Effect of Ultrasonic Impact on the Microhardness and Microstructure of Friction Stir Welded Aluminum Alloy 2024

In this paper, the effect of ultrasound on the microhardness and microstructure of friction stir welding joints is investigated. It has been found that the area with minimum microhardness is located in the thermomechanically affected zone on the retreating side. An ultrasonic impact resulted in an increase in the size of this area. The weakening of the region is attributed primarily to the low content of hardening particles due to overaging. It was also found that the ultrasonic impact during welding resulted in a 5 times reduction of residual stresses.