Berlin 2008 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 29: Mechanical Properties I

MM 29.1: Talk

Wednesday, February 27, 2008, 14:00–14:15, H 0111

Molecular Dynamics Simulations of Grain Boundary Plasticity — •Yvonne Ritter, Alexander Stukowski, and Karsten Albe — Institut f. Materialwissenschaft, TU Darmstadt, Petersenstr. 23, D-64287 Darmstadt

Dislocation nucleation at grain boundaries (GB) and as well as grain boundary sliding are relevant mechanisms governing the deformation behavior of nanocrystalline metals. By means of molecular dynamics simulations we examine well defined bicrystal geometries under different loads. The simulations are performed for copper and aluminum in order to investigate the influence of various stacking fault (SF) energies. For a Σ 7 (111) twist boundary GB sliding occurs by a collective movement of all atoms in the boundary plane, but no dislocation activity can be detected. A Σ 33 (225) tilt boundary with a dissociated structure dos not deform by GB sliding but reacts by the growth of pre-existing intrinsic stacking fault facets when exposed to a shear deformation. Under tensile deformation partial dislocations nucleate from both GBs. The nucleation mechanism is thermally activated in both cases. In the case of the Σ 7 GB the dislocations are statistically emitted from tetrahedral nucleation sites. The partial dislocations, that are emitted from the Σ 33 GB, emerge at well defined positions determined by the GB structure.