2013 Volume 85 Issue 5 Pages 255-261
It is known the application of ultrasonic vibration to molten metals during solidification results in the formation of fine-grained structures. We have previously reported that the fine-grained structure formed by applying ultrasonic vibration was caused not by mechanical destruction of dendrite but by promotion of nucleation. It is particularly important to apply ultrasonic vibration to the alloy crystal when it starts to solidify and cross over the liquidus. In this study, we controlled the solidified structure of Al-Si alloy in the supercooled state by applying ultrasonic vibration for a short time. After the Al-Si alloy was completely melted at 1123K, a ceramic horn was immersed and the ultrasonic vibration applied. The application of ultrasonic vibration for a short time provided fine-grained structures. Specifically, when ultrasonic vibration was applied to Al-6%Si alloy supercooled to 1K for 10 seconds, fine-grained structures were formed under the horn. It was concluded that the application of ultrasonic vibration to the molten metal in the supercooled state under the liquidus for a very short time enables control of the fine-grained structure of alloy due to promotion of instantaneous nucleation.
