A facile fine-grain strategy to fabricate (Ta0.2Nb0.2Ti0.2Hf0.2Zr0.2)C-SiC ceramics with enhanced strength and toughness

(Ta0.2Nb0.2Ti0.2Hf0.2Zr0.2)C high-entropy ceramic (HEC) is a potential candidate material for use in extreme environments. However, improving HEC ceramics' toughness is a great challenge. In this study, a facile fine-grain method has been used to fabricate the HEC-SiC ceramics with enhanced strength and toughness. The influence of SiC particle size in the densification, microstructure, and mechanical properties of the HEC-SiC ceramics was studied. With the addition of fine SiC particles (HS-0.5 sample), its relative density increases from 91.23 % to 97.19 %, and the HEC phase shows a reduction in grain size from 3.48 to 0.83 mu m on average, compared with the monolithic HEC ceramics (HS-0 sample). Additionally, the HEC phase exhibits an increased lattice distortion from 0.044 % to 0.151 % with the addition of SiC fine particles. The HS-0.5 sample exhibits superior mechanical properties with a fracture toughness of 5.48 MPa m1/2, a Vickers hardness of 26 GPa, and a flexural strength of 530 MPa, which is 56.1 %, 44.4 %, and 60.1 % higher than that of the monolithic HEC ceramics. This encouraging enhancement of hardness, toughness, and strength of HEC-SiC ceramics is ascribed to the improvement of ceramics sintering, fine-grain strengthening, solid solution strengthening, and particle toughening by the fine SiC particles.