Evaluation of the wettability of liquid aluminum with ceramic particulates (SiC, TiC, AI2O3) by means of pressure infiltration

One of the major problems in the fabrication of aluminum-ceramic composites is the wettability of ceramic reinforcements by liquid aluminum. In this article, the wettability at the liquid metal/ ceramic particulates interface has been evaluated by means of an infiltration technique that permits a determination of the threshold pressure and the infiltration kinetics. The aim of the present article is to check the reliability of the experimental technique. The work was carried out on pure aluminum and A1₂O₃, SiC, and TiC particulates of average diameters D in the range 7.5 to 150 μm. An Al-1 wt pct Pb alloy was also used to investigate the effects of surface tension. All infiltrations were carried out in air. The results for the infiltrated height vs applied pressure or time follow Darcy's law. On the other hand, threshold pressures are proportional to 1/ D (capillary law) and some deviations can be ascribed to differences in the shape of the particulates (especially TiC). More than 75 pct of the reduction in the threshold pressure promoted by 1 wt pct of lead can be related to the decrease in the surface tension of pure Al. The results indicate that effects due to changes in wetting should be very small, as expected when aluminum is covered with an oxide layer.