The association of compositional fluctuations with clusters of cavities in irradiated alloys

The microstructure of Fe-12% Cr-15% Ni alloys irradiated with neutrons at 645degC has been studied in detail. These materials display intragranular fluctuations in composition with an irregular size and spacing. The alloys also contain a distribution of small, helium-filled cavities. It is shown that these cavities are clustered, and that the clusters of cavities are associated with regions rich in nickel and depleted in iron and chromium. It is believed that the cavities are the dominant point defect sinks and that the nickel enrichment associated with the clusters of cavities is a result of radiation-induced segregation. Possible explanations for the clustering of cavities are discussed. (orig.)