Effect of CuAl₂ phase on properties and microstructure of Cu/Al brazed joint

Cu/Al dissimilar metals were brazed with Zn-Al filler metals by torch-brazing technology,and the effects of Al on the spreadability and microstructure of Zn-Al filler metal were investigated separately.Moreover,the strength and microstructure of the brazed joint were also studied.Results indicate that the strength of the brazed joints achieves the optimum status when the Al content of filler metals is 15%.SEM and EDS are used to study the microstructure and phase constitution of the filler metals and brazed joints respectively.Experimental results show the microstructures of brazed joints are mainly consisted of Zn-based solid solution when Al content is low.However,CuAl₂ intermetallic compounds can form in the brazing seam region with increase of Al content.When Al content is 22 wt.%,CuAl₂ intermetallic compounds become coarse,and the strength of brazed joint decreases.