Mössbauer study of the local atomic environments in metastable crystalline Fe-B alloys

We have applied the Mössbauer effect to study the local atomic environments in metastable crystalline ${\mathrm{Fe}}_{100\mathrm{?}(\mathrm{hyx}}$ ${\mathrm{B}}_{\mathrm{x}}$ alloys (1≤x≤12) produced by rapid quenching from the melt. For concentrations up to 9 at. % B, the spectra revealed the existence of three distinct ${}_{}{}^{57}{}_{}{}^{}\mathrm{Fe}$ sites, characterized by room-temperature hyperfine fields of 330, 267, and 236 kOe, the first of which is that of Fe in bcc α-Fe. The other two sites were populated in the ratio 1:2, while the total amount of Fe atoms in them was nearly three times the number of B atoms present in the alloys. Furthermore, the temperature dependences of the hyperfine fields at these two sites were the same, although distinctly different from that of the α-Fe site. The Mössbauer results presented here, together with a nuclear-magnetic-resonance investigation previously reported, demonstrate that these alloys are not random solid solutions. Instead, they indicate that the alloys consist of a dispersion of very small regions, which have an orthorhombic-${\mathrm{Fe}}_3$B-like structure, embedded in an α-Fe matrix.