As the fabricating process of continuous M40J carbon fiber reinforced aluminum alloys composite wires by using ultrasonic infiltration method, the mechanism of the infiltration of molten alloys into the bundle of the carbon fibers was examined especially from the viewpoints of wettability, acoustic cavitation and threshold pressure for infiltration. It was found that the infiltratability of the alloys was proportional to the maximum intensity of the acoustic cavitation. Both the infiltratability and the intensity were enhanced by the addition of surfactant elements for molten aluminum. Thus, decrease in surface tension will cause the generation of acoustic cavitation to increase. When the ultrasonic vibration is applied to molten aluminum alloys, acoustic cavitation would be formed on/in the bundle of carbon fibers. Then the shock wave, which was caused by the cavitation collapsed, would lead to leave the distance between fibers in the bundle. From the results of the direct observation of the bundle in the aqueous solution using high speed camera during applied ultrasonic vibration, the diameter of the bundle was increased by generating the cavitation. Thus, this phenomenon will also cause the decrease in the threshold pressure for infiltration. Therefore, both the generation of the acoustic cavitation and increase in the interval between fibers will be the controlling factors of the infiltration in the fabricating process of this kind of composites by using ultrasonic vibration.
