Effect of ultrasonic vibration on the grain refinement and SiC particle distribution in Zn-based composite filler metal

Refining the matrix microstructure of the composite is an effective method to avoid severe reinforcement particle pushing by the advancing solid-liquid interface during solidification. The effect of the ultrasonic vibration, which was injected into the melt at various stages of solidification, on the grain refinement and particle distribution in a Zn-based solidified composite filler metal was investigated. Perfect grain refinement was obtained with the application of continuous ultrasonic vibration. However, severe particle pushing by the sound radiation pressure was observed, resulting in serious particle segregation. Uniform distribution of SiC particles as well as grain refinement was obtained when proper intermittent ultrasonic treatment was applied. (C) 2008 Elsevier B.V. All rights reserved.