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2014 ANNUAL REPORT 91 Figure 3. LEAP tip reconstructions of top neutron- and bottom proton-irradiated HT9 to 3 dpa at 500C showing left to right Si Mn Ni P Cu Si-Mn-Ni-P-Cu cluster identification and Cr. Distributed Partnership at a Glance ATR NSUF and Partners Facilities and Capabilities Idaho National Laboratory AdvancedTest Reactor PIE facilities Center for Advanced Energy Studies Microscopy and Characterization Suite Collaborators Boise State University Janelle Wharry principal investigator Jatuporn Burns collaboratorYaqiao Wu collaborator Corey Dolph M.S. graduate student Matthew Swenson Ph.D. graduate student University of Idaho JoannaTaylor collaborator Figures 2 and 3.These clusters are comprised of approximately 3.57 at. Si 35 at. Mn 2.57 at. Ni and 0.251.0 at. P. Clusters in the proton- irradiated specimens contain a higher at. Si Mn Ni and P than do those in the neutron-irradiated specimens. Cu-rich clusters are found in both the proton- and neutron-irradiated HCM12A. Much like the Si-Mn-Ni-P clusters they are finer and more popu- lous in the neutron-irradiated specimen than in the proton-irradiated specimen. They are often but not always found coincident with the Si-Mn-Ni-P clusters Figure 2. Cu-rich clusters are not found in HT9 Figure 3 due to the low bulk concentration of Cu in HT9. Cr-rich clusters are found in both HCM12A and HT9 specimens but only in the alloys neutron-irradiated samples.These clusters are found at a very high number density on the order of 1024 m-3 . Their sizes are on the order of 0.5 nm.As such these clusters can only contain a few atoms each. LEAP tip reconstructions from irradiated HT9 Figure 3 show the differences in Cr clustering between neutron and proton irradiations.The mechanism for this Cr clustering is not yet understood. Work on this project was completed by Corey Dolph and Matthew Swenson graduate students at Boise State University.The project team wishes to acknowledge the assistance ofYaqiao Wu Jatuporn Burns and JoannaTaylor all of whom were instrumental in assisting with scheduling instrument training and LEAP analysis. Future Activities This project was completed in 2014. Future work will include additional irradiation experiments and computa- tional studies to further understand the mechanisms of nanoscale clustering in these alloys and their implications on mechanical behavior irradiation dose rate and particle type effects and to compare Cr clustering with radiation- induced segregation of Cr. Publications and Presentations 1. M.J. Swenson J.P.Wharry 2015 The strengthening mechanism transition in nanofeatured ferritic- martensitic alloys. The Minerals Metals Materials Society Annual Meet- ingOrlandoFL.March 2015. 2. M.J. Swenson J.P.Wharry. The comparison of microstructure and nanocluster evolution in proton and neutron irradi- ated Fe-9Cr oxide dispersion strengthened ODS steel to 3 dpa at 500C Submitted to Jour- nal of Nuclear Materials.