CNA 2001 Summer School




Multiscale Simulation of Grain Growth in Nanocrystalline Materials

Dieter Wolf

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 W-3l-l09-Eng-38.

Dieter Wolf
Materials Science Division, Argonne National Laboratory
Argonne, IL 60439, USA