A study of thermodynamic properties of dilute Fe-Au alloys by the ⁵⁷Fe Mössbauer spectroscopy

The room temperature Mössbauer spectra of ⁵⁷Fe were measured for Fe_{1-x}Au_x with the gold concentration ranging from 1 at.% till 4.8 at.%. They were analysed in terms of hyperfine parameters of their components related to unlike surroundings of the iron probes, determined by different numbers of gold atoms existing in the neighbourhood of iron atoms. Basing on the intensities of the spectrum components we determined binding energy E_b between two gold atoms in the studied materials. The latter was done for properly annealed samples using the extended Hrynkiewicz-Królas idea. It was found that the binding energy is positive or Au atoms interact repulsively. The extrapolated value of E_b for x =0 was used for computation of an enthalpy of solution of Au in Fe. Finally the obtained value of the enthalpy was used to predict the mixing enthalpy for the Fe-Au solid solutions. The results were compared with both the corresponding values resulting from the cellular atomic model of alloys by Miedema and those derived from experimental calorimetric data given in the literature.