Boron Carbide–Zirconium Boride In Situ Composites by the Reactive Pressureless Sintering of Boron Carbide–Zirconia Mixtures

Abstract

The heating of B4C–YTZP (where YTZP denotes yttria‐stabilized zirconia polycrystals) mixtures, under an argon atmosphere, generates B4C–ZrB2 composites, because of a low‐temperature (<1500°C) carbide–oxide reaction. Composites derived from mixtures that include ≥15% YTZP are better sintered than monolithic B4C that has been fired under the same conditions. Firing to ∼2160°C (1 h dwell) generates specimens with a bulk density of ≥91% of the theoretical density (TD) for cases where the initial mixture includes ≥15% YTZP. Mixtures that include 30% YTZP allow a fired density of ≥97.5% TD to be attained. The behavior of the B4C–YTZP system is similar to that of the B4C–TiO2 system. Dense B4C–ZrB2 composites attain a hardness (Vickers) of 30–33 GPa.