PRESSURELESS SINTERING AND RELATED REACTION PHENOMENA OF AL2O3-DOPED B4C

The effects of alumina on the densification of boron carbide and related reaction phenomena in alumina-doped B4C were studied. Pressureless sintering was conducted at various temperatures for 15 min in a flowing Ar atmosphere. The addition of alumina improved the densification of boron carbide. Maximum density of 96% theoretical was obtained with the 3 wt% alumina-doped B4C sintered at 2150-degrees-C. Abnormal (or exaggerated) grain growth was observed in the specimen containing more than 4 wt% alumina. In the B4C-Al2O3 reaction couples, good wetting of the liquid phase on the boron carbide grains was observed. X-ray diffraction and Auger electron spectra showed that the AlB12C2 phase was formed by the reaction between boron carbide and alumina. It is suggested that these phenomena promote the densification of boron carbide.