Atomic-scale modeling of plastic deformation of
nanocrystalline copper
Center for Atomic Scale Materials Physics (CAMP) and
Department of Physics, Building 307, Technical University of Denmark,
DK-2800 Lyngby, Denmark
Abstract
Atomic-scale simulations of nanocrystalline copper with grain sizes
from 5 to 50 nm have been performed. The simulations show a clear
maximum in the flow stress when the grains are 10-15 nm in
diameter. At this grain size, there is a shift in deformation
mechanism, from dislocation-mediated plasticity at larger grain sizes
to grain boundary sliding at smaller. Above the maximum in hardness,
the grain size dependence of the hardness is consistent with the
Hall-Petch relation, conventionally explained by the creation of
dislocation pile-ups in the grains. It has not been clear if this
explanation of the Hall-Petch effect is valid for sub-micrometre
grains, but the simulations presented here clearly show the existence
of pile-ups in the simulation with average grain size of 50 nm. The
dislocation dynamics in the grains is dominated by the grain
boundaries, as almost all dislocation nucleation occurs at the grain
boundaries, which also act as efficient dislocation sinks. During the
plastic deformation, a large number of stacking faults and a much
lower number of twin boundaries are created. These do not contribute
significantly to the flow stress, as no work hardening is seen whereas
the number of stacking faults increase with strain.
Scripta Materialia 51, 837-841 (2004).
doi:10.1016/j.scriptamat.2004.05.013
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Last modified: 20 August 2004.
Jakob Schiøtz,
schiotz@fysik.dtu.dk
