NSUF 19-1734: Atom Probe Tomography Investigation on the Precipitation of Neutron-Irradiated Alloy 800H/800H-TMP
The goal of the project is to investigate the chemical composition of γ’ precipitates and the solute distribution in austenitic stainless steels 800H and 800H-TMP (thermomechanical processed) after neutron irradiation. Alloy 800H and its grain-boundary-engineered 800H-TMP are promising alloys interested by the Advanced Radiation-Resistant Materials (ARRM) and Light Water Reactor Sustainability (LWRS) programs. Previous ion irradiation studies of Alloy 800H, conducted by different research groups using different types of ion irradiation, showed interconnected γ’ precipitates at lower irradiation temperatures and dispersive spherical morphology at higher irradiation temperatures. Limited neutron irradiation studies revealed dispersive nanometer-sized γ’ precipitates at ~500°C. In addition, a preliminary study indicated beneficial effects of TMP on radiation resistance of Alloy 800H. For example, reduced number density of γ’ precipitates was reported for Alloy 800H-TMP, as compared to Alloy 800H after neutron irradiation to ~3 dpa. Therefore, several knowledge gaps still exist for Alloy 800H, such as the consistency between ion and neutron irradiation induced γ’ precipitates, the morphology changes of γ’ precipitates, and the beneficial effect sustainability of TMP on radiation resistance. One of the factors limiting thorough understanding of radiation-induced γ’ precipitates is attributable to the ultrafine precipitates that are difficult to be well characterized by electron microscopy.
In this project, we propose to use atom probe tomography (APT) to characterize neutron-irradiation-induced γ’ precipitates in Alloy 800H and 800H-TMP, with an expected performance period of six months after the award of the proposal. APT allows us to quantify the chemical composition, size distribution, and number density, and to visualize the morphology of the precipitates. The selected samples of Alloy 800H and 800H-TMP were neutron-irradiated to ~7 and ~9 dpa at two temperatures. The APT results will be compared to understand the TMP effects, which will be also compared with the transmission electron microscopy results of the same samples, together with the previous results of ion- and neutron-irradiated Alloy 800H, to have a better picture about the radiation-induced γ’ precipitates under different irradiation conditions. The work proposed here focused on the precipitation behavior of Alloy 800H and 800H-TMP after neutron irradiation, and the outcome of this research is to provide comprehensive understanding of the morphology, size distribution, number density, and chemical composition of γ’ precipitates at different temperatures and doses, and consequently fill most of the knowledge gaps as described before. The comprehensive microstructural results will also help establish a reliable correlation with the mechanical properties of the alloys.
Additional Info
| Field | Value |
|---|---|
| Abstract | The goal of the project is to investigate the chemical composition of γ’ precipitates and the solute distribution in austenitic stainless steels 800H and 800H-TMP (thermomechanical processed) after neutron irradiation. Alloy 800H and its grain-boundary-engineered 800H-TMP are promising alloys interested by the Advanced Radiation-Resistant Materials (ARRM) and Light Water Reactor Sustainability (LWRS) programs. Previous ion irradiation studies of Alloy 800H, conducted by different research groups using different types of ion irradiation, showed interconnected γ’ precipitates at lower irradiation temperatures and dispersive spherical morphology at higher irradiation temperatures. Limited neutron irradiation studies revealed dispersive nanometer-sized γ’ precipitates at ~500°C. In addition, a preliminary study indicated beneficial effects of TMP on radiation resistance of Alloy 800H. For example, reduced number density of γ’ precipitates was reported for Alloy 800H-TMP, as compared to Alloy 800H after neutron irradiation to ~3 dpa. Therefore, several knowledge gaps still exist for Alloy 800H, such as the consistency between ion and neutron irradiation induced γ’ precipitates, the morphology changes of γ’ precipitates, and the beneficial effect sustainability of TMP on radiation resistance. One of the factors limiting thorough understanding of radiation-induced γ’ precipitates is attributable to the ultrafine precipitates that are difficult to be well characterized by electron microscopy. In this project, we propose to use atom probe tomography (APT) to characterize neutron-irradiation-induced γ’ precipitates in Alloy 800H and 800H-TMP, with an expected performance period of six months after the award of the proposal. APT allows us to quantify the chemical composition, size distribution, and number density, and to visualize the morphology of the precipitates. The selected samples of Alloy 800H and 800H-TMP were neutron-irradiated to ~7 and ~9 dpa at two temperatures. The APT results will be compared to understand the TMP effects, which will be also compared with the transmission electron microscopy results of the same samples, together with the previous results of ion- and neutron-irradiated Alloy 800H, to have a better picture about the radiation-induced γ’ precipitates under different irradiation conditions. The work proposed here focused on the precipitation behavior of Alloy 800H and 800H-TMP after neutron irradiation, and the outcome of this research is to provide comprehensive understanding of the morphology, size distribution, number density, and chemical composition of γ’ precipitates at different temperatures and doses, and consequently fill most of the knowledge gaps as described before. The comprehensive microstructural results will also help establish a reliable correlation with the mechanical properties of the alloys. |
| Award Announced Date | 2019-05-14T15:55:05.33 |
| Awarded Institution | Center for Advanced Energy Studies |
| Facility | Microscopy and Characterization Suite |
| Facility Tech Lead | Yaqiao Wu |
| Irradiation Facility | None |
| PI | Weicheng Zhong |
| PI Email | [email protected] |
| Project Type | RTE |
| RTE Number | 1734 |