Radiation Effects in Metals and Ceramics: Irradiation of Zircinium, Tungsten and Copper Systems
Sponsored by: TMS Structural Materials Division, TMS: Nuclear Materials Committee
Program Organizers: Djamel Kaoumi, North Carolina State University; Thak Sang Byun, Oak Ridge National Laboratory; Dane Morgan, University of Wisconsin-Madison; Maria Okuniewski, Purdue University; Mahmood Mamivand; Geoffrey Beausoleil, Idaho National Laboratory; Philip Edmondson, The University Of Manchester; Khalid Hattar, University of Tennessee Knoxville; Aurelie Gentils, Université Paris-Saclay; Joel Ribis, Cea
Thursday 2:00 PM
February 27, 2020
Room: Theater A-7
Location: San Diego Convention Ctr
Session Chair: Khalid Hattar, Sandia National Laboratory; Chad Parish, Oak Ridge National Laboratory
2:00 PM
Atom Probe Examinations of Zircaloy Irradiated at Nominally 410C: Brian Cockeram1; Phil Edmondson2; 1Naval Nuclear Bettis Laboratory; 2Oak Ridge National Laboratory
Atom Probe Tomography (APT) examinations were performed on Zircaloy-2 and Zircaloy-4 following irradiation in the Advance Test Reactor (ATR) to neutron fluences of 2.9-3.1x1025 n/m2 (E>1 MeV). Irradiation at higher temperatures of nominally 410C resulted in about 10-80% less hardening than observed in the literature for irradiations at 260-326C. Clustering of Fe, Sn, and Cr solute at features consistent with the size and shape of <a> loops and line dislocations was observed. These features likely result in the high barrier strength for dislocation loops that correlated with the measured irradiation hardening. Nucleation of isolated clusters of Fe, Sn and Cr were also observed that produce an additional hardening barrier. Local variation in the type and distribution of clusters is observed that is correlated with differences in starting microstructure, precipitates, and local microchemistry,
2:20 PM
Study of Niobium Clustering in Zr-1.0%Nb Alloy Irradiated with Kr2+ Ions or Neutrons to ~9 dpa at 310 °C: Saheed Adisa1; Matthew Swenson1; Jing Hu2; 1University of Idaho; 2Argonne National Laboratory
The objective of this study is to evaluate the evolution of Nb-rich nanoclusters in a model Zr-1.0%Nb alloy following irradiation with Kr2+ ions or neutrons to a common dose and temperature. Zirconium-niobium alloys are commonly used as cladding materials for both light and heavy water reactors, and it has been shown that the irradiation induces clustering of Nb. But the mechanism of irradiation-induced Nb clustering in Zr is not fully understood. In this study, an RXA Zr-1.0%Nb alloy was irradiated with Kr2+ or neutrons to a common dose of ~9 dpa (each at 310 °C). The resulting nanoclusters are characterized using atom probe tomography, while the clustering mechanism is modeled using a simple simulation based on rate theory. Following each irradiation, similar Nb-rich cluster morphologies are observed, suggesting charged particles potentially emulate neutron irradiation reasonably well. However, modeling results indicate this emulation may not be accurate at higher doses.
2:40 PM
Analysis of Neutron Irradiation Induced Element Redistribution in Ceramic and Metallic Alloy TPBAR Components: Arun Devaraj1; Bethany Mathews1; Bruce Arey1; Elizabeth Kautz1; Danny Edwards1; Gary Sevigny1; David Senor1; 1Pacific Northwest National Laboratory
Tritium, a hydrogen isotope of significant importance, is generated by neutron irradiation of Tritium Producing Burnable Absorber Rods (TPBARs), which are specifically designed to produce and capture tritium. Inside each TPBAR there are lithium aluminate pellets, enriched in 6Li, that produces tritium upon neutron irradiation. Tritium is then absorbed by a Zircaloy-4 getter tube that surrounds the LiAlO2 pellet. These components are encapsulated inside a stainless steel cladding. Most traditional characterization methods including electron microscopy and diffraction studies using X-rays do not have sufficient sensitivity or spatial resolution needed for understanding how the distribution of various elements in each component gets redistributed under neutron irradiation, especially when it comes to light elements. Hence in this work we utilized Atom probe tomography correlated with electron microscopy to systematically analyze the solute distribution in both as-fabricated and neutron irradiated TPBAR components to obtain a comprehensive understanding of the microstructural evolution under irradiation.
3:00 PM
Dual Beam Irradiation of Tungsten Materials: Synergistic Effects and Comparison with Sequential and Single Beam Irradiation
: Osman El-Atwani1; William Cunningham2; Jason Trelewicz2; Wei-Ying Chen3; Meimei Li3; Stuart Maloy1; 1Los Alamos National Laboratory; 2Stony Brook University; 3Argonne National Laboratory
Performing detailed morphology analysis of tungsten surfaces under dual beam irradiation and investigating the synergistic effects of the different energetic beams are decisive steps to evaluate tungsten performance as a plasma material interface (PMI) in a reactor-similar environment. Here, we test fine grain tungsten under in-situ sequential beam irradiation (heavy ion irradiation followed by helium implantation or helium implantation followed by heavy ion irradiation) and compare the results to dual beam irradiation (simultaneous heavy ion irradiation and helium implantation). Loop type and damage profiles including loop density, loop area and overall damage are presented as a function of dose in every case. Void damage is also presented at the final dose. The results are also compared to single beam irradiation. The synergistic effects of the different energetic beams are elucidated and the importance of dual beam irradiation as a testing protocol for PMI materials is illustrated.
