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In order to check conventional results obtained by the traditional experimental methods, the concentration and temperature ranges of the miscibility gap are closely examined by Mossbauer spectroscopy. The present result does not support the earlier Williams' result that the upper limiting temperature of the miscibility gap is about 830 K, but proposes that it is about 950 K. The proposed miscibility gap is well expressed by the regular solution treatment on the whole, and lies over the concentration range from 10 to 86 at%Cr at low temperatures around 750 K.

Many binary ferrous alloys were synthesized by mechanical attrition in a high-energy ball mill. X-ray diffractometry and transmission electron microscopy were used to measure grain sizes, which were as small as a few nanometers in several alloys. The nanocrystalline alloys showed new features in their Mössbauer spectra, which we associated with 57Fe atoms at and near grain boundaries. The experimental data on the fraction of 57Fe atoms at and near grain boundaries were correlated to the measured grain sizes to obtain an average width of the grain boundaries. The average grain-boundary widths of the fcc alloys Fe–Mn and Ni–Fe were approximately 0.5 nm, but the average widths of grain boundaries in the bcc alloys Cr–Fe, Mo–Fe, and Fe–Ti were somewhat larger than 1 nm.

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