Microstructure and magnetic properties of Fe79-xB20NbxCu1 fibers with annealing

The Fe79-xB20NbxCu1 (x = 0, 2, 4, 6, 8) fibers were fabricated using the melt-spinning method and the microstructure and magnetic property of the fibers after annealing were investigated. The results showed that coercivity of the as-spun fibers increased slightly with the growth of Nb/Fe atomic ratio. Fe23B6-type phase precipitated from amorphous matrix after annealed at 550 °C and then transformed into α-Fe, Fe2B and FeNbB phases with the increase of annealing temperature which corresponded to specific crystallization processes. The Fe23B6-type phase with a lattice parameter of 1.0735 nm was obtained by selected-area electron diffraction pattern and high-resolution transmission electron microscope images. Moreover, after annealed at 530 °C for 3 min, the minimum Hc at 7 A/m of Fe77B20Nb2Cu1 fibers was found.