NSUF 17-951: Performance of Nanocrystalline and Ultrafine Tungsten Under Irradiation and Mechanical Extremes
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
Additional Info
| Field | Value |
|---|---|
| Abstract | 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 |
| Award Announced Date | 2017-04-26T10:15:48.963 |
| Awarded Institution | None |
| Facility | None |
| Facility Tech Lead | Wei-Ying Chen |
| Irradiation Facility | None |
| PI | Osman El Atwani |
| PI Email | [email protected] |
| Project Type | RTE |
| RTE Number | 951 |