Effects of vibration and grain refiner on microstructure of semisolid slurry of hypoeutectic Al-Si alloy

The effects of vibration and grain refiner on the microstructure of semisolid slurry of hypoeutectic Al-Si alloy were studied. The impact of vibration on the convection of liquid was conducted by using a system of water-particle tracer. The 356 melt at temperature of 630-660 degrees C with or without grain refiner Al-5%Ti-1%B was poured into a metal cup as the vibrating vessel, then it was cooled to 590-610 degrees C in the semisolid zone and kept for some time, subsequently vibration with different frequencies was applied. The results show that the primary alpha(Al) particles become finer and rounder with the increase of vibration frequency. The slurry with primary a(Al) equivalent particle diameter(EPD) of about 90 pm and average shape coefficient(ASC) of about 0.5 can be prepared under vibration of 20 Hz. With the combined action of vibration and grain refiner Al-5Ti-B, even smaller and rounder spheroids with EPD of about 85 pin and ASC of about 0.6 are obtained.