Multiscale Simulation of Grain Growth in
ABSTRACT: We have combined molecular-dynamics (MD) simulations with mesoscale
simulations to elucidate the mechanism and kinetics of grain growth in a
nanocrystalline face-centered-cubic metal with a columnar grain structure.
The conventional picture of grain growth assumes that the process is
governed by curvature-driven grain-boundary (GB) migration. Our MD
simulations demonstrate that, at least in a nanocrystalline material,
grain growth can also be triggered by the coordinated rotations of
neighboring grains so as to eliminate the common GB between them. Such
rotation-coalescence events result in the formation of highly elongated,
unstable grains which then grow via the GB-migration mechanism. These
insights can be incorporated into mesoscale simulations in which, instead
of the atoms, the objects that evolve in space and time are discretized
GBs, grain junctions and the grain orientations, with a time scale
controlled by that associated with grain rotation and GB migration and
with a length scale given by the grain size. These mesoscale simulations,
with physical insight and input materials parameters obtained by MD
simulation, enable the investigation of the topology and long-time
grain-growth behavior in a physically more realistic manner than via
mesoscale simulations alone. An outlook is presented on how the efffects
of external stress on grain growth can be incorporated, via a combination
of the mesoscale simulations for the grain-boundary microstructure with a
finite-element approach for the grain interiors.
The submitted manuscript has been created by the University of Chicago as
Operator of Argonne National Laboratory ("Argonne") under Contract No.
W-31-109-ENG-38 with the U.S. Department of Energy. The U.S. Government
retains for itself, and others acting on its behalf, a paid-up, non
exclusive, irrevocable worldwide license in said article to reproduce,
prepare derivative works, distribute copies to the public, and perform
publicly and display publicly, by or on behalf of the Government.
Abstract of an invited lecture to be presented at the 2001 Summer School
of the Center for Nonlinear Analysis on Multiscale Problems in Nonlinear
Analysis, Carnegie Mellon University, to be held in Pittsburgh, PA, May 31
- June 9, 2001.
Work supported by the U.S. Department
of Energy, Basic Energy Sciences-Materials Sciences, under Contract
Materials Science Division, Argonne National Laboratory
Argonne, IL 60439, USA