CYCLIC HARDENING AND SLIP LOCALIZATION IN SINGLE SLIP ORIENTED COPPER-CRYSTALS

A static-dynamic model is applied to the interpretation of slip locali zation modes observed in a systematic study of the evolution of disloc ation structures in single slip intermediate amplitude fatigue in copp er deformed at room temperature. The model assumes that veins do not d eform plastically, unless their critically soft interiors are destabil ized to produce an embryonic PSB. This assumption is shown to be fully consistent with slip homogeneity. The model predicts that the vein st ructure remains active during cyclic saturation. This prediction expla ins the present novel observation that in intermediate amplitude fatig ue, after the initial formation of PSBs by ''collapse'' of matrix wall s, triggered by long-range internal stresses, there is continued forma tion of new PSBs by ''splitting'' of matrix veins. The model shows tha t the long-range internal stresses in the thin PSB lamellae and in the more extended wall structures produced by this process are about equa l. Nevertheless, the model and microscopy suggest convincingly that mi nimization of dislocation line energy in the dynamic structure between glissile walls and veins controls the condensation mode and the equil ibrium wall spacing of PSBs.