Numerical simulation of acoustic pressure field for ultrasonic grain refinement of AZ80 magnesium alloy

Ultrasound with different intensities was applied to treating AZ80 alloy melt to improve its solidification structure. The average grain size of the alloy could be decreased from 303 to 148 μm after the ultrasound with intensity of 30.48 W/cm2 was applied. To gain insight into the mechanism of ultrasonic treatment which affected the microstructure of the alloy, numerical simulations were carried out and the effects of different ultrasonic pressures on the behaviors of cavitation bubble in the melt were studied. The ultrasonic field propagation in the melt was also characterized. The results show that samples from different positions are subjected to different acoustic pressures and the effect of grain refinement by ultrasonic treatment for these samples is different. With the increase of ultrasonic intensity, the acoustic pressure is increased and the grain size is decreased generally.