3:20 PM
Microstructure and Mechanical Properties of Neutron Irradiated Tungsten Fibers for Fusion Applications: Lauren Garrison1; Chad Parish1; Maxim Gussev1; John Echols1; Johann Riesch2; 1Oak Ridge National Laboratory; 2Max-Planck-Institut für Plasmaphysik
Tungsten fiber, tungsten matrix composites can improve the mechanical properties of tungsten in the divertors of fusion reactors. Such composites can improve the toughness as compared to standard sintered tungsten in the unirradiated condition, but their behavior after neutron irradiation is not known. Because the fibers are an integral part of the composite, individual fibers were neutron irradiated in the High Flux Isotope Reactor at temperatures between 400–1100°C to doses of ~0.2–0.7 dpa. Two types of fibers were irradiated: unalloyed tungsten and tungsten with 60 ppm potassium. All fibers had 150 µm diameter and approximately 40 mm length. For the irradiation, groups of fibers were held in small graphite bottles to prevent damage or loss during irradiation. The microstructure of the fibers was investigated with scanning and transmission electron microscopy and the mechanical properties were evaluated with tensile tests.
3:40 PM Break
4:00 PM
Coupled Irradiation Induced Grain Growth and Damage Evolution in Solute Stabilized Nanocrystalline Tungsten: Streit Cunningham1; Khalid Hattar2; Jason Trelewicz1; 1Stony Brook University; 2Sandia National Laboratories
The unique thermodynamic state occupied by nanocrystalline alloys presents opportunities for designing materials against instabilities while simultaneously enhancing their radiation tolerance through the deliberate introduction of defect sinks. In this study, we probe the coupling between microstructural evolution and irradiation damage state in nanocrystalline W-20 at.% Ti using ion irradiation experiments. Defect evolution is mapped up to 20 dpa through in situ measurements and bridged to high-dose stability using ex situ experiments up to 400 dpa. The nanostructure is shown to exhibit a transient peak damage state followed by a reduction in defect density, which is attributed to the interaction of defect loops with migrating grain boundaries during irradiation induced grain growth. Grain size stabilizes around 50 nm, still well within the nanocrystalline regime, and is shown to be accompanied by a saturation of the loop density that continues out to the maximum dose of 400 dpa.
4:20 PM Cancelled
Defect-Interface Interactions in Irradiated Cu/Ag Nanocomposites: Interface Vacancy Pump Effect: Weizhong Han1; Min Wang1; 1Xi'an Jiaotong University
In this work, we employ TEM and helium ion irradiation to study the response of biphase interfaces to radiation induced point defect fluxes from the two adjoining phases. Analysis of interface-affected defect accumulation was carried out over a wide range of radiation damage levels. Results show a strong interface density dependence radiation response. The concomitant development of a bubble-free zone in Cu that was independent of defect levels and interface-contacting bubbles zone in Ag. This finding is explained by bias segregation to the interface of interstitials from Ag and vacancies to misfit dislocation nodes in the interface from Cu. The point defect transfer across the interface can be explained by the spatial variation in interface pressure within the interface and gradient in pressure across the interface, both originating from the lattice mismatch and surface energy difference between the two crystals. Refs. Acta Mater-2018-160-211, Scripta Mater-2019.
4:40 PM
Elucidating Atomistic Mechanisms for Interface- and Grain Boundary-mediated Radiation Defects Annihilation: Penghui Cao1; Miaomiao Jin2; Kangpyo So2; Ju Li2; Michael Short2; 1University of California, Irvine; 2Massachusetts Institute of Technology
Effective and efficient removal of defects is of crucial importance to design radiation damage-tolerant materials. Here, atomistic simulations and in-situ irradiation transmission electron microscopy experiments of nanocrystalline Cu and carbon nanotube (CNT)-Al composite reveal the atomic details of defect nucleation and migration, and the mechanisms for the annihilation of defect clusters during irradiation. For nanocrystalline Cu, stacking fault tetrahedra formed due to radiation damage cascades show preferential migration to irradiated grain boundary. Interstitial-loaded grain boundaries are observed to be dynamically resilient, and persistently interact with the stacking fault tetrahedra, revealing a self-healing response to radiation damage. For CNT-Al composite, experiments and atomistic simulations together reveal the dynamic evolution and convergent diffusion of radiation-induced defects to CNTs, facilitating defect recombination and enhancing radiation tolerance. The occurrence of CNT-biased defect convergent migration is tuned by the thermodynamic driving force of stress gradient in Al matrix due to the CNT phase transformation.