NSUF 25-5278: Radiation-induced segregation at coherent twin boundaries in 316L steels after low dose proton irradiation
The project objective is to irradiate two 316L austenitic steel samples with 2 MeV Protons at 360C to the low doses of 0.1 and 0.5 dpa utilizing the University of Michigan’s Ion Beam Laboratory, and then to characterize the radiation-induced segregation at coherent twin boundaries using scanning transmission electron microscopy (STEM) and specifically energy dispersive x-ray spectroscopy (STEM/EDS) at the Michigan Center for Materials Characterization (MC2). TEM bars of 316L austenitic stainless steel will be machined via electrical discharge machining and submitted to the MIBL for irradiation. It is requested that these TEM bars are electropolished following the procedure commonly used in the MIBL before irradiation, to ensure an EBSD quality finish. Two separate irradiation batch experiments with 2 MeV protons at 360C and a dose rate of 10-5 dpa/s are proposed in order to create a set of samples with a dose of ~0.5 dpa and a set of samples with a dose of ~0.1 dpa. This material will be characterized at MC2 to determine the impact of grain boundary character on low-dose radiation-induced segregation (RIS). Two coherent 3 twin grain boundaries (CTWGBs) and one high-angle grain boundary (HAGB) will be selected by EBSD. One TEM sample will be prepared for each GB using SEM-FIB lift-out. Two STEM-EDS maps, about 500 nm by 500 nm, will be acquired for each TEM sample to quantify the levels of Cr, Ni, Si, Mo and P segregation on the GBs. Prior work supported by an NEUP award on an intermediate dose (~4 dpa) proton irradiated 316L steel specimen revealed significant segregation at coherent 3 twin boundaries (CTWGBs), as we reported in a manuscript recently accepted for publication in the Journal of Nuclear Materials (https://doi.org/10.1016/j.jnucmat.2024.155470). This is striking as there are historic literature studies reporting that these special boundaries as poor sites for point defect elimination and thus display minimal RIS. A few recent studies, however, suggest that CTWGBs are capable of progressively developing significant levels of RIS. The current state-of-knowledge on this area seems therefore contradictory. The investigation of the low-dose proton irradiated specimens via this proposal will enable us to quantify RIS and the radiation damage build-up at coherent Sigma3 twin at low doses, revealing how these GBs develop into efficient point defect sinks. Furthermore, the results of this analysis should be of special interest to studies of RIS in grain boundary-engineered steels, as these alloys typically have higher fractions of twin boundaries.
Informações Adicionais
| Campo | Valor |
|---|---|
| Award Announced Date | 2025-08-06T10:09:22.98 |
| Awarded Institution | University of Illinois at Urbana-Champaign |
| Facility Tech Lead | Kevin Field |
| Irradiation Facility | Michigan Ion Beam Laboratory |
| PI | Pascal Bellon |
| PI Email | [email protected] |
| Project Type | RTE |
| RTE Number | None |