Ultra-high strength medium-entropy (Ti,Zr,Ta)C ceramics at 1800 degrees C by consolidating a core-shell structured powder

We report for the first time the synthesis of a core-shell structured composite powder with a core of Zr(Ti,Ta)C and a shell of Ti,Ta(Zr)C at 1700 degrees C and investigate the formation mechanism for the core-shell structure. The medium-entropy (Ti,Zr,Ta)C ceramics with fine grains (1.1 +/- 0.4 mu m) and relative density of 94.8% was prepared by hot-pressing at 2100 degrees C. The flexural strength of (Ti,Zr,Ta)C at 1000 degrees C (493 +/- 21 MPa) was close to the room temperature (511 +/- 52 MPa). As the temperature increased from 1600 degrees C to 1800 degrees C, the flexural strength was increased significantly, with an ultra-high flexural strength of 725 +/- 32 MPa at 1800 degrees C. The existence of the core-shell structure in the powder suppressed the grain growth due to the sluggish diffusion effect. The ultra-high strength of (Ti,Zr,Ta)C ceramics was attributed to its fine microstructures, high fracture toughness, and the reinforced the grain boundary strength.