X-ray line-broadening analysis of dislocations in a single crystal of Zr

摘要

The X-ray diffraction line broadening due to micro-strains near dislocations is complicated by the effect of grain size and inter-granular strain distributions on the line pro-file for deformed polycