Dresden 2011 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 18: Mechanical Properties I

MM 18.5: Talk

Tuesday, March 15, 2011, 15:00–15:15, IFW B

Controlling the strength of nanocrystalline metals and alloys: On the role of the grain boundary relaxation state — •Jonathan Schäfer, Alexander Stukowski, and Karsten Albe — TU Darmstadt, Darmstadt, Germany

Plastic deformation in various nanocrystalline metals and their alloys is studied by means of atomic scale computer simulations.

The distribution of solutes is equilibrated in nanocrystalline model structures of different grain sizes and compositions using a combination of Monte-Carlo and molecular dynamics methods. The resulting samples are deformed under uniaxial load. The role of grain boundary relaxation is analyzed in detail by comparing chemically and structurally relaxed samples with model structures that were only structurally relaxed. The relaxation state of the grain boundary is measured by means of the atomic free volume. The defect evolution within the grains of our nanocrystalline model structures is monitored, using a novel dislocation extraction algorithm.

The main goal of this work is to make a connection between the atomistic configuration within the microstructures and the characteristics of the observed stress-strain behaviour.

The simulations reveal that the relaxation state of the GBs is of great importance for the maximum strength in the case of all studied material systems and grain sizes. The (chemical) equilibration is proven to raise the barrier for GB mediated processes. Also in the case of grain sizes, where the major carrier of plastic deformation is dislocation slip, the relaxation state of the GB is shown to have a significant effect.