Industrial Application of Ultrasonic Vibrations to Improve the Structure of Al-Si Hypereutectic Alloys: Potential and Limitations

This work presents the results of research conducted by the authors over the past years in Nippon Light Metal Co., ltd. In the first stage, highly durable ceramic sonotrodes were designed and manufactured to introduce ultrasonic vibrations into molten metal in a launder or in a hot top during DC casting. It was shown that ultrasound can greatly refine the crystals of primary silicon in 75 to 178-mm billets, if vibration amplitude exceeds 40 μm (p–p). The structure uniformity was insufficient in launder treatment and fairly good in hot-top treatment. Care must be taken in controlling the passage of melt through the cavitation zone in order to fully exploit the refining potential of ultrasonic vibrations. The results suggest that if the treatment conditions are controlled properly, up to 20 kg/min of molten metal can be effectively treated using a 2-kW ultrasonic installation equipped with one ceramic sonotrode of 40 to 60 mm in diameter.