INSTABILITIES IN COMPRESSIVE CREEP OF COPPER SINGLE-CRYSTALS

The aim of the work was to provide new experimental evidence of deform ation instability in conditions of high temperature creep. Copper sing le crystals in five different orientations were subjected to creep in compression at the temperatures 723 and 773 K applying stresses in a r ange where instabilities in the creep process can appear. The present paper focusses on the phenomenology of the processes. Stable creep was analysed with respect to its sensitivity to applied stress and temper ature. An analytical description for the creep curves is given. It was found that the instability has a latent stage in the course of the st able creep. Creep conditions favourable for unstable behaviour are pro bably given by a certain resolved shear stress. Stable creep is relate d to dislocation glide; the relation for the unstable process, however , is less apparent.