Non-stoichiometry of (TiZrHfVNbTa)Cx and its significance to the microstructure and mechanical properties

Abstract

(TiZrHfVNbTa)Cx with variable stoichiometry are fabricated by pressureless sintering utilizing self-synthesized carbide powders via carbothermal reduction reaction. The densification behavior and microstructure evolution coupled with corresponding adjustable mechanical properties are investigated. The single-phase rock-salt crystal structure is retained despite the carbon stoichiometry approaching 0.6, indicating (TiZrHfVNbTa)Cx can maintain structural stability even containing high carbon vacancy. The carbon vacancy is beneficial for promoting densification procedure. The relative density of (TiZrHfVNbTa)C0.6 sintered at 2150 °C can reach 97.9 %, while the similar value for (TiZrHfVNbTa)C1.0 is obtained even at 2400 °C. While, remarkable grain growth accompanied by decline in relative density also occurs for lower carbon stoichiometry. With the variation of carbon content, the concentration of carbon-metal bonds changes gradually, leading to the adjustable mechanical properties. This work provides a potential approach to synthesize non-stoichiometric high-entropy carbides with high carbon vacancy via low-temperature pressureless sintering.