Study of the microstructure of α-Fe/Nd2Fe14B nanocomposites prepared by electropulsing heating amorphous NdFeCoB

The microstructure of the α-Fe/Nd2Fe14B nanocomposite magnets prepared by electropulsing heating amorphous Nd8Fe84Co3B5 has been studied by employing X-ray diffraction (XRD) and transmission electronic microscopy (TEM). The grain size d of the α-Fe phase keeps almost invariable, e.g., d ≈ 18-19 nm, with the increase of its volume fraction during the electropulsing heating process, indicating that the crystallization process of the α-Fe phase dominantly depends on the enhancement of nucleation rate. The grain sizes of both the α-Fe and the Nd2Fe14B phases, dα-Fe = 19 nm and dNdFeB = 27 nm, are smaller as compared to those in the nanocomposites prepared by annealing Nd8Fe84Co3B5 in a normal furnace, dα-Fe = 23 nm and dNdFeB = 39 nm. This leads to an enhanced maximum energy product (BH)max = 128 kJ/m3 in the nanocomposite magnets.