Dresden 2017 – scientific programme
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O: Fachverband Oberflächenphysik
O 39: Oxide and Insulator Surfaces: Structure, Epitaxy and Growth II
O 39.8: Talk
Tuesday, March 21, 2017, 15:45–16:00, WIL C107
Transport along grain boundaries through alumina investigated by atom probe tomography — •Torben Boll1,2, Kinga A. Unocic3, Bruce A. Pint3, and Krystyna Stiller2 — 1Institut für Angewandte Materialien, Karlsruhe Institut für Technologie, 76344 Eggenstein Leopoldshafen — 2Department of Physics, Chalmers University of Technology, SE-412 96 Göteborg, Sweden — 3Materials Science and Technology Division, Oak Ridge National Laboratory, Oak, Ridge TN, 37831, USA
It is generally agreed upon that transport through growing alumina scales occurs predominantly due to inward oxygen diffusion along grain boundaries (GBs). However, it is also accepted that there exists some amount of concurrent outward aluminum diffusion along the GBs. Moreover, the effect of alloying elements on oxidation behavior and how they affect diffusional fluxes still remains uncertain.
For this study different Ni-Al alloys with additions of Hf, Y and Zr were investigated. The materials were subjected to an initial exposure in O2 at 1100∘C. The initial exposure was continued again at 1100∘C for 5h after a smoothing of the surface. After this double exposure SEM a growth of ridges above the GBs, as an indication foroutward diffusion were observed. Scanning transmission electron tomoggraphy energy dispersive X-Ray spectroscopy investigations were complemented with atom probe tomography, which gave quantitative information about the concentration of the different elements at the GBs. This helped to calculate the Gibbsian excesses and to discuss the influence of different dopants.