Nanostructured Materials in Extreme Environments: Nanostructured Metals in Irradiation Environments
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS Structural Materials Division, TMS: Nanomechanical Materials Behavior Committee, TMS: Advanced Characterization, Testing, and Simulation Committee, TMS: Mechanical Behavior of Materials Committee, TMS: Nuclear Materials Committee
Program Organizers: Haiming Wen, Missouri University of Science and Technology; Nan Li, Los Alamos National Laboratory; Youxing Chen, University of North Carolina Charlotte; Yue Fan, University of Michigan; Niaz Abdolrahim, University of Rochester; Khalid Hattar, University of Tennessee Knoxville; Ruslan Valiev, UFA State Aviation Technical University; Zhaoping Lu, University of Science and Technology Beijing

Monday 8:30 AM
March 20, 2023
Room: Aqua 303
Location: Hilton

Session Chair: Haiming Wen, Missouri University of Science and Technology


8:30 AM Introductory Comments

8:35 AM  Invited
Nanostructured Ferritic Alloys for Advanced Nuclear Reactors: Stuart Maloy1; David Hoelzer2; Eda Aydogan3; G.R. Odette4; 1Pacific Northwest National Laboratory; 2ORNL; 3METU; 4UCSB
    Much excitement arose in nuclear energy research communities around the globe with the discovery of nanostructured ferritic alloys (NFA) at the beginning of the 21st century. NFA’s evolved from oxide dispersion strengthened (ODS) alloys, which have been around for many decades, due to refinement in the microstructure consisting of an ultra-fine grain structure and high concentration of nano-size (~2-5 nm) oxide particles. Many studies have demonstrated that NFA’s possess remarkable high-temperature strength resulting in outstanding creep performance combined with very low swelling rates and less hardening during exposure to high-dose irradiations. This presentation will cover progress made in the Nuclear Technology Research and Development Program’s Advanced Fuels Campaign that emphasizes understanding fabrication methods for producing thin wall tubing, including studies dealing with recrystallization, texture and plastic deformation and the response of microstructure and mechanical properties of NFA exposed to neutron irradiation.

9:00 AM  Invited
Role of Electronic Energy Loss on Interface Stability of Nanostructured High-Entropy Alloys: Yanwen Zhang1; Chinthaka Silva2; Timothy Lach1; Matheus Tunes3; Philip Rack4; Stephen Donnelly5; William Weber4; 1Oak Ridge National Laboratory; 2Lawrence Livermore National Laboratory; 3Los Alamos National Laboratory; 4University of Tennessee; 5University of Huddersfield
    Some high-entropy alloys (HEAs) exhibit improved structural stability in harsh environments. Energetic ion irradiation is often used as a surrogate for neutron irradiation; however, the impact of electronic energy deposition and dissipation is often overlooked. In many chemically complex alloys, their decreased thermal conductivity and slow dissipation of radiation energy can have noticeable effects on displacement cascade evolution. Irradiation response of nanocrystalline Ni20Fe20Co20Cr20Cu20 and (NiFeCoCr)97Cu3 reveals that the overall grain growth results from both inelastic thermal spikes via electron-phonon coupling and elastic thermal spikes via collisions among atomic nuclei. The growth follows a power law dependence on the total deposited ion energy. The derived high value of the power-exponent is attributed to the sluggish diffusion and delayed defect evolution arising from the chemical complexity intrinsic to HEAs. This work calls attention to quantified fundamental understanding of radiation damage processes beyond that of simplified displacement events.

