Synthesis, microstructure, properties of nonstoichiometry high entropy carbide (MoNbTaTiW)C4.5

Abstract

AbstractA dense, fine‐grained, and toughened nonstoichiometry high entropy carbide (HEC) (MoNbTaTiW)C4.5 was synthesized via a two‐step way of carbothermal reduction‐solid solution using metal oxides and carbon. The effects of carbothermal reduction temperature, sintering temperature, and carbon content on the phase, microstructure, mechanical and thermal properties of (MoNbTaTiW)C4.5 were studied. The results showed dense and single phase (MoNbTaTiW)C4.5 were synthesized through reduction of metal oxides at 1600°C and sintered at and above 1950°C by spark plasma sintering. Reduced carbon content and higher solid solution temperature were beneficial to obtain dense HECs with better mechanical properties. With a carbon content of 90%, a reduction temperature of 1600°C, a holding time of 20 min, and a sintering temperature of 1950°C, the as‐synthesized (MoNbTaTiW)C4.5 showed a higher fracture toughness (5.2 MPa·m1/2). Besides, the (MoNbTaTiW)C4.5 showed a low thermal conductivity (5.9 W/m·K, at room temperature).