Mechanical Behavior of Nuclear Reactor Materials and Components III: Poster Session
Sponsored by: TMS Structural Materials Division, TMS: Nuclear Materials Committee, TMS: Mechanical Behavior of Materials Committee
Program Organizers: Assel Aitkaliyeva, University of Florida; Clarissa Yablinsky, Los Alamos National Laboratory; Osman Anderoglu, University of New Mexico; Eda Aydogan, Middle East Technical University; Kayla Yano, Pacific Northwest National Laboratory; Caleb Massey, Oak Ridge National Laboratory; Djamel Kaoumi, North Carolina State University
Tuesday 5:30 PM
March 21, 2023
Room: Exhibit Hall G
Location: SDCC
Session Chair: Osman Anderoglu, University of New Mexico
O-30: Computer Vision-assisted Oxide Thickness Determination of 304 Stainless Steel in PWR Environments: Txai Sibley1; Rachel English1; Bryan Webler1; Elizabeth Holm1; 1Carnegie Mellon Unviversity
Environmentally assisted cracking (EAC) can be a critical factor in determining the operational safety and plant life extension of pressurized water reactors (PWRs). Oxidation kinetics, which play a key role in predicting EAC, can be determined by tracking the inner oxide thickness as a function of material exposure time. This requires the time intensive analysis and segmentation of numerous images. To expedite and standardize these measurements, automated image segmentation of the inner oxide is performed using the convolutional neural network (CNN) based U-Net architecture. Machine learning (ML) and traditional segmentation methods are compared. Removing human subjectivity in inner oxide determination and implementing high throughput segmentation and analysis enables insights into the oxidation kinetics.
O-8: Effects of Helium Implantation on Mechanical Properties Near the Tungsten-carbide Interfaces of Dispersion Strengthened Tungsten Alloy: Ashrakat Saefan1; Xing Wang1; Eric Lang2; Jean Paul Allain1; 1Pennsylvania State University; 2University of Illinois at Urbana-Champaign
Tungsten is a promising candidate for plasma-facing materials for fusion reactors but suffers from embrittlement due to irradiation and recrystallization. Adding second-phase dispersoids has been shown to improve the material thermomechanical properties. Here we used micromechanical testing to study the changes of mechanical properties of carbide dispersoid strengthened tungsten (DS-W) under helium (He) irradiation, which is a unique challenge for fusion materials. Micropillar compression found no failure at the carbide-tungsten interfaces regardless the 2 MeV He irradiation, indicating a tight bonding between dispersoids and matrix. Nano-indentation is applied to measure the local hardness near the interfaces. It is expected that the He irradiation would reduce the hardness at the interfaces, since the trapped He clusters and bubbles could either break the bonds at the interface or facilitate the dislocation nucleation. Microscopy analysis will be conducted to characterize the He distribution in DS-W to explain the observed changes in mechanical properties.
O-32: Fabrication and Characterization of Oxide Dispersion Strengthened Nickel Alloys for Advanced Molten Salt Reactor Components: Jaeyoon Bae1; Sumin Lee1; Juwook Lee1; Sanghoon Noh1; 1Pukyong National University
ODS alloy has been developed as most prospective structural material for next-generation nuclear systems because of its excellent high strength and irradiation resistance. Finely dispersed nano-oxide particles with a high number density in homogeneous grains can be very attractive to achieve superior mechanical properties at high temperatures, and these favorable microstructures can be significantly changed with various fabrication process parameters. A preliminary work has been performed to develop ODS Ni alloys as structural materials for the MSR components. Pre-mixed powders with Y2O3 were mechanically alloyed for various milling parameters using a planetary ball-mill apparatus. Uniaxial hot pressing was employed to consolidate the milled powders instantly. Microstructural observation indicated that the refinement and homogeneity of grain structures were considerably increased and these led excellent mechanical properties at room and elevated temperatures. Results suggest a promising applicability of Ni-Mo ODS alloy for the MSR components with higher reliability and economic competitiveness.
O-9: Hyper-localized Strengthening of Inconel 617 for Very High Temperature Reactor Applications: Noah Holtham1; Keivan Davami1; 1University of Alabama
In this work, Inconel 617 (IN617), a choice material for next-gen nuclear reactors, was treated with a surface hardening technique known as laser peening (LP) which has been shown to aid in the wear resistance of IN617. However, the work-hardening effects induced through LP tend to decay significantly under thermal loading. For this reason, IN617 samples were given an aging treatment at 650 °C following LP to encourage heterogeneous precipitation at LP-induced defect sites and consequently enhance thermal stability. The size, orientation, and distribution of these precipitates were investigated via scanning and transmission electron microscopy. Metal carbides as well as nanoscale γ’ particles were dispersed throughout the LP-affected zone. Multi-cycle nanoindentation fatigue tests showed that the modified LP treatment increased resistance to localized time-dependent deformation. Results strongly suggest that the modified LP approach described here shows great promise for enhancing the structural integrity of next-generation nuclear reactor components.
