High Bs Fe-B-P-C-Cu nanocrystalline alloy with longtime annealing stability and low heating rate sensitivity

To solve the sensitivity of soft magnetic properties of Fe-B-P-C-Cu alloy system without transition metal addition on heat treatment process parameters, the effect of P content on the heat treatment process parameters and soft magnetic properties of Fe83B12-xPxC4Cu1 (x = 3, 5 and 7) alloys have been investigated. It is found that increasing P can effectively reduce the sensitivity of microstructure and soft magnetic properties on the annealing holding time (th). The th of Fe83B7P5C4Cu1 and Fe83B5P7C4Cu1 alloys can be extended to 60 min compared to the th of 6 min for Fe83B9P3C4Cu1 alloy to obtain a low coercivity (Hc) below 8.5 A/m. However, too high P content will reduce the stability of residual amorphous phase and shorten the optimal th. The results indicate that increase of P can also reduce the sensitivity of microstructure and soft magnetic properties on the heating rate (β). The β of Fe83B7P5C4Cu1 and Fe83B5P7C4Cu1 alloys can be as low as 40 K/min and 20 K/min to obtain high saturation magnetic flux density (Bs) of 1.80 T and 1.73 T, and low Hc of 8.4 A/m and 8.1 A/m, respectively.