Nature of defect clusters in neutron-irradiated iron-based alloys deduced from small-angle neutron scattering

Small-angle neutron scattering (SANS) was applied to investigate Fe-based model alloys with intentionally varied Cu levels. The aims are to provide size distributions of scatterers and to interpret deviations of the measured ratio of magnetic and nuclear scattering cross-sections from the ratios calculated for pure vacancy clusters and pure Cu clusters. For the case of the low-Cu alloy the SANS results indicate the average scatterer to be an Fe-Cu-vacancy cluster of about 1 nm radius, the composition of which is constricted according to given inequalities. For the case of the Cu-enriched alloy the SANS results are consistent with Cu-rich clusters of about 1.5 nm radius containing 15% vacancies per bcc lattice site.