Abstract: In order to reduce the pores and coarse grains in the aluminum alloy produced by arc additive manufacturing, the method of ultrasonic vibration assisted CMT (cold metal transfer) arc additive manufacturing was used to accumulate the thin-walled parts of 4043 aluminum alloy, and the effect of ultrasonic amplitude on microstructure and mechanical properties of the deposited material was studied. The results show that the aid of ultrasonic vibration breaks dendrites and promotes the formation of more nuclei to refine the grains. The columnar grains are also transformed into fine equiaxed grains under the vibration and stirring of the molten pool. Compared with the specimens without ultrasonic vibration, the average grain size is reduced by 22.5%. At the same time, the cavitation and acoustic flow effects caused by ultrasonic vibration reduce the size and number of pores in the specimens. However, as the ultrasonic amplitude increases, the energy inside the molten pool gradually increases, and the increase in heat input also causes the grains to coarsen. At the same time, excessive ultrasonic energy also destroys the structural integrity of the weld, resulting in holes in the weld. The tensile strength of the specimen with ultrasonic vibration is increased by 8.2%-16.3% compared with that of the specimen without ultrasonic vibration, and the anisotropy of the tensile and elongation gradually decreases with the increases of amplitude.

Key words: ultrasonic vibration, wire arc additive manufacturing, microstructure, mechanical properties