Mechanical and Microstructural Properties of Friction Stir Welded Dissimilar Aluminum Alloys and Pure Copper Joints

Joining dissimilar metal alloys such as aluminum and copper is very difficult to be done because of alterations in chemical, metallurgical and physical behavior. Friction Stir Welding (FSW) is a solid-state welding technique which is one of the new methods used for joining the dissimilar metal. The material used is aluminum alloy 5052 and pure copper plates. The welding parameters were carried out with variable geometry shape of pin tools: taper and threaded cylindrical pin tools. Also preheating were performed on the part of copper plates with temperatures at both 25°C and 200°C. The friction stir welding of dissimilar joints was carried out at the rotary tool speed of 2800 rpm with the angle of 1 degree and the welding travel speed of 2 mm/sec. All welds were then carried out to several mechanical testing and microscopic observation. The results show that the variable geometry shape of pin tools and pre-heating on the copper part affect the microstructure grain size and the formation of Al-Cu inter-metallic phases. The creation of different structures influences the mechanical properties of the friction stir welds. The hardness of welds using threaded pin tools is higher than the tapper one. However, the tensile strength of dissimilar welds using the threaded cylindrical pin tools is lower than the tapper one. The fracture location commonly occurs at the part of aluminum plates having a brittle intermetallic phase.