Calculation of the solvent and solute enhancement factors in BCC metals assuming a hypothetical structure with fourteen first nearest neighbors

Abstract

In this paper the solute and solvent enhancement factors in a hypothetical body centered cubic (b.c.c) structure having fourteen first nearest neighbors are calculated by using a statistical model for diffusion in dilute alloys. Inherent to the model is the assumption of the equality of the first and second nearest neighbor jump distances, since in the b.c.c structure the difference between these distances, respectively, is only ∼13.5%. The number of parameters required for fitting to evaluate the enhancement factors (b and B) is substantially reduced in comparison to existing models and therefore fewer experiments are necessary. Correlation effects are implicit in the calculated values of b and B. The results of the fitting provide values for the frequency ratios, the additional energies required to form a vacancy in the vicinity of a solute and for the binding energies between solute pairs, i.e., between the reference and tracer solute. Values of b and B in several dilute alloys were calculated at different temperatures. In general there is a good agreement between experimental and calculated values of b and B in the alloys tested. The equations for b and B can be used for temperatures where no experimental data exist.