The dependence on temperature and strain rate of the flow stress of cyclically hardened copper single crystals

Copper single crystals were strained cyclically with a plastic tensile strain amplitude of 0.5%. The variation of flow stress with strain rate and temperature was measured. Comparison measurements were made on specimens strained unidirectionally in the same apparatus. The variation of flow stress with temperature was considerably larger for the cyclically strained specimens than for the unidirectionally strained ones. The variation with strain rate was slightly larger. It is concluded that the frequency factor of the thermally activated rate-controlling process is considerably higher in the cyclically strained specimens.Considerable long-range internal stresses were present. They appeared to be a larger fraction of the applied stress in the unidirectional tests.