2, Sandia National Laboratories, Albuquerque, New Mexico, United States
Small-angle neutron scattering is a powerful technique for measuring bulk averaged nanometer length scale structures in a variety of materials nondestructively. It provides complementary information to direct-geometry small-volume or surface techniques like electron microscopy and atom probe tomography. This technique is well-suited for use in studying the properties of alloys due to the widely varying contrasts of different transition metal isotopes when viewed with neutrons, the sensitivity of neutrons to magnetic structure, and the high penetrating power of neutrons in many materials regardless of atomic number. These properties, together with the high flux available at modern neutron scattering user facilities and the existing infrastructure for working with radioactive materials, make SANS a uniquely powerful technique for studying reactor structural alloys.
In this work, we describe how SANS is used to characterize the growth of irradiation induced precipitates in Fe-Cr-Al model alloys ranging in composition from 10-18 wt.% Cr and 3-5 wt.% Al that have been irradiated in the Oak Ridge National Laboratory High Flux Isotope Reactor at nominal damage doses up to 13.8 dpa as a function of dose and to probe the in-situ dissolution of the radiation damage precipitates in a single alloy as a function of temperature and time. We also describe the procedures used to perform measurements using on highly radioactive samples shielded to minimize personnel radiation dose and the risk of contamination.