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Cyclic deformation and fatigue crack initiation of silver bicrystals and component single crystals were discussed based on three aspects: (1) affected by the grain boundary (GB), the plateau stress of the bicrystal is slightly higher than that of any component crystal; (2) owing to the limitation of GB, dislocations pile up near GB, which simplifies the occurrence of secondary slip; and (3) cracks in bicrystals are more likely to form where persistent slip band (PSB) interacts with GB, rather than more advanced dislocation patterns such as cell and labyrinth structures. Therefore, the initiation priority of fatigue crack initiation in bicrystals is as follows: PSB-GB > PSB-PSB (cell or labyrinth) > PSB > vein.

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