Atomic-scale observation of grain boundary motion

Atomic-scale grain boundary (GB) migration mechanisms are investigated by high-resolution transmission electron microscopy (HREM). For the first time, atomic-scale motion of high-angle twist as well as general GBs is directly observed by HREM. GB motion was found to proceed by the propagation of atomic-scale steps for two quite different GB geometries. Time-resolved HREM indicates that migration mechanisms of high-angle GBs also include cooperative effects, whereby groups of atoms spontaneously rearrange their lattice positions to be incorporated into the growing grain. (C) 2001 Elsevier Science B.V. All rights reserved.