EFFECT OF GRAIN-SIZE AND ANNEALING TEXTURE ON THE CYCLIC RESPONSE AND THE SUBSTRUCTURE EVOLUTION OF POLYCRYSTALLINE COPPER

In attempting to interpret the mechanical response of polycrystalline copper, for which the results in the literature show marked scatter, the effects of microstructure on the cyclic behavior and the substructure evolution of copper polycrystals have been investigated. The microstructure is described by a complex factor-grain size and texture combined. It is found that there is a very significant effect of microstructure in the cyclic response of copper at low and intermediate strain amplitudes, where dislocation structures which localize deformation are expected to be present. In general, the cyclic response of coarse-grained copper shows a much more pronounced cyclic hardening and higher saturation stresses than those for fine-grained copper. This behavior is associated with a well defined hard [111]-[100] fiber texture, inherited in the coarse-grained material after annealing at relatively high temperatures. The multiple slip associated with the [111]-[001] oriented grains homogenizes the deformation very early, resulting in strong cyclic hardening, and a faster substructure evolution into cell structure.