In-situ TEM investigation of structural transformation from LEDS to twin in fatigued Cu single crystal during annealing

Low-energy dislocation structure is one classical self-organised dislocation pattern, among which persistent slip band (PSB) ladders is the most representative. Periodically distributed PSB ladders consist of two phases: matrix phase and pattern phase. In the new two-phase model, the appearance of pattern phase results in the softening of PSBs with lower elastic constant. The formation of PSB ladders reflects two kinds of dynamic equilibriums: (i) bowing out and annihilation between unlike screw dislocations; (ii) multiplication and annihilation between unlike edge dislocations in the rung. Subsequently, in-situ annealing experiments indicate that most of the dislocations are annihilated and a few dislocations rearrange to result in the nucleation and growth of the twin. In a word, both the evolution of dislocation patterns and the transition from LEDS to twin structures are the process of energy redistribution. Controlling the stored energy per unit area will effectively improve the formation of distribution of defects, which will benefit to design the metallic materials based on the defect-engineering strategy.