Ultrasonic vibration assisted friction stir welding of aluminium alloy and pure copper

A new ultrasonic vibration assisted friction stir welding (UVaFSW) system was used to successfully join AA6061-T6 aluminium alloy and C10100 pure copper plates. The effect of ultrasonic vibration on the joint formation, macrostructural features, microstructure and mechanical properties of the joints was investigated. The novel UVaFSW process was found to enhance the joint formation mechanism and mechanical properties. The joint strength was found to increase with rotational speed up to 600 rev/min and then decrease due to higher heat inputs. Material flow behaviour of the reacting materials was enhanced, the structured layers exhibited more homogenous features, and the intermesh of the joint interfaces was improved. Ultrasonic vibration influences the fracture mechanism of the Al-Cu joint by shifting the fracture location to the heat affected zone in the Al side of the joint, and the fracture surface displayed a ductile fracture mode. Whereas, in the joints without ultrasonic vibration, the fracture occurred mainly at the thermomechanically affected zone in the Cu side of the joints, and the fracture surface showed a mixed brittle-ductile fracture characteristic.