Evolution of dislocations in large grains of polycrystalline copper under low cycle fatigue with reduced strain amplitude

This work examines the evolution of the dislocation structure in large grains of polycrystalline copper with decreasing strain amplitude. The experimental results show that (1) dislocation reversal is initially triggered by the operation of a final slip system, which is formed by the previously high strain amplitude when the strain amplitude is reduced; and (2) the region that is occupied by the dislocation reversal structures called loop patches. It is small in large grains because a more homogenous internal stress distribution induces a more uniform evolution of dislocations in large grains.