9:25 AM  Invited
Global Compositional Patterning and Self-organization in Irradiated Alloys: Gabriel Bouobda Moladje1; Sourav Das1; Amit Verma1; Robert Averback1; Pascal Bellon1; 1University of Illinois at Urbana-Champaign
    Past modeling and experiments have established that irradiation can induce the self-organization of phase-separating alloy systems into nanoscale compositional patterns (CP) owing to the competition between finite-range ballistic mixing and thermodynamically driven decomposition. We extend these results to self-organization reactions that include both grain interiors and grain boundaries (GBs). We introduce a phase-field model to investigate this coupled self-organization in model phase-separating A-B nanocrystalline alloys. GBs, described as arrays of dislocations, act as defect sinks where solute segregation and precipitation can take place owing to coupling between point defect and solute fluxes. Ballistic mixing, however, promotes homogenization of the composition field and thus dissolution of precipitates. This competition can result in CP at GBs and in the grain interiors. Steady-state phase diagrams predicted by the model determine the irradiation parameters required for the stabilization of these nanostructures. These predictions are tested on Al-base and Ni-base alloys subjected to ion irradiation.

9:50 AM  
Microstructural Evolution in Dilute Nanocrystalline Al Alloys During Ion-irradiation: Sourav Das1; Sung Eun Kim1; Pascal Bellon1; Robert Averback1; 1University of Illinois, Urbana-Champaign
    Nanocrystalline alloys have long been considered for nuclear applications owing to their high density of point defect sinks. Fluxes of point defects to grain boundaries, however, can lead to segregation, phase separation, and changes in corrosion and mechanical properties. Presently, little is known about phase stability in grain boundaries during irradiation and how it couples to the phase evolution in the grain interiors. In the present study, we report on phase evolution in dilute nano-crystalline microstructural Al-Sb and Al-Sc alloys during thermal annealing and ion-irradiation. Thermal annealing leads to precipitation at the grain boundaries and loss of alloy strength, while ion-irradiation leads to precipitate dissolution and strengthening. We interpret our results in terms of grain boundary strengthening by solute doping and the competition between dissolution and precipitation during irradiation. Al-Sb is particularly interesting since irradiation results in extensive segregation of Sb to the grain boundaries and enhanced strengthening.

10:10 AM Break

10:30 AM  Invited
Nanostructured Mechanical Martensites in Ni Alloys: Defects and Ordering Effects: Janelle Wharry1; Caleb Clement1; Chao Yang1; Daniel Hong2; Yu Lu3; Sheng Cheng3; Peter Anderson2; Donna Guillen4; David Gandy5; 1Purdue University; 2The Ohio State University; 3Boise State University; 4Idaho National Laboratory; 5Electric Power Research Institute
    This talk will explore the role of defects and chemical ordering on deformation-induced nanostructured martensite in Ni alloys. Diffusionless solid-state martensitic transformations are either stress-induced (reversible) or strain-induced (plastic). Chemical ordering and defects, such as those generated by irradiation, influence transformability and transformation mode in Ni alloys. This work combines nanoindentation experiments and molecular dynamics simulations toward understanding these influences. Work focuses on three Ni alloys, namely Alloy 625, Alloy 690, and Nitinol, which span varying degrees of chemical ordering, Ni/Fe ratios, and transformation mode (stress- versus strain-induced). Material synthesis will also be considered, with both PM-HIP and forged versions of Alloys 625 and 690. Defects are generated through ion and neutron irradiations. We will show that defects tend to suppress the extent of transformations across all alloys, by pinning the growth of nanoscale martensite needles. These results show promise for nanoscale tuning of mechanical behaviors of Ni alloys.

10:55 AM  Invited
Nanostructured BCC Materials for Applications in Extreme Environments: Osman El-Atwani1; Enrique Martinez2; Saryu Fensin1; Stuart Maloy3; Jonathan Gigax1; Hyosim Kim1; 1Los Alamos National Laboratory; 2Clemson University; 3Pacific Northwest National Laboratory
     Nanocrystalline materials were postulated as irradiation resistant materials due to the high density of grain boundaries (defect sinks). These materials can be synthesized via severe plastic deformation methods, material deposition or through mechanical alloying. Here we give an overview and new insights on the performance of different nanocrystalline BCC materials (W, Fe, HT-9 alloy, W- alloys, and W-based high entropy alloys) exposed to extreme irradiation and implantation conditions. We demonstrate the performance of these materials as a function of grain size and we compare some of them to their coarse grained counterparts. The dependence of the performance of nanocrystalline materials on the irradiation conditions is elucidated. Finally, assessment of mechanical properties of irradiated nanocrystalline materials and limitations of some characterization methodologies are presented.

