Investigation on the interface of Cu/Al couples during isothermal heating

The evolutionary process and intermetallic compounds of Cu/Al couples during isothermal heating at a constant bonding temperature of 550℃ were investigated in this paper. The interfacial morphologies and microstructures were examined by optical microscopy, scanning electron microscopy equipped with energy dispersive X-ray spectroscopy, and X-ray diffraction. The results suggest that bonding is not achieved between Cu and Al at 550℃ in 10 min due to undamaged oxide films. Upon increasing the bonding time from 15 to 25 min, however, metallurgical bonding is obtained in these samples, and the thickness of the reactive zone varies with holding time. In the interfacial region, the final microstructure consists of Cu₉Al₄, CuAl, CuAl₂, and α-Al + CuAl₂. Furthermore, these results provide new insights into the mechanism of the interfacial reaction between Cu and Al. Microhardness measurements show that the chemical composition exerts a significant influence on the mechanical properties of Cu/Al couples.