Formation of Intermetallic Phases on the Bond Interface of Aluminum-Clad Copper

It is difficult to bond dissimilar metals such as aluminium and copper using diffusion bonding of dissimilar materials because intermetallic compounds are easily produced at the bond interface and they cause the decline of bonding strength. However, as the aluminium clad copper were produced by vacuum roll bonding, hundreds nm of intermetallic phases are formed on the bond interface. On the tensile testing, it is broken from the base metal of aluminium and high bond tensile strength is available. In this study, heat-treatment has been taken to aluminium-clad copper produced by vacuum roll bonding. Observation of microstructure, EPMA, and XRD have been carried to the investigation of the formation of inter-metallic phases. As a result, it is clarified that 3 types of intermetallic phases such as CuAl2, CuAl and Cu9Al4 are formed at the bond interface of Al/Cu clad materials after heat-treatment. And the apparent activation energy of the intermetallic phases for growth behavior has been calculated. It was clarified that the apparent activation energy of CuAl and Cu9Al4 is lower than CuAl2. The affect of intermetallic phases on bond strength has also been carried to investigate with the growth of intermetallic phases. The decrease of tensile strength has been clarified. The broken position is in the CuAl2 or between CuAl2 and CuAl. Furthermore, the bond strength of Al/Cu clad material is seriously affected by the thickness of CuAl2.