Superior Strength‐Ductility Synergy Enabled by Magnetic‐Field‐Driven Structural Metastability in Spinodal High Entropy Alloys

Achieving superior strength‐ductility synergy in advanced structural materials remains a long‐standing challenge. Here, a high magnetic field aging (HMFA) strategy is proposed that leverages extreme‐field physics to engineer spinodal decomposition structures (SDS) in a non‐equiatomic Al 0.5 Cr 0.9 FeNi 2.5 V 0.2 high entropy alloy (HEA), resulting in an extraordinary combination of 1988 MPa tensile strength and 19.6% ductility. HMFA significantly amplifies compositional fluctuations within the SDS, thereby generating intensified coherency stress fields that enhance spinodal hardening by 91% relative to conventional aging. Simultaneously, the magneto‐modulated SDS lowers the matrix stacking fault energy, triggering structural metastability that activates deformation twins, stacking faults, and 9R phases under straining. These hierarchical deformation mechanisms collectively promote strain hardening while preserving dislocation mobility, thus overcoming the classical strength‐ductility trade‐off. Comprehensive microstructural characterizations and theoretical simulations demonstrate this strategy markedly improves the mechanical performance of spinodal HEAs, establishing HMFA as a groundbreaking extreme‐field processing technique for next‐generation high‐performance structural alloys.