2016 | ANNUAL REPORT 73 Distributed Partnership at a Glance NSUF and Partners Facilities and Capabilities Center for Advanced Energy Studies Microscopy and Characterization Suite Collaborators Argonne National Laboratory Yiren Chen (co-principal investigator), University of Florida YongYang (principal investigator), Zhangbo Li (collaborator) Atom ProbeTomography characterization really provides an unprecedented insight into the chemical evolution of materials under irradiation. —YongYang,Associate Professor, Nuclear Engineering Program, University of Florida Accomplishments Microstructural evolutions including spinodal decomposition (SD) (Figure 1) and G-phase precipitation were quantified using the atom probe tomography for the ferrite phase in a duplex structure cast stainless steel irradiated to 5, 10, 20, and 40 dpa, respectively.The SD wavelength was calculated using the radial distribution function (RDF) analysis and the amplitude was obtained from Cr-frequency distribution. Both the SD wavelength and amplitude increases follow a logarithmic curve and begin to saturate after 20 dpa (Figure 2). For the G-phase precipitates, a decrease in number density and an increase in mean size were observed with the increase of neutron irradiation dose from 5 to 40 dpa (Figure 3). Overall, this project is the first reported study on the ferrite phase in a duplex stainless steel ever irradiated to such a high neutron irradiation dose and it shows that the microstructural changes may saturate at a much higher dose than normally expected: 5 dpa at a LWR relevant condition. Future Activities The project is now completed.