SANS investigation of a neutron-irradiated Fe-9at%Cr alloy

Available experimental results indicate that the addition of Cr to Fe and steels significantly influences the response of Fe-Cr alloys and ferritic/martensitic high-Cr steels to neutron irradiation. A level of 9 at% Cr is of particular interest because this composition is close to the boundary of the Fe-Cr miscibility gap. Furthermore, it corresponds to the composition of several candidate steels for application in nuclear technology. However, experimental evidence has been incomplete so far. The reported study by means of small-angle neutron scattering is devoted to the effect of neutron irradiation at 300°C up to fluences of 0.6 and 1.5 dpa on the microstructure of an Fe-9at%Cr alloy. We have observed a pronounced irradiation-induced increase of scattering cross-sections for both magnetic and nuclear scattering. Bimodal size distributions of irradiation-induced defect-solute clusters have been reconstructed. The restrictions on the composition of these clusters have been discussed in terms of the scattering contrast. We have found that vacancy clusters and alpha’-particles alone cannot explain the full set of experimental findings. The remaining inconsistency can be solved by taking into account a contribution of impurity carbon.