Regensburg 2013 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 40: Topical Session: TEM-Symposium - In-Situ I

MM 40.3: Talk

Wednesday, March 13, 2013, 15:45–16:00, H25

Superdislocation characterization by means of large angle convergent beam electron diffraction (LACBED) — •Julian Müller and Erdmann Spiecker — Center for Nanoanalysis and Electron Microscopy (CENEM), Department Werkstoffwissenschaften, Universität Erlangen-Nürnberg

Superdislocations (SD) play an important role for the mechanical properties of ordered intermetallic compounds. For instance, in Ni base superalloys the formation of SDs and their glide/climb across the ordered γ’ phase are key elementary processes in high-temperature creep. A key step of the microscopic characterization of dislocations in the transmission electron microscope is the determination of the Burgers vector (BV) which is typically performed by identifying two-beam conditions for which the dislocation is invisible. However, in the case of SDs difficulties in the conventional BV analysis often arise due to pronounced residual contrast. In this work we demonstrate that LACBED is well suited for reliable BV analysis of SDs even in cases where the conventional analysis fails. We confirm that SDs with BVs of type a<110> and a<100> coexist in high temperature crept Ni-base superalloys, which means that the SDs are composed of partials with identical or different BVs of type a/2<110>, respectively. We use weak-beam dark field imaging and STEM tomography to reveal the corresponding splitting of the SDs into partials.
The authors gratefully acknowledge the DFG RTG 1229 and SFB/TRR 103 for financial support and L. Agudo and G. Eggeler from Ruhr University Bochum for providing the samples.