Soft magnetic properties and thermal stability of bulk Fe83B17 alloy prepared by undercooling and Cu-mold casting methods

•Thermal stability of the nano-lamellar eutectic structure was obtained.•Thermal stability of the metastable Fe3B phase was obtained.•The soft magnetic properties of the sample remain stability by annealing.•Nano-lamellar eutectic structures enhance the soft magnetic properties.

The thermal stability and soft magnetic properties of bulk Fe83B17 rods with nano-lamellar eutectic structures and metastable Fe3B phases were investigated by annealing at 973–1273 K for 1.5 h. Samples with a diameter of 3 mm were prepared by undercooling solidification combined with Cu-mold casting. The decomposition of Fe3B and the transformation of nano-lamellar eutectic structures were finished after annealing at 1173 K for 1.5 h. Increasing annealing temperature showed that the soft magnetic properties of the sample were kept relatively stable. The saturation magnetization and retentivity were decreased only slightly, while the coercivity was decreased significantly.