Processing of silicon carbide–boron carbide–aluminium composites

The aim of this work was to shed light on the wetting mechanism in the SiC–B4C–Al system and to explore processing routes that enable infiltration of Al alloys into these ceramic powder mixtures without the formation of the deleterious reaction product Al4C3. For this purpose, powder mixtures consisting of SiC and pre-treated B4C were pressureless infiltrated with Al alloys at relatively low temperatures under an inert gas atmosphere. Depending on the characteristics of the starting powders fully infiltrated composites were achieved in the temperature range of 935–1420 °C. It was observed that addition of pre-treated B4C to SiC enabled complete infiltration of the ∼0.6 cm thick preforms. The bulk density of all produced composites was >98% of the X-ray density. By controlling the surface chemistry and particle size of the starting powders as well as the processing conditions, the wetting behaviour and reaction kinetics of this system could be tailored so as to render fully dense SiC–B4C–Al composites devoid of Al4C3.