Improvement of SMPs in Fe-Si-B-P-C-Cu-Nb alloys via harmonizing P and B

The effect of P content on crystallization behavior, microstructure, magnetic domain structure, and magnetic properties of Fe81.5Si3B13-xP0.5+xC0.2Cu0.8Nb1 (x = 0, 1, 2, and 3 at. %) alloys have been investigated. The results of XRD and DSC suggest that the moderate increase in P content improves the amorphous forming ability (AFA) of the alloys and enlarges the temperature interval to 153 K between two crystallization peaks. The activation energy indicates that the relative increase in P content prompts the precipitation of alpha-Fe phase and improves the thermal stability. Through optimal annealing treatments, the nanocrystalline alloy with x = 3 exhibits excellent soft magnetic properties (SMPs), including high Bs above 1.65 T, high mu(e) about 19000, low H-c below 3 A/m and P-10/50 around 0.12 W/kg. The microstructures of the alloys annealed at optimal conditions were detected via XRD and TEM, the results of which show that harmonizing P and B not only refines grains but enhances the nanostructure homogeneity. The investigation with magneto-optical Kerr microscopy reveals the magnetic domain evolution of x = 3 alloy including stress domain removing, domain differentiating and broadening process.