Regensburg 2016 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 3: Interfaces I: Mechanical properties
MM 3.1: Vortrag
Montag, 7. März 2016, 10:15–10:30, H39
Migration mechanisms of grain boundaries deviating from the symmetric tilt orientation — •Sherri Hadian1, Blazej Grabowski1, Chris Race2, and Jörg Neugebauer1 — 1Max-Planck-Institut für Eisenforschung GmbH, Max-Planck-Str. 1, 40237 Düsseldorf, Germany — 2Dalton Nuclear Institute, University of Manchester, Manchester M13 9PL, United Kingdom
We have studied the migration kinetics and atomistic mechanisms of mixed tilt and twist grain boundaries systematically deviated from the symmetric tilt Σ7 <111> {1 2 3} orientation as they constitute the majority of experimentally observed mobile grain boundaries. Using physically converged simulations and investigating dense motion snapshots in 3D, we find unique characteristic mechanisms in the motion of non-symmetric grain boundaries as compared with the symmetric one. The mixed grain boundaries show nano-faceting, which enables two heterogeneous atomistic migration mechanisms and critically changes the previously reported island nucleation mechanism in the symmetric Σ7 tilt boundary [1]: Depending on the orientation of the nano-facets/steps either a double kink nucleation and propagation or a pure kink flow drives the motion. We show that these atomistic mechanisms are the origin of the observed change from a strongly non-Arrhenius behavior towards a more Arrhenius one and subsequently a change in the asymptotic behavior of the migration barrier at low driving forces as we change the grain boundary from a symmetric tilt to a general mixed one. In the end, connections were made between grain boundary migration processes and those of the surface epitaxial growth.