Mechanical Behavior of Nuclear Reactor Materials and Components III: Early Career
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
Wednesday 8:30 AM
March 22, 2023
Room: 28D
Location: SDCC
Session Chair: Osman Anderoglu, University of New Mexico; Djamel Kauomi, North Carolina State University
8:30 AM Invited
Understanding the Mechanisms Involved in Chlorine-Induced Stress Corrosion Cracking of Stainless Steel 304 under a Simulated Marine Environment: Ryan Schoell1; Li Xi1; Yuchen Zhao1; Xin Wu2; Yu Hong2; Zhenzhen Yu2; Peter Kenesei3; Jonathan Almer3; Zeev Shayer2; Khalid Hattar4; Djamel Kaoumi1; 1North Carolina State University; 2Colorado School of Mines; 3Argonne National Laboratory; 4Sandia National Laboratories
Chlorine Induced Stress Corrosion Cracking (CISCC) is a concern for dry storage canisters around the coastal United States. A mechanistic understanding of the process could help predict crack growth rates. In situ synchrotron x-ray tomography and diffraction were performed on different heats of 304SS (representing spent fuel canister material) during chlorine induced stress corrosion cracking in a simulated marine environment. The role of martensite was probed using x-ray diffraction data while the role of crack branching was studied using the x-ray tomography data. Additionally, the role of stress intensity was probed using both x-ray tomography and stress intensity analysis. Post experimental electron microscopy was used to determine the chemical and structural compounds formed around the crack. A mechanism based on the experimental evidence of atmospheric chlorine induced stress corrosion cracking was then proposed. SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525.
8:55 AM Invited
Probing Neutron Irradiation Simulated Damage with Ion Irradiation and In-situ Mechanical Testing: Eric Lang1; Nathan Madden2; Dustin Ellis2; Bethany Matthews3; Patrick Price2; Nan Li4; Paul Kotula2; Rajan Tandon2; Arun Devaraj3; Khalid Hattar2; 1University of New Mexico; 2Sandia National Laboratories; 3Pacific Northwest National Laboratory; 4Los Alamos National Laboratory
Ion bombardment is commonly used as a surrogate for neutron damage or to mimic He production in materials. In this work, we use in-situ TEM compression and tension experiments to investigate the impact of ion irradiation on the nano-mechanical properties of 316 stainless steel and Er hydrides. We compare the effects of dual beam Au and He irradiation with neutron irradiation on the nanomechanical compressive properties of 316 stainless, and the effects of He implantation to natural He aging in a metal hydride to correlate the ion irradiation damage and implantation with the mechanical properties changes. This study compares the impact of ion irradiation to the nano-mechanical properties of radioactive materials. SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525.
9:20 AM Invited
Deformation Mechanisms in Gen-IV Candidate Structural Steels Studied by In-situ Micromechanical Testing Techniques: Tanvi Ajantiwalay1; Cheng-Han Li1; Tingkun Liu1; Christopher San Marchi2; Assel Aitkaliyeva3; Arun Devaraj1; 1Pacific Northwest National Laboratory; 2Sandia National Laboratories; 3University of Florida
Austenitic and ferritic/martensitic steels are extensively researched for their use as structural materials in advanced Gen-IV reactors. Constant exposure to the extreme reactor environments such as constant stresses and temperatures, however, can degrade their mechanical properties. The main goal of this study is to understand the deformation mechanisms of 316 and HT-9 steels using in-situ micromechanical techniques such as nanoindentation, micro-pillar compression and micro-tensile testing. The results show that for 316, a mechanical anisotropy exists between different crystal orientations and the deformation occurs via slip along the closely packed planes. The transmission electron microscopy of the deformed surfaces reveals the formation of nano-twins in the slipped region. HT-9, however, shows slipping along the lath boundaries and the failure mechanisms are largely dependent on their microstructural features. Such a specific deformation-based study of these steels will help create a baseline to further estimate their overall behavior in the actual reactor environments.
