The importance of nano-characterization in the radiation induced segregation (RIS) phenomena in ferritic model alloys

with Olivier Tissot, 
French Alternative Energies and Atomic Energy Commission Saclay
Friday, November 18, 2022, 10:10 AM

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Dr. Tissot will present the methodology of characterization used to study the effect of radiation on segregation in ferritic model alloys. These alloys are composed of basic elements of industrial ferritic/martensitic steels and were used to understand the main segregation mechanisms involved under irradiation. Atom Probe Tomography (APT) is a very powerful tool to study nanoscale phenomena but its application to grain boundary characterization is complicated. In fact, once samples with a grain boundary (GB) have been successfully prepared, the tip can still break during APT experiments due to the brittleness of the sample. In addition, depending on the GB orientation, the resolution of the characterization will change, thus the GB has to be correctly orientated or chosen during tip preparation. This presentation will show how important is the EBSD/TKD/APT (Electron Back Scattered Diffraction/Transmission Kikuchi Diffraction) coupling to fully characterize the segregation at GBs and its response under ion irradiation. TEM and APT measurements of the same grain boundary are shown. Comparison between low angle, high angle and coincidence (Σ3) GBs will be shown. Finally, the unexpected observed behavior will be discussed and compared to the previous paper on the subject.

Olivier Tissot performed his PhD at French Alternative Energies and Atomic Energy Commission Saclay (CEA), in 2016. Then, he joined the CEA as a researcher to study the effect of irradiation in FeCr based alloys using Atom Probe Tomography (APT) and Transmission Electron Microscopy (TEM). During the past 5 years, he mainly worked on characterizing ferritic model alloys before and after irradiation. He notably studied radiation induced damage in FeCr model alloys including defect creation, and nucleation and growth of precipitates. His current main topic of research focuses on the effect of radiation on grain boundary segregation in ferritic alloys. In addition, he is in charge of the High Voltage Electron Microscope (HVEM) facility. He also gives some courses on radiation effects in metals in the engineering school Paris-Saclay.