A study of dislocation evolution in polycrystalline copper during low cycle fatigue at low strain amplitudes

The dislocation structures evolution on the polycrystalline copper at constant strain amplitude during low cycle fatigue is well understood. However, the dislocation structures developments at variable strains, which change from high to low strain amplitude, are seldom reported. In order to realize the dislocation morphology evolution at reduced strain amplitude, the polycrystalline copper is used in this study. The results show that. (1) The S–N curve at reduced strain amplitude from high to low reveals softening, and it is lower than S–N curve which is fatigue in constant strain amplitude at low strain amplitude. (2) The dislocation structures of walls, labyrinth walls, cells or misorientation cells transfer into scattering walls, loop patches or cells. (3) The dislocation morphology development at decreased strain amplitude is determined by the magnitude of reduction in strain amplitude.