9:45 AM Break
10:05 AM Invited
Deformation Twinning Versus Slip in Ni-based Alloys, Containing Pt2Mo-structured, Ni2Cr-typed Precipitates: Hi Vo1; K Dang1; Fei Teng2; Matthew Schneider1; Stuart Maloy3; Julie Tucker4; Laurent Capolungo1; Peter Hosemann1; 1Los Alamos National Laboratory; 2Idaho National Laboratory; 3Pacific Northwest National Laboratory; 4Oregon State University
Nickel-based alloys are extensively used in a wide range of extreme environments because of their exceptional mechanical properties. The interactions between the dislocations and LRO precipitates, in these alloys, dictate the deformation modes and plastic response. While the majority of studies have focused on L12-structured precipitate-strengthened Ni-based alloys, less work has considered the Ni-based alloys containing Pt2Mo-structured, Ni2(Cr,Mo)-typed precipitates. In these alloys, Pt2Mo-structured precipitates enable room-temperature deformation twinning in addition to slip, which increases strain hardenability measured from bulk mechanical testing. In this work, molecular dynamics examined the possible types of dislocation and Pt2Mo-structured precipitate interactions at low temperature. Combined with in situ micromechanical testing, the role of resolved shear stresses on dislocation partials was shown to directly influence the activation of slip versus twinning. Additionally, using an energy-based approach, molecular dynamics results demonstrated a novel twin formation process, caused by the dislocation interaction with the Pt2Mo-structured precipitates.
10:30 AM Invited
Castable Nanostructured Alloy Steels and the Graded Transition to Tungsten for Fusion Reactors: Tim Graening1; Isthiaque Robin2; Ying Yang1; Weicheng Zhong1; Wei Tang1; T.M. Kelsy Green3; Kevin Field3; Yutai Kato; Yutai Katoh1; 1ORNL; 2The University of Tennessee; 3University of Michigan
Castable nanostructured alloy (CNA) steels were developed as improved reduced activation ferritic martensitic steels. Currently, a multi-ton-scale heat is being manufactured to demonstrate scale-up, initiate code qualification, and conduct in-depth radiation tolerance evaluations. Tensile properties up to 650 ºC and hardness measurements were conducted for qualification of the as-produced material. Relatedly, to be useful, the CNA steel needs to be joined to plasma-facing materials like tungsten required in divertors in fusion reactors. Here, a novel transitional multilayer structure joining CNA and tungsten was investigated. Each interlayer was selected based on computational thermodynamics and diffusion kinetics to prevent the formation of a brittle intermetallic phase region in the temperature range of 620~1150 ºC. Nano hardness measurements across the multilayered interfaces of SPS samples were performed and analyzed in comparison to nano hardness results of direct energy deposition additively manufactured gradients. The microstructure was investigated to explain the mechanical properties.
10:55 AM Invited
Data-driven Surrogate Constitutive Modeling of Mechanical Creep Behavior under Extreme Conditions: Andre Ruybalid1; Aaron Tallman2; Christopher Matthews1; Laurent Capolungo1; 1LANL; 2Florida International University
Nuclear reactor materials are expected to operate safely for decades under extreme environmental circumstances, governed by temperature and pressure cycles, and varying irradiation conditions. In particular, long-term mechanical creep is a prominent deteriorating factor. To extrapolate the measurable creep response into experimentally inaccessible regimes, mechanistic models provide a powerful tool that takes into account the microstructure changes of the material, but are computationally costly and therefore lack direct applicability at the engineering scale. Surrogate constitutive modeling has the potential to bridge the gap between the micro-mechanical models and the engineering scale. In the presented work, a data-driven, constitutive, surrogate model is developed, validated on mechanistic simulations, and integrated within a finite element framework for HT9 and Gr.91 steel alloys. Its predictiveness is demonstrated on various realistic and experimental test-cases, while detailed sensitivity analysis allows for a thorough understanding of how creep in real-world structures is affected by the underlying microstructure.
11:20 AM Invited
Examining Microstructural Effects on Tensile Properties in Irradiated Inconel 718 using Miniaturized Tensile Specimens: Stephen Taller1; Caleb Massey1; 1Oak Ridge National Laboratory
Ni-based superalloys are a candidate alloy class for high temperature applications because of their intrinsic resistance to creep, adequate resistance to corrosion and high strength gained through secondary phases. High densities of secondary phases and radiation-induced defects enable the use of progressively smaller volumes to provide meaningful quantitative assessments of irradiated material properties. Three heat treatments of superalloy 718, two with distinct mixtures of δ ,γʹ and γʹʹ precipitates, and one completely homogenized, were irradiated in HFIR nominally to 2 DPA at either 300°C or 600°C to provide microstructures with orders of magnitude differences in dislocation obstacle spacing. Uniaxial tensile tests before and after irradiation were performed at room temperature and 300-600°C on subsize SS-J2 specimens, and at room temperature on a relatively new miniature SS-Tiny geometry cut from the SS-J2 specimen head. Comparing mechanical properties and microstructure yielded a guide for miniaturized irradiation specimens.