A Maximum in the Strength 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
We used molecular dynamics simulations with system sizes up to 100
million atoms to simulate plastic deformation of nanocrystalline
copper. By varying the grain size between 5 and 50 nanometers we show
that the flow stress and thus the strength, exhibit a maximum at a
grain size of 10 to 15 nanometers. This maximum is because of a shift
in the microscopic deformation mechanism from dislocation-mediated
plasticity in the coarse-grained material to grain boundary sliding in
the nanocrystalline region. The simulations allow us to observe the
mechanisms behind the grain-size dependence of the strength of
polycrystalline metals.
The white lines are dislocations formed during the simulated
deformation of a piece of nanocrystalline copper with an average grain
diameter of about 50 nm. The green dots are atoms in the
boundaries to the next grains. Inset: The hardness of nanocrystalline
copper as a function of grain size. Click on the image for a larger
version.
The figure is adapted from figures 1B and 3 in the paper.
|
Science 301,
pp. 1357-1359 (5 September 2003).
An electronic version is available here:
Abstract
(and PDF version for printing).
Full
text (for online reading).
Last modified: 13 September 2003.
Jakob Schiøtz,
schiotz@fysik.dtu.dk
The white lines are dislocations formed during the simulated
deformation of a piece of nanocrystalline copper with an average grain
diameter of about 50 nm. The green dots are atoms in the
boundaries to the next grains. Inset: The hardness of nanocrystalline
copper as a function of grain size. Click on the image for a larger
version.