Phase Stability in Extreme Environments: Phase Stability in Nuclear Environments I
Sponsored by: TMS Structural Materials Division, TMS Materials Processing and Manufacturing Division, TMS: Corrosion and Environmental Effects Committee, TMS: Nuclear Materials Committee, TMS: Phase Transformations Committee
Program Organizers: 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
Monday 8:30 AM
March 20, 2023
Room: 28C
Location: SDCC
Session Chair: Pin Lu, Solvus Global; Djamel Kaoumi, North Carolina State University
8:30 AM Invited
Advanced Additively Manufactured Materials for Fission and Fusion Nuclear Applications: Pin Lu1; Tanner Kirk1; 1QuesTek Innovations LLC
The rapid development of and increasing focus on advanced fission and fusion-based nuclear energy have called for design of novel materials solutions to address the various materials challenges in the harsh service conditions. This presentation provides overview of two materials and processing development efforts aiming to overcome the materials degradation issues in extreme nuclear applications. The first effort is development of cold spray-enabled bimetallic structures consisting of refractory-based molten salt resistant coatings on an ASME code-certified substrate for molten salt reactors, while the second focuses on design and fabrication of a functionally graded joint between RAFM steel and tungsten-based plasma facing component in fusion reactors via multi-hopper direct energy deposition (DED). Immersion corrosion results and surface characterization of the cold sprayed refractory coatings in representative chloride molten salts will be presented. The computational approach of intelligently designing an optimized gradient path between RAFM steel and W will also be described.
9:00 AM
Dynamic Sink Strength Effects of Irradiation-induced Precipitates in Advanced Steels for Fusion Reactor Applications: T.M. Kelsy Green1; Tim Graening2; Weicheng Zhong2; Ying Yang2; Kevin Field1; 1University of Michigan Ann Arbor; 2Oak Ridge National Laboratory
Castable Nanostructured Alloy (CNA) steels developed at Oak Ridge National Laboratory (ORNL) represent an advancement of alloy design and manufacturing for structural materials in nuclear fusion reactors. The compositions of CNAs were designed to maintain a high density of stable precipitates over a large temperature and dose range, thereby acting as sinks for irradiation point defects. This work studied two model CNAs irradiated at elevated temperature in single-effect, high-fidelity ion irradiation experiments that varied temperature, dose, dose rate, and He co-implantation rate. The competing effects of radiation-enhanced diffusion and ballistic dissolution will be discussed to understand the evolution of radiation-induced and pre-existing precipitates. Precipitate stability, composition, and coherency as a function of irradiation conditions and the effects of these parameters on sink strength will be explored. Such a systematic study helps to provide new knowledge on how each parameter impacts the microstructure, which can help to explain ion irradiation-induced phenomena.
9:20 AM
Influence of Crystal Structure on Helium-induced Nano-tendril Formation in a Multiphase, Multicomponent Alloy: Amy Gandy1; Svenja Lohmann2; Gregor Hlawacek2; Rene Hübner2; Le Ma1; Russell Goodall1; 1University of Sheffield; 2Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf
Plasma-facing materials (PFMs) for magnetic fusion will experience a unique set of challenges, including plasma-surface interactions. In tungsten, helium ions diffuse through the surface resulting in the formation of nano-tendrils which may contaminate the fusion plasma. Multicomponent alloys are being considered as alternative PFMs though little is known about how they will behave in a plasma environment. Using a focused helium beam provided by a helium ion microscope (HIM), we irradiated equiatomic FeCoCrNiV, which comprises FCC and BCT crystal structures with similar compositions, enabling us to determine the influence of crystal structure on the formation of nano-tendrils. Irradiations were performed up to 500°C, and fluences between 6e17 and 1e20 He ions/cm2. Here, we present HIM images from the irradiated regions, and cross-sectional TEM/EDX images on selected samples. The data reveals a critical temperature for tendril formation dependent on crystal structure, helium bubbles, and helium-induced changes in composition.
