Microstructure and Properties of Zn-Al Filler Metal Brazing Cu/Al Joint

Microstructure and properties of Zn-xAl alloy were investigated, moreover, the strength and microstructure of the Cu/Al brazed joint had been studied. The results indicate that the massive microstructure is granular and fine when Al content is under 15 wt.% in the cast microstructure of Zn-xAl filler metal. Meanwhile, the drawability properties of the filler metal is excellent. Thus, the massive microstructure become dendritic and coarse when Al content exceeds 15wt.%. At the same time, the drawability properties of the filler metal become bad. In the microstructure of the brazed joint, the interface layer exists in the interface between the Cu base metal and the brazed seam. The interface layer is mainly consisted of Cu9Al4 and CuAl IMCs. When Al content is under 15wt.%, the interface layer shape is a visibly serrated edge, so the adhesive strength between the interface layer and the brazed seam is higher and the mechanical property of the brazed joint is excellent. The brazed joint strength of Zn-15Al filler metal get highest. But the interface zone become relatively straight when Al content exceeds 15wt.%. In the meantime, the strength of the brazed joint decreases.