Publikationsrepositorium - Helmholtz-Zentrum Dresden-Rossendorf

Ferritic-martensitic chromium steels are candidate materials for future applications in both Gen-IV fission and fusion technology. Experimental investigation of neutron-irradiated Fe-Cr model alloys is important in order to gain a better understanding of the interplay of chromium content and irradiation behaviour. Small-angle neutron scattering (SANS) is particularly well suited to unfold the size distribution of non-planar irradiation-induced nanoscale features such as defect-solute clusters, nanovoids and ’-particles. This size distribution represents a statistically reliable average over a macroscopic volume. Assumptions on the dominant type of features can be checked against the ratio of magnetic and nuclear scattering.
The materials investigated in this work are commercial-purity Fe-Cr alloys of nominal compositions Fe-2.5Cr, Fe-5Cr, Fe-9Cr and Fe-12.5Cr (at%). Neutron irradiation was performed in the reactor BR2 at Mol (Belgium) at a temperature of 300°C and neutron flux of 9 x 1013 cm-2 s-1 (E > 1 MeV) [Matijasevic, JNM 377 (2008) 147]. The neutron exposures expressed in units of displacements per atom correspond to 0.6 and 1.5 dpa. A wavelength of 0.58 nm and three detector-sample distances of 1, 4 and 16 m were used in the SANS experiments carried out at the SANS-2 facility of GKSS Geesthacht (Germany). The samples were placed in a saturation magnetic field in order to separate magnetic and nuclear contributions. The scattering curves obtained for the unirradiated conditions of the four Fe-Cr alloys were taken as reference.