Regensburg 2013 – wissenschaftliches Programm
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KR: Fachgruppe Kristallographie
KR 4: Quantitative Materialanalyse (MI jointly with KR)
KR 4.7: Vortrag
Dienstag, 12. März 2013, 11:45–12:00, H5
Analysis of impurity diffusion and recrystallisation processes of Fe and FeNi polycrystals with low energy electron microscopy — •Benjamin Borkenhagen, Gerhard Lilienkamp, and Winfried Daum — Institute of Energy Research and Physical Technologies, TU Clausthal, Leibnizstraße 4, 38678 Clausthal-Zellerfeld
We use low energy electron microscopy (LEEM) and laterally resolved low energy electron diffraction (µLEED) to characterize surface properties of polycrystalline materials as well as structural and dynamic properties of grain boundaries. In this contribution, we report on our analyses of segregation and diffusion processes taking place at the surface of polycrystalline Fe and FeNi. Previously we have shown that bulk impurities, mostly sulphur, segregate from the bulk of a heated polycrystal to the surface and form two-dimensional impurity islands. At a suitable temperature we observe Ostwald ripening of these islands and, at elevated temperature, dissolution of the islands. Here we present a quantitative study of impurity diffusion processes, which yields both linear and t1/2 time dependencies for the impurity concentrations on different grains. These different time dependencies point to different bulk impurity concentration profiles in different grains. In addition to impurity diffusion, we studied recrystallisation processes and their effects on surface topography in real time. By measuring tripel-point speeds and geometries of the grain boundaries, the rate-limiting step of the recrystallisation process – grain boundary mobility or tripel point mobility – was identified.