Abstract

Radiation-induced segregation (RIS) is driven by fluxes of point defects to sinks. RIS can induce composition fluctuations in irradiated stainless steels, which can result in microstructural and property changes, including precipitation, austenite instability, strengthening, embrittlement, and irradiation-assisted sensitization and stress corrosion cracking. Analytical electron microscopy (AEM) provides a powerful technique to study such segregation. RIS in several irradiated stainless steels has been investigated. AEM was performed in a Philips EM400T/FEG equipped with an EDAX 9100/70 analysis system. The specimens were neutron irradiated to 15 displacements per atom (dpa) at 520 ° C in the Fast Flux Test Facility (FFTF) and were only mildly radioactive (<50/μCi = 1.85 MBq), thus permitting high spatial resolution X-ray microanalysis to be employed. Typical acquisitions were performed for 100 s in the STEM mode with <2-nm-diam probes containing >0.5 nA current. Subtraction of “in-hole” spectra from the measured spectra corrected for both the normal “in-hole” counts and those associated with the radioactivity of the specimen.

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