The Stability, Mechanical and Thermodynamic Behaviors of (Ti _0.2Zr _0.2Hf _0.2Ta _0.2Me _0.2)C (M = Nb, Mo, W, V, Cr) High-Entropy Carbide Ceramics

Abstract

Multicomponent high entropy carbide ceramics (HECCs) have drawn increasing attentions owing to their potential applications in ultra-high temperature and superhard materials. The stability, mixing behavior, mechanical and temperature-dependent properties of rock-salt (Ti_0.2Zr_0.2Hf_0.2Ta_0.2Me_0.2)C (M = Nb, Mo, W, V or Cr) HECCs were firstly systematically investigated by density functional theory (DFT) and Debye-Grüneisen model methods. Five HECCs are thermodynamically stable due to negative formation enthalpies and cohesive energies. They are able to form the single-phase high entropy solid solution ceramics, which are evaluated by the atom size and lattice differences, and mixing enthalpy criteria. Except Cr containing system, existence of others are already confirmed by experimental findings. Among them, (Ti_0.2Zr_0.2Hf_0.2Ta_0.2Nb_0.2)C is easiest to form the homogeneous solid solution phase, and is the most stable, brittlest and hardest HECC material of all. Significantly, (Ti_0.2Zr_0.2Hf_0.2Ta_0.2V_0.2)C behaves somewhat better than (Ti_0.2Zr_0.2Hf_0.2Ta_0.2Nb_0.2)C with the growth of temperature, due to comparable bulk modulus and Debye temperature, smaller volumetric expansion, and lower anharmonic effect contribution. This work provides the instructive information to predict and design the high-performance ultrahigh temperature ceramic materials applicable in extreme environments.

Keywords: High-entropy carbide, Density functional theory, Debye-Grüneisen model, High-hardness, Ultra-high temperature