High-pressure sintering of ultrafine-grained high-entropy diboride ceramics

Herein the ultrafine-grained (Hf0.2Zr0.2Ta0.2Nb0.2Ti0.2)B(2)high-entropy diboride ceramics were successfully fabricated by high-pressure sintering technology for the first time. The results showed that the grain size, relative density, and Vickers hardness of the as-fabricated samples all increased gradually with increasing sintering temperatures from 1373 K to 1973 K. The relative density and mean grain size of the as-sintered samples at 1973 K were 97.2% and 684 nm, respectively, and simultaneously they exhibited excellent comprehensive mechanical properties, combining a Vickers hardness of 26.2 GPa and a fracture toughness of 5.3 MPa center dot m(1/2), which were primary attributed to the fine grain strengthening mechanism and microcrack deflection toughening mechanism.