9:40 AM Invited
Phase Transformations Driven by Non-Equilibrium Lattice Point Defects: Fe-based Alloys under Irradiation: Maylise Nastar1; Quentin Tencé1; Lisa Belkacemi1; Estelle Meslin1; Marie Loyer-Prost1; 1C.E.A
In alloys with lattice point defects (PDs) in excess, non-coherent phase transformations compete with the formation of PD clusters. For instance, a joint aggregation of self-interstitials and Ni atoms in Fe-Ni under irradiation, yields the precipitation of the unexpected austenite phase in undersaturated ferrite. The competition between PD and solute-PD clustering reactions depends on composition, phase density, temperature and PD supersaturation. To predict the dominant nucleation paths, we introduce the concept of constrained phase diagrams, including axes for non-equilibrium PD concentration. This non-equilibrium concentration results from concurent production, clustering and elimination reactions, thereby depends on the grown-in microstructure and irradiation conditions. By relying on a combined experimental and modeling atomic scale approach, we highlight the role of non-equilibrium PDs on the selection of phases in model alloys of steels and high entropy alloys, and simulate the interplay between second phase precipitation and the formation of dislocation loops and voids.
10:10 AM Break
10:30 AM
Examining the Contribution of Solute Nano-clustering in MA957 to Neutron Irradiation Induced Hardening and Embrittlement: Samara Levine1; Steven Zinkle1; Jonathan Poplawsky2; David Hoelzer2; Arunodaya Bhattacharya2; 1University of Tennessee; 2Oak Ridge National Laboratory
Radiation hardening and embrittlement of the first wall/blanket (FW/B) structure is expected to limit the lower operating temperature for fusion reactors. Despite oxide dispersion strengthened (ODS) steels being a leading candidate material for the FW/B, their low temperature hardening and embrittlement behavior remains an open question. Here, the relationship between microstructure and mechanical properties will be presented for ODS variant MA957 that was neutron irradiated in the High Flux Isotope Reactor at 287°C to 500°C (5.1 – 51.5 dpa). The development of Cr- and Ni-Ti-rich solute nano-clusters as a function of irradiation temperature and dose is characterized by atom probe tomography and compared to uniaxial tensile and Vicker’s hardness results through the dispersed barrier hardening model. Hardening and embrittlement is shown to persist over the entire temperature range with Cr-rich solute clusters providing the main contribution. The effect of solute additions on Cr solubility will be discussed.
10:50 AM
Reversible Disorder Transformation of Fe3O4 under Ion Irradiation Evidence by In-situ TEM: Angelica Lopez Morales1; Djamel Kaoumi1; 1North Carolina State University
This work reports the ion-irradiation effects in Fe3O4 irradiated in-situ in a TEM with 1 MeV Kr ions at 50 K up to a maximum dose of 38 dpa. Evidence of the Verwey transition during the cooling process in some of the magnetite grains is presented. In addition, extinction of first-order reflection was observed at doses as low as 1 dpa. Upon natural warm-up of the sample from 50 K to room temperature, total recovery of the Fe3O4 structure was evidenced. The formation of a metastable crystalline phase related to the disordering and displacement of the cation lattice during ion irradiation of Fe3O4 at the cryogenic temperature is proposed to explain the results. The Order-Disorder-Order and self-annealing processes involved will be discussed and compared with the literature.
11:10 AM
Exploring Temperature and Radiation Damage Induced Phase Transformations in Ta-V-Ti (W,Cr,Fe) Multicomponent Alloys: Amy Gandy1; Christina Hofer2; Paul Bagot2; Michael Moody2; Dhinisaben Patel1; Hamed Shahmir1; David Armstrong2; Junliang Liu2; Alexander Carruthers3; Ed Pickering3; Russell Goodall1; Shavkat Akhmadaliev4; 1University of Sheffield; 2University of Oxford; 3University of Manchester; 4Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf
Materials for fusion will operate in the most extreme environment on Earth. Specifically, the plasma-facing materials will experience levels of neutron irradiation orders of magnitude greater than in current fission reactors and fluctuating temperatures up to 1300 °C. Some multicomponent alloys have been reported to offer excellent high temperature phase stability and radiation damage resistance but will undergo neutron-induced transmutations becoming intermediate/high-level radioactive waste. To address this issue, we have developed reduced-activation multicomponent alloys. In this contribution, we report on the high temperature thermal stability and low temperature-induced phase transformations of these alloys, as determined by XRD, SEM and TEM. Selected samples were implanted at 500 °C with 2 MeV Ti ions and characterised using atom probe tomography to explore the impact of secondary phase formation on radiation damage resistance. In this contribution, APT results will also be presented and discussed in terms of defect formation and evolution.