Lawrence Berkeley National Laboratory

SiC was hot-pressed with aluminum, boron, and carbon additives. The Al content was modified either to obtain SiC samples containing a continuous Al gradient, or to vary the average Al content. In both cases, dramatic changes in microstructure, phase composition, and grain boundary structure were observed as a result of the Al variation. Similar processing and characterization were done with modified boron and carbon average contents. The systematic experiments allowed identification of the roles of Al, B, and C in developing grain morphology and phase composition. The experiments also clarified the mechanical property responses to microstructural modification. Tailoring of the SiC microstructure to suit different applications would be possible.