Phase Stability in Extreme Environments II: Irradiation Damage on Phase Changes
Sponsored by: TMS Structural Materials Division, TMS: Corrosion and Environmental Effects Committee, TMS: Alloy Phases Committee, TMS: Nuclear Materials Committee
Program Organizers: David Frazer, Idaho National Laboratory; Andrew Hoffman, Catalyst Science Solutions; Kinga Unocic, Oak Ridge National Laboratory; Janelle Wharry, Purdue University; Kaila Bertsch, Lawrence Livermore National Laboratory; Raul Rebak, GE Global Research; Tianyi Chen, Oregon State University; Marie Romedenne, Oak Ridge National Laboratory
Wednesday 8:30 AM
March 6, 2024
Room: Bayhill 18
Location: Hyatt
Session Chair: Andrew Hoffman, General Electric
8:30 AM Invited
Exploring and Quantifying Degradation Mechanisms in Irradiated Structural Materials: Steven Zinkle1; Qinyun Chen1; Zehui Qi1; Ryan Thier1; Emily R. Proehl1; Samara Levine2; Yajie Zhao3; Yan-Ru Lin3; 1University of Tennessee; 2Tokamak Energy; 3Oak Ridge National Laboratory
Structural materials for next-generation fission and proposed fusion reactors need to satisfactorily operate under extreme particle irradiation doses along with high temperatures and stresses. Improved understanding of degradation mechanisms in these coupled extreme environments is needed to provide the foundation for design and fabrication of the next generation of high-performance phase-stable structural materials. In particular, different types of precipitates exhibit widely different phase stability under particle irradiation. This presentation will summarize recent results on the stability of carbide, nitride, oxide, gamma prime, and alpha-prime (Cr-enriched) precipitates in ferritic/martensitic steels, Fe-Cr alloys, nickel alloys, and austenitic steels following particle irradiation at a wide range of temperatures, knock-on energies, doses and dose rates. The competing mechanisms of ballistic dissolution and precipitate renucleation and growth assisted by radiation enhanced diffusion are crucial for determining overall precipitate stability. Potential mechanisms responsible for high temperature helium embrittlement of grain boundaries will also be discussed.
9:00 AM
Improving Radiation Resistance in Metal Alloys via the Use of Multiple Synergistic Solutes: Soumyajit Jana1; Pascal Bellon1; Robert Averback1; 1University of Illinois Urbana Champaign
Strong binding between point defects like vacancies and matrix-specific solutes can reduce defect diffusion, resulting in higher recombination rates and thus higher radiation resistance. These solutes, however, are very mobile and thus quickly dragged to point defect sinks, where they segregate. To prevent this, we consider the addition of a second solute ‘C’ to a vacancy trapping A-1 at. % B alloy. We show using transport theory calculations and KMC simulations that adding 1 at. % of a non-vacancy trapping solute ‘C’ can extend the resistance against drag by more than an order of magnitude in dose if ‘C’ is a slow diffuser in ‘A’ and binds to ‘B’. Motivated by these simulations, Cu-Sn-Nb dilute thin films are characterized by electron microscopy and atom probe tomography before and after 2 MeV Ti ion irradiation to probe the effectiveness of Nb in suppressing Sn solute drag under irradiation.
9:20 AM
Microstructural Evolution and Hardness Changes in Ion Irradiated Ni-based Superalloys: Qinyun Chen1; Siwei Chen1; Yan-Ru Lin2; Yajie Zhao2; Ryan Thier1; Steven Zinkle1; 1University of Tennessee; 2Oak Ridge National Laboratory
Nickel-based superalloys are promising structural material candidates for molten salt reactors and other advanced nuclear reactors. However, traditional Ni alloys exhibit severe mechanical degradation after neutron irradiation, and the gamma-prime precipitates in these alloys are susceptible to dissolution during irradiation. Several high-performance commercial Ni-base superalloys (solid solution-strengthened Haynes 244 and Haynes 214, precipitation-strengthened Haynes 244) were irradiated with 8 MeV Ni ions to midrange doses of 1 and 10 dpa at 600 ℃ and 750 ℃. During 750℃ irradiation to 10 dpa, the Ni2(Mo,Cr) precipitates in aged Haynes 244 exhibited remarkable stability. However, such precipitates were partially dissolved in the 600 ℃ samples. The post-irradiation nanoindentation analysis revealed significant hardening for both solution-annealed Haynes 214 and Haynes 244. TEM analysis confirmed Ni2(Mo,Cr) precipitates in irradiated regions. In addition to gamma-prime precipitates, an unidentified radiation-induced/modified phase was observed in Haynes 214. Detailed chemical composition from STEM-EDX and APT will be summarized.
9:40 AM
Behavior of Tritium Breeder Ceramics under Ion Irradiation: Weilin Jiang1; Libor Kovarik1; Mark Wirth1; Zihua Zhu1; Yeong-Shyung Chou1; Satoru Kikuchi2; Kazuya Sasaki2; Zhihan Hu3; Lin Shao3; Andrew Casella1; David Senor1; 1Pacific Northwest National Laboratory; 2Hirosaki University; 3Texas A&M University
The performance of tritium breeder materials is critical to fusion power economy. As the facility for fusion neutron irradiation is currently unavailable, this work employs energetic ion beams to emulate fusion environments for study of lithium ceramic materials with low to high Li/O ratios. Compared to Li-poor ceramics, Li-rich ones have an intrinsic property for both increasing tritium production rates and providing fast tritium diffusion paths, and are thus outstanding candidates for fusion blanket applications. A dramatic change in the microstructure has been observed, including second-phase precipitation, platelet formation and full amorphization. Significant Li loss also occurs. Our data suggest that surface coating with nickel can effectively prevent Li loss while allowing for a rapid deuterium (and tritium by inference) release. This presentation will provide a behavior comparison of lithium ceramic pellets under ion irradiation at elevated temperatures, including microstructural and compositional evolutions as a function of dose and temperature.
