ATOMIC-SCALE MODELING OF THE DEFORMATION OF NANOCRYSTALLINE METALS

J. SCHIØTZ1,2, T. VEGGE1,2, and K. W. JACOBSEN1

1Center for Atomic-scale Materials Physics and Department of Physics, Technical University of Denmark, DK-2800 Lyngby, Denmark
2Materials Research Department, RisøNational Laboratory, DK-4000 Roskilde, Denmark.

Abstract

Nanocrystalline metals, i.e. metals with grain sizes from 5 to 50 nm, display technologically interesting properties, such as dramatically increased hardness, increasing with decreasing grain size. Due to the small grain size, direct atomic-scale simulations of plastic deformation of these materials are possible, as such a polycrystalline system can be modeled with the computational resources available today.

We present molecular dynamics simulations of nanocrystalline copper with grain sizes up to 13 nm. Two different deformation mechanisms are active, one is deformation through the motion of dislocations, the other is sliding in the grain boundaries. At the grain sizes studied here the latter dominates, leading to a softening as the grain size is reduced. This implies that there is an ``optimal'' grain size, where the hardness is maximal.

Since the grain boundaries participate actively in the deformation, it is interesting to study the effects of introducing impurity atoms in the grain boundaries. We study how silver atoms in the grain boundaries influence the mechanical properties of nanocrystalline copper.

To appear in: V. Bulatov et al., Multiscale Modeling of Materials, vol 538 of Mater. Res. Soc. Symp. Proc.

A preprint is available as compressed PostScript (10 pages, 409 KB compressed (gzip), 1.35 MB uncompressed).

The preprint is also available (in various formats incl. PDF) from the preprint server as preprint number cond-mat/9812102.

Last modified: 7 December, 1998.

Jakob Schiøtz, schiotz@fysik.dtu.dk