Research on interface characteristic of laser welding joints of steel/aluminum dissimilar materials

Abstract

With increasingly serious environmental pollution, automotive lightweight has become an indispensable problem to be solved, and using welding structure of dissimilar metal for steel/aluminum is an effective means to solve the problem of lightweight. Due to rapid speed, high energy density and small deformation, laser welding is regarded as one of prospective methods to join steel to aluminum successfully. It is shown that when welding speed and laser power are 20 mm/s and 0.82-0.83 kW with steel above Al alloy, the formation quality of the lap joint between steel and aluminum joint without interlayer is well. The continuous and island Fe-Al intermetallic compounds forming at the interface of the welded joint are Fe3Al, FeAl, FeAl2, Fe2Al5, FeAl3, and some of FeAl3 show needle-like morphology. When Fe-B-Si is used as interlayer, the interface is more flat, the thickness of Fe-Al intermetallic compounds becomes thinner and the number of island zone and needle-like FeAl3 decreases. The tensile-shear testing shows that the addition of Fe-B-Si can improve joints' mechanical property.