Effect of ultrasonic vibration on the intermetallic compound layer formation in Al/Cu friction stir weld joints

Abstract Dissimilar aluminium alloy and pure copper joints were produced using a novel ultrasonic vibration assisted friction stir welding (UVaFSW) assembly. The intermetallic compounds (IMCs) formed at the Al-Cu interfaces were characterized using a scanning electron microscope and energy-dispersive X-ray spectroscopy analysis. The thermodynamic prediction of the first intermetallic compound formation using effective Gibbs free energy change of formation (EGFEF) model was used to calculate the first intermetallic compound layer to nucleate or form during each process condition at the joint interface. The results show that irrespective of the welding conditions (with and without ultrasonic vibrations) intermetallic compounds are formed at the interface. However, the ultrasonic vibration effectively reduced the thickness of the IMC layer at the joint interface and consequently improved the mechanical properties of the joints.