Reactive hot pressing of B$_4$C–CrB$_2$ ceramics and its mechanical properties

Ceramic composites based on B$_4$C with a mole fraction of CrB$_2$ 0–30% were obtained by reactive hot pressing of a mixture of B$_4$C, Cr$_2$O$_3$, and nanofibrous carbon at a press force of 17.5 MPa, a temperature of 2000$^\circ$C and an exposure time of 10 min. The possibility of the chemical reduction reaction of metal oxide with boron carbide during hot pressing was studied. During the synthesis of CrB$_2$, the density of B$_4$C was found to increase due to the formation of the CrB$_2$–B$_4$C eutectic liquid phase. The relative density of all B$_4$C–CrB$_2$ composites obtained under these conditions exceeds 90%. The dependences of the microhardness and elastic modulus of samples on the concentration of the plastic phase were obtained. The dependence of the elastic modulus of the heterogeneous material on the volume fraction of chromium diboride taking into account porosity was determined by sequentially using the Reuss and Voigt averaging schemes.