Mechanical Properties of Non‐Equimolar High‐Entropy Carbides

High‐entropy carbides are ultra‐high temperature structural materials with great potential for application. However, their inherently poor fracture toughness has significantly restricted their practical deployment. Herein, non‐equimolar compositional design is proposed as a highly feasible paradigm to fundamentally optimize the mechanical properties of high‐entropy carbides. (Ti 0.25 Zr 0.25 Nb 0.25 Ta 0.2 W 0.05 )C and (Ti 0.3 Zr 0.2 Nb 0.2 Ta 0.2 Mo 0.1 )C were developed by meticulously adjusting the W and Mo contents to elucidate the influence of non‐equimolar stoichiometry on macroscopic mechanical behavior. The results demonstrate that the as‐prepared non‐equimolar high‐entropy carbides exhibit an exceptional combination of mechanical properties far superior to their equimolar counterparts. Specifically, (Ti 0.25 Zr 0.25 Nb 0.25 Ta 0.2 W 0.05 )C yielded an excellent fracture toughness of 7 MPa·m 1/2 with remaining high strength 689.49 MPa and hardness 28.87 GPa, while (Ti 0.3 Zr 0.2 Nb 0.2 Ta 0.2 Mo 0.1 )C achieved outstanding strength 823.4 MPa with high toughness 6.27 MPa·m 1/2 and hardness 26.59 GPa. The underlying performance‐enhancing mechanisms are governed by the synergistic effects of tailored lattice distortion, sluggish diffusion, and extreme grain‐refinement strengthening. Ultimately, this study confirms that the comprehensive mechanical properties of refractory high‐entropy carbides can be profoundly tailored through judicious non‐equimolar design, successfully shattering the traditional strength‐toughness trade‐off.