Misorientation dependence of intrinsic grain boundary mobility: Simulationand experiment

Both experimental and atomistic simulation measurements of grain boundary m obility were made as a function of temperature and boundary misorientation using the same geometry that ensures steady-state, curvature-driven boundar y migration. Molecular dynamics simulations are performed using: Lennard-Jo nes potentials on a triangular lattice. These simulations represent the fir st systematic study of the dependence of intrinsic grain boundary mobility on misorientation. The experiments focus on high purity Al, with [111] tilt boundaries, which are isomorphic to those examined in the simulations. Exc ellent agreement between simulations and experiments was obtained in almost all aspects of these studies. The boundary velocity is found to be a linea r function of the curvature and the mobility is observed to be an Arrhenius function of temperature, as expected. The activation energies for boundary migration varies with misorientation by more than 40% in the simulations a nd 50% in the experiments. In both the simulations and experiments, the act ivation energies and the logarithm of the pre-exponential factor in the mob ility exhibited very similar variations with misorientation, including the presence of distinct cusps at low Sigma misorientations. The activation ene rgy for boundary migration is a logarithmic function of the pre-exponential factor in the mobility, within a small misorientation range around low Sig ma misorientations. (C) 1999 Acta Metallurgica Inc. Published by Elsevier S cience Ltd. All rights reserved.