Study by Mössbauer effect of diffusion of interstitials (C or N) in austenite

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Abstract
Theoretical results are presented for the temperature-dependence of Mössbauer spectra of Fe57 in austenite. The low-temperature spectrum is the superposition of a quadrupole-split doublet due to those Fe57 atoms which have a nearest-neighbour interstitial (C or N) and an unsplit line due to those Fe57 atoms which do not have a nearest-neighbour interstitial. At high temperatures, when the interstitials are jumping rapidly from site to site, the doublet collapses because the quadrupolar interaction averages out to zero. A theoretical model which describes this collapse over a range of temperatures is worked out. The concentration of the interstitials, the temperature-dependence of the diffusion constant for motion of the interstitials and other quantities of metallurgical interest can be obtained from a comparison of the theoretical results with experimental spectra