Processing, microstructure, and mechanical properties of B4C-TiB2 particulate sintered composites I. Pressureless sintering and microstructure evolution

Pressureless sintering of boron carbide ceramics containing 0-35 vol. % TiB 2 phase, produced via an in-situ chemical reaction between B4C, TiO2, and e lemental carbon, was studied in the isothermal and constant-heating-rate re gimes. The presence of TiB2 results in a decrease in activation energy for sintering from 717 kJ/mol at 0 vol. % TiB2 to 266 kJ/mol at 25 vol. % TiB2. Ceramic bodies of B4C - TiB2 particulate composites with relative densitie s of up to 99% were sintered without pressure at temperatures of 2050-2100 degreesC. Grain boundary diffusion is the primary mechanism of TiB2 particl e coarsening. TiB2 particle size is bimodal depending on whether the partic le is confined within a B4C grain or located on the grain boundary. Densifi cation behavior of the B4C - TiB2 system is identical at different heating rates in the temperature range of 1800-2150 degreesC.