Effect of ZnAl filler metals on the characteristics of the joint made by the high-frequency induction brazing of 304 stainless steel and 6A02 aluminum

Abstract High-frequency induction brazing Al/Steel dissimilar metals with different composition Zn Al filler metals was performed. Before the brazing experiment, the wettability of the filler metals on steel and aluminum alloy plates was investigated, respectively. The results shown that the Zn 15Al (wt%) filler metal had the best wettability on the aluminum. The brazing experiment indicated that when the brazing gap was 0.3 mm, the maximum wetting length and best filling performance of the joint were obtained. The most serious dissolution of aluminum in the brazing seam was observed when using Zn 2Al filler metal. The three-layered structures, which were composed of IMCs layer, Zn rich layer (occurred in particular situation) and Zn Al eutectoid structure, were found near the steel interface. Experiments and thermodynamic calculations were applied for analyzing microstructure evolution and elemental diffusion behavior. The highest shear strength reached 81.52 MPa when the Zn 15Al filler metal was used in 773 K for 30 s. The fracture morphology indicating that brittle fracture occurred in all the joints. But partial breaking in filler metal not in the IMCs layer, which means that the Zn Al filler metal improved the shear strength of the joint.