Performance of Nanocrystalline and Ultrafine Tungsten Under Irradiation and Mechanical Extremes
Principal Investigator
- Name:
- Osman El Atwani
- Email:
- [email protected]
- Phone:
- (208) 526-6918
Team Members:
| Name: | Institution: | Expertise: | Status: |
|---|---|---|---|
| Stuart Maloy | Los Alamos National laboratory | Reactor Materials NEET-3 Technical Lead, FCRD Advanced Reactor Core Materials Technical Lead | Other |
| Benjamin | Eftink | Nuclear materials, electron microscopy | Post Doc |
| Li Meimi | Argonna National Laboratory | Nuclear reactor materials, electron microscopy | Other |
Experiment Details:
- Experiment Title:
- Performance of Nanocrystalline and Ultrafine Tungsten Under Irradiation and Mechanical Extremes)
- Work Description:
- Experimental • Samples o Electropolished 3 or 2.3 mm (depending on the high temperature holder in the IVEM-Tandem facility at ANL) TEM samples of nanocrystalline and coarse grained tungsten • Preparation o TEM samples of nanocrystalline tungsten are prepared from bulk sample. The bulk samples are formed using orthogonal machining process. Other bulk samples will be annealed to form coarse grained tungsten. From the bulk samples, 3 mm discs are cut and mechanically polished to 50-100 µm thickness. Electropolishing with 0.5% NaOH solution (in water) are followed as a final TEM sample preparation step. All the above steps, in addition to TEM and EBSD imaging will be performed at Los Alamos National Laboratory (LANL) prior to our visit to Argonne National Laboratory. • Instrument Requested o IVEM-Tandem facility at Argonne National Laboratory. o In-situ TEM/Irradiation will be performed on the TEM samples. • Imaging Conditions o 200 or 300 keV electron beam is requested. • Irradiation Conditions o The samples will be irradiated with MeV krypton ions. The holder requested is the double tilt high temperature one. The flux requested is about 1012 ion.m-2 . The temperature will range between RT and over 600 °C (900 °C is preferred for the high temperature experiments). • Procedure o About 8 samples will be studied. 1- Imaging as a function of fluence (for plotting defect density as a function of ion dose for specific grains) The sample will be inserted into the TEM. Images before irradiation will be performed at multibeam conditions. An area will be chosen to run the in-situ/TEM irradiation on. Video capture will start few seconds before starting the irradiation. Irradiation will then start. Irradiation will be stopped at intermediate steps depending on our observation of the phenomena occurring. At least 6 intermediate steps will be performed. After each intermediate step, the sample will be imaged. The magnification of the TEM during irradiation will be about 20-50K depending on the grain size investigated. The final dose should be about 5 x 1015 ion.m-2 (about 2500 seconds of irradiation time). This procedure will run for the nanocrystalline and coarse grained tungsten samples. For each type of samples, RT, 500 °C and 900 °C (if applicable at the time of the visit). The total number of samples to be investigated using this procedure is 6 samples (3 nanocrystalline and 3 coarse grained tungsten). Ex-situ TEM imaging and EBSD of these samples will be performed at LANL. Defect (interstitial and possibly void) density as a function of grain size will be plotted in this case. Denuded zone a function of grain boundary type will also be plotted. 2- High dose irradiation Two samples (one nanocrystalline and one coarse grained) will be irradiated inside the TEM at high magnification to a high dose (over 25 dpa) using the highest flux possible and at high temperature (900 °C is preferred) with one or two intermediate steps depending on the phenomena observed. Specific grain boundaries (one for each sample) will be examined in this case at high magnification.
Project Summary
Performance of Nanocrystalline and Ultrafine Tungsten Under Irradiation and Mechanical Extremes:
Suppression of point defect accumulation by annihilating the freely migrating defects (interstitial and vacancy) to defect sinks such as grain boundaries is believed to enhance the performance of irradiated cladding materials [1]. In-situ irradiation-transmission electron microscopy (TEM) experiments are crucial tests to address the importance of grain boundaries and grain size in mitigating the irradiation damage, and correlate small scale phenomena to large scale ones (such as morphological changes and mechanical properties degradation). In this work, nanocrystalline tungsten formed by a severe plastic deformation technique (orthogonal machining [2]) will be used as a BCC model material to study the irradiation response of heavy ion irradiated nuclear fission materials. The use of tungsten will permit the investigation of nanocrystalline materials at very high temperatures, where defect (loops and voids) mobilities are high but no grain growth can occur. This will offer the benefit of modeling high strength, nanocrystalline alloy materials which do not exhibit grain growth at temperatures at which their pure form counterparts suffer from rapid grain growth. In-situ irradiation/transmission electron microscopy is proposed to be performed in the In-situ TEM/irradiation (IVEM-Tandem) facility at Argonne National Laboratory on tungsten materials. The irradiations are to be performed on nanocrystalline and ultrafine tungsten samples as well as coarse grained ones using high energy krypton to mimic neutron transmutation reaction and study the effect of grain boundary density (grain size) in limiting irradiation-induced defect densities. These experiments should also reveal the effect of grain boundary misorientation angle and grain boundary plane (the 5 macro degrees of freedom of a gain boundary) on the sink efficiency of the boundary by examining denuded zone formation (defect-free zone in the vicinity of the boundary) and denuded zone width change as a function of time. Mechanical property test of the irradiated materials will be performed in the Material Science and Technology Division (MST-8) at Los Alamos National Laboratory using nanomechanical testing. Micropillar testing and in-situ TEM-Tensile testing will be performed on samples irradiated at similar conditions to those irradiated via IVEM-Tandem. A figure of merit” correlating the materials morphological and mechanical response with irradiation parameters will then be generated. The proposal will answer several outstanding fundamental questions on the performance of nanocrystalline materials to severe environments at the small and large scales, and will have a universal impact on the materials and nuclear fission communities working on designing novel irradiation resistant materials. The expected period to run this project is one and half year starting from May 2017.
