A study of the ultrasonic technique applied in fabrication of SiC fiber-reinforced aluminum composites
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H. Fukunaga Department of Mechanical Engineering, Hiroshima University, Saijo, Higashi-Hiroshima 724, Japan (Received 15 November 1993; accepted 12 November 1994)
By comparing the ultrasonic cavitation in several kinds of transparent liquid mediums, we have investigated the cavitation effect in liquid. It is considered that the shock wave created by the cavitation in aluminum melt induces a high pressure and an elevated temperature field around the fibers, which can promote the wetting between fiber and aluminum and have aluminum melt infiltrate into the fibers. Moreover, the experiment result shows that the fiber resonance matching with the cavitation is also an important factor for SiC/Al composites preparation. There exists a damage of the ultrasonic vibration on SiC fiber, if the fiber is acted long enough.
I. INTRODUCTION In continuous fiber-reinforced aluminum composites, there are two main problems that are unfavorable for fabricating composites and enhancing their mechanical properties. One is the wettability of fiber by liquid aluminum. Previous research showed that the wetting angle 0 between SiC (Nicalon) fiber and aluminum is 142 /tm), SiC (Nicalon, 0 12 ^ m ) , and C (T300 4> 7 fxm) fiber-
2. Ultrasonic infiltration mechanisms and the influence factors When we inputted ultrasound into molten aluminum melt (at 700 °C) and had the transducer vibrated by adjusting the generator frequency and power, we found that the minimum power and acoustic frequency were in the same range as in the other liquid mediums (see Table I). Consequently, the cavitation effect that was demonstrated to be in water, castor oil, or paraffin wax melt should exist in liquid aluminum also. Therefore, we can consider the cavitation to be a reason for ultrasonic infiltration. The air brought in aluminum melt by fiber and the gas dissolved in aluminum melt may become the cavitation nuclei. If the nuclei collapse, a high pressure will be created around the individual fiber; therefore, the TABLE III. Properties of two kinds of SiC/Al composite wire. Diameter (mm)
Section
Vf (%)
Wire strength (GPa)
Fiber strength remains (%)
0.45 0.41
Round Hexagon
48 84
1.54 1.93
95 82
SiC (Nicalon)/Al SiC (SCS-2)/Al
599
J. Mater. Res., Vol. 10, No. 3, Mar 1995
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J. Pan et al.: A study of the ultrasonic technique applied in fabrication of SiC fiber-reinforced aluminum composites
reinforced aluminum composite wires, the one with the largest diameter was found to be the easiest, and the one with the smallest diameter was the most difficult. Three kinds of fiber have to have different specific surface areas (/u,m2//u,m3), which are calculated to be 0.028, 0.33, and 0.57, respectively. For the fiber with a large specific surface area, the attenuation of ultrasonic energy is believed to be serious, due to the reflection and absorption by fiber surfaces. This reason leads us to the difference for the infiltration ability of three fibers by aluminum melt. The fi
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