Crystallization of Fe-B amorphous alloys: A NMR and x-ray study

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Abstract
Based on a knowledge of the NMR spectra for FeB, Fe2B, orthorhombic Fe3B (o‐Fe3B), and body‐centered‐tetragonal Fe3B (bct‐Fe3B), the phases produced during the annealing of Fe‐B amorphous alloys can be identified with greater sensitivity by NMR techniques than by x‐ray diffraction. In the present work, a combination of x‐ray diffraction experiments and spin‐echo NMR measurements of the hyperfine field distributions for the 10B, 11B, and 57 Fe nuclei has been performed on both as‐quenched and annealed Fe100−xBx (14≤x≤25) amorphous alloys. In general terms, it was found that annealing at temperatures near 400 °C resulted in crystallization products which included bct‐Fe3B, while annealing at approximately 800 °C leads to the formation of o‐Fe3B. The behavior of the B hyperfine field indicates that, for the Fe100−xBx amorphous alloys, an o‐Fe3B‐like local order is favored in the low B concentration regime, and a bct‐Fe3B‐like local order is favored in the high B concentration regime.