NSUF 22-4389: Irradiation effects on microstructure and mechanical properties in a laser welded ODS alloy
The objective of this project is to evaluate the combined effects of laser weld joining and irradiation on the microstructure and mechanical properties of a commercial ODS alloy candidate for advanced nuclear reactor applications. Nanostructured ferritic alloys (NFAs) such as oxide dispersion strengthened (ODS) alloys are leading candidates for structural components due to their dimensional stability upon irradiation and their high temperature mechanical properties. As such, it is important to establish reliable and repeatable processes for fabrication and joining of components made with these advanced alloys. Unfortunately, most established joining processes (arc welding and friction stir welding to a lesser extent) result in significant alteration of the microstructures, including elimination of the same nanoscale features that make these alloys highly desirable and irradiation resistant. Furthermore, traditional methods create relatively large regions of disrupted microstructures including weld zones and surrounding heat-affected zones, which can result in significantly compromised mechanical properties of joined components. On the other hand, laser welding is a promising candidate for joining nanostructured alloys due to its small length scales and fast cooling rates that can limit the impact of joining on the microstructure and mechanical properties of the alloys, likely maintaining the desired irradiation resistance.
Laser welding will be done in collaboration with an industry partner (MacKay Manufacturing, Inc.) located in Spokane, WA to weld two physical pieces together. Following welding, mechanical property characterization will be accomplished via tensile testing (with the weld joint located at the middle of the sample) and nanoindentation across the weld (providing adequate resolution to differentiate the weld hardness from the bulk). Finite Element Analysis in correlation with tensile testing will be used to understand strain-hardening behavior in the bulk alloys and within the welds. With a comprehensive understanding of mechanical property and microstructure evolution, multiple hardening models will be applied to systematically allocate the relative impacts of welding and irradiation on the microstructures and resulting mechanical performance of the joined alloys in an irradiation environment. In parallel, irradiation of laser welded specimens will be conducted at Sandia National Laboratory (SNL) via partnership with Dr. Khalid Hattar. Each specimen will be irradiated with Fe2+ ions to 7 dpa and separately to 25 dpa, each at 400 °C. Nanoindentation on the irradiated specimens will enable evaluation of mechanical property evolution and correlation with microstructure evolution resulting from irradiation.
This project aims to conduct post irradiation examination (PIE) microscopy on laser welded ODS alloy MA956 irradiated to two separate doses (7 dpa and 25 dpa) at a common temperature of 400 °C. Following irradiation, PIE is planned to characterize microstructure and nanocluster irradiation evolution, enabling evaluation of dose dependence on the bulk and welded microstructures. In addition, it will allow direct comparison with prior characterization results from friction stir welding of the same MA956 alloy (accomplished via RTE 17-906) to the same 25 dpa irradiation conditions.
Additional Info
| Field | Value |
|---|---|
| Abstract | The objective of this project is to evaluate the combined effects of laser weld joining and irradiation on the microstructure and mechanical properties of a commercial ODS alloy candidate for advanced nuclear reactor applications. Nanostructured ferritic alloys (NFAs) such as oxide dispersion strengthened (ODS) alloys are leading candidates for structural components due to their dimensional stability upon irradiation and their high temperature mechanical properties. As such, it is important to establish reliable and repeatable processes for fabrication and joining of components made with these advanced alloys. Unfortunately, most established joining processes (arc welding and friction stir welding to a lesser extent) result in significant alteration of the microstructures, including elimination of the same nanoscale features that make these alloys highly desirable and irradiation resistant. Furthermore, traditional methods create relatively large regions of disrupted microstructures including weld zones and surrounding heat-affected zones, which can result in significantly compromised mechanical properties of joined components. On the other hand, laser welding is a promising candidate for joining nanostructured alloys due to its small length scales and fast cooling rates that can limit the impact of joining on the microstructure and mechanical properties of the alloys, likely maintaining the desired irradiation resistance. Laser welding will be done in collaboration with an industry partner (MacKay Manufacturing, Inc.) located in Spokane, WA to weld two physical pieces together. Following welding, mechanical property characterization will be accomplished via tensile testing (with the weld joint located at the middle of the sample) and nanoindentation across the weld (providing adequate resolution to differentiate the weld hardness from the bulk). Finite Element Analysis in correlation with tensile testing will be used to understand strain-hardening behavior in the bulk alloys and within the welds. With a comprehensive understanding of mechanical property and microstructure evolution, multiple hardening models will be applied to systematically allocate the relative impacts of welding and irradiation on the microstructures and resulting mechanical performance of the joined alloys in an irradiation environment. In parallel, irradiation of laser welded specimens will be conducted at Sandia National Laboratory (SNL) via partnership with Dr. Khalid Hattar. Each specimen will be irradiated with Fe2+ ions to 7 dpa and separately to 25 dpa, each at 400 °C. Nanoindentation on the irradiated specimens will enable evaluation of mechanical property evolution and correlation with microstructure evolution resulting from irradiation. This project aims to conduct post irradiation examination (PIE) microscopy on laser welded ODS alloy MA956 irradiated to two separate doses (7 dpa and 25 dpa) at a common temperature of 400 °C. Following irradiation, PIE is planned to characterize microstructure and nanocluster irradiation evolution, enabling evaluation of dose dependence on the bulk and welded microstructures. In addition, it will allow direct comparison with prior characterization results from friction stir welding of the same MA956 alloy (accomplished via RTE 17-906) to the same 25 dpa irradiation conditions. |
| Award Announced Date | 2022-06-14T07:28:02.357 |
| Awarded Institution | Idaho National Laboratory |
| Facility | Advanced Test Reactor |
| Facility Tech Lead | Alina Zackrone, Yaqiao Wu |
| Irradiation Facility | None |
| PI | Matthew Swenson |
| PI Email | [email protected] |
| Project Type | RTE |
| RTE Number | 4389 |