Effect of ultrasonic vibration on welding load, temperature and material flow in friction stir welding

The main process variables were measured, characterized and compared in friction stir welding with/without ultrasonic vibration. The exerted ultrasonic vibration causes reduction in traverse force, tool torque and axial force of welding. Based on the measurement of thermal cycles in friction stir welding process, the thermal effect of ultrasonic vibration is negligible, and the mechanical coupling between ultrasonic vibration and tool action plays a more important role in affecting both the welding process effectiveness and the joint quality. Ultrasonic vibrations improved weld formation by either reducing or eliminating the weld defects, and the suitable process-parameter window is expanded. Dissimilar welding of AA6061-T6 to AA2024-T3 with ultrasonic vibration was used to characterize the enhanced material flow which results in the better weld formation.