Suppression of intermetallic reaction layer by ultrasonic assistance during friction stir welding of Al and Mg based alloys

This article aims to discover the effects of ultrasonic vibration during friction stir butt welding of AA6061-T6 and AZ31B Mg alloys. In the present attempt, the ultrasonic vibrations are enforced along the welding direction via novel horn attachments and welding tool. The experimental outcomes result in a significant improvement in weldment mechanical properties (ultimate tensile strength 22.1%, and weld efficiency 22.0%) with ultrasonic assistance. A major reduction in intermetallic layer thickness is also obtained across the dissimilar interfaces treated with ultrasonic vibrations. The correlation analysis evidence that at the parameters, where the ultrasonic joints exhibit maximum improvement in weld strength, the intermetallic layer thickness shows a maximum reduction. The energy dispersive X-ray spectrometry analysis of the weld interface confirms the formation of intermetallic phases beta Al3Mg2 and gamma Al12Mg17 whose thicknesses are reduced across the acoustic regions. Furthermore, a significant improvement in interfacial bonding, enhanced material mixing and subsequent diminution in weldment anomalies have been found in the joints made with ultrasonic assistance. (C) 2020 Elsevier B.V. All rights reserved.