Effect of grain size/texture on the cyclic stress–strain behavior of polycrystalline copper

The cyclic stress–strain behavior of copper with different grain sizes/textures has been studied. The results show that at high plastic strain amplitudes, secondary hardening occurs after the primary hardening stage in small-grained specimens; and cyclic softening occurs after the primary hardening stage in large-grained specimens. At low plastic strain amplitudes, the effect of grain size/texture is small, saturation occurs after the primary hardening stage in all specimens. The secondary hardening found in small-grained specimens is associated with the formation of equiaxed cells. In a small-grained specimen, it contains more twin and grain boundaries and twin steps than a large-grained specimen; these boundaries and twin steps in particular promote secondary slip activity, therefore enhance the formation of equiaxed cells. The cyclic softening found in large-grained specimens is mainly associated with the condensation of loop patches into dense dislocation walls.