Effect of microstructure on mechanical, electrical and thermal properties of B4C-HfB2 composites prepared by arc melting

B4C-HfB2 composites were prepared by arc-melting using B4C and HfB2 as raw materials. The eutectic composition of B4C-HfB2 system was 70B4C-30HfB2 (mol%) with a lamellar eutectic microstructure. HfB2 about 1 μm in thickness was dispersed in B4C matrix uniformly of the eutectic composite, much smaller than raw powders. At the eutectic composition, the B4C-HfB2 composites showed the maximum Vickers hardness (31.2 GPa) and fracture toughness (5.3 MPa m1/2) at room temperature, and maximum thermal expansion coefficient (7.1 × 10−6 K−1) from 293 to 1273 K. The electrical and thermal conductivity of B4C-HfB2 composites increased with increasing HfB2 content. The electrical conductivity of B4C-HfB2 eutectic composites decreased from 8.94 × 104 to 7.43 × 104 Sm−1 with increasing temperature from 298 to 800 K, showing a metallic electrical behavior. The thermal conductivity of B4C-HfB2 eutectic composite was 16-18 WK−1 m−1 from 298 to 973 K.