Linear friction welding of Al-Cu: Part 1-Process evaluation

Aluminium-copper assemblies are used as power connectors in various industrial processes. Fusion welding of aluminium to copper faces two main challenges that are related to the high thermal conductivity of the materials and the aggressive reaction between the materials that forms brittle intermetallic phases at the interface. Though high energy density techniques such as electron beam welding can overcome the thermal conductivity issue, only solid state joining techniques can viably manufacture the aluminium-copper assemblies while minimising the formation of the intermetallic phases that are problematic for the electrical conductivity and efficiency of the connector. In this work, an alternative approach for manufacturing the aluminium-copper assemblies has been developed using linear friction welding, an emergent solid state joining technology. The influence of process conditions on the joint integrity and the characteristics of the interface were studied using optical microscopy and electrical conductivity measurements. Under optimum processing conditions, integral joints with limited intermetallic phases at the interface could be repeatedly produced. In comparison with aluminium-copper assemblies manufactured by explosive welding, the fraction and size of the intermetallic phases located at the interface, as well as the extent of the interfacial region over which changes in the properties occur, were determined to be considerably reduced when employing linear friction welding.