Influence of ultrasonic vibration on molten pool behavior, cladding layer microstructure and pore defects for directed energy deposition

Ultrasonic vibration, as an auxiliary method, can better regulate the microstructure and pore defects within the formed part after understanding the flow state and heat transfer mechanism. In this paper, a heat-flow coupling model has been developed and corresponding experiments of in situ high-speed imaging technology are conducted under different manufacturing parameters. The results show that the ultrasonic vibration leads to a larger molten pool size and a more uniform temperature distribution, as well as a significant grain refinement, and the vibration frequency and amplitude can directly change the length and flow velocity of the molten pool, in which a porosity reduction of 64 % and a reduction of pores diameter from 45 µm to 18 µm also can be found. By comparing the simulation with the experiment, the error can be controlled within 4.93 %, which can deepen the understanding of ultrasonic vibration assisted directed energy deposition for the process optimization and industrial application.