SMALL-ANGLE NEUTRON-SCATTERING STUDY OF DEFECT CLUSTERS AND PRECIPITATES IN METALLIC ALLOYS

This article summarizes the principles of the small-angle neutron scattering technique, and presents some examples of application: characterization of defect clusters in neutron-irradiated ferritic steels, of copper-rich precipitates in electron-irradiated iron-based alloys and of the gamma' precipitates in quenched industrial superalloys. In the case of ferromagnetic alloys, one emphasizes the specific information brought by experiments performed under magnetic field. Our studies show that the defects responsible for radiation-induced embrittlement of pressurized-water nuclear reactors are nanosized clusters consisting mainly of copper precipitates or impurity-point defect clusters depending on whether the residual copper content of the steel is larger or smaller than 0.1%.