Ultrasonic infiltration in alumina particle/molten aluminum system

Ultrasonic vibration is expected to improve the apparent wettability between reinforcements and molten metals and to achieve full infiltration with an extremely low applied pressure in the liquid processing of metal matrix composites. Non-infiltrated defects at contact points of reinforcements are, then, inhibited. In this work, ultrasonic vibration (resonant frequency=20.5kHz) was applied to alumina particle/molten aluminum as a model composite system at 1023K. The threshold infiltration pressure of 19.5kPa drops to zero by applying ultrasonic vibration with the power of 500kW/m2. Therefore, full infiltration is achieved even with no applied pressure. Non-infiltrated defects are not formed at contact points of the particles in the pressure-less ultrasonic infiltration, while they are formed in the pressure infiltration without ultrasonic vibration. The infiltrated region with a semi-sphere was observed in the ultrasonic infiltration using particle preforms fixed by alumina sol. Ultrasonic vibration yields an ultrasonic pressure distributed radially throughout molten aluminum ahead of an ultrasonic horn. The ultrasonic pressure plays a vital role in the pressure-less infiltration as well as the hysteresis effect of contact angles at the interface between particle and molten aluminum does due to melt vibration.