| Abstract Scope |
High-entropy carbide powders were synthesized by a two-step process consisting of carbothermal reduction followed by solid solution formation. Nominally pure (Hf,Zr,Ti,Ta,Nb)C in a single-phase rock salt structure had an average particle size of about 550 nm and an oxygen content of 0.2 wt%. Nominally pure and dense (Hf,Zr,Ti,Ta,Nb)C ceramics with an average grain size of 1.2 µm were produced at 1900°C by hot pressing. Dense ceramics had a Young’s modulus of 452 GPa, Vickers hardness of 24.8±0.8 GPa, fracture toughness of 3.5±0.3 MPa·m1/2, and flexural strength of 421±27 MPa at room temperature. With increasing the temperature, flexural strength was maintained until 1800°C, then decreased from 318±21 MPa at 2000°C to 93±10 MPa at 2300°C.The degradation of flexural strength above 1800°C was attributed to a decrease in dislocation density that was accompanied by an increase in dislocation motion. These are the first reported flexural strengths of HEC ceramics at elevated temperatures. |