QUANTIFICATION OF DEFECT SOLUTE COUPLING FROM INVERSE-KIRKENDALL SEGREGATION

A method has been adopted for quantifying and validating inverse-Kirke ndall segregation during irradiation of an Fe-Cr-Ni stainless steel. M odel predictions of calculated chromium depletion compared with calcul ated nickel enrichment were in accord with several hundred composition measurements. Compositions were measured at and near grain boundaries in a nickel-ion irradiated stainless steel. The method allows assessm ent of relative defect-solute coupling efficiencies independent of kin etic opportunity for segregation. The alloy had approximately 21 at % Cr and 20 at % Ni. The analysis of relative composition changes establ ished that the Fe diffusivity is 2.0 times faster than the Ni diffusiv ity and the Cr diffusivity is 2.55 times faster than Ni diffusivity in the temperature range of 230 to 550 degrees C. The relative rates are consistent with unirradiated ternary diffusion rates at higher temper atures reported in the literature.