Ultrasonic cavitation and acoustic streaming effects during liquid phase separation and dynamic solidification of ternary Al-Sn-Si immiscible alloy

Ultrasonic melt treatment is an environmentally friendly and no-polluting external field technology and has great application potential in materials fabrication. Power ultrasound with different intensities was introduced into the liquid phase separation and solidification process of ternary Al-45%Sn-5%Si immiscible alloy to explore the effects of ultrasound on the formation of macro- and microstructure. It was found that the previously apparent macrosegregation caused by the large density difference between immiscible liquid (Al) and (Sn) phases was gradually reduced and even suppressed with the increase of ultrasonic amplitude. Meanwhile, the ultrasonic waves also significantly modified monotectic structures, within which (Al) phase transformed from coarse dendrites to refined equiaxed grains, and (Si) phase evolved from long strips to small blocks. The introduction of ultrasound weakened the texture of solidified structure, whereas the growth orientation relationship between monotectic (Al) and (Si) phases remained unchanged. The theoretical analysis and calculation results indicated that ultrasonic cavitation and acoustic streaming were the dominant effects to modulate the macro- and microstructural evolution. This would improve the exploiting and utilization of immiscible alloys by ultrasonic processing technology.