Effect of Acoustic Streaming on Degassing Level of A356 Al Alloy by Ultrasonic Melt Treatment

The cavitation bubble is essential for the ultrasonic degassing, however, the bubble could not be developed at the whole melt because of the threshold intensity for the bubble generation. The intensity of the ultrasound decreases exponentially with the propagation distance. The melt should be transferred to the effective volume that has the sufficient ultrasonic intensity to exceed the threshold for the cavitation generation. The important parameter to make melt transfer is the acoustic streaming induced by the ultrasound. This study is focused on the melt flow and the effect on the degassing level with the ultrasonic frequency to improve efficiency of ultrasonic degassing. The increase of the ultrasonic frequency and amplitude made the cavitation bubble density and the velocity of the melt flow increase, respectively. As the result, the degassing velocity could increase dramatically.