Abstract:The mechanical properties and microstructural distribution of the Cu/Al brazing joints formed by torch-brazing with different Zn−Al filler metals were investigated. The microstructure of the Zn−Al alloys was studied by optical microscopy and scanning electron microscopy, and the phase constitution of the Cu/Al joints was analyzed by energy dispersion spectrometry. The results show that the spreading area of the Zn−Al filler metals on the Cu and Al substrates increases as the Al content increases. The mechanical results indicate that the shear strength reaches a peak value of 88 MPa when Al and Cu are brazed with Zn−15Al filler metal. Microhardness levels from HV122 to HV515 were produced in the three brazing seam regions corresponding to various microstructure features. The Zn- and Al-rich phases exist in the middle brazing seam regions. However, two interface layers, CuZn₃ and Al₂Cu are formed on the Cu side when the Al content in the filler metals is 2% and more than 15%, respectively. The relationship between intermetallic compounds on Cu side and Zn−xAl filler metals was investigated.

Key words: Cu/Al brazing joint; Zn−Al filler metals; mechanical property; interface layer