ON THE MEASUREMENT OF RADIATION-INDUCED SEGREGATION (RIS) AT POINT-DEFECT SINKS

A theoretical investigation has been conducted into the measurement of the composition of grain boundary regions using STEM-EDX in irradiate d austenitic alloys. The calculations attempt to account for recent ex perimental observations where Cr enrichment at the boundary co-exists with depletion in the adjacent matrix. The effects of probe size and e lectron scattering within the foil are convoluted with theoretical con centration distributions of RIS and predictions made of the visibility of segregations to the grain boundary. Two important predictions are that, depending on experimental variables, up to 0.4 monolayers of Cr segregation might be present at the boundary but not explicitly reveal ed, and that the visibility of segregation in the presence of depletio n is not optimised in the thinnest specimens.