Briggs, Samuel A.. Dose rate effects on irradiation-enhanced precipitation in FeCrAl alloys

Principal Investigator
First Name:
Samuel A.
Last Name:
Oregon State University
Assistant Professor
Team Members:
Name: Institution: Expertise: Status:
Kevin Field Oak Ridge National Laboratory Nuclear Materials, Radiation Effects, materials, Microstructural Analysis, Irradiated Concrete Faculty
Experiment Details:
Experiment Title:
Dose rate effects on irradiation-enhanced precipitation in FeCrAl alloys
Describe the work that you are proposing in detail. Please include as many specifics as possible (e.g., dose, dose rate, ion energy, types of ions, beam line x-ray energy, irradiation temperature, analysis temperature, atmosphere, etc.):
The proposed work seeks to characterize the precipitate microstructure of a low-dose self-ion irradiated vs. unirradiated Fe-18Cr-3Al model alloy following a series of post-irradiation heat treatments using atom probe tomography. This sample has been previously irradiated at the Michigan Ion Beam Laboratory (MIBL) with 5 MeV Fe2+ ions to a nominal damage dose of 0.5 dpa at 400 °C and 10-6 dpa/s. The proposed work will be carried out at the CAES MaCS facility following initial sample preparation and annealing heat treatments at Oregon State University. Samples for APT analysis will be prepared from both the irradiation and unirradiated regions of this sample following 10, 100, and 1,000 hr anneals at 400 °C in addition to the as-received condition. Final tip sharpening will be carried out on the FIB at the CAES MaCS facility just prior to analysis in the LEAP. Data will be reconstructed and visualized using the IVAS software with analysis be carried out in a commensurate fashion to previous investigations of α’ precipitation in this system.
Technical Abstract
The objective of this project is to investigate the role of irradiation-induced defect clusters and pre-clustering on the formation of alpha’ precipitates in FeCrAl alloys and other high-Cr ferritic alloys. First-order dependencies of alpha’ phase precipitation in FeCrAl alloys have been investigated in a number of previous studies. However, higher-order factors affection this phase change are not well understood at this time. Further information on this subject is expected to support licensing of this class of alloys for LWR systems and ultimately impact development of a broader class of high-Cr ferrous-based alloys for nuclear applications. To this end, the proposed work seeks to characterize the precipitate structure of a low-dose rate, ion irradiated specimen following a series of heat treatments. The sample is a Fe-18Cr-3Al model alloy that has been ion irradiated at the Michigan Ion Beam Laboratory (MIBL) with 5 MeV Fe2+ ions to a nominal damage dose of 0.5 dpa at 400 °C at a low dose rate of approximately 10-6 dpa/s. APT specimens will be prepared from the sample using FIB at the Oregon State University Electron Microscopy Facility (EMF) from the irradiated and unirradiated region in the as-received condition as well as after a series of heat treatments at 400 °C for 10, 100, and 1000 hrs. Final tip sharpening will be performed using the FIB at the Microscopy and Characterization Suite (MaCS) at the Center for Advanced Energy Studies (CAES) just prior to data collection on the LEAP 4000HR. Data analysis and reconstruction will be performed using the IVAS software using established techniques for quantifying alpha’ precipitates in this class of alloys. The resulting reconstructions should allow for a definitive determination regarding whether irradiation-induced defect clusters serve as preferential nucleation sites to further promote phase separation alongside irradiation-enhanced diffusion effects. This project is projected to take approximately 6 months to complete. Sample preparation and heat treatments can begin immediately following the notification of award, though heat treatments will take some time. Sample preparation and data collection is expected to take no more than 3 months. Data analysis and reporting will take approximately 3 months from the date of final data collection.