Ultra‐Low Coercivity and High Saturation Magnetization in a Strong Ductile Multicomponent Alloy via High Antiphase Boundary Energy

Soft magnetic materials (SMMs) with good mechanical properties are indispensable for functional devices under mechanical loading. However, conventional strengthening strategies rely on introducing microstructural obstacles that impeding dislocation motion (e.g., precipitates, dislocations, grain/phase boundaries) by adding high concentrations of non‐ferromagnetic elements. This generally leads to a drastic degradation in saturation magnetization, coercivity, and ductility of the alloy. Herein, we propose a novel strategy to coordinate these properties in Fe‐Co‐Ni‐Nb multicomponent alloy (MCA) by embedding coherent ordered nanoprecipitates with extremely high antiphase boundary energy (APBE) (325 mJ/m 2 ) into the ferromagnetic face‐centered cubic matrix. The extremely high APBE endows the precipitates with ultrahigh strengthening efficiency, which significantly improves the utilization efficiency of non‐magnetic strengthening elements used for synthesizing the precipitates. The achieved alloy exhibits a combination of high saturation magnetization (151 Am 2 /kg), low the coercivity (49 A/m), and high mechanical yield strength (926 MPa), and uniform elongation (28%), surpassing the existed soft magnetic high‐entropy alloys (HEAs) with similar composition and commercial Fe‐Si and Fe‐Co soft magnetic alloys. This work provides a viable route toward for developing high‐performance soft magnetic alloys.