Mechanical properties of hot-pressed boron suboxide with chromium boride additive

This study investigated and compared the mechanical properties of boron suboxide (B6O) with and without chromium bromide (CrB2) additive, hot pressed at 1900°C and 1850°C and for 20 minutes, with applied pressures of 50 and 80 MPa respectively. The theoretical density attained for these materials was More than 96%. The phase relationship, microstructures and mechanical properties of these materials were examined and good combination of mechanical properties was obtained with the B6O-CrB2 material (HV 32.1 GPa, K1C 4.5 MPa.m0.5) compared to pure B6O material. Mixing with a small amount (1.7 wt.%, equivalent of 0.4 vol.%) of CrB2 additive resulted in a pronounced improvement in both the hardness and fracture toughness values. The improvement in the fracture toughness was attributed to the introduction of the second phase and the toughening mechanism is presumed to be by crack bridging and deflection due to bimetallic stress.