Advanced Characterization of Materials for Nuclear, Radiation, and Extreme Environments: Fusion Materials and Metals
Sponsored by: TMS Nuclear Materials Committee
Program Organizers: Cody Dennett, Commonwealth Fusion Systems; Samuel Briggs, Oregon State University; Christopher Barr, Department Of Energy; Michael Short, Massachusetts Institute of Technology; Janelle Wharry, Purdue University; Cheng Sun, Clemson University; Caitlin Kohnert, Los Alamos National Laboratory; Emily Aradi, University of Manchester; Khalid Hattar, University of Tennessee Knoxville
Monday 8:00 AM
October 18, 2021
Room: A215
Location: Greater Columbus Convention Center
Session Chair: Michael Short, Massachusetts Institute of Technology; Jason Trelewicz, Stony Brook University
8:00 AM Invited
Real-time Thermal Oxidation Process of PFM Tungsten Under Fusion-relevant Conditions Revealed by In-situ Environmental TEM: Maanas Togaru1; Rajat Sainju1; Lichun Zhang1; Weilin Jiang2; Yuanyuan Zhu1; 1University of Connecticut; 2Pacific Northwest National Laboratory
Tungsten has been selected as the plasma-facing divertor material at the ITER. With a view to transient events, air ingress accidents and future DEMO PFM safety, engineering tungsten with enhanced oxidation resistance and mechanical performance including ductility and DBTT has attracted increasing attention in the fusion community. However, significant knowledge gaps exist in the understanding of the oxidation mechanism and kinetics of tungsten and associated alloys, and how passivating elements conflict and/or compromise the mechanical properties. In this talk, we will demonstrate how a novel MEMS-based in-situ environmental TEM, capable of mimicking the air ingress, can be utilized to directly observe the evolution of scale phases and elucidate the mechanisms underpinning the oxidation onset and kinetics. New insights into the irradiation-assisted tungsten and tungsten alloy oxidation hold a great promise for reinforcing design criteria that balance mechanical properties with oxidation resistance for the development of next-generation tungsten-based PFMs.
8:20 AM Invited
Uncovering the Effect of Grain Boundary Dopants on Irradiation Induced Grain Growth Through In Situ Microscopy: Jason Trelewicz1; William Cunningham1; Danny Edwards2; Yuanyuan Zhu3; 1Stony Brook University; 2Pacific Northwest National Laboratory; 3University of Connecticut
Displacement damage under irradiation promotes microstructural coarsening in nanocrystalline metals containing a high interfacial area per unit volume. Targeted doping of grain boundaries has a profound impact on thermal stability, but insights on its role in radiation stability are needed to inform nanocrystalline alloy design models. Leveraging in situ electron microscopy to map dynamic events under ion irradiation, we explore the coupling between microstructural evolution and irradiation damage in a titanium doped nanocrystalline tungsten alloy. Relative to undoped tungsten, the alloy exhibits smaller defect loops and a delayed saturation dose with a period of irradiation induced grain growth during the transient damage accumulation and recovery stages. Application of a thermal spike grain growth model reveals that the nanostructure in the doped alloy plateaus to a much finer grain size relative to predictions for pure tungsten, indicating that doping for enhanced thermal stability also stabilizes the material against irradiation instabilities.
8:40 AM
Femtosecond Laser Induced Surface Damages in Tungsten and Tungsten Carbide in High Heat Flux Conditions: Minsuk Seo1; Shukai Yu1; Venkatraman Gopalan1; Leigh Winfrey1; 1The Pennsylvania State University
Tungsten is a divertor material for the tokamak fusion reactor, and tungsten carbide could be a potential material. Tungsten and tungsten carbide were irradiated by high heat flux (59.6GW/m2) femtosecond laser with different angles (0°, 30°, 45°, 60°) up to ~5000 shots in ambient air to emulate surface damages by hypothetically synchronized edge localized modes (ELMs) and loss of vacuum accident (LOVA). The surface crater contained laser-induced periodic surface structure (LIPSS), grooves, and morphologies were changed by laser influence spatially and angularly. The periods of low spatial frequency LIPSS (LSFL) have increased, and high spatial frequency LIPPS (HSFL) has decreased for both tungsten and tungsten carbide surfaces as the incident angle increased. The high-temperature surface oxides were detected by linear energy dispersive spectroscopy (EDS). The possible oxide forms are tungsten oxide, cobalt oxide, or cobalt tungstate, all potentially detrimental to nuclear fusion operation.
9:00 AM Invited
Characterization of Materials Exposed to Coupled Nuclear Environments Using Positron Annihilation Spectroscopy and Electrical Impedance Spectroscopy: Peter Hosemann1; Rasheed Auguste1; Farida Selim2; Oskar Linke3; Maik Butterling3; Hong Chan4; Junsoo Han4; Jie Qiu1; John Scully4; Ryan Schoell5; Djamel Kaoumi5; 1University of California, Berkeley; 2Bowling Green University; 3Helmholz Zentrum Dresden Rossendorf; 4University of Virginia; 5North Carolina State University
Radiation effects do alter physical, mechanical, and chemical properties in materials. The underlying cause of these effects is the generation of point defects generated by displacement cascades. Most property changes are a result of the interaction of these defects with each other and with pre-existing defects. Especially the effects, defect structures may have on corrosion properties need to be considered for combinatorial (corrosion & irradiation) environments. This work features positron annihilation spectroscopy (PAS) on Fe, Cr, Ni based materials previously exposed to a corrosive and irradiation environment. Electrical impedance spectroscopy (EIS) is performed to compare to PAS data and quantify the properties. Of course, transmission electron microscopy allows to shed light to the larger structure and puts PAS and EIS in context.The systematic study of passive films formed on metal surfaces using these advanced techniques provides the baseline for a fundamental understanding of transport under reactor extremes.
9:20 AM
Richtmyer-Meshkov Instability Testing and Accompanying Analysis: A Surface Sensitive Approach to High Strain Rate Testing of Irradiated Material without Bulk Volumes: Calvin Lear1; David Jones1; Daniel Martinez1; Jeremy Payton1; Michael Prime1; Saryu Fensin1; 1Los Alamos National Laboratory
The inherent difficulties of handling bulk irradiated materials (expense, safety) are well known. While advances in sample preparation and small-scale mechanical testing now allow reduced volumes of these materials to be studied in otherwise low-hazard facilities, high strain rate mechanical testing (> 103/s) still requires large specimens (~1 cm3) and often destructive testing. Surface sensitive techniques thus offer an attractive alternative, requiring only that researchers modify a thin layer of the target to simulate the structure of the bulk irradiated material. Here, Richtmyer-Meshkov instability (RMI) experiments were carried out on bulk copper targets with helium implanted surface layers to study the effects of bubbles on material strength. The experimental process will be discussed at length, including the newly developed SAVER software package and comparison to hydrodynamics simulations, and the implications of differences between low and high strain rate mechanical properties of these samples will be explored.