Effects of Depth and Method of Cooling upon Applying Ultrasonic Vibration on the Solidification Structures of Pure Aluminum

Ultrasonic vibration of 170W was imposed on an aluminum melt of 750℃ temperature. Effects of different tool rod working depths and melt cooling methods with the application of ultrasonic vibration on the solidification structure of casting ingot were studied and the mechanism of grain refinement by ultrasonic was analyzed. The results showed that solidification structures were all refined in different degrees when the aluminum melt was treated. Ultrasonic cavitation and acoustic effect played an important role in it. When depth of vibration was increased, mechanical quality factor of vibration system reduceds, vibrating intensity and amplitude output decreased, and ultrasonic refinement effect was weakened. There existed a least time of grain refinement by ultrasonic. When cooling intensity increased, melt solidifying time shortened and ultrasonic treating time shortened too, so the capacity of grain refinement was restricted and grain size grew up.