Effect of ultrasonic treatment on microstructures of hypereutectic Al–Si alloy

The hypereutectic Al–23%Si alloy was treated with ultrasonic wave. A novel horn crucible was designed specially for this experiment. The horn crucible was a part of ultrasonic horn, and the molten alloy was treated direct in this crucible. The morphology, size, and distribution of the microstructures of the Al–Si alloy were observed by means of an optical microscope. The results show that after the hypereutectic Al–23%Si alloy was treated by ultrasonic wave, the hydrogen bubbles in the alloy melt were removed, the primary Si phase was refined, the morphology of the primary α-Al dendritic crystal was changed to equiaxial crystal, and the eutectic lamellar spacing increased. The mechanisms of ultrasonic treatment improving the microstructures of the hypereutectic Al–Si alloy were discussed.