Strain-induced coarsening in nanocrystalline metals
under cyclic deformation
Center for Atomic Scale Materials Physics (CAMP) and
Department of Physics, Building 307, Technical University of Denmark,
DK-2800 Lyngby, Denmark
Abstract
Atomic-scale computer simulations have previously identified a
deformation mechanism, which becomes important in nanocrystalline
metals with grain sizes below 10 - 15 nm. Instead of proceeding
through dislocation activity in the grains, the deformation occurs by
slip events in the grain boundaries, leading to a reverse Hall-Petch
effect, i.e. a decrease in hardness with decreasing grain size. In
this paper, the consequences of this shift in deformation mode are
investigated for systems subjected to large strains in a cyclic
deformation pattern.
In most coarse-grained metals, severe plastic deformation leads to
grain refinement. Indeed, severe plastic deformation is often used to
generate nanocrystalline metals with grain sizes down to hundred
nanometres. The simulations indicate that these processes are
suppressed in sufficiently small grains, and instead the sliding
events in the grain boundaries dramatically enhance diffusion
processes, and lead to grain coarsening as the deformation proceeds.
Submitted to the proceedings from the 11th conference on Rapidly
Quenched and Metastable Materials (RQ11), Oxford, August 2002.
A preprint is available in PDF
format (256 kB).
Last modified: 23 August 2002.
Jakob Schiøtz,
schiotz@fysik.dtu.dk