Abstract: The introduction of ultrasonic energy field in GMA welding of aluminum alloy could effectively decrease the pore defects and improve weld formation. Ultrasonic vibration of welding wire is a feasible method to introduce ultrasonic energy field in welding process, which could avoid the disadvantages of low conversion rate of ultrasonic energy and complex welding torch. However, the effect of ultrasonic vibration of welding wire on weld formation and pore behavior in GMA welding of aluminum alloy is unclear. The results show that after the ultrasonic vibration of the welding wire, the fluctuation range and surface roughness of the weld are reduced, and the surface brightness of the weld is also increased. The weld surface formation is the best when the vibration amplitude of the welding wire is 26.3 μm. The width and depth of weld increased in different degrees. With the increase of vibration amplitude of welding wire, the depth to width ratio generally increased. The depth to width ratio increased by 9.72 % when the vibration amplitude of welding wire was 26.3 μm. The porosity defect of weld is obviously improved. When the ultrasonic horn amplitudes was 22.8 μm, 24.9 μm and 26.3 μm, the number of pore in the weld decreased by 76.9 %, 65.7 % and 71.8 %, respectively, and the pores were mainly distributed in the upper part of the weld. The acoustic simulation results show that the ultrasonic energy mainly propagates along the axial direction of welding wire, and the acoustic pressure amplitude at the lower part of the weld pool is larger. This result has a good correlation with the increase of weld penetration and the decrease of porosity at the bottom of the weld. This study is of great significance for the development of ultrasonic assisted aluminum alloy GMA welding technology and the enrichment of theory.

Key words: Aluminum alloy, Welding wire vibration, GMAW, Ultrasonic, Weld formation, Pore