Radiation-induced segregation in multicomponent alloys: Effect of particle type

Abstract

The problem of irradiation-assisted stress-corrosion cracking (IASCC) in reactor cores is currently being addressed using different types of particle irradiation (electrons, protons, and heavy ions) to study the effect of neutron damage. The effect of radiation damage of greatest interest to the IASCC problem is the segregation of impurities or redistribution of alloying elements in the vicinity of the grain boundary. Differences among the types of irradiation include particle type, temperature, dose, and dose rate. The different particle type results in different "effective" displacement rates due to fundamental differences in the radiation damage state. The effect of displacement efficiency is incorporated into existing models for radiation-induced segregation and compared with experimentally determined values. Comparisons between theory and experiment were made using neutron-,proton-, and ion-irradiated stainless steels. Results showed that the measured chromium depletion profile is generally narrower and shallower than that calculated from theory. Agreement between experiment and model was better in almost all cases when the particle efficiency was taken into account. Agreement was best for proton-irradiated steels, and less so for neutron and heavy ion-irradiated steels. The origins of this difference are probably due to spatial and depth resolution of the scanning transmission electron microscopy and Auger electron spectrometry measurement techniques, respectively, the lack of knowledge of the material parameters in modeling, and the uncertainty in the true displacement rate. Nevertheless, beyond 2 nm from the grain boundary, the shape of the experimental and calculated profiles agree reasonably well.