Nucleation of ordered particles at dislocations and formation of split patterns

We investigated the effect of nucleation of ordered precipitates at dislocations and the subsequent growth of particle morphology through computer simulations using a phase-field model. The model treats simultaneously precipitates, dislocations and precipitate-dislocation interactions within a single algorithm. In particular, the model takes into account the structural discontinuity associated with a dislocation that leads to the formation of antiphase domains if the dislocation is within an ordered particle. Three long-range order parameters are used to describe the antiphase domains associated with L1(2) ordering and an additional set of non-conserved order parameters is introduced to characterize dislocations. We show that heterogeneous nucleation and subsequent growth of ordered precipitates at dislocations yield various "split" patterns, whose formation has been attributed to different mechanisms in literature. (C) 2007 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.