Ultrasonic levitation processing and rapid eutectic solidification of liquid Al-Ge alloys

Containerless solidification of hypoeutectic Al-50%Ge and eutectic Al-51.6%Ge alloys has been carried out with an ultrasonic levitator. The undercooling of the two alloys achieves 112 K(0.16T_L) and 95 K(0.14T_E), respectively. In both of these alloys, (Al) phase always nucleates and grows primarily in Al-51.6%Ge eutectic alloy at small undercoolings. When the undercooling is larger than 80 K, competitive nucleation between (Al) and (Ge) phases occur and (Ge) solid solution can nucleate as primary phase. The (Al)+(Ge) eutectic composed of branched (Ge) phase and interspacing (Al) phase is much refined under ultrasonic levitation condition. Divorced eutectic of the two phases is obtained near the surface of acoustically levitated Al-50%Ge hypoeutectic alloy.