Breaking Hardness–Toughness Trade‐Off in Novel (V, Nb)C Carbides via Nanoscale Phase Separation and Local‐Chemical‐Order Dislocation Network

ABSTRACT Transition metal carbides demonstrate exceptional mechanical properties but confront a critical hardness–toughness trade‐off. Spinodal decomposition‐mediated phase separation is an effective approach to enhance mechanical properties in carbide ceramics through high‐temperature treatment. Guided by thermodynamic phase diagrams, this study designed a novel (V, Nb)C system wherein nanoscale phase separation was realized via controlled aging processes. Unlike traditional carbide ceramics, the aged (V, Nb)C carbides present a unique dual‐scale microstructure: nanoscale intragranular spinodal decomposition coexists synergistically with a grain‐boundary dislocation network associated with locally ordered phases. This unique structure effectively impedes dislocation motion, leading to superior mechanical performance enhancement compared to conventional carbide ceramics. Following controlled aging treatments, the material achieves a simultaneous enhancement of hardness (45% increase) and fracture toughness (25% improvement) relative to the as‐fabricated state, thereby overcoming the intrinsic hardness–toughness trade‐off inherent to carbide systems. This study elucidates the crucial role of spinodal decomposition in the microstructural evolution of composite carbides and highlights the efficacy of the chemically ordered dislocation network in suppressing diffusion and dislocation motion. These insights establish a robust theoretical framework for optimizing mechanical properties and designing ceramic materials with exceptional service performance.