Mechanical behavior of high entropy ceramic (TiZrHfVNb)C₅ under extreme conditions: A first-principles density functional theory study

Abstract

Multi-component high-entropy carbides (HECs) have garnered extensive attention owing to their excellent serviceability in harsh environments characterized by ultra-high temperatures and high pressures. However, the microstructure, electronic structure, and chemical bonding of materials are significantly influenced by high pressure. This study investigates the effects of high-pressure conditions on the stability and properties of (TiZrHfVNb)C₅ phases using the first-principles calculation. According to the judgment analysis in thermodynamics, mechanics, and kinetics, HECs can form a single solid-solution phase which is stable in 0–100 GPa. When pressure is applied, HECs undergo more significant property changes. With increasing pressure, there are some increases in lattice distortion, elastic modulus, mechanical anisotropy, sound velocity, and Debye temperature of (TiZrHfVNb)C₅ ceramic. It is worth noting that hardness has a perverse behavior at high pressures, and the hardness decreases with increasing pressure. At 40–50 GPa, HECs also experience a brittle–ductile transition. A shift in HECs' electronic structure under pressure is what essentially causes the changes in brittle–ductile transition and hardness. This work provides instructive insights for predicting and designing high-performance high-entropy carbide ceramics tailored for extreme environmental conditions.