Effect of ultrasonic impact during welding on microstructures and mechanical properties of TIG welded joint of 2A14 aluminum alloy

In order to improve the microstructures and mechanical properties of tungsten inert gas(TIG) welded joint of 2A14 aluminum alloy, ultrasonic horn periodically impacts the seam during TIG welding. The ultrasound propagates into the weld pool through the weld and base material, so that the ultrasonic energy can effectively influence the fluidity and crystallization of weld pool. Finally, the grain was refined and the mechanical properties were improved for welded joints. The results show that the microstructures are significantly improved after applying the ultrasonic impact. The grain is changed from the column grain to the equiaxed grain in the weld center and the fusion zone, and the grain size decreases in the weld center. Moreover, the distribution of the second phase becomes more uniform and the size becomes smaller after applying the ultrasonic impact. The ultrasonic impact during TIG welding can improve the tensile strength of welded joint and it is improved from 246.18 MPa to 265.50 MPa. The elongation is improved from 5.33% to 6.47%. The ultrasonic impact can improve the fluidity of weld pool, which results in an uniform temperature, so that the form of equiaxed grain and the grain refinement can be promoted.