BORON CARBIDE BASED CERAMIC COMPOSITES HOT PRESSED WITH ALUMINIUM ADDITIVE

Ceramic composite materials consisting of B4C matrix and Al8B4C7 secondary phase were prepared by in situ reactive sintering of the initial powder mixture B4C-Al with concentration from 5 to 25 wt.% Al sintering additives. The composite samples were hot pressed at the temperature of 1850 °C, pressure of 35 MPa, for 15 min in a vacuum atmosphere. The portion of Al8B4C7 secondary phase increased from 3.3 to 22.1 wt.% when increasing the concentration of Al sintering additive from 5 to 25 wt.% Al. Significant improving of densification and mechanical properties was measured at increasing of Al sintering additive concentration from 5 to 10 wt.% Al. The highest average hardness of 28.74 GPa was achieved when adding 15 wt.% Al sintering additive. The fracture toughness increased with concentration of Al sintering additive in whole concentration range with the highest average value of 5.92 MPa.m1/2 at 25 wt.% Al sintering additives.