Mössbauer-effect study of iron-boron-beryllium metallic glasses

Abstract

$^{57}\mathrm{Fe}$ M\ossbauer spectra have been obtained at both liquid-nitrogen and room temperatures for a series of metallic glasses ${\mathrm{Fe}}_{82}{\mathrm{B}}_{18\ensuremath{-}x}{\mathrm{Be}}_{x}$ with $0l~xl~6$. With the use of Window's program the spectra were fitted and deconvoluted to obtain the probability distribution function of the effective magnetic hyperfine field $P(H)$, and the results show a well-defined symmetric shape for these metallic glasses. The width of $P(H)$, $\ensuremath{\Delta}H$, remains approximately constant at a value of 80 kOe for all samples. However, the most probable value of the effective magnetic hyperfine field ${H}_{1}$ at liquid-nitrogen temperature initially increases with the Be content to 4 at.%, but starts to decrease as $x$ exceeds 4. The isomer shift has a value of -0.032 mm/sec for samples with $xl~4$ but changes to -0.050 mm/sec for samples with $xg4$. The crystallization products obtained upon annealing the ${\mathrm{Fe}}_{82}$${\mathrm{B}}_{18}$ metallic glass at ${T}_{a}=420$\ifmmode^\circ\else\textdegree\fi{}C were identified as tetragonal ${\mathrm{Fe}}_{3}$B and $\ensuremath{\alpha}$-Fe. The annealing of the samples with $xg0$ between ${T}_{x1}$ and ${T}_{x2}$ yields a metastable amorphous phase and crystalline solid solutions of an Fe-Be phase. Annealing of the samples with $xg0$ above ${T}_{x2}$ yields crystalline Fe-Be solid solutions and the ${\mathrm{Fe}}_{2}$B intermetallic compound. The intensity ratios in the M\ossbauer spectra clearly indicate that annealing of samples between ${T}_{x1}$ and ${T}_{x2}$ led to the alignment of the ${\overline{H}}_{\mathrm{eff}}$ direction close to the ribbon plane, but annealing above ${T}_{x2}$ left ${\overline{H}}_{\mathrm{eff}}$ randomly oriented.