Abstract:The movement and evolution of the dislocation for a low-angle grain boundary (GB) with orientation of 7.70° under stress were simulated by using the phase-field crystal model. The dislocation reaction of separation, annihilation and mergence and these mechanisms were analyzed from the energy point of view, and the activation energy of dislocation separation was calculated. The difference of feature stages for the annihilation process of dislocation under stress was shown through comparing two grain boundaries with different misorientations. The results show the obvious difference of typical stages of the annihilation process of GB. The main stages of GB annihilation include the dislocation climb, dislocation separation and dislocation slide, dislocation annihilation; again the dislocation climb and dislocation separation, dislocation annihilation, or instead of the dislocation climb, some new stages presented during the GB annihilation. For example, the sliding dislocation is merged by the dislocation inside the GB or absorbed by GB, or one sliding dislocation reacts with another sliding dislocation in the grain to merge into a new dislocation pairs, or the sliding dislocation reacts with another dislocation to present annihilation and disappear. The essence of dissociation of the full dislocation is that the new dislocation pairs with opposite Burgers vector are created, while that of annihilation or merge of dislocations is that the pair opposite Burgers vectors between the partial dislocation and the full dislocation on the grain boundary bring about to counteract. The annihilation of two dislocation pairs in the grain is produced by perfect counteracting of the two-opposite-pair Burgers vectors of these two dislocation pairs.

Key words: grain boundary; dislocation; annihilation; separation; phase-field crystal