From single high-entropy phase to multi-phase transition: Microstructural evolution of multi-component carbide (ZrHfVNbMoW)C realized by adjusting Hf content and temperature

Abstract

(ZrHfxVNbMoW)C ceramics with different Hf contents are consolidated by hot-pressing sintering at 2100 °C for 1 h. The influence of Hf content and temperature on phase transition are investigated. The phase transition from single high-entropy phase to multi-phase containing (ZrHfNb)C-rich and (VMoW)C-rich intermediate phases occurs with adding Hf, in relation with relevant larger lattice distortion. Remarkable microstructure refinement is observed with Hf content variation, due to the poor sinterability of Hf and the intermediate phases restricting the atomic motion and diffusion. The refined microstructure and severe lattice distortion lead to the improvement in mechanical properties. The annealing at different temperatures further proves the phase stability, sluggish diffusion effect as well as solid solution diffusion in high-entropy and multi-phase carbides.