ICAMS / Interdisciplinary Centre for Advanced Materials Simulation
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Grain-boundary plasticity in nanocrystalline alloys studied by hybrid MD/MC simulations: coupled motion versus grain-boundary sliding and dislocation slip

Date: 17.12.2012
Time: 4:30 p.m.
Place: Seminar room 0.08

Karsten Albe, TU Darmstadt, Darmstadt, Germany

Plastic deformation of miscible and immiscible binary nanocrystalline alloys is studied by means of atomic scale computer simulations. The microstructures are specifically chosen to facilitate mesoscopic grain boundary sliding.
The influence of segregating solutes on the deformation mechanisms is studied and different cases of solute distributions are compared. We find that the competition between mesoscopic grain boundary sliding and coupled grain boundary motion is controlled by the concentration and distribution of segregating solutes.
By analyzing the microstructural evolution and dislocation activity we make a connection between the atomistic solute distribution and the mechanisms of deformation, explaining the observed stress-strain behaviour. The detailed analysis of the normal GB motion reveals a stick-slip behaviour and a coupling factor which is consistent with results from bicrystal simulations. Using a novel method to quantify the amount of crystal slip strain from atomistic data, it is demonstrated how plastic deformation carried by dislocation changes as a function of the local relaxation. The results indicate that conventional molecular dynamics simulations overestimate the contributions of dislocation slip to the overall plastic deformation of nanocrystalline samples.

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