Decomposition of pre-existing Au–P clusters induced in situ α-Fe grains uniformization in Fe–P-based nanocrystalline alloys

In Fe-based amorphous-/nanocrystalline ribbons, the uniformization and refinement of α-Fe grains are key aspects for optimizing their soft magnetic and mechanical properties. Herein, the Fe–P–C–B nanocrystalline alloy system was selected for investigation. We produced as-spun ribbons with pre-existing nanocrystals through melt-quenching and then obtained a well-distributed α-Fe nanocrystalline structure through annealing below the first crystallization onset temperature (633 K), resulting in excellent magnetic properties (saturation magnetization of 1.65 T and coercivity of 1.6 A·m⁻¹), ultra-wide annealing temperature window (from 613 to 733 K), and extremely high annealing stability (up to 480 min at 633 K). Furthermore, we propose a new in situ two-step mechanism for the uniformization of α-Fe nanocrystals, which is separately induced by the decomposition of the Au–P clusters and the pre-existing α-Fe nanocrystals during annealing. This work underscores the crucial significance of micro-alloying via metastable clusters primarily influenced by metal-phosphide interactions in the process of refining α-Fe nanocrystals. Furthermore, it introduces a new principle for optimizing the comprehensive properties of Fe-based amorphous/nanocrystalline alloys.