The structure and properties of sintered boron carbide

An analysis of the crystallochemical structure of boron carbides has shown that, despite strong covalent atomic bonds, directional mass transfer in boron carbide can occur during activated sintering of disperse powders. Dilatometry and electrical conductivity methods were used to investigate the kinetics of densification for boron carbide specimens obtained by pressing powders with particle sizes smaller than 1 μm. The processes that occurred on heating the samples were studied and the mechanisms of mass transfer at various temperatures were identified. The kinetics of recrystallization in sintered and hot-pressed boron carbide were investigated. The process of recrystallization was found to start at temperatures above 18000C; at temperatures above 22000C grains grew rapidly. Deformation by twinning is characteristic of boron carbide. These twins can be removed very slowly by high temperature annealing. (Auth.)