Berlin 2018 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 35: Interfaces

MM 35.3: Talk

Wednesday, March 14, 2018, 12:15–12:30, H 0107

Atom probe tomography of grain boundary segregation in the FeCr system — •Helena Solodenko, Patrick Stender, Sebastian Eich, and Guido Schmitz — Institute for Materials Physics, University of Stuttgart, Heisenbergstraße 3, 70569 Stuttgart, Germany

Nanocrystalline materials have unique properties. This is due to the small grain size and high amount of interfaces, like grain boundaries (GB) or even triple junctions (TJ). Unfortunately, nanocrystalline materials are not thermally stable. The high amount of interfaces usually leads to a high interfacial excess energy, which is reduced by grain growth. A chance to overcome this problem is segregation of solutes to GBs, which can lower the interfacial energy and thus the driving force for grain growth. Density functional theory and experimental data suggest that the iron-chromium (Fe-Cr) system is expected to show exceptional thermodynamic behavior, which was also recently predicted by atomistic simulations based on a thermodynamically accurate embedded-atom potential. The key prediction is a distinctive negative GB energy for very specific compositions close to the phase boundary on the chromium-rich side, thus inhibiting grain growth. In this work, the segregation behaviour of Fe-Cr is investigated by atom probe tomography (APT). Nanocrystalline APT samples of a Cr(Fe) alloy with predefined compositions are produced by ion beam sputtering and focused ion beam. Reconstructed samples show strong segregation of the minority component Fe to Cr grain boundaries. The segregation isotherm is investigated at different compositions and compared with available atomistic studies.