Conversion electron Mössbauer spectroscopy and x-ray photoemission spectroscopy studies of thermal oxidation of Fe67Co18B14Si1 metallic glass

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Abstract
The oxidation kinetics and associated structural and chemical transformations in the Fe67Co18B14Si1 metallic glass have been investigated by using the techniques of conversion electron Mössbauer spectroscopy (CEMS) and x‐ray photoemission spectroscopy (XPS). The as‐quenched as well as vacuum‐annealed samples of the metallic glass have been subjected to thermal treatment in air at 100, 300, and 390 °C for 1/2 h in each case. The information regarding the structural transformations and chemical reactions has been obtained by deconvoluting the complex CEMS spectra and analyzing the contributions of various elements to the XPS spectra. It is shown that oxygen incorporation in the glass initiates the process of recrystallization of the glassy state at a temperature which is lower as compared to its temperature of recrystallization in vacuum. The oxygen‐coordinated phases in the oxide scale and the other phases precipitated due to the reactive thermal treatment have been identified and the physical mechanisms underlying the observed effects have been commented upon. Experiments have also been performed to examine the transformations occurring in the metallic glass upon its prolonged thermal treatment in air at a typical temperature (∼100 °C) within the recommended temperature range (25–125 °C) for its use in applications. It has been demonstrated that the surface layers of the as‐received glass are affected by such a treatment, though the sample preannealed at 300 °C remains relatively unaffected. The observations made on the basis of CEMS and XPS studies have been supported by x‐ray diffraction and resistance‐annealing measurements.

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