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MM: Fachverband Metall- und Materialphysik

MM 30: Interfaces

MM 30.2: Vortrag

Mittwoch, 14. März 2018, 10:30–10:45, H 0107

Direct observation of novel structures and transitions in [111] tilt grain boundaries — •Thorsten Meiners¹, Timofey Frolov², Christian H. Liebscher¹, and Gerhard Dehm¹ — ¹Max-Planck-Institut für Eisenforschung GmbH, Düsseldorf — ²Lawrence Livermore National Laboratory

It is well known that grain boundaries (GBs) have a significant influence on the materials macroscopic mechanical properties. Recently, thermodynamic models and atomistic calculations have predicted the possibility of GB phase transitions, which can alter the GB properties. In our study, we investigate the structure of symmetric and asymmetric [111] tilt GBs in copper by aberration-corrected scanning transmission electron microscopy (STEM) and molecular dynamics simulations (MD). The structural units of two symmetric Σ 19b tilt boundaries (46.83° [111]/{253} and 46.83° [111]/{178}) agree well with that obtained by the molecular static simulations. The symmetric 46.83° [111]/{178}) GB shows a regular pattern consisting of two structural units. In case of a asymmetric 46.83° [111]/{1-10}{9-2-7} tilt boundary we observe the same structural units, but now irregularly interrupted by a defect. These different structural units are also in agreement with MD simulations. At a special location, a sharp transition of the structural units with a stronger disorder at the asymmetric GB is observed. The coexistence of both structural motives provides first experimental evidence for the coexistence of two different GB phases. The differences in atomic ordering of the irregular structural units and transitions between structural motives will be discussed in detail.