Dual‐Regulation of Continuous and Discontinuous Precipitation via Carbon Alloying for Enhanced Strength‐Ductility Synergy in a Medium‐Entropy Alloy

ABSTRACT

The exceptional ductility of face‐centered cubic high/medium‐entropy alloys (H/MEAs) is counterbalanced by intrinsically restrained yield strength, fundamentally compromising their application in structural and functional materials. Here, a novel carbon (C)‐driven precipitation strategy is introduced to promote discontinuous precipitation (DP) without significantly suppressing the continuous precipitation (CP) reaction in (FeCo) ₅₅ Ni ₃₅ Al ₁₀ MEA, thereby enhancing strength‐ductility synergy. Remarkably, C‐alloying markedly improves the strength through enhanced ordering strengthening, with a strengthening efficiency surpassing those previously reported C‐containing H/MEAs. The first‐principles calculations show that C‐alloying reduces the total energy difference of the system, that is, enhancing the thermodynamic driving force for L1 ₂ precipitate formation, in turn, indirectly promoting the nucleation and growth of Fe‐Co‐enriched body‐centered cubic DP precipitates. Moreover, C‐alloying lowers the critical precipitate size required for dislocation coupling, facilitating microband formation and improving plastic deformation accommodation. Importantly, grain boundaries act as DP nucleation sites but hinder microband development, underscoring the critical role of grain size in deformation compatibility. This study reveals a novel C‐driven precipitation mechanism to enhance ordering strengthening, offering a strategic pathway for designing high‐performance L1 ₂ ‐strengthened H/MEAs.