Influence of P content on SMPs in Fe-Si-B-P-C-Cu-Nb amorphous alloys under longitudinal field annealing

The influence of P content on Curie temperature, magnetic properties and microstructures of Fe81.5Si3B10+xP3.5-xC0.2Cu0.8Nb1 (x = 0, 1, 2, and 3 at.%) alloys subjected to magnetic field annealing has been studied. Here, the decrease in P content can improve Curie temperature of alloys from about 575 to 584 K, which increases the operating temperature of magnetic device. Via optimal field annealing technique, the amorphous alloy with x = 3 exhibits good soft magnetic properties, including saturation magnetic flux density of 1.53 T, high effective permeability above 12,000, low coercivity below 3 A/m, and low core loss around 0.18 W/kg. The hysteresis loops show that tuning down the content of P relative to B can increase the saturation magnetic flux density of alloy system. Besides, the investigation about the microstructures of alloys annealed at optimal conditions indicates that longitudinal magnetic field annealing can improve the stability of amorphous phase, thereby ensuring the amorphous structure annealed at a higher annealing temperature compared with the general annealing for alloys.