11:20 AM  
Study of the Microstructural Evolution of Ultrafine-grained Austenitic Stainless Steel Irradiated by Neutrons by Atom Probe Tomography and Transmission Electron Microscopy: Frederic Habiyaremye1; Bertrand Radiguet1; Auriane Etienne1; Solène Rouland1; Xavier Sauvage1; Benoit Tanguy2; Joël Malaplate2; Christophe Domain3; Remy Bonzom3; Nariman Enikeev4; Marina Abramova5; 1Université et INSA de Rouen; 2Université Paris-Saclay; 3EDF Lab; 4Ufa State Aviation Technical University; 5Saint Petersburg State University
    Austenitic stainless steels (ASS) used as a structural material for pressurized water reactors' internal structures suffer from radiation-induced microstructural evolutions that may lead to component degradation and dimensional change. One approach to improving the irradiation resistance is to increase the number of point defect sinks, e.g., grain boundaries. Ultrafine-grained (UFG) ASS have been suggested for this purpose because they have a large density of grain boundaries. This study investigates microstructure under irradiation of a 316 UFG ASS processed by equal channel angular pressing at 400 and 500°C. Neutron irradiation was performed at CEA Saclay (France) in OSIRIS experimental reactor with neutron doses of 3.9 and 11.6 displacements per atom pa at 350°C. Microstructures are examined with atom probe tomography and transmission electron microscopy. The results are compared to the current 316L ASS reported in the literature to assess the potential application of this alloy for the Gen. II and IV nuclear reactors.

11:40 AM  
Irradiation Response of Nanostructured HEAs: Matthew Luebbe1; Haiming Wen1; Khalid Hattar2; 1Missouri University of Science and Technology; 2Sandia National Laboratory
    High entropy alloys (HEAs) are a new class of materials with great potential for nuclear applications owing to their unique radiation resistance and phase stability at room temperature and elevated temperatures. Due to Co long-term activation concerns, HEAs without Co must be developed, and nano structuring in the form of precipitates or reduced grain size can improve their already excellent radiation resistance properties. Two HEAs, a single-phase FeNiMnCr10 alloy and a precipitation hardened (FeNiMnCr10)88Ti4Al8 alloy, were fabricated and processed to produce nanograins and nanoprecipitates, respectively. Both alloys were ion irradiated at room temperature, 500 oC, and 700 oC, with evolution of radiation defects observed in-situ in a transmission electron microscope. At room temperature, only dislocations and dislocation loops were observed in both. At elevated temperatures, FeNiMnCr10 showed void formation, while (FeNiMnCr10)88Ti4Al8 exhibited irradiation-induced precipitation of additional intermetallic phases.

12:00 PM  
Review of Irradiation-induced Grain Growth in Nanocrystalline FCC Metals: Marie Thomas1; Eric Lang2; Trevor Clark2; Heather Salvador3; Khalid Hattar2; Suveen Mathaudhu3; 1Colorado School of Mines; 2Sandia National Laboratories; 3University of California, Riverside
     Nanocrystalline materials have been proposed as promising candidates for radiation environments due to their high grain boundary density. Indeed, grain boundaries are known as efficient sinks for irradiation-induced defects and studies have presented evidence of enhanced radiation damage tolerance in various systems. However, nanocrystalline materials are not thermodynamically stable and can be prone to irradiation-induced grain growth, reducing the amount of recombination sites and therefore their ability to tolerate damage. A clear understanding of the grain growth during service will accelerate implementation of nanocrystalline materials. In this presentation, we report summary knowledge of nanocrystalline FCC materials, including conflicting data on the applicability of nanocrystalline metals for radiation tolerance. The effect of irradiation and processing conditions on grain growth of FCC metals and the implications in terms of grain size control will be discussed. SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525.