Radiation Effects in Metals and Ceramics: Advanced Techniques of Radiation Damage Characterization
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
Monday 8:00 AM
February 24, 2020
Room: Theater A-7
Location: San Diego Convention Ctr
Session Chair: Djamel Kaoumi, North Carolina State University; Aurelie Gentils, Universite Paris Saclay
8:00 AM Invited
Applications of Advanced Electron Microscopy to Understand Irradiation Damage of Fusion and Fission Materials: Chad Parish1; Daniel Morrall1; Yutai Katoh1; Arunodaya Bhattacharya1; Andrew Lupini1; Philip Edmondson1; 1Oak Ridge National Laboratory
Advanced fission—much less fusion—reactors will subject materials to unprecedented neutron irradiation damage and helium transmutation. Most of the current design approaches to advanced radiation-tolerant materials involve highly engineered nanostructures. The question of how radiation will alter, and ultimately degrade, these nanostructures requires we push the boundaries of electron microscopy. Here at ORNL, we are developing new techniques to understand both metallic and ceramic materials' structural changes under neutron and ion irradiation. HREM combined with machine learning has unbiasedly identified defects in neutron-irradiated silicon carbide. Aberration-corrected STEM has identified the structure of the dislocation loops in ion-irradiated refractory diboride ceramics. Transmission Kikuchi diffraction allows us to probe grain boundary character in irradiated tungsten and compare to STEM X-ray analysis of segregation. Overall, modern electron microscopy allows us to probe irradiation-induced defects in heretofore unimagined detail. This talk will review recent applications to irradiated materials.
8:30 AM
Depth-dependent Characterization and 3D Tomography of In-situ Ion Irradiated Microstructure: Wei-Ying Chen1; Meimei Li1; 1Argonne National Laboratory
TEM with in-situ ion irradiation has the advantage of capturing the real time microstructural evolution in materials under irradiation. Because of the limitation of electron penetration, thin foil with a thickness less than 200-300 nm needs to be used. The effect of the foil surface on the defect evolution can sometimes be noticeable especially at higher irradiation temperatures. The surface effect, on one hand, makes the in-situ data deviate from the bulk behavior; on the other hand, it provides an opportunity for understanding the interaction of surface with point defects and small defect clusters. In this study, we performed depth-dependent characterization and 3D tomography on nickel and Al0.3CoCrFeNi irradiated with 1 MeV krypton ions at 500°C and 600°C to 1 dpa. The depth dependence of stacking-fault tetrahedral, dislocation loops and voids was quantitatively analyzed to understand the observed heterogeneous spatial distribution of defect clusters.
8:50 AM
Effect of Chemical Compositions on Precipitate Coherency Loss After In-situ Irradiations: Ling Wang1; Wei-Ying Chen2; David Martin1; Peter Baldo2; Meimei Li2; Brian Wirth1; Steven Zinkle1; 1University of Tennessee; 2Argonne National Laboratory
The dose dependence for loss of precipitate coherency depends on the initial precipitate size and irradiation temperature due to their differences in atomic relaxation during absorption of point defects. The effect of chemical compositions on precipitate coherency loss in three dilute Cu-based binary alloys (1%Co, 1%Fe and 0.4%Cr) were investigated using in situ ion irradiations. These Cu alloys were thermally treated to produce coherent Co-, Fe- and Cr-rich precipitates with two different sink strengths (1013 and 1014/m2), respectively, and irradiated with 1 MeV Kr ions to dose of 0.2dpa at room temperature and post annealed to 500 °C. The lobe-lobe contrast under dynamical diffraction condition of different type coherent precipitates disappeared after irradiation to 0.01dpa. However, only Fe-rich precipitates show lobe-lobe contrast after post annealing to 450 °C. Molecular dynamics simulations were performed to understand the evolution of the Co-rich precipitate coherency loss for different sink strengths.
9:10 AM
Probing Thermal Diffusivity Degradation and Point Defect Density in self-ion Implanted Tungsten with Transient Grating Spectroscopy: Mohamed Abdallah Reza1; Hongbing Yu1; Kenichiro Mizohata2; Felix Hofmann1; 1Department of Engineering Science, University of Oxford; 2Materials Physics, University of Helsinki
Irradiation damage significantly changes the properties of tungsten, the main candidate material for fusion reactor armor. Using transient grating spectroscopy (TGS) we study the reduction of thermal diffusivity in self-ion implanted tungsten from 0.0001 to 10 dpa. Room temperature thermal diffusivity decreases by up to ~55% at 0.1 dpa and saturates thereafter. A kinetic theory model is used to estimate the irradiation-induced point defect density from the measured thermal diffusivity data. This is compared to prior molecular dynamics (MD) simulations and TEM observations of ion-irradiation-induced defects in tungsten. Defects visible in TEM alone cannot account for the measured reduction in thermal diffusivity. However, when point defects predicted by MD but too small to be seen by TEM are accounted for, the defect densities agree well with those estimated from TGS measurements spanning 3 orders of magnitude in dose. This highlights the importance of TEM “invisible” defects for material property evolution.
