Laser beam joining of Al/steel dissimilar metals with Sn-Zn filler wire in overlap configuration

A laser beam joining an Al-on-steel overlap configuration of 5052 aluminum alloy and Q235 steel was conducted with Sn-30Zn filler wire. The influence of processing parameters on weld appearance was investigated. The microstructures and mechanical property of the joints were analyzed. The results show that Sn-Zn filler wire could well wet 5052 aluminum alloy and the steel under heating of defocusing laser. Good weld appearance was obtained by suitable processing parameters. The solid solution interface was formed at the aluminum alloy side and intermetallic compounds (IMCs) interface was formed at the steel side. With increasing laser power, intergranular penetration of the Al side aggravated, and the thickness of the IMCs layer at the steel side increased. It was found that all of the joints fractured in the seam according to the results of the tensile tests. The intergranular penetration and IMCs did not reduce the mechanical property of the joint. The maximum value of fracture load reached 312 N/mm. The fractured surface was characterized as a ductile fracture. The influence of processing parameters on the microstructures and mechanical property was discussed.