ATOMIC-SCALE SIMULATIONS OF THE MECHANICAL
DEFORMATION OF NANOCRYSTALLINE
METALS
Center for Atomic Scale Materials Physics (CAMP) and
Department of Physics, Building 307, Technical University of Denmark,
DK-2800 Lyngby, Denmark
(1) Also at: Materials Research Department, Risø National
Laboratory, DK-4000 Roskilde, Denmark.
(2) Present address: SISSA, Via Beirut 2-4, I-34014 Grignano
(TS), Italy.
Abstract
Nanocrystalline metals, i.e.\ metals in which the grain size is in
the nanometer range, have a range of technologically interesting
properties including increased hardness and yield strength. We
present atomic-scale simulations of the plastic behavior of
nanocrystalline copper. The simulations show that the main
deformation mode is sliding in the grain boundaries through a large
number of uncorrelated events, where a few atoms (or a few tens of
atoms) slide with respect to each other. Little dislocation
activity is seen in the grain interiors. The localization of the
deformation to the grain boundaries leads to a hardening as the
grain size is increased (reverse Hall-Petch effect), implying a
maximum in hardness for a grain size above the ones studied here.
We investigate the effects of varying temperature, strain rate and
porosity, and discuss the relation to recent experiments. At
increasing temperatures the material becomes softer in both the
plastic and elastic regime. Porosity in the samples result in a
softening of the material, this may be a significant effect in many
experiments.
Physical Review B 60, 11971 (1999).
Available from the PRB website.
A locally stored copy (in PDF format) is available
here.
Last modified: 8 October 2002.
Jakob Schiøtz,
schiotz@fysik.dtu.dk