Mechanical Behavior and Degradation of Advanced Nuclear Fuel and Structural Materials: Novel Nuclear Materials & Characterization II
Sponsored by: TMS Structural Materials Division, TMS: Mechanical Behavior of Materials Committee, TMS: Nuclear Materials Committee
Program Organizers: Dong Liu, University of Oxford; Peng Xu, Idaho National Laboratory; Simon Middleburgh, Bangor University; Christian Deck, General Atomics; Erofili Kardoulaki, Los Alamos National Laboratory; Robert Ritchie, University of California, Berkeley

Wednesday 2:00 PM
March 2, 2022
Room: 204A
Location: Anaheim Convention Center

Session Chair: Joshua White, LANL; Robert Ritchie, Lawrence Berkeley National Laboratory

2:00 PM
Helium Implantation Responses of Co-deposited Copper-tungsten Nanocomposites: Kelvin Xie¹; Digvijay Yadav¹; Michael Demkowicz¹; ¹Texas A&M University
    In this study, we investigate microstructure and helium (He) implantation responses in copper (Cu)-tungsten (W) nanocomposites fabricated by co-deposition at 400, 600, and 800 °C. Neutron reflectometry analysis (NRA) reveals that the He retention in the nanocomposites is ~25% lower than those in single-phase pure Cu and W. Despite the microstructural differences, the He retention is similar among all nanocomposites. We employed scanning electron microscopy (SEM), precession electron diffraction (PED), and high-magnification transmission electron microscopy (TEM) to observe and quantify the differences in the number density of grain boundaries and phase boundaries of all three nanocomposites. The microstructural feature is then correlated with the He bubble size and density. Our observations suggest that nano-grain boundaries and phase boundaries may play a similar role in He retention in the co-deposited Cu-W nanocomposites.

2:20 PM
A Case Study on Radiation-induced Degradation of High-entropy Alloys: Matheus Araujo Tunes¹; Osman El-Atwani¹; Stuart Maloy¹; ¹Los Alamos National Laboratory
    Significant progress has been made over the past years to understand radiation effects in novel high-entropy alloys (HEAs), that are now considered candidate materials for application in future nuclear reactors. Up-to-date the great majority of reports indicate that HEAs have superior radiation tolerance compared with conventional metallic alloys, and degradation mechanisms such as chemical instabilities, radiation-induced segregation and precipitation (RIS and RIP), and matrix phase decomposition at high-temperatures and large irradiation doses are largely unexplored fields of research. The (limited) literature on radiation-induced degradation (RID) of HEAs will be reviewed. A case study will focus in the RID of two distinct HEAs – the FeCrMnNi and CoCrCuFeNi – upon exposure to both high radiation doses (50-200 dpa) using light- and heavy-ions at high-temperatures. The use of in situ TEM methods is herein proposed as a methodology to fast-screening and identify potentially unstable HEAs for application in extreme environments.

2:40 PM
In Situ Microstructural Evolution in Face-centered Cubic Compositionally Complex Alloys under Dual-beam Heavy-ion Irradiation: Calvin Parkin¹; Michael Moorehead¹; Kumar Sridharan¹; Weiying Chen²; Meimei Li²; Adrien Couet¹; ¹University of Wisconsin-Madison; ²Argonne National Laboratory
    Compositionally complex alloys (CCAs) with a base matrix of four or more principal alloying elements may resist radiation degradation by void swelling due to unique energy and mass transport properties. Because the steady-state swelling rate of austenitic alloys is consistent after voids nucleate (1%/dpa), it is essential to study the effect of composition on void nucleation in a void-stabilizing He environment, which typically is determined by the microstructural evolution and level of vacancy supersaturation. Heavy-ion irradiation of two CCAs, Cr₁₈Fe₃₅Mn₁₅Ni₃₅ and Cr₁₈Fe₂₇Mn₂₇Ni₂₈, was performed at the IVEM-Tandem facility at ANL using 1 MeV Kr⁺⁺ and 12 keV He⁺ co-implantation to doses up to 10 dpa and 0.5% He/dpa at temperatures of 773K and 873K. 2-beam TEM allowed determination of the nucleation dose and characterization of the microstructural evolution. Results are compared to less compositionally complex single-phase FCC materials and discussed alongside single-beam high-temperature in situ and high-dpa ex situ irradiations.

3:00 PM
Hydrogen Accommodation in the TiZrNbHfTa High Entropy Alloy: Christopher Moore¹; Jack Wilson¹; Michael Rushton¹; Jack Astbury²; Simon Middleburgh¹; ¹Bangor University; ²Tokamak Energy Ltd
    The TiZrNbHfTa high entropy alloy (HEA), and its hydrides (TiZrNbHfTaH_0.4-1.6) have been modelled as special quasi-random structures, with density functional theory calculations to analyse key thermodynamic processes such as vacancy formation energies and hydrogen absorption. A calculated Schottky energy of 1.43 eV is lower than expected compared to other simple metallic systems. Investigations reveal the formation of split vacancy like defects which reduce vacancy formation energy barriers but may also allow for energetically favourable recombination after radiation damage events. Hydrogen interstitials preferentially adopt tetrahedral sites at both low and high hydrogen concentrations and were also found to promote vacancy formation within the HEA. Interstitials positioned around vacancies display a change in site preference to octahedral site occupation. Hydride decomposition was modelled and a release of hydrogen over a range of temperatures was predicted, in agreement with recent experimental results, contrary to that seen in simple metal hydride systems.

3:20 PM Break

3:40 PM
Effect of Residual Strain on Short Time Oxidation Behavior of Machined 304 Stainless Steel in High Temperature, High Pressure Deaerated Water: Rachel Turfitt¹; Bryan Webler¹; ¹Carnegie Mellon University
    The effect of residual strain was studied on machined 304 stainless steel for short times in high temperature, high pressure deaerated water. A hot loop/cold loop testing apparatus allowed precise short time hot water exposures. Specimens were exposed for 10, 50 or 100 hours after straining up to 60% engineering strain. Energy dispersive x-ray spectroscopy in a transmission electron microscope indicated a chromium rich spinel inner oxide, with metallic particles rich in iron and nickel embedded within. Single crystal nickel rich particles formed a discrete outer layer, with no evidence of an outer oxide. Parabolic oxide growth rates were observed at rates higher than reported in literature. No effect of residual strain was observed; potential residual strain effects were outweighed by the effects of machining. Machining also affected the composition of the layers formed from that reported in literature. Additional analysis of polished specimens with residual strain is underway.