NSUF 10-230: Study of an Irradiated Ferritic Steel by Synchrotron XRD and XAS
The purpose of this project is to explore the viability of using synchrotron x-ray diffraction (XRD) and x-ray absorption spectroscopy (XAS) techniques to characterize radiation damage in a class of ferritic steels. Ferritic-martensitic steels are the lead structural materials for all types of advanced fission and fusion energy systems. These alloys have excellent resistance to irradiation-induced swelling, good thermal properties, and low cost. This study will use mod.9Cr-1Mo steel as an example material, because of its wide nuclear applications, representative microstructure, and availability of irradiated specimens. Mod.9Cr-1Mo is a Fe-9%Cr-1%Mo ferritic-martensitic steel modified with V and Nb. Prior to irradiation, the microstructure of the alloy consisted of tempered martensite stabilized by M23C6 carbides and a fine distribution of vanadium/niobium carbon-nitride (MX) precipitates, giving rise to high creep strength. Molybdenum in the solution contributes to the strength of mod.9Cr-1Mo through solution strengthening. The mod.9Cr-1Mo steel examined in this study was irradiated to 0.2-12 dpa at temperatures of 30-160?C. Irradiation at the low temperatures produces a large number of dislocation loops, leading to significant hardening and embrittlement.Synchrotron XRD measurements are proposed to measure non-irradiated and irradiated specimens at room temperature to identify phases and determine their volume fraction before and after irradiation. This information is to confirm that there is no dissolution and precipitation in mod.9Cr-1Mo during low-temperature irradiation. The second purpose of the XRD measurements is to explore the possibility of determining statistic populations of irradiation defects and defect clusters as a function of doses by analysis of lattice parameter changes and diffraction peak broadening due to irradiation. The XRD measurements of defect clusters will be compared with TEM observations. Synchrotron XAS measurements are designed to investigate solute trapping and sink effects at precipitate/matrix interfaces. The extended xray absorption fine structure spectroscopy (EXAFS) data at the Fe, Cr and Mo K-edges will be analyzed to study the solute-defect interactions. The EXAFS data at the V and Nb edges will be analyzed to obtain the structural information of the fine precipitates of the MX phase in non-irradiated and irradiated mod.9Cr-1Mo. Thermal annealing and post-anneal XRD and XAS experiments are proposed to assist data interpretation of radiation damage in mod.9Cr-1Mo. The applications of synchrotron radiation techniques in the investigation of radiation damage are still in their infancy. An important aspect of this proposal is to explore the applications of synchrotron techniques for characterization of radiation-induced microstructural changes in a broad range of material systems. Ferritic-martensitic steels, as the lead structural materials in advanced nuclear energy systems, should be considered in this exploratory effort.
Additional Info
| Field | Value |
|---|---|
| Abstract | The purpose of this project is to explore the viability of using synchrotron x-ray diffraction (XRD) and x-ray absorption spectroscopy (XAS) techniques to characterize radiation damage in a class of ferritic steels. Ferritic-martensitic steels are the lead structural materials for all types of advanced fission and fusion energy systems. These alloys have excellent resistance to irradiation-induced swelling, good thermal properties, and low cost. This study will use mod.9Cr-1Mo steel as an example material, because of its wide nuclear applications, representative microstructure, and availability of irradiated specimens. Mod.9Cr-1Mo is a Fe-9%Cr-1%Mo ferritic-martensitic steel modified with V and Nb. Prior to irradiation, the microstructure of the alloy consisted of tempered martensite stabilized by M23C6 carbides and a fine distribution of vanadium/niobium carbon-nitride (MX) precipitates, giving rise to high creep strength. Molybdenum in the solution contributes to the strength of mod.9Cr-1Mo through solution strengthening. The mod.9Cr-1Mo steel examined in this study was irradiated to 0.2-12 dpa at temperatures of 30-160?C. Irradiation at the low temperatures produces a large number of dislocation loops, leading to significant hardening and embrittlement.Synchrotron XRD measurements are proposed to measure non-irradiated and irradiated specimens at room temperature to identify phases and determine their volume fraction before and after irradiation. This information is to confirm that there is no dissolution and precipitation in mod.9Cr-1Mo during low-temperature irradiation. The second purpose of the XRD measurements is to explore the possibility of determining statistic populations of irradiation defects and defect clusters as a function of doses by analysis of lattice parameter changes and diffraction peak broadening due to irradiation. The XRD measurements of defect clusters will be compared with TEM observations. Synchrotron XAS measurements are designed to investigate solute trapping and sink effects at precipitate/matrix interfaces. The extended xray absorption fine structure spectroscopy (EXAFS) data at the Fe, Cr and Mo K-edges will be analyzed to study the solute-defect interactions. The EXAFS data at the V and Nb edges will be analyzed to obtain the structural information of the fine precipitates of the MX phase in non-irradiated and irradiated mod.9Cr-1Mo. Thermal annealing and post-anneal XRD and XAS experiments are proposed to assist data interpretation of radiation damage in mod.9Cr-1Mo. The applications of synchrotron radiation techniques in the investigation of radiation damage are still in their infancy. An important aspect of this proposal is to explore the applications of synchrotron techniques for characterization of radiation-induced microstructural changes in a broad range of material systems. Ferritic-martensitic steels, as the lead structural materials in advanced nuclear energy systems, should be considered in this exploratory effort. |
| Award Announced Date | 2009-11-24T00:00:00 |
| Awarded Institution | None |
| Facility | None |
| Facility Tech Lead | Jeff Terry |
| Irradiation Facility | None |
| PI | Meimei Li |
| PI Email | [email protected] |
| Project Type | APS |
| RTE Number | 230 |