Neutron & X-ray scattering studies of Fe-based materials

Small-angle scattering technique uses the scattering of radiation (e.g. neutrons or X-rays) at small angles to probe large-scale structures withjn matter, up to thousands of Angstroms. It is proven a valuable tool for investigating precipitation in reactor pressure vessel (RPV) steels and Fe-Ga alloys offering a statistical average over a large volume of samples. RPV steels, being of crucial importance for the longevity of a nuclear reactor, have been a long-standing theme for investigations. The main topics of such investigations are the effects of irradiation upon the steels and the consequent implications on their macroscopic properties. In this thesis, small-angle neutron scattering is employed to investigate irradiation induced precipitates in low- and high-Cu RPV steels. After irradiations with protons to low damage levels, precipitates could be clearly observed only in the high-Cu RPV steels. Stable preirradiation formed features are attributed to precipitation of carbides. Fe-Ga binary alloys have attracted much attention due to the still unexplained high magnetostriction they exhibit. To investigate the composition of nanoheterogeneities in a Fe-Ga sample, anomalous small-angle X-ray scattering is employed exploiting the energy dependence of the Fe and Ga atoms near their respective absorption edges. The nanoprecipitates are found to have a Fe3Ga stoichiometry