CYCLIC DEFORMATION BEHAVIOR AND DISLOCATION STRUCTURES OF [001] COPPER SINGLE CRYSTALS-I CYCLI STRESS-STRAIN RESPONSE AND SURFACE FEAURE

摘要

Cyclic deformation behavior of [001] copper single crystals was investigated in symmetrical pull-push fatigue tests at the ambient temperature and with constant plastic shear strain amplitudes (γpl) in the range of 1.0 x 10~4to 3.0 x 10~3. The formation and development of surface slip bands (SBs) were examined in situ by a light microscope. A rapid initial hardening stage followed by a pronounced overshooting or significant softening was found with the crystals tested at γ_pl≥4.8 x 10~4. The cyclic stress-strain curve of [001] crystals does not show any plateau behavior, instead it follows, if corrected with the Taylor factor, the power law function for copper polycrystals.