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MM: Fachverband Metall- und Materialphysik

MM 8: Topical session (Symposium EPS and MM): Mechanical Properties at Small Scales

MM 8.1: Topical Talk

Montag, 12. März 2018, 11:45–12:15, TC 006

Deformation twinning in nanostructured metallic systems: molecular dynamics study — •Sandrine Brochard, Romuald Béjaud, and Julien Durinck — Institut PPRIME - Poitiers-Futuroscope - France

At the nanoscale, mechanical twinning seems to be promoted, as shown e.g. in thin films or nanocrystalline materials. This trend is also true for metallic nanolayered composites obtained by severe plastic deformation processes. In such materials, interfaces may act as partial dislocation and deformation twin sources, and the interfaces structure is expected to have a key role in twin propagation and thickening.

In this study, we investigate how different interface types influence the main stages of mechanical twinning. Because of the small length and times scales at which the elementary plasticity mechanisms involved occur, molecular dynamics simulations prove to be relevant and efficient tools.

Heterophase interfaces in a bimetallic Cu/Ag system, as well as a coherent twin boundary (CTB), are examined in a similar thin film geometry. A reference case with no planar defect inside the thin film is also considered. For both systems with "heterotwin" heterophase interface and CTB, the deformation twins are smaller, consistent with the low permeability of these interfaces to dislocations. But twins are more numerous, which is correlated to Lomer dislocation nucleation. For the Cu/Ag film with a "cube on cube" type interface, our simulations reveal the specific role of the misfit dislocation mesh in twin extension from the interface.