10:00 AM Break
10:20 AM Invited
Investigating the Coupling between Short-range Order and Radiation Damage in Multi-component Alloys: Miaomiao Jin1; Hyeonwoo Kim2; Yang Yang1; Sangtae Kim2; 1Pennsylvania State University; 2Hanyang University
Chemical short-range order (CSRO), a form of nanoscale special atom arrangement, has been found to significantly alter material properties such as dislocation motion and defect dynamics in various multi-component alloys. The stability of CSRO can in turn be affected by defects. Under radiation conditions, the coupling effect between CSRO and radiation damage may strongly affect the long-term radiation performance. In this work, we use Fe-Ni-Cr and Ni-Co-Cr alloys to demonstrate and discuss the co-evolution of defects and CSRO, based on extensive molecular dynamics simulations. We found that the degree of CSRO can achieve steady state regardless of the initial condition, i.e, CSRO is dynamically evolving to stable level in a decreasing or increasing manner upon continuous irradiation. Furthermore, we consider how grain boundary as defect sinks, would affect CSRO stability. These new understandings assist in clarifying the issue of incorporating the effect of CSRO in investigating radiation-driven microstructural evolution.
10:50 AM
Radiation-induced Partial Disordering of Heusler Phase in Intermetallic Dispersion Strengthened Ferritic Superalloys: Kan Ma1; Robert Abernethy2; Sophia von Tiedemann1; Nianhua Peng3; Graeme Greaves4; Anamul H Mir4; Christina Hofer5; Thomas Pfeifer66; Kai Sun7; Lumin Wang7; Pedro Ferreirós8; Christopher Hardie2; Alexander Knowles1; 1University of Birmingham; 2UK Atomic Energy Authority; 3Surrey Ion Beam Centre, Surrey University; 4MIAMI Facility, University of Huddersfield; 5University of Oxford; 6University of Virginia; 7University of Michigan; 8VTT Technical Research Centre of Finland Ltd
Advanced steels strengthened by intermetallics have been in rapid development in the last decade. Mirroring to Ni superalloys, a new class of ferritic steels, ferritic “bcc-superalloys”, have been designed comprising a disordered body-centred cubic (bcc) matrix reinforced by ordered-bcc intermetallics, such as B2-NiAl and L21-Ni2AlTi. The A2-B2/L21 microstructure meets strategies to create radiation-tolerant materials: utilising a radiation-resistant body-centred cubic (bcc) matrix and a large interface area as sinks for point defects. However, their irradiation behaviour is still rarely known. This work addresses novel ferritic superalloys FeNiAlTi, comprising nanoscale L21 precipitates with various sink strengths. Ex-situ irradiation with Fe+ ions at 300°C was performed followed by nano-indentations to study the radiation-induced hardening. Transmission electron microscopy and atom probe tomography were conducted to study the irradiated microstructure. A partial disordering of the L21 phase into a B2 phase was revealed. In-situ experiments showed that the disordering depends on the temperature and dose.
11:10 AM
Effect of Damage, Temperature, and Helium on Irradiated Nanoprecipitation in Advanced Ferritic/Martensitic (F/M) Fe9Cr Steel: T.M. Kelsy Green1; Kevin Field1; Ying Yang2; Tim Graening2; Weicheng Zhong2; Lizhen Tan2; 1University of Michigan-Ann Arbor; 2Oak Ridge National Laboratory
Nanoprecipitation is an important microstructural feature to prevent helium-driven materials degradation in steels for nuclear fission and fusion reactors. In this work, the behavior of TiC-MX nanoprecipitates in a novel Fe-9 wt% Cr reduced-activation FM (RAFM) steel alloy were systematically studied under various ion damage conditions with parameters ranging from 300-600°C, 1×10-4 - 7×10-4 dpa/s, 1-100 dpa, and 0-25 appm He/dpa. Results showed that helium affected the evolution of precipitates via the suppression of irradiation-enhanced Ostwald ripening but did not affect the overall high-dose (>15 dpa) dissolution behavior. The TiC precipitates sequestered helium in the form of nanobubbles at their interfaces near the peak swelling temperature. The importance of this phenomena to elongating the incubation period of swelling in RAFM steels, the applicability of previous theories on precipitate stability under irradiation, and the growth of cavities at the precipitate-matrix interface will be discussed.
11:30 AM
Stability of Hydrogen/Helium-filled Nanocavities in Structural Alloys after Low Temperature Irradiation with Simultaneous High Energy Protons and Spallation Neutron: Timothy Lach1; Maxim Gussev1; Kinga Unocic1; Amy Godfrey1; Weicheng Zhong1; David McClintock1; 1Oak Ridge National Laboratory
Simultaneous high-energy proton and spallation neutron irradiation induce behaviors in structural materials that are unique from fission neutrons or ion beams. In addition to recoil damage at moderate temperatures (~100°C), transmutation reactions produce large levels of helium and hydrogen. The target module (TM) and proton beam window (PBW) at the Spallation Neutron Source (SNS) at ORNL are irradiated in these unique environments during operation. To extend SNS component lifetimes, accurate understanding of the radiation-induced changes to the microstructure and properties is essential, with particular focus here on the transmutation gas/matrix interactions. TM 316L stainless steel and alloy 718 PBW materials were characterized using analytical electron microscopy, differential scanning calorimetry, and thermal desorption spectrometry to investigate the interaction of transmutation gases and stored energy in the matrix after irradiation and annealing. The in-operando stabilization of nanoscale gas-filled cavities and its effects on radiation-enhanced ductility and strain localization will be discussed.