Design, preparation, and enhanced mechanical properties of novel plate-like grains toughened (Zr, Ti, W, Ta)C medium-entropy ceramics fabricated by in-situ reaction hot-pressing

Novel plate-like (Ti, Zr)B2 toughened (Zr, Ti, W, Ta)C medium-entropy ceramics were designed based on the atomic scale, nanoscale, and microscale, and prepared via the in-situ reaction hot-pressing adopting (Ti, W, Ta)C and ZrB2 powders. The multiphase ceramics were primarily composed of the (Zr, Ti, W, Ta)C matrix and plate-like (Ti, Zr)B2. When the addition of ZrB2 exceeds 50 mol%, the residual ZrB2 causes the secondary primary phase to change from (Ti, Zr)B2 to (Zr, Ti)B2. The improvement of fracture toughness is primarily influenced by the plate-like (Ti, Zr)B2 on crack propagation mechanisms such as bridging effect and crack deflection. (Ti, W, Ta)C- 50 mol% ZrB2 (raw powder composition) exhibits outstanding mechanical properties, boasting a Vickers hardness of 24.9 GPa, fracture toughness of 5.5 MPa·m1/2, and flexural strength of 552 MPa, which present a novel avenue for achieving a synergistic enhancement in Vickers hardness and fracture toughness within medium-entropy carbide ceramics.