Mechanical Properties of sintered B₆0-Alkaline earth metal oxide materials

Pure BtO powder and B₆0 powders admixed with 1.5 wt% of MgO, 1.4 wt% of CaO, and 0.7 wt% of CaCOj, were sintered and the microstructure, phase composition and mechanical properties were investigated. Pure B₆0 powders were sintered at a temperature of 1900°C and a load of 50 MPa for 20 minutes in an argon environment, while the B₆0-Admixed powders were sintered at a temperature of 1850°C and loads from 50-80 MPa, under the same environment. The addition of the alkaline earth metal oxide additives resulted in the formation of boride and borate phases, depending on the oxide used. More than 96% of theoretical densities were achieved and the result indicates a good combination of hardness (between 31.6-32.1 GPa) and fracture toughness (between 6.1-6.8 MPa.m0-5) in the B₆0-Alkalinc earth oxide materials. The introduction of the additive enhances the improvement in the fracture toughness of the pure B₆0- materials. The fracture mode observed in the sintered materials is mainly transgranular.