NSUF 15-586: Investigation of dislocation loop hardening and stability in irradiated RPV steels
Safe operation of nuclear reactors requires an understanding of how material properties change during operation. Reactor pressure vessel (RPV) steels are susceptible to embrittlement caused by both precipitation and clustering of defects formed under irradiation. In some cases, these defect clusters, for example dislocation loops, can also become enriched in solutes causing further embrittlement. The purpose of this RTE is to provide additional information about the strength and character of dislocation loops and their thermal stability which will then inform and improve hardening models. We will use atom probe tomography (APT) and transmission electron microscopy (TEM) to measure the precipitates and dislocation loops in two irradiated RPV steels with high Cu (0.4 wt.%), containing very little or no Ni (0.02-0.18 wt.%. While APT is only able to sample very small volumes, it can detect very low levels of solute enrichment at dislocations. TEM on the other hand is not as sensitive of a chemical analysis tool, but it can sample much larger volumes, which is required for good statistics as well as determining relationships between various features, such as dislocation loop densities near and away from grain boundaries. The proposed microstructural investigations will then be combined with a large database of microstructural and mechanical property data for a wide range of alloy compositions. This will help determine the relative contribution of precipitates and dislocation loops to the overall hardening, as well as determine the relationship between alloy composition and the balance of hardening features. It should be noted that the implications of these results are not limited to just RPV steels, since almost all ferritic and martensitic steels are susceptible to the same types of radiation induced hardening and embrittlement. This work can be completed over two separate trips to the Center for Advanced Energy Studies over a 6 month period.
Additional Info
| Field | Value |
|---|---|
| Abstract | Safe operation of nuclear reactors requires an understanding of how material properties change during operation. Reactor pressure vessel (RPV) steels are susceptible to embrittlement caused by both precipitation and clustering of defects formed under irradiation. In some cases, these defect clusters, for example dislocation loops, can also become enriched in solutes causing further embrittlement. The purpose of this RTE is to provide additional information about the strength and character of dislocation loops and their thermal stability which will then inform and improve hardening models. We will use atom probe tomography (APT) and transmission electron microscopy (TEM) to measure the precipitates and dislocation loops in two irradiated RPV steels with high Cu (0.4 wt.%), containing very little or no Ni (0.02-0.18 wt.%. While APT is only able to sample very small volumes, it can detect very low levels of solute enrichment at dislocations. TEM on the other hand is not as sensitive of a chemical analysis tool, but it can sample much larger volumes, which is required for good statistics as well as determining relationships between various features, such as dislocation loop densities near and away from grain boundaries. The proposed microstructural investigations will then be combined with a large database of microstructural and mechanical property data for a wide range of alloy compositions. This will help determine the relative contribution of precipitates and dislocation loops to the overall hardening, as well as determine the relationship between alloy composition and the balance of hardening features. It should be noted that the implications of these results are not limited to just RPV steels, since almost all ferritic and martensitic steels are susceptible to the same types of radiation induced hardening and embrittlement. This work can be completed over two separate trips to the Center for Advanced Energy Studies over a 6 month period. |
| Award Announced Date | 2015-08-10T00:00:00 |
| Awarded Institution | None |
| Facility | None |
| Facility Tech Lead | Yaqiao Wu |
| Irradiation Facility | None |
| PI | G. Robert Odette |
| PI Email | [email protected] |
| Project Type | RTE |
| RTE Number | 586 |