Computer simulation of ledge migration under elastic interaction

The diffusional growth of a phase by the motion of disconnections (ledges which contain transformation or misfit dislocations) was studied by a finite difference computer model. The elastic stress of these dislocations is considered to alter the (local equilibrium) solute concentration at the riser of ledges and cause a complex diffusion field interaction among ledges as they migrate. In some cases, however, the ledges forming a train can migrate all at the same speed in the presence of elastic interaction. The condition under which ledges overcome the elastic barrier and form a multiple-height ledge was determined. The model was applied to the migration of ledges/Shockley partial dislocations at gamma'-plate interfaces in Al-Ag alloys.