Grain boundary finite length faceting

We study symmetrical and asymmetrical aluminium grain boundary faceting with molecular dynamics simulations employing two embedded atom method potentials. Facet formation, coarsening, and the reversible phase transition of Sigma 3{1 1 0} boundary into Sigma 3{1 1 2} twin, and vice versa, are demonstrated in the simulations and the results are consistent with earlier experimental studies and theoretical models. The Sigma 11{0 0 2}(1)/{6 6 7}(2) boundary shows faceting into {2 2 5}(1)/{4 4 1}(2) and {6 6 7}(1)/{0 0 1}(2) boundaries and coarsens with a slower rate when compared to Sigma 3{1 1 2} facets. However, facets formed by {1 1 1}(1)/{1 1 2}(2) and {0 0 1}(1)/f{1 1 0}(2) boundaries from a {1 1 6}(1)/{6 6 2}(2) boundary are stable against finite temperature annealing. In the above faceted boundary, elastic strain energy induced by atomic mismatch across the boundary creates barriers to facet coarsening. Grain boundary tension is too small to stabilize the finite length faceting in both Sigma 3{1 1 2} twin and asymmetrical {1 1 1}(1)/{1 1 2}(2) and {0 0 1}(1)/{1 1 0}(2) facets. The observed finite facet sizes are dictated by facet coarsening kinetics which can be strongly retarded by deep local energy minima associated with atomic matching across the boundary. (C) 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.