Reactive sintering of dual-phase high-entropy ceramics with superior mechanical properties

Abstract

• The dual-phase high-entropy ceramics (HECs) were first designed and fabricated using reaction-driven inter-diffusion processes among ZrB 2 , HfB 2 , NbB 2 , TaB 2 , and TiC. • The inhomogeneity of element distribution in boride and carbide phases was quantitatively investigated. • The novel diboride-carbide HECs showed outstanding mechanical properties as compared with other single-phase HEC samples. Fully dense dual-phase high-entropy ceramics (HECs) were fabricated by hot-pressing at 2000 °C for 1 h based on the in-situ reaction and solid solution processes among equimolar ZrB 2 , NbB 2 , HfB 2 , TaB 2 and 30–70 mol% TiC. The negligible porosity, fine grain size, and plate-like diboride grains are found by microstructure observation. The element distribution is not uniform in different phases: Ti and Nb are enriched in the diboride phase, while Zr, Hf, and Ta are preferentially dissolved into the carbide phase. The reactive sintering dual-phase HECs exhibit superior mechanical properties of hardness 28.4 ± 1.5 GPa, flexural strength 1017 ± 91 MPa, elastic modulus 565 GPa, and fracture toughness 4.7 ± 0.3 MPa m 1/2 , respectively, which surpass most of diboride and carbide high-entropy ceramics in the previous reports.