Radiation-induced segregation in Fe-Cr-Ni alloys

Calculations of composition profiles of radiation-induced segregation (RIS) in irradiated Fe-Cr-Ni alloys are presented and compared with experimental data. The model allowed only the inverse Kirkendall effect due to vacancies to drive the segregation, and the ratios of the relevant vacancy jump rates were taken from Rothman et al.'s thermal diffusion measurements. The measurements of RIS were those made by Sethi and Okamoto at the surface of Fe-20Cr-12Ni alloys ion-irradiated at 430 to 675 deg C, and at grain boundaries in Fe-15Cr-42.5Ni irradiated at 600 deg C made by the present authors. Calculated segregation rates were found to be much higher than those measured, but fairly good agreement between measurement and calculation was achieved if the calculation was run only to doses about 5% of the actual ones. The discrepancy is tentatively ascribed to the small probability of production of a freely diffusing vacancy for each atom displaced in a collision cascade. (author)