Effect of ultrasonic impact time on VPPA-MIG welded joint of 7A52 aluminum alloy

In order to study the effect of ultrasonic impact time on microstructure and properties of VPPA-MIG composite welded joint of 7A52 aluminum alloy, ultrasonic impact treatment of 2.5, 5, 10, 15, 30, and 75 min was carried out on the welded joint per unit area. By observing the surface morphology of the joint and testing the mechanical properties of the joint, the effect of ultrasonic impact treatment time on the joint was analyzed. The results show that the surface of 7A52 aluminum alloy welded joint is obviously strengthened after ultrasonic impact treatment. The grain size of weld surface reaches 26.28 nm when ultrasonic impact time is 15 min; the hardness of weld surface is 138.8 HV when ultrasonic impact time is 75 min, which is 36.3% higher than that of original weld; the maximum residual compressive stress is 243.3 MPa after ultrasonic impact treatment for 30 min.