SANS investigation of irradiation-induced phase separation in binary Fe-Cr-alloys

Ferritic-martensitic chromium steels are candidate materials for future applications in both Gen-IV and fusion technology. Investigations of related binary Fe-Cr alloys will significantly contribute to the understanding of the behaviour of more complex alloys. The presented SANS results are focused on a Fe-9at.% Cr alloy neutron-irradiated up to a dose of 1.5 displacements per atom (dpa).
We have observed a pronounced increase of scattering intensities for two different irradiation conditions at scattering vectors Q > 0.2 nm-1 for both magnetic (figure (a)) and nuclear scattering. The reason for the increased intensities are irradiation-induced clusters with size distributions presented in figure (b). The A-ratio is about 2.8 for both irradiation conditions. This value is far from a value of 1.45 corresponding to nanovoids as scattering objects. This indicates that the irradiation-induced clusters are different from pure nanovoids and must contain Cr-atoms with the same or very similar average composition for both irradiation conditions. These clusters are interpreted as alpha’-phase. The volume fraction of clusters of this type increases slightly with neutron dose.