Fine-grained dual-phase high-entropy ceramics derived from boro/carbothermal reduction

In the current work, fine-grained dual-phase, high-entropy ceramics (Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2)B-2-(Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2)C with different phase ratios were prepared from powders synthesized via a boro/carbothermal reduction approach, by adjusting the content of B4C and C in the precursor powders. Phase compositions, densification, microstructure, and mechanical properties were investigated and correlated. Due to the combination of pinning effect and the boro/carbothermal reduction approach, the average grain size (similar to 0.5-1.5 mu m) of the dual-phase high-entropy ceramics was roughly one order of magnitude smaller than previously reported literature. The dual-phase high-entropy ceramics had residual porosity ranging from 0.3 to 3.2 % upon sintering by SPS and the material with about 18 vol% boride phase exhibited the highest Vickers hardness (24.2 +/- 0.3 GPa) and fracture toughness (3.19 +/- 0.24 MPam(-1/2)).

Automated summary

In this work, fine-grained dual-phase high-entropy ceramics were successfully prepared by adjusting the content of B4C and C in the precursor powders. The combination of pinning effect and the boro/carbothermal reduction approach significantly reduced the average grain size, resulting in improved hardness and fracture toughness of the ceramics.