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Berlin 2018 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 37: Microstructure and Phase Transformations

MM 37.3: Talk

Wednesday, March 14, 2018, 12:15–12:30, TC 010

Atomic scale structural transitions at stacking faults in C14 Fe2Nb Laves Phase — •Christian Liebscher1, Michaela Šlapáková1,2, Sharvan Kumar3, and Frank Stein11Max-Planck-Institut für Eisenforschung GmbH, 40237 Düsseldorf, Germany — 2Charles University, Department of Physics of Materials, 12116 Prague, Czech Republic — 3Brown University, School of Engineering, Providence, RI 02912, USA

Laves phases belong to the group of tetrahedrally closed-packed phases (TCP) and are commonly observed to exist in many material systems. The complex crystal structure of the C14 Fe2Nb Laves phase can be described by a layered arrangement of small (Fe) and large (Nb) atoms forming interpenetrating single and triple layers. By combining aberration-corrected scanning transmission electron microscopy (STEM) with atomic scale chemical spectroscopy, we unravel composition-induced atomic scale structural transitions at stacking faults in a Nb-rich Fe2Nb Laves phase. The fault density is observed to significantly increase with the presence of excess Nb atoms. Two basic variants, confined and highly extended faults are present. In the case of basal faults extending over several micrometers, nanometer-thin layers of the Fe7Nb6-phase are observed to form by the intercalation of multiple three-layer stacks of Nb atoms into the host Laves structure. At confined basal stacking faults, the formation of a fragmentary Fe7Nb6-phase is established, where a complete Fe kagomé layer is absent. This complexion is stablized by the imposed elastic and compositional constraints at the stacking fault.

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