Regensburg 2016 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 53: Microstructure and Phase Transformations II

MM 53.5: Vortrag

Donnerstag, 10. März 2016, 12:45–13:00, H39

Multi-scale modeling of phase transitions around dislocations — •Gerard Paul Leyson, Blazej Grabowski, and Jörg Neugebauer — Max Planck Institute for Iron Research, Max-Planck-Straße 1, 40237 Düsseldorf

Classic nucleation theory does not take into account local stress gradients present in the material. In particular, the stress field around a dislocation is large and can provide a strong driving force for phase transition and stabilize phases that would otherwise be unstable in the unstressed bulk material. To describe the impact of dislocation strain on nucleation we have developed a multi-scale framework. First, classic nucleation theory is generalized to include the effects of external stress gradients. As input the dislocation stress field is determined using a semi-empirical embedded atom (EAM) method. Second, the change in formation energy due to the phase transformation is calculated using ab-initio calculations. Using this approach we identify conditions that lead to a quasi-one-dimensional defect that is stable against coarsening. The mechanism identified here is general and applies e.g. to the recently found linear complexions in Fe-Mn alloys [1] or the formation of nano-hydrides at dislocations [2].

[1] Kuzima M, Herbig M, Ponge D, Sandlöbes S and Raabe D. Science 2015; 349: 1080-1083. [2] Leyson GP, Grabowski B and Neugebauer J. Acta Materialia 2015; 89:50-59