Influence of vanadium content on the microstructural evolution and mechanical properties of (TiZrHfVNbTa)C high-entropy carbides processed by pressureless sintering.

• The adding vanadium to (TiZrHfVNbTa)C favors eliminating Nb segregation and enhancing densification. • Excess adding vanadium reduces single-phase-forming ability of (TiZrHfVNbTa)C, due to the lattice distortion increment. • Mechanical properties of (TiZrHfVNbTa)C is optimized via adjusting vanadium content and sintering temperature. A series of (TiZrHfVNbTa)C high-entropy ceramics with different vanadium contents have been fabricated by pressureless sintering at 2300 °C–2500 °C for 1 h, utilizing self-synthesized carbide powders obtained by carbothermal reduction. The addition of vanadium is beneficial to promote densification process and refine grain, as well as facilitate the homogeneous distribution of metal elements. The distribution of pores is also modified, almost entirely existing at grain boundary, and the integral mechanical properties achieve optimization. However, excess adding vanadium does not favor forming a single-phase (TiZrHfVNbTa)C high-entropy ceramic. The optimal (TiZrHfVNbTa)C high-entropy ceramic sintered at 2300 °C possesses a high relative density of 97.5 % and homogeneous microstructure with small grain size of 1.2 μm. The flexural strength and Vickers hardness reach 473 MPa and 24.9 GPa, respectively. This work has established a cost-effective and convenient preparation of novel (TiZrHfVNbTa)C high-entropy carbide ceramics. [ABSTRACT FROM AUTHOR]