Thermal stability of a supersaturated Fe-Ge-Nb solid solution produced by ball milling

Description

Thermal evolution of Fe neighbourhood in a supersaturated bcc Fe(Ge,Nb) solid solution, obtained as the final product of mechanical alloying of Fe75Ge20Nb5, was studied. No changes in Fe neighbourhood were detected after heating up to 473 K, although differential scanning calorimetry shows a clear deviation of the baseline at 400 K. After heating up to 723 K, a similar nanocrystalline microstructure is derived from X-ray diffraction. However, Mössbauer spectra evidence changes in the Fe neighbourhood. A proposed deconvolution of the hyperfine field distribution yields a Ge content of ~10 at. %, in agreement with the maximum solubility of Ge in bcc Fe in thermodynamical equilibrium.

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