NSUF 17-1105: The effectiveness of coherent and incoherent twin boundaries in alleviating radiation damage in heavy-ion-irradiated 316L austenitic stainless steels
The proposed experiment will consist in carrying out TEM in-situ ion irradiation up to about 2 dpa of 316L stainless steel samples at 400°C. One annealed sample and one lightly cold-worked (2%) sample will be used. Annealing twin boundaries will be present in the annealed specimens and deformation twin boundaries will be present in the cold-worked specimen, as observed multiple times by the PI. Samples will be 3-mm disks prepared with conventional double jet electro-polishing with electrolyte A2. The high-temperature in situ TEM stage will be provided by IVEM and allow heating and double tilt (±40°, ±20°). The irradiation will be done at 400°C with 1MeV Kr+ ion at a flux of 1011 ions/cm2/s (corresponding to about 10-4 dpa/s). At this energy, Kr+ ions are not deposited in the thin foil and the energy lost is deposited primarily in the formation of sub-cascades, which should produce relatively homogenous damage throughout the foil thickness (loops). The effect of twin and grain boundaries on radiation damage will be observed in real-time in a two-beam condition near a [110] zone axis – the team has successfully prepared samples with grain containing twin boundaries having an appropriate orientation for in situ observation. Videos will be acquired so as to be able to precisely determine i) the location (with respect to the boundary) of visible defects formation, and ii) defect diffusivity with respect to distance from the boundary, which will be estimated by following the trajectory of single defect clusters/loops with time. Irradiation will be regularly paused to tilt the specimen to various conditions and take images so as to characterize defects types and sizes. Close attention will also be given to potential twin boundary distortion, which has been shown to play a role in defect absorption in Ag [7]. The project will be complemented with ex-situ STEM EDS examinations conducted at University of Wisconsin Madison of radiation-induced segregation (RIS) at the studied twin boundaries, which is known to affect IASCC susceptibility. The observations will address the following unanswered questions pertaining to 316L stainless steel and to austenitic alloys in general: is there a twin boundary affected zone with reduced defect accumulation? In terms of sink strength, how do twin boundaries compare to high-angle grain boundaries, and how do their sink strengths evolve with time? What is the difference in sink strength between annealing (typically more coherent) and deformation (typically less coherent) twin boundaries? Measurements of defect kinetics in the vicinity of twin boundaries could be used to improve models of component degradation in nuclear reactor environment. The requested time is 8 days. Four samples will be used so as to observed twins of two types - annealing and deformation - and two different thicknesses. About 2 days per samples will be required to achieve about 2 dpa per sample while regularly pausing irradiation to take images.
Additional Info
| Field | Value |
|---|---|
| Abstract | The proposed experiment will consist in carrying out TEM in-situ ion irradiation up to about 2 dpa of 316L stainless steel samples at 400°C. One annealed sample and one lightly cold-worked (2%) sample will be used. Annealing twin boundaries will be present in the annealed specimens and deformation twin boundaries will be present in the cold-worked specimen, as observed multiple times by the PI. Samples will be 3-mm disks prepared with conventional double jet electro-polishing with electrolyte A2. The high-temperature in situ TEM stage will be provided by IVEM and allow heating and double tilt (±40°, ±20°). The irradiation will be done at 400°C with 1MeV Kr+ ion at a flux of 1011 ions/cm2/s (corresponding to about 10-4 dpa/s). At this energy, Kr+ ions are not deposited in the thin foil and the energy lost is deposited primarily in the formation of sub-cascades, which should produce relatively homogenous damage throughout the foil thickness (loops). The effect of twin and grain boundaries on radiation damage will be observed in real-time in a two-beam condition near a [110] zone axis – the team has successfully prepared samples with grain containing twin boundaries having an appropriate orientation for in situ observation. Videos will be acquired so as to be able to precisely determine i) the location (with respect to the boundary) of visible defects formation, and ii) defect diffusivity with respect to distance from the boundary, which will be estimated by following the trajectory of single defect clusters/loops with time. Irradiation will be regularly paused to tilt the specimen to various conditions and take images so as to characterize defects types and sizes. Close attention will also be given to potential twin boundary distortion, which has been shown to play a role in defect absorption in Ag [7]. The project will be complemented with ex-situ STEM EDS examinations conducted at University of Wisconsin Madison of radiation-induced segregation (RIS) at the studied twin boundaries, which is known to affect IASCC susceptibility. The observations will address the following unanswered questions pertaining to 316L stainless steel and to austenitic alloys in general: is there a twin boundary affected zone with reduced defect accumulation? In terms of sink strength, how do twin boundaries compare to high-angle grain boundaries, and how do their sink strengths evolve with time? What is the difference in sink strength between annealing (typically more coherent) and deformation (typically less coherent) twin boundaries? Measurements of defect kinetics in the vicinity of twin boundaries could be used to improve models of component degradation in nuclear reactor environment. The requested time is 8 days. Four samples will be used so as to observed twins of two types - annealing and deformation - and two different thicknesses. About 2 days per samples will be required to achieve about 2 dpa per sample while regularly pausing irradiation to take images. |
| Award Announced Date | 2017-09-20T12:34:06.49 |
| Awarded Institution | Center for Advanced Energy Studies |
| Facility | Microscopy and Characterization Suite |
| Facility Tech Lead | Alina Zackrone, Wei-Ying Chen, Yaqiao Wu |
| Irradiation Facility | None |
| PI | Gabriel Meric de Bellefon |
| PI Email | [email protected] |
| Project Type | RTE |
| RTE Number | 1105 |