High-temperature toughening in ternary medium-entropy (Ta_1/3Ti_1/3Zr_1/3)C carbide consolidated using spark-plasma sintering

We report for the first time the effect of temperature on the mechanical properties of (Ta_1/3Ti_1/3Zr_1/3)C carbide. Flexural strength and fracture toughness were investigated using the three-point bending technique in argon. Using commercially available carbide powders with an equimolar ratio and performing spark plasma consolidation at 1973°C, we obtained a bulk single-phase medium-entropy carbide ceramic with the lattice parameter a= 4.458 Å. The flexural strength and fracture toughness at room temperature reached on average 700 MPa and 3.2 MPa m^1/2, respectively. At 1800°C, local decomposition of the medium-entropy carbide took place as a structure with a local chemical gradient was observed after high-temperature tests, which increased fracture toughness by 30% (to 4.4 MPa m^1/2).