Abstract: Molecular dynamics simulations of high temperature annealing of copper bicrystals have been carried out. The bicrystals have planar grain boundaries, and the gain size varies in nano range. An EAM(Embedded Atom Method) potential of FS type is used for calculating the interatomic forces. The results show that in nanocrystalline copper, GB migration driven by inter-GB reaction can take place. A critical grain size is identi¯ed, below which the inter-GB reaction becomes strong enough to trigger GB motion, which accelerates rapidly and leads to annihilation of the grain bound- aries. The critical size is found to be 16 atomic radii. A \through intermediate grain mechanism" is identi¯ed for the nano-grain boundary motion observed, which is never reported for GB migrations of conventional polycrystalline metals.

Key words: grain boundary migration, nanocrystal, copper