Arrangement and density of geometrically necessary dislocations at the scale of strain-induced substructure of copper deformed in tension

Orientation dependent dislocation substructure evolves inside grains of polycrystalline copper during tensile deformation, together with the development of two-component texture. In order to study peculiarities of dislocation arrangement and quantify the geometrically necessary component of dislocation density at the scale of substructure, a thin foil has been cut from the necked copper specimen and its microstructure was examined through electron backscatter diffraction (EBSD) and transmission electron microscopy. True plastic strain in the foil location was about 0.7. It was shown that the use of 0.1 μm EBSD scan step allows detecting orientation gradients that occur in the interior of disoriented cell blocks and evaluating the density of geometrically necessary dislocations within the volume of these cell blocks. Such fine-scale orientation gradients arise inside cell blocks formed within the grains having <111> axis parallel to the tensile direction, and the density of corresponding geometrically necessary dislocations is close to that found within <100> oriented grains where the cell block structure is almost absent. A comparison of results obtained by electron backscatter diffraction and transmission electron microscopy shows that considerable part of dislocations distributed in the interior of cell blocks are geometrically necessary, that is, they form clusters of dislocations of the same sign producing a crystal curvature.