The x-ray line profiles of an ultrafine grained copper crystal, produced by equal-channel angular pressing, were measured by a special high resolution diffractometer with negligible instrumental line broadening. The analysis of the line breadths and the Fourier coefficients have shown that taking into account the contrast caused by dislocations on line profiles gives new scaling factors in the Williamson–Hall plot and in the Warren–Averbach analysis, respectively. When strain is caused by dislocations the new procedure proposed here enables a straightforward determination of particle size and strain, the latter in terms of the dislocation density.

It has been shown recently that in many cases strain anisotropy in powder diffraction can be well accounted for by the dislocation model of the mean square strain. The practical application assumes knowledge of the individual contrast factors C of dislocations related to particular Burgers, line and diffraction vectors or to the average contrast factors C Å . A simple procedure for the experimental determination of C Å has been worked out, enabling the determination of the character of the dislocations in terms of a simple parameter q. The values of the individual C factors were determined numerically for a wide range of elastic constants for cubic crystals. The C Å factors and q parameters were parametrized by simple analytical functions, which can be used in a straightforward manner in numerical analyses, as e.g. in Rietveld structure re®nement procedures.

Two different methods of diffraction profile analysis are presented. In the first, the breadths and the first few Fourier coefficients of diffraction profiles are analysed by modified Williamson–Hall and Warren–Averbach procedures. A simple and pragmatic method is suggested to determine the crystallite size distribution in the presence of strain. In the second, the Fourier coefficients of the measured physical profiles are fitted by Fourier coefficients of well established ab initio functions of size and strain profiles. In both procedures, strain anisotropy is rationalized by the dislocation model of the mean square strain. The procedures are applied and tested on a nanocrystalline powder of silicon nitride and a severely plastically deformed bulk copper specimen. The X‐ray crystallite size distributions are compared with size distributions obtained from transmission electron microscopy (TEM) micrographs. There is good agreement between X‐ray and TEM data for nanocrystalline loose powders. In bulk materials, a deeper insight into the microstructure is needed to correlate the X‐ray and TEM results.

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A computer program has been developed for the determination of microstructural parameters from diffraction pro®les of materials with cubic or hexagonal crystal lattices. The measured pro®les or their Fourier transforms are ®tted by ab initio theoretical functions for size and strain broadening. In the calculation of the theoretical functions, it is assumed that the crystallites have log-normal size distribution and that the strain is caused by dislocations. Strain and size anisotropy are taken into account by the dislocation contrast factors and the ellipticity of the crystallites. The ®tting procedure provides the median and the variance of the size distribution and the ellipticity of the crystallites, and the density and arrangement of the dislocations. The ef®ciency of the program is illustrated by examples of severely deformed copper and ball-milled lead sul®de specimens.