Interfacial Microstructure of Diffusion-Bonded Cu/Cu-Ag/Al Hybrid Alloy

Cu and Al6061 alloys were diffusion-bonded at 530°C with Cu-15 wt. % Ag alloy as an intermediate layer and the interface microstructure were analyzed. The presence of Cu 9 Al 4 , CuAl and CuAl 2 intermetallic layers were confirmed along with Ag 3 Mg and AgMg intermetallics. Ag was found to diffuse into Al, forming needle-shaped Ag 2 Al precipitates in Al substrate close to Al/Cu-Ag interface region. Micro-Vickers indentation aimed at the interface regions, CuAl/CuAl 2 and CuAl 2 /Ag 3 Mg-AgMg lamella revealed that cracks were formed mostly around the indenter mark in CuAl 2 layer more than in CuAl and no cracks in the Ag 3 Mg-AgMg lamella region, suggesting CuAl 2 is more brittle than CuAl and Ag 3 Mg-AgMg lamella is rather ductile. Ag 3 Mg-AgMg lamella was found to be formed at the interface between Al and CuAl 2 . The formation of ductile Ag 3 Mg-AgMg lamella at the Al interface suggests that the diffusion bonding Cu and Al with Cu-Ag or Ag as a intermediate layer may increases the interface reliability of Cu/Al hybrid alloy.