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Dislocation densities, arrangements and long range internal stresses in cold rolled polycrystalline Cu, Ni, and Al, as well as in cold torsioned Fe, were determined by X-ray diffraction profile analysis using synchrotron radiation. At different deformation degrees, scanning measurements across single grains with a focal spot of less than 50 μm were carried out, in order to inform on the features of the deformation induced substructure. At small deformations including stage III, the dislocation densities and internal stresses are uniform within single grains while at higher deformations in stages IV and V, the dislocation densities and long range internal stresses exhibit opposite fluctuations. In stage IV these fluctuations correspond to the formation of polarized tilt walls (PTW’s) from polarized dipole walls (PDW’s). In contrast to the PDW’s, the PTW’s cause a much higher misorientation in between adjacent lattice areas. This transformation, which is the main element of the progressing fragmentation process during large strain deformation, occurs in all metals studied regardless of dislocation mobility and/or lattice type. Approaching higher strains in stage V, however, these parameters gain some importance especially when the deformation occurs in an iterative way. If the mobility is high, marked static recovery takes place between the single deformation passes, which results in decreases of both dislocation density and local internal stress, and no formation of PTW’s is observed.

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The paper is concerned with the problem of constructing equivalent stress-equivalent strain curves at large strains. For the equivalent strain, the average accumulated crystallographic shear is used, while for the equivalent stress, the resolved shear stress is employed. The latter is obtained from the work conjugacy condition. In such a construction of the hardening curve, the Taylor factor appears to be the major factor that can be calculated from polycrystal deformation texture models. In this paper, the viscoplastic Taylor and self-consistent approaches are employed to calculate the Taylor factors. The self-consistent model was calibrated on the torsion texture development which is the most sensitive to the polycrystal model parameters at large strains. The obtained Taylor factors show important variations in torsion, compression and rolling. They have been used to convert experimentally measured work hardening data on copper into resolved shear stress-resolved shear strain curves. The effect of the Taylor factor on the absolute hardening rate was found to be significant at a large strain range of deformation. The simulation textures were markedly different from the measured textures at very large strains where both polycrystal texture deformation models fail to predict the correct texture evolution. For this reason, the textures were measured at increasing strains at 11 points in rolling, at 12 points in compression and at four points in torsion from where the Taylor factors were calculated by both of the models in order to construct the equivalent stress-equivalent strain curves.

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