Microstructures and mechanical properties of high-entropy (Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2)C ceramics with the addition of SiC secondary phase

The relationships between microstructures and mechanical properties especially strength and toughness of high entropy carbide based ceramics are reported in this article. Dense (Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2)C (HEC) and its composite containing 20 vol.% SiC (HEC-20SiC) were prepared by spark plasma sintering. The addition of SiC phase enhanced the densification process, resulting in the promotion of the formation of the single-phase high-entropy carbide during sintering. The high-entropy carbide phase demonstrated a fast grain coarsening but SiC particles remarkably inhibited this phenomena. Dense HEC and HEC-20SiC ceramics sintered at 1900 degrees C exhibits four-point bending strength of 332 +/- 24 MPa and 554 +/- 73 MPa, and fracture toughness of 4.51 +/- 0.61 MPa.m(1/2) and 5.24 +/- 0.41 MPa.m(1/2), respectively. The main toughening mechanism is considered to be crack deflection by the SiC particles.