A plastic iron-based nanocrystalline alloy with high saturation magnetic flux density and low coercivity via flexible-annealing.

• A flexible-annealing technique has been invented, which can achieve fast heating rate and uniform temperature distribution. • The (Fe 0.8 Co 0.2) 85 Si 2 B 12 Cu 0.8 Mo 0.2 nanocrystalline alloy exhibits high B s up to 1.88 T, low coercivity of 6.3 A/m, as well as good plasticity. • The excellent properties are attributed to the controllable construction of diluted amorphous-nanocrystalline structure caused by flexible-annealing. The traditional high-temperature annealing process is difficult to control the morphology and size of the crystallization phases in amorphous alloy systems with high ferromagnetic element content, leading to mechanical brittleness and soft magnetic properties deterioration. Here, we developed a flexible-annealing technique and successfully achieved a fine nanocrystalline structure in a high-ferromagnetic-content system of (Fe 0.8 Co 0.2) 85 Si 2 B 12 Cu 0.8 Mo 0.2. It is exciting that the (Fe 0.8 Co 0.2) 85 Si 2 B 12 Cu 0.8 Mo 0.2 nanocrystalline alloy exhibits high B s up to 1.88 T, low coercivity of 6.3 A m^–1, as well as good plasticity. The excellent comprehensive properties are attributed to the controllable construction of diluted amorphous-nanocrystalline structure, the rapid release of internal stress, and the suppression of relaxation-induced uniformity achieved by the flexible annealing process. The results provide a fast and new paradigm for the development of next-generation high- B s soft magnetic materials. [Display omitted] [ABSTRACT FROM AUTHOR]