Typical slip patterns and dislocation sub-structures of polycrystalline Cu under cyclic torsion were experimentally investigated. The cyclic stress-strain curve consisted of 3 regions; resembling those of single-crystal Cu oriented for single slip. During the formation of persistent slip bands, cross-slip bands between primary slip bands were often observed. Under cyclic torsion at a high shear strain amplitudes, cross slip between the slip bands of each slip system was important for the collapse of dislocation tangles into dislocation cell walls. During the transient stage of the formation of dislocation cells, the stress amplitude was inversely proportional to the average diameter of dislocation cells. This relationship was identical to that between the saturated stress magnitude and the corresponding dislocation cell size. The formation of typical dislocation patterns in Cu under cyclic loading was closely associated with the cross-slip of screw dislocations.

An Experimental Study of the Formation of Typical Dislocation Patterns in Polycrystalline Copper under Cyclic Shear. J.Zhang, Y.Jiang: Acta Materialia, 2007, 55[5], 1831-42