ZRO2 AND ZRO2-SIC PARTICLE REINFORCED MOSI2 MATRIX COMPOSITES

ZrO2-MoSi2 and (ZrO2-SiC)-MoSi2 composites were fabricated by hot pressing and hot pressing-hot isostatic pressing at 1700-degrees-C. No reactions between ZrO2, SiC and MoSi2 were observed. An amorphous silica glassy phase was present in all composites. Composites with unstabilized ZrO2 particles exhibited the highest room temperature fracture toughness, reaching a level three times that of pure MoSi2. Both the room temperature toughness and 1200-degrees-C strength of (ZrO2-SiC)-MoSi2 composites were higher than those of ZrO2-MoSi2 composites, indicating beneficial effects of combined reinforcement phases. Low strength levels were observed at 1400-degrees-C as a result of the presence of the silica glassy phase. Elimination of glassy phases and refinements in microstructural homogeneity are processing routes important to the optimization of the mechanical properties of these types of composites.