Transformations of dominant deformation systems in copper single crystals

A close relation between the origin of tensile instability and the onset of deformation stage IV of copper single crystals was found. The tensile inst ability in single glide oriented copper single crystals belongs to the end of the overshoot phenomena resulting from a change of dominant deformation system - the changeover from primary to conjugate slip dominance. The ident ical transformation in deformation mechanism was found to be responsible fo r the onset of stage IV of plastic deformation of copper single crystals te sted in rolling. Structural and mechanical observations and 4.2 K electrica l resistivity measurements performed on the deformed crystals show, that th e change in deformation mechanism causes a significant decrease in the rate of work hardening, a sudden change in the rate of dislocation accumulation , and the redistribution of dislocation arrangements in crystal lattice. It is concluded that the transformation of dominant deformation systems may s trongly control deformation properties of face centered cubic crystals at l arge plastic strains. Finally the low temperature slip-twin transformation is discussed in terms of the change of a dominant deformation system.