The enhancement of wettability of SiC particles in cast aluminium matrix composites

Many methods have been proposed to overcome the problem of poor wettability between ceramic reinforcement particles and molten aluminium for metal matrix composite (MMC) production by casting. Some of these methods are expensive and complex, and a cheap and simple technique still to be found. In this paper, an innovative approach to fabricating cast MMCs is proposed. In order to study the enhancement of wettability of SiC particles by the matrix alloy A359, a casting rig was specially designed, and tests carried out using the A359 matrix alloy, SiC particles, and magnesium (as a wetting agent). Stirring of these mixtures was performed under several different conditions, and the effect of this stirring action on the wettability enhancement was studied. The percentage of particles entrapped in the resulting composite was used as a measure of wettability, and plotted against cooling time and volume percentage of SiC particles. The use of clean SiC particles, magnesium as a wetting agent, and stirring continuously while the MMC slurry is solidifying were found to promote wettability of SiC with A359 matrix alloy. Decreasing this solidification time was also found to improve the wettability, whereas increasing the volume fraction of SiC particles present will give the opposite effect. (C) 2001 Elsevier Science B.V. All rights reserved.