparison of laser welding-brazing 5052 aluminum alloy to unbeveled galvanized steel using pure Al, AlSi5, AlMg5, AlCu6, and ZnAl2 filler wires were conducted with varied laser beam offset. The comparison was carried out in terms of weld formation, interfacial microstructures, and mechanical properties. The results show that the fluidity of liquid filler is Pure Al < AlSi5 < AlMg5 < AlCu6 < ZnAl2. Too small or too large fluidity will lead to poor weld formation. The interfacial intermetallic compound consisted of layered Fe2Al5 and scattered FeAl3 when pure Al, AlMg5, and AlCu6 filler wires were used. When pure Al filler wire was used, cracks were most likely to occur in the reaction layer. The other four filler wire all improved the crack resistance. The thickness of the reaction layer significantly decreased when AlSi5 filler wire was used. Si element was found as a solid solution in the reaction layer to form Fe2(Al, Si)5 and Fe(Al, Si)3. A large amount of FeZn10 was mixed between Fe2(Al, Zn)5 when using ZnAl2 filler wire. The order of maximum tensile strength of the joints using different filler wires was AlSi5 > AlMg5 > AlCu6 > ZnAl2 > pure Al. The fracture of the joints all occurred at the brittle intermetallic layers when five different filler wires were used.