Boron carbide-zirconium boride in situ composites by the reactive pressureless sintering of boron carbide-zirconia mixtures

The heating of B4C-YTZP (where YTZP denotes yttria-stabilized zirconia poly crystals) mixtures, under an argon atmosphere, generates B4C-ZrB2 composite s, because of a low-temperature (<1500<degrees>C) carbide-oxide reaction. C omposites derived from mixtures that include greater than or equal to 15% Y TZP are better sintered than monolithic B4C that has been fired under the s ame conditions. Firing to similar to 2160 degreesC (1 h dwell) generates sp ecimens with a bulk density of greater than or equal to 91% of the theoreti cal density (TD) for cases where the initial mixture includes greater than or equal to 15% YTZP. Mixtures that include 30% YTZP allow a fired density of greater than or equal to 97.5% TD to be attained, The behavior of the B4 C-YTZP system is similar to that of the B4C-TiO2 system. Dense B4C-ZrB2 com posites attain a hardness (Vickers) of 30-33 GPa.