9:30 AM Break
9:50 AM Invited
Quantitative Analysis of Atomic Scale Defects in Irradiated Materials: Farida Selim1; Sahil Agarwal1; Aaron Kohnert2; Jacob Cooper3; Nan Li2; Yongqiang Wang2; Djamel Kaoumi3; Danny Edwards4; Laurent Capolungo4; Peter Hosmann5; Blas Uberuaga2; 1Bowling Green State University; 2Los Alamos National Laboratory; 3North Carolina State University; 4Pacific Northwest National Laboratory; 5 University of Califorina, Berkeley
Positron annihilation spectroscopy (PAS) is as a powerful tool for measuring atomic scale defects as well as characterizing them and distinguishing between isolated vacancies, dislocations and vacancy clusters. In this study we combine high resolution transmission electron microscopy (HRTEM) and PAS to study defect production and evolution in ion irradiated Fe and Fe alloys. Both Positron annihilation lifetime spectroscopy (PALS) and Doppler broadening spectroscopy (DBS) of annihilation radiation were carried out to provide qualitative and quantitative information about the size and density of vacancies and clusters, while TEM measurements provided information about larger clusters and voids,The measurements reveal how the original point defects and dislocations in Fe films evolve with irradiation and the impact of alloying on their evolution or annihilation. We further calculate the density of each defect type and monitor both the change of defect structure and their electronic structure with irradiation dose and alloying.
10:20 AM
Raman Signature of Point Defects in Boron Carbide: Guido Roma1; Gaëlle Gutierrez1; Kevin Gillet1; Dominique Gosset1; 1CEA
Raman spectroscopy is a widespread technique to characterize irradiated materials. However, the interpretation of experimental spectra in terms of atomic scale modifications is often far from straightforward. In this paper we combine the first principles simulation of Raman spectra of carbon-rich boron carbide with the experimental results obtained before and after heavy ion irradiation. Relying on an embedding procedure we compute the first order Raman tensor of impurities or intrinsic defects at low concentration. Previous works show that the calculated first order Raman spectrum cannot fully explain the experimental spectra obtained for boron carbide. We insert vacancies, interstitials and other defects and we analyze their influence on the spectral features at various concentrations. By comparison with experimental spectra obtained in different conditions, before and after irradiation, we discuss which of the intrinsic defects could be present in the measured samples, also according to their formation energies.
10:40 AM
Noble Gas Bubble Superlattice in bcc Metals under Irradiation: Cheng Sun1; D. Sprouster2; S. Gill2; M. Topsakal2; L. Ecker2; J. Gan1; 1Idaho National Laboratory; 2Brookhaven National Laboratory
Self-organization of gas bubbles can cause the formation of gas bubble superlattice in materials under ion irradiation. Here we report the formation of noble gas (He, Ne, Ar and Kr) bubble superlattice in bcc metals (Mo, Fe, W) under ion irradiation. Transmission electron microscopy (TEM) and synchrotron-based small angle X-ray scattering (SAXS) are used to characterize the evolution of gas bubble lattice constant and bubble size, and X-ray Absorption Near Edge Structure (XANES) is used to measure the pressure of ordered Kr bubbles. The stability of gas bubble superlattice under irradiation and thermal annealing is also discussed. Our study advances the understanding on formation mechanism of gas bubble superlattice and provides new insights on the design of stable defect superlattice in harsh environments.
11:00 AM
Study of Neutron Irradiation Damage of HT-UPS Steel Using Synchrotron X-ray Techniques: Sri Tapaswi Nori1; Alejandro Figueroa1; Jonova Thomas1; Gyuchul Park1; Walter Williams1; Hemant Sharma2; Jun-Sang Park2; Peter Kenesei2; Jonathan Almer2; Zhengrong Lee3; Mark Warren3; Jeff Terry3; Maria Okuniewski1; 1Purdue University; 2Argonne National Laboratory; 3Illinois Institute of Technology
High-temperature ultra-fine precipitation strengthened (HT-UPS) steel is a high-strength, creep resistant advanced austenitic stainless steel at elevated temperatures (>400℃). It is a candidate structural material for advanced nuclear reactors. However, its neutron irradiation tolerance is not well understood. In this context, this research utilizes non-destructive synchrotron X-ray techniques such as high-energy diffraction microscopy (HEDM), micro-computed tomography (μ-CT), and X-ray absorption spectroscopy (XAS) to characterize the neutron-irradiation induced defect structures at multiple length scales. HEDM and μ-CT provide three-dimensional micromechanical state information for the grains and microstructural density changes due to the varying compositions within a material, respectively. XAS provides the local chemical environment information around an absorbing atom. These experiments were conducted on samples that were unirradiated and neutron-irradiated up to ~0.3 dpa at ~600℃. A comparative study between these irradiation conditions will be presented to explain the microstructural and micromechanical effects of irradiation.
11:20 AM
Ion Beam Synthesis of Nano-metallic Oxide Particles in High Purity FeCr: Stephanie Jublot-Leclerc1; Martin Owusu-Mensah1; Joël Ribis2; Vladimir Borodin3; Ryan Schoell4; Ce Zheng4; Djamel Kaoumi4; Aurélie Gentils1; 1CSNSM, Univ Paris-Sud and CNRS, Université Paris-Saclay; 2DEN, SRMA, CEA, Université Paris-Saclay; 3NRC “Kurchatov Institute”, and National Research Nuclear University MEPhI, Moscow; 4Department of Nuclear Materials, North Carolina State University
Ferritic-martensitic steels reinforced with oxide dispersions exhibit improved creep and radiation resistance at high temperatures, being promising structural materials for future fission and fusion reactors. Getting basic understanding of nano-oxide precipitation could simplify optimisation of mechanical properties of ODS steels. For this aim, we have studied nano-oxide precipitation in a high purity Fe10wt%Cr alloy using the ion beam synthesis approach. The synthesis of oxide particles was performed by consecutive implantation of keV Ti+, and/or Y+, and O+ ions at room temperature followed by thermal annealing between 600 and 1100°C. The induced microstructural and chemical changes were characterized by conventional TEM, EFTEM, HRTEM and ChemiSTEM. It was found that the nature and size of synthesized nano-oxides strongly depends on implantation and annealing conditions, and particularly on the order of sequence of implantations. The main characteristics of oxide particles are presented and discussed in comparison with the data for conventional ODS steels.