NSUF 18-1380: TEM and APT Characterization of Ion-Irradiated High-Entropy Alloys for Sodium-Cooled Fast Reactors
Technical Abstract
Methods to be Employed: To investigate the enhanced irradiation resistance of high-entropy alloys (HEAs), two alloy compositions have been selected (Cr0.66FeMnNi and NbTaTiV) and samples have been produced through arc melting. The proposed experiment uses samples of each alloy which have been ion irradiated at the PI’s home facility using both protons and Fe2+ ions to reproduce irradiation damage levels at several points in an SFR core lifetime (0.1, 0.5, 10, 100, 200 dpa) at two temperatures, 100 °C and 700 °C. As part of the RTE, the samples would be sent to the Materials and Characterization Suite at CAES. There, transmission electron microscopy (TEM) and atom-probe tomography (APT) samples will be prepared by the PI using the FEI QUANTA 3D FEG dual beam focused ion beam (FIB). TEM samples will then be examined using the FEI Technai TF-30-FEG STwin scanning transmission electron microscope to measure the size distribution and density of radiation-induced voids in the irradiated HEAs. To assess the presence and extent of chemical ordering following irradiation, APT samples will be examined using the Cameca 4000X HR local electrode atom probe (LEAP). The INL senior staff scientist collaborating with for work will assist the PI in data acquisition using the TEM and LEAP as well as interpreting data collected.
Potential Impact: Current alloy development for nuclear applications relies primarily on microstructure optimization (e.g. cold-working, nano-sized grains, etc.) to produce a higher density of sinks for radiation-induced defects to be eliminated at. In contrast, rather than increased sink densities, HEAs are expected to have lower defect mobility which would result in increased defect recombination locally with respect to the initial damage cascade. Understanding the mechanisms behind and the extent of the enhanced irradiation resistance of HEAs may be transformative in the way alloys are developed for nuclear applications.
Expected Period of Performance: A total of twelve (12) days of machine time is expected to be needed for this experiment, to be executed at the Materials and Characterization Suite in CAES. Below is breakdown of the anticipated machine time usage:
FEI QUANTA 3D FEG dual beam focused ion beam [FIB]: Six (6) days FEI Technai TF-30-FEG STwin scanning transmission electron microscope [TEM]: Three (3) days Cameca 4000X HR local electrode atom probe (LEAP) [APT]: Three (3) days
Anticipated Scientific Outcome: At the conclusion of this RTE, several TEM and APT samples will be produced and analyzed. TEM samples will be used to study the size distribution and number density of radiation-voids, as well as the formation of second-phase precipitates, and any macroscopic chemical repartitioning as a result of ion irradiation. Analysis of the APT from samples originating within the bulk of the HEA samples (i.e. away from any grain boundaries or second-phase precipitates) should yield insight into the presence and extent of any chemical ordering caused by ion irradiation. Together, these complimentary characterization techniques should elucidate the mechanisms behind the enhanced irradiation resistance of HEAs for nuclear applications, and more specifically, next-generation SFR cladding.
Additional Info
| Field | Value |
|---|---|
| Abstract | Technical Abstract Methods to be Employed: To investigate the enhanced irradiation resistance of high-entropy alloys (HEAs), two alloy compositions have been selected (Cr0.66FeMnNi and NbTaTiV) and samples have been produced through arc melting. The proposed experiment uses samples of each alloy which have been ion irradiated at the PI’s home facility using both protons and Fe2+ ions to reproduce irradiation damage levels at several points in an SFR core lifetime (0.1, 0.5, 10, 100, 200 dpa) at two temperatures, 100 °C and 700 °C. As part of the RTE, the samples would be sent to the Materials and Characterization Suite at CAES. There, transmission electron microscopy (TEM) and atom-probe tomography (APT) samples will be prepared by the PI using the FEI QUANTA 3D FEG dual beam focused ion beam (FIB). TEM samples will then be examined using the FEI Technai TF-30-FEG STwin scanning transmission electron microscope to measure the size distribution and density of radiation-induced voids in the irradiated HEAs. To assess the presence and extent of chemical ordering following irradiation, APT samples will be examined using the Cameca 4000X HR local electrode atom probe (LEAP). The INL senior staff scientist collaborating with for work will assist the PI in data acquisition using the TEM and LEAP as well as interpreting data collected. Potential Impact: Current alloy development for nuclear applications relies primarily on microstructure optimization (e.g. cold-working, nano-sized grains, etc.) to produce a higher density of sinks for radiation-induced defects to be eliminated at. In contrast, rather than increased sink densities, HEAs are expected to have lower defect mobility which would result in increased defect recombination locally with respect to the initial damage cascade. Understanding the mechanisms behind and the extent of the enhanced irradiation resistance of HEAs may be transformative in the way alloys are developed for nuclear applications. Expected Period of Performance: A total of twelve (12) days of machine time is expected to be needed for this experiment, to be executed at the Materials and Characterization Suite in CAES. Below is breakdown of the anticipated machine time usage: FEI QUANTA 3D FEG dual beam focused ion beam [FIB]: Six (6) days FEI Technai TF-30-FEG STwin scanning transmission electron microscope [TEM]: Three (3) days Cameca 4000X HR local electrode atom probe (LEAP) [APT]: Three (3) days Anticipated Scientific Outcome: At the conclusion of this RTE, several TEM and APT samples will be produced and analyzed. TEM samples will be used to study the size distribution and number density of radiation-voids, as well as the formation of second-phase precipitates, and any macroscopic chemical repartitioning as a result of ion irradiation. Analysis of the APT from samples originating within the bulk of the HEA samples (i.e. away from any grain boundaries or second-phase precipitates) should yield insight into the presence and extent of any chemical ordering caused by ion irradiation. Together, these complimentary characterization techniques should elucidate the mechanisms behind the enhanced irradiation resistance of HEAs for nuclear applications, and more specifically, next-generation SFR cladding. |
| Award Announced Date | 2018-05-17T10:52:57.393 |
| Awarded Institution | Center for Advanced Energy Studies |
| Facility | Microscopy and Characterization Suite |
| Facility Tech Lead | Alina Zackrone, Yaqiao Wu |
| Irradiation Facility | None |
| PI | Michael Moorehead |
| PI Email | [email protected] |
| Project Type | RTE |
| RTE Number | 1380 |