High‐Coercivity Nd ₂ Fe ₁₄ B/α‐Fe Nanocomposites With Ultrafine Nanocrystalline Structure via Zr‐Induced Synchronous Precipitation

ABSTRACT Nanocomposite permanent magnets with reduced rare‐earth content represent a promising class of materials for next‐generation high‐performance applications. However, asynchronous precipitation of soft and hard magnetic phases often results in grain size mismatch and limited coercivity. In this study, zirconium is utilized to modulate the eutectic reaction temperature among the soft magnetic, hard magnetic, and boron‐rich phases, aligning it with the solidification point of the hard phase. This thermal alignment enables synchronous precipitation, leading to the formation of ultrafine dual‐phase nanocomposites with an average grain size of approximately 20 nm and a 75.8% improvement in coercivity. Furthermore, zirconium addition induces the formation of a ferromagnetic ZrFe 2 three‐dimensional network that encapsulates both soft and hard magnetic grains, significantly enhancing intergranular exchange coupling and magnetization uniformity. The synergistic effects of grain refinement and phase compatibility result in the concurrent enhancement of coercivity and energy product, while substantially lowering rare‐earth consumption. These findings offer a practical strategy for grain size synchronization and phase integration in multiphase nanocomposites.