Surface analysis of Fe–Co–Nb–Cu–B metallic glasses using a miniaturised Mössbauer spectrometer ‘MIMOS’

A miniaturised Mössbauer spectrometer ‘MIMOS’ operating in a backscattering geometry using 6.4 keV X-ray Mössbauer radiation and 14.4 keV backscattered γ-ray Mössbauer radiation has been used to obtain information about the depth-selective surface crystallization of thermally annealed Fe58Co25Nb7Cu1B9 and Fe60Co25Nb6Cu1B8 alloys. Crystallization of the specimens starts after annealing at 390 °C. An increase of the annealing temperature increases the hyperfine field showing the increase of Co-content in the crystalline phase from 2% to 10%. The relative abundance of Fe in the crystalline phase ranges between 8% and 42%. An increase in the annealing temperature enhances the order in the crystalline phase and randomises the atomic spins, which are preferentially aligned within the ribbon plane in the as-cast state.