Dissociation of lattice dislocations in coincidence boundaries

The possible dislocation reactions in coincidence boundaries with Σ ≦19 in fee and b cc crystals were systematically analysed in consideration of energetics according to the coincidence site lattice theory. The elastic energy reduction during dissociation of lattice dislocations suggests to be more easily absorbed into coincidence boundaries with large Σ-values. Transmission electron microscopy showed a large difference in the absorption rate between coincidence and random boundaries in crept specimens. The absorption of the lattice dislocation depends strongly on its Burger's vector even in the same grain boundary. Experimental results showed that most of EGBDs observed in the coincidence boundaries were of the Burger's vectors which give rise to smaller energy reduction due to the dissociation reaction.