Use is made of the theory of dislocation-induced Xray diffraction line broadening in the form presented by Krivoglaz, Martynenko & Ryaboshapka [Fiz. Metall. Metalloved. (1983), 55, to express the socalled orientation factors occurring in the relations of diffraction profile parameters (e.g. Fourier coefficients, line widths) in a form which systematically takes into account both the lattice geometry and the elastic behaviour of the scattering crystals. The formalism can be used, in principle, for any materials and types of dislocations. In the case of elastically isotropic media the orientation factors can be described by analytical expressions. The application of the formalism is demonstrated in some detail for various slip systems in hexagonal polycrystals with random orientation of grains.

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Procedures of X‐ray diffraction line profile analysis for the evaluation of the dislocation content in plastically deformed hexagonal materials were tested by means of conventional powder diffractometry on polycrystalline zirconium deformed under tension at 77 K. In order to obtain a representative picture of the dislocation‐induced X‐ray line broadening a series of reflections was measured. The integral breadths and the Fourier coefficients were evaluated by both direct profile‐shape analysis and profile fitting with analytical functions. The results show a significant anisotropy of the line broadening. The 0001 reflections are clearly less broadened than most of the others. According to the theoretical calculations presented previously such a phenomenon can be expected if the plastic deformation favours generation of dislocations with Burgers vectors a/3 〈20〉.

Cold‐working of metallic materials up to large strains is usually characterised by simultaneous substructure evolution on different length scales and accompanied by the formation of significant lattice rotations. A promising tool for the description of such microstructure development is the concept of partial disclinations. Transmission electron microscopy (TEM) studies illustrate clearly, that defects of this kind are frequently existent in cold‐worked metals and have to be accepted as an important defect entity in the substructure evolution at larger strains. Moreover, it is shown that substructure modelling on the base of a coupled dislocation–disclination dynamics leads to satisfying correspondence of calculated substructure characteristics with experimental results obtained by TEM, X‐ray diffractometry, and EBSD (electron backscattering diffraction), and to a satisfying prediction of the macroscopic deformation behaviour, i.e., especially the transition from stage

X‐ray (or neutron) scattering by crystals with local rotation fields arising from dislocations is treated on the basis of the formalism of the kinematical diffraction theory. Such fields mostly change the intensity distribution of reflections in the azimuthal plane. Scattering intensity in the azimuthal plane for crystals with one or two sets of different‐type dislocation walls, causing local rotations in the lattice, is analysed. In this case the intensity distribution is close to Lorentzian in the radial direction and to Gaussian in the azimuthal direction. The expressions for the scattering intensity are valid when averaging over a large statistical ensemble of defects. If this condition is not fulfilled, the intensity distribution in the azimuthal plane will split into several spikes. The mean distance between these spikes in the reciprocal‐lattice space is connected with the disorien­tation between the walls. The conditions necessary for such splitting of the reflection into spikes are considered. The values of the limiting disorientation angle for some common scattering volumes and distances between dislocation walls are evaluated.