A new method was used to study the dependence of Mössbauer spectrum parameters on the temperature of the diffusion annealing which led to the redistribution of 57Co atoms between various states in polycrystalline Ta. For all annealing temperatures between 660 and 1425K, two types of state were found to be populated in the zone of intercrystalline diffusion of 57Co. State type-I was localized in the cores of the crystallite-conjugation regions. State type-II was localized in lattice regions that were adjacent to the core of the crystallite-conjugation regions. Depletion of atomic probes from the crystallite-conjugation regions was revealed for the first time in the present system. No change in the populations of the states occurred during isochronal annealing of the system at progressively increasing homologous temperatures of between 0.2 and 0.35. Rapid changes in the population occurred only at homologous temperatures above 0.38. The activation enthalpy for the disappearance of component-I of the Mössbauer spectra was 337kJ/mol. This value coincided with the activation enthalpy for the bulk diffusion of Co in Ta.

Intercrystalline Diffusion of Cobalt in Polycrystalline Tantalum: a Mössbauer Study. V.N.Kaigorodov, S.M.Klotsman, M.I.Kurkin, V.V.Dyakin, D.V.Zherebtsov: Physics of Metals and Metallography, 1998, 86[4], 386-93