Ultrasonic Resistance Spot Welding of Aluminum AA6061T6

In this study, effects of ultrasonic vibrations (~ 20 kHz) on the spot weldability of Al 6061T6 is investigated. AC resistance spot welding machine has been modified to apply in situ ultrasonic waves during the spot welding process. Ultrasonic assisted spot welding process has shown superior joint properties. Better mechanical strength in terms of peak load during lap shear displacement test is observed. Up to 190 % increase in the energy absorbed prior to failure is observed in the presence of ultrasonic waves. Ultrasonic waves eliminates the spot welding defects especially porosities. It promoted the equiaxed structure at the weld center and minimizes the length of the columnar zone. Moreover, ultrasonic assisted spot welds have shown lower heating and cooling rates possibly due to breakdown of the surface asperities, oxide layer and contaminants. This decreases the contact resistance and heating/cooling rates.