O-10: Mechanical Testing and Characterization of an Integrated Welding and Thermal Processing Method on Eurofer97: Daniel Codd1; Joseph McCrink2; Tim Lach3; Xiang (Frank) Chen3; 1University of San Diego/KVA Stainless; 2KVA Stainless; 3Oak Ridge National Laboratory
Reduced Activation Ferritic Martensitic (RAFM) steels, such as Eurofer97, have been identified as attractive candidates for fusion structural materials. Conventional weldments require post weld heat treatments (PWHT) to restore material performance, which can be associated with risks of distortion and cracking; alternative solid-state or adhesive joining methods can limit design flexibility. This study examines Eurofer97 GTAW weld specimens created using a novel integrated welding and thermal process, designed to improve the ductility and toughness of as-welded joints without subjecting the assembly to a separate energy intensive PWHT. Mechanical performance is compared for conventional welds and the integrated process, including cross-weld tensile, creep and guided weld bend ductility testing. Microstructural analysis, hardness mapping and advanced characterization methods are also employed to compare the resultant welded joints.
O-11: Migration of Intergranular He Gas Bubbles under a Thermal Gradient in Fe by Phase-field Modeling: Yixi Shen1; Peng Wen1; An Ta1; Simon Phillpot1; Douglas Spearot1; 1University of Florida
A phase-field model is employed to study thermal gradient driven kinetics of He gas bubble interactions with Fe grain boundaries. First, the contact angle of intergranular He gas bubbles with different ratios of grain boundary energy to He bubble surface energy are measured. In agreement with theory, the contact angle decreases with an increase in the energy ratio. Then, the dependence of He bubble velocity along the grain boundary on energy ratio, temperature gradient, and diffusivity of He is measured. It is found that He gas bubble migration velocity is slower in the grain boundaries than in the matrix and that the intergranular He bubble migration velocity increases as the energy ratio increases. Diffusivity of He in the grain boundary has negligible effect on the intergranular bubble migration. Finally, the trapping effect of a grain boundary on He bubbles is studied by applying temperature gradient perpendicular to the grain boundary.
Multi-scale Modeling of Defect Recombination in Collision Cascade with Molecular Dynamics and Binary Collision Monte Carlo: Md Riaz Kayser1; Benjamin Beeler2; Andrea Jokisaari1; 1Idaho National Laboratory; 2North Carolina State University
Current needs of the nuclear energy sector drive the demand for quantitative prediction of irradiation-driven microstructure evolution. The binary collision Monte Carlo (BCMC) method is a fast method to calculate defect production from irradiation damage, but the method overestimates the residual defect population due to the lack of defect recombination. A BCMC code developed at Idaho National Laboratory, Magpie, contains a novel defect recombination model designed to address this issue. We rigorously test this defect recombination model to determine its effect on residual defect populations in several metals after BCMC collision cascade modeling. We compare the residual defect populations obtained from molecular dynamics collision cascade simulations and Magpie BCMC-plus-recombination simulations for a variety of primary knock-on atom energies and examine the effect of the Magpie input variables (binding energy, displacement energy, recombination radius etc.) on the accuracy of the residual defect populations.
O-12: Welding Repair : Behavior Study of the Heat-Affected Zone Regarding the Risk of HAC: Alexandre Paget1; Abdelali Oudriss2; Vincent Robin3; Jefri Draup3; Sofiane Hendili3; Stéphane Cohendoz2; Josselin Delmas3; Xavier Feaugas2; Michael C. Smith4; 1EDF & The University of Manchester; 2La Rochelle University; 3EDF; 4The University of Manchester
Electric arc welding can be used as a cladding technic after preliminary scouring to repair pressurized equipment. Specifically, we are focusing on nickel-based alloys as a filler material applied to low-alloyed ferritic steel components of the nuclear steam supplier system. Nowadays, bead tempering methods allow to reduce or suppress additional heat treatment generally utilized for mitigating the material property changes of the heat affected zone. The research works presented here are motivated by the necessity to increase the understanding of these innovative methods prior to their deployment in the nuclear industry. These changes are mainly induced by microstructural modification inherent to the high temperatures, and possibly also by hydrogen embrittlement. These two factors are strongly coupled and both lead to a drop in the metal ductility. Hence, a study to characterize this drop quantitatively was carried out through various experimental analyses and numerical simulations.