[1] Shen, T. D. et al. Enhanced radiation tolerance in nanocrystalline MgGa2O4. Appl. Phys. Lett. 90, 263115 (2007)
[2] Efe, M., El-Atwani, O., Guo, Y. & Klenosky, D. R. Microstructure refinement of tungsten by surface deformation for irradiation damage resistance. Scripta Mater. 70, 31-34 (2014
Suppression of point defect accumulation by annihilating the freely migrating defects (interstitial and vacancy) to defect sinks such as grain boundaries is believed to enhance the performance of irradiated cladding materials [1]. In-situ irradiation-transmission electron microscopy (TEM) experiments are crucial tests to address the importance of grain boundaries and grain size in mitigating the irradiation damage, and correlate small scale phenomena to large scale ones (such as morphological changes and mechanical properties degradation). In this work, nanocrystalline tungsten formed by a severe plastic deformation technique (orthogonal machining [2]) will be used as a BCC model material to study the irradiation response of heavy ion irradiated nuclear fission materials. The use of tungsten will permit the investigation of nanocrystalline materials at very high temperatures, where defect (loops and voids) mobilities are high but no grain growth can occur. This will offer the benefit of modeling high strength, nanocrystalline alloy materials which do not exhibit grain growth at temperatures at which their pure form counterparts suffer from rapid grain growth. In-situ irradiation/transmission electron microscopy is proposed to be performed in the In-situ TEM/irradiation (IVEM-Tandem) facility at Argonne National Laboratory on tungsten materials. The irradiations are to be performed on nanocrystalline and ultrafine tungsten samples as well as coarse grained ones using high energy krypton to mimic neutron transmutation reaction and study the effect of grain boundary density (grain size) in limiting irradiation-induced defect densities. These experiments should also reveal the effect of grain boundary misorientation angle and grain boundary plane (the 5 macro degrees of freedom of a gain boundary) on the sink efficiency of the boundary by examining denuded zone formation (defect-free zone in the vicinity of the boundary) and denuded zone width change as a function of time. Mechanical property test of the irradiated materials will be performed in the Material Science and Technology Division (MST-8) at Los Alamos National Laboratory using nanomechanical testing. Micropillar testing and in-situ TEM-Tensile testing will be performed on samples irradiated at similar conditions to those irradiated via IVEM-Tandem. A figure of merit” correlating the materials morphological and mechanical response with irradiation parameters will then be generated. The proposal will answer several outstanding fundamental questions on the performance of nanocrystalline materials to severe environments at the small and large scales, and will have a universal impact on the materials and nuclear fission communities working on designing novel irradiation resistant materials. The expected period to run this project is one and half year starting from May 2017.
[1] Shen, T. D. et al. Enhanced radiation tolerance in nanocrystalline MgGa2O4. Appl. Phys. Lett. 90, 263115 (2007)
[2] Efe, M., El-Atwani, O., Guo, Y. & Klenosky, D. R. Microstructure refinement of tungsten by surface deformation for irradiation damage resistance. Scripta Mater. 70, 31-34 (2014
Relevance
Performance of Nanocrystalline and Ultrafine Tungsten Under Irradiation and Mechanical Extremes
Program: RTE-NSUF
ABSTRACT:
The proposed research is highly relevant to the programs funded by the Office of Nuclear Energy and its two mission goals. First, the proposed research serves as a project that benefits the Nation’s nuclear fission energy capability. The project describes the use of novel tungsten materials to compare their performance with commercial tungsten. These materials are expected to have better performance due to their high strength and grain boundary density [1]. For fission power, tungsten can act as a BCC model material and the fundamental small scale studies involved in this proposal (such as grain boundary sink efficiency investigation, grain size threshold determination for enhanced irradiation tolerance, defect densities vs grain size trends, etc.) are designed to answer several outstanding research questions for several materials [2,3] in Generation IV fission reactors concepts. Therefore, this proposal is also relevant for the other program goal of the Office of Nuclear Energy, which is the development of new nuclear generation technologies (next-generation advanced reactors and fuel cycles).
[1] I.J. Beyerlein, Progress in Materials Science, 74 (2015) 125-210
[2] L.K Mansur, J. Nucl. Mater. 329-333 (2004) 166-172
[3] Steven J. Zinkle , Jeremy T. Busby, Materials Today (2009) 12-19
Book / Journal Publications
"Nanohardness measurements of heavy ion irradiated coarse- and nanocrystalline-grained tungsten at room and high temperature" Osman El Atwani, Jordan Weaver, JESUS ALFREDO ESQUIVEL, Yongqiang Wang, Stuart Maloy, Nathan Mara, Journal of Nuclear Materials 509 2018 276-284 Link
"Unprecedented irradiation resistance of nanocrystalline tungsten with equiaxed nanocrystalline grains to dislocation loop accumulation" Osman El Atwani, Acta Materialia 165 2019 118-128 Link
"In-situ irradiation tolerance investigation of high strength ultrafine tungsten-titanium carbide alloy" Osman El Atwani, Acta Materialia 164 2019 547-559 Link
"Outstanding radiation resistance of tungsten-based high-entropy alloys" Osman El Atwani, Science Advances 5 2019 eaav2002 Link
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About Us
The Nuclear Science User Facilities (NSUF) is the U.S. Department of Energy Office of Nuclear Energy's only designated nuclear energy user facility. Through peer-reviewed proposal processes, the NSUF provides researchers access to neutron, ion, and gamma irradiations, post-irradiation examination and beamline capabilities at Idaho National Laboratory and a diverse mix of university, national laboratory and industry partner institutions.
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