NSUF 21-4238: Verifying Wigner energy measurements by in-situ TEM annealing of neutron-irradiated Ti
Videre est non sempre credere (Seeing is not always believing).
Radiation damage evaluation is hindered by the limitations of the characterization techniques chosen to investigate the microstructure. Many defects are below the resolution of TEM, or unable to be detected by PAS or resistivity recovery measurements. However, all defects have an associated excess energy, and thus may be detected by annealing the material and measuring the stored energy release. We have conducted DSC experiments of neutron-irradiated Ti to investigate the defects responsible for stage V recovery. In contrast to the prior literature, we have observed two energetically-distinct defect reactions where the model predicts only one. Our MD simulations show that the first reaction may be associated with point defect-induced glide of -type dislocations loops sweeping through a field of sub-TEM-visible defects. The second process occurs at temperatures equivalent to cold-work recovery in Ti, and previous TEM studies on neutron-irradiated Ti report the coalescence of dislocation loops to form a network of (linear) dislocations. In order to confirm the defects responsible for the two processes within stage V recovery, we propose to conduct in-situ TEM heating of the same neutron-irradiated and unirradiated Ti samples. Cryo-FIB will be used to minimize H pickup during lift-out of the TEM lamellae. In-situ TEM heating will then be conducted to visualize the microstructural evolution at the associated temperatures. From these experiments, we expect to confirm the annealing mechanism behind stage V radiation damage recovery in Ti, and to correlate the density, mobility, and stability of dislocations with the results from DSC and MD. Determining the defects responsible for the substages of stage V annealing will lead to a more accurate model for the recovery of radiation damage at reactor-relevant temperatures. In-situ TEM heating will provide the final confirmation necessary to demonstrate the characterization of radiation damage through the energy stored in defects. Successful demonstration will establish this as a novel strategy to determine the full spectrum of defects present in irradiated materials, using Eugene Wigner’s original 1940’s theory for far more practical uses. This concept also has the potential to validate decades of radiation damage simulations, and may yield insight into how sub-TEM-visible defects affect mechanisms at higher length scales. In addition, this may enable the a posteriori measurement of how much dose has been received by a material, critical for forensic nuclear security applications and validation of reactor physics simulations. The impact of this work is much greater than just nuclear materials science. Achieving an accurate characterization of defects present in a material will advance us towards one of the ultimate goals in materials science: the deterministic and readily measured relationship between atomistic structure and macroscopic properties of ultimate interest.
Additional Info
| Field | Value |
|---|---|
| Abstract | Videre est non sempre credere (Seeing is not always believing). Radiation damage evaluation is hindered by the limitations of the characterization techniques chosen to investigate the microstructure. Many defects are below the resolution of TEM, or unable to be detected by PAS or resistivity recovery measurements. However, all defects have an associated excess energy, and thus may be detected by annealing the material and measuring the stored energy release. We have conducted DSC experiments of neutron-irradiated Ti to investigate the defects responsible for stage V recovery. In contrast to the prior literature, we have observed two energetically-distinct defect reactions where the model predicts only one. Our MD simulations show that the first reaction may be associated with point defect-induced glide of <a>-type dislocations loops sweeping through a field of sub-TEM-visible defects. The second process occurs at temperatures equivalent to cold-work recovery in Ti, and previous TEM studies on neutron-irradiated Ti report the coalescence of dislocation loops to form a network of (linear) dislocations. In order to confirm the defects responsible for the two processes within stage V recovery, we propose to conduct in-situ TEM heating of the same neutron-irradiated and unirradiated Ti samples. Cryo-FIB will be used to minimize H pickup during lift-out of the TEM lamellae. In-situ TEM heating will then be conducted to visualize the microstructural evolution at the associated temperatures. From these experiments, we expect to confirm the annealing mechanism behind stage V radiation damage recovery in Ti, and to correlate the density, mobility, and stability of dislocations with the results from DSC and MD. Determining the defects responsible for the substages of stage V annealing will lead to a more accurate model for the recovery of radiation damage at reactor-relevant temperatures. In-situ TEM heating will provide the final confirmation necessary to demonstrate the characterization of radiation damage through the energy stored in defects. Successful demonstration will establish this as a novel strategy to determine the full spectrum of defects present in irradiated materials, using Eugene Wigner’s original 1940’s theory for far more practical uses. This concept also has the potential to validate decades of radiation damage simulations, and may yield insight into how sub-TEM-visible defects affect mechanisms at higher length scales. In addition, this may enable the a posteriori measurement of how much dose has been received by a material, critical for forensic nuclear security applications and validation of reactor physics simulations. The impact of this work is much greater than just nuclear materials science. Achieving an accurate characterization of defects present in a material will advance us towards one of the ultimate goals in materials science: the deterministic and readily measured relationship between atomistic structure and macroscopic properties of ultimate interest. |
| Award Announced Date | 2021-06-07T15:48:08.813 |
| Awarded Institution | Idaho National Laboratory |
| Facility | Advanced Test Reactor |
| Facility Tech Lead | Alina Zackrone |
| Irradiation Facility | None |
| PI | Charles Hirst |
| PI Email | [email protected] |
| Project Type | RTE |
| RTE Number | 4238 |