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Abstract

In many interface-dominated nanostructured materials the role of interfaces during deformation is not yet completely clarified. Very fine spacing of interfaces leads to a competition between dislocation controlled and grain boundary sliding based plasticity. To improve our understanding of this competition we have to investigate the atomistic origin of ductility in the interface region. A multi-scale concept is introduced to capture effects of both the electronic and the atomistic level at interfaces in nano-lamellar TiAl alloys. First, we carried out quasistatic calculations of multi-planar generalized stacking fault energy (M-γ) surfaces of the interface plane as well as the adjacent layers. Second, molecular dynamics simulations guided by ab initio γ-surface calculations were carried out for different bicrystal cells under different shear loading conditions. The results show various shear mechanisms such as twin nucleation and migration/absorption, interface partial dislocation nucleation, and rigid grain boundary sliding/migration. The comparison with the M-γ-surfaces allows to create a link between physical properties and deformation mechanisms, and hence between the results of ab-initio calculations and molecular dynamics simulations. Furthermore we discuss the interplay between interface geometry, atomistic structure, and loading conditions, and its impact on the deformability of lamellar microstructures.