Effect of ultrasonic vibration on microstructure of semi-solid hypereutectic Al-Si alloy slurry

The effects of process parameters on microstructures of hypereutectic Al-Si semi-solid slurry were investigated. The A390 melt was imposed with ultrasonic vibration once it was poured into the metal cup and controlled in the liquid-solid temperature range, and the effects of ultrasonic vibration time, isothermal holding time, rest-work ratio on the semisolid slurry were studied. The results show that the primary Si phase is refined to about 20 μm. And with the increase of the isothermal holding time after ultrasonic vibration period, the primary Si particles grow up rapidly at the velocity of 8 μm/min, and the primary Si particles remain globular in 2 min while the morphologies deteriorate after 2 min. The primary Si particles grow slowly at the speed below 2.5 μm/min with relative stable morphology under ultrasonic vibration within 0.5-10 min. Ultrasonic vibration with rest-work ratio of 0.5 other than continuous ultrasonic vibration achieves the best refinement result.