He, Li. Examining microstructural evolution of HT9 under neutron and ion irradiations from 370 °C to 570 °C

Principal Investigator
First Name:
Last Name:
University of Wisconsin
Assistant Scientist
Team Members:
Name: Institution: Expertise: Status:
T.M. Kelsy Green University of Michigan FIB sample preparation, TEM characterization, data analysis Graduate Student
Ying Yang Oak Ridge National Laboratory Thermodynamics, kinetics, phase stability and phase transformation of metals and alloys Faculty
Todd Allen University of Michigan Corrosion, cladding, radiation damage, fuels, fission, TRISO Faculty
Experiment Details:
Experiment Title:
Examining microstructural evolution of HT9 under neutron and ion irradiations from 370 °C to 570 °C
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.):
We propose a transmission electron microscopy study of four neutron-irradiated HT9 samples and three ion-irradiated HT9 samples, totaling seven samples. This study will use an FEI Talos STEM and JEOL 2100F TEM at the Low Activation Materials Development and Analysis Facility (LAMDA), Oak Ridge National Laboratory for nine days. Six days of focused ion beam usage at LAMDA is also proposed to prepare TEM lift outs of the neutron-irradiated samples. TEM lift outs of ion-irradiated samples will be prepared at the researchers’ home institutes. The neutron and ion-irradiated HT9 samples are available to us through the High Fidelity Simulation of High Dose Neutron Irradiation project (University of Michigan). Table 1 and 2 in the proposal narrative list the proposed work and sample information.
Technical Abstract
Secondary phase precipitates (SPP) play an important role of controlling mechanical property of HT9, a 12Cr ferritic-martensitic steel aimed for applications in next-generation nuclear reactors. Understanding of irradiation-induced SPP could help predict HT9 performance and is pursued through experimental studies and theoretical modeling. However, there is inconsistency in literature about irradiation-induced SPP phases. Either one or a few SPPs of α’, G-phase, χ, M6C and Laves phases have been reported under similar nominal irradiation conditions, which may be attributed to difference in HT9 heats, thermal history, or irradiation conditions among different facilities. Experimental studies of spatial relationship between SPP and other microstructures are rare. On the other hand, the damage rate of neutron irradiation is orders of magnitude lower than that of ion irradiation. This damage rate difference is likely to shift the temperature range at which neutron and ion irradiation will form specific SPPs. Therefore, an experiment on the same HT9 heat irradiated by the same facilities is needed to achieve a clear understanding of temperature/damage rate effect to microstructure evolution and help link modeling and experiments. We propose to examine SPP in HT9 (AC0-3 from Los Alamos National Laboratory), including four samples irradiated at BOR-60 fast reactor in Russia at 376 °C, 415 °C, 426 °C, 524 °C, and three samples irradiated at the University of Michigan with Fe and He ions at 445 °C, 460 °C and 570 °C to 15 – 20 dpa. The neutron and ion irradiated samples chosen for this work were irradiated to similar levels of damage, but the ion irradiated materials were irradiated at higher temperatures, as based on Mansur’s temperature shift theory, to produce comparable microstructures between them. Transmission electron microscopy in conjunction with x-ray energy dispersive spectroscopy study will be employed to measure SPPs, cavities, dislocation loops, and irradiation-induced segregation at grain boundaries. Because the samples are already available, we expect to start the characterization experiments in September to October 2019, analyze the data, conduct the second experiment to complete the data acquisition in January to February 2020. The result will be a systematic data set of microstructures in HT9. It may help answer two fundamental questions about SPP: the temperature shift under irradiation, and whether there is spatial correlation between SPP and other microstructures.
Book / Journal Publications
Name Title
Li He Enhanced diffusion of Cr in 20Cr-25Ni type alloys under proton irradiation at 670 °C
Li He Structural Evolution of Oxidized Surface of Zirconium-Silicide under Ion Irradiation
Li He Microstructural evolution in Fe-20Cr-25Ni austenitic alloys under proton irradiation at 670 ºC
Li He Measurement of Irradiation-induced Swelling in Stainless Steels with a New Transmission Electron Microscopy Method
Li He Evolution of small defect clusters in ion-irradiated 3C-SiC: Combined cluster dynamics modeling and experimental study
Li He Size distribution of black spot defects and their contribution to swelling in irradiated SiC
Li He Radiation-induced mobility of small defect clusters in covalent materials
Li He Atomic Resolution Imaging of Black Spot Defects in Ion Irradiated Silicon Carbide
Li He High-Resolution Scanning Transmission Electron Microscopy Study of Black Spot Defects in Ion Irradiated Silicon Carbide
Conference Publications
Name Title
Li He Study of gamma irradiation effect on the corrosion of zirconium alloy with scanning precession electron diffraction
Li He The Effect of Photon Irradiation on the Corrosion of Zirconium Alloys
Li He Ion irradiation for nuclear materials research at University of Wisconsin-Madison
Li He Heat treatment Effects on Precipitation in Irradiated HT9 Steel
Li He Poster - Examining microstructural differences in irradiated HT9 correlated with differences in processing prior to irradiation
Li He Study of B2 and Laves Phase E volution in a Novel Ferr itic Steel under Ion Irradiation
Li He Microstructure Evolution in Dual Ion irradiated HT9 at 445 C and 460 C to 16.6 dpa
Li He Ion Irradiation Defects in Austenitic Alloy 709 and Ferritic-Martensitic Steel Grade 92 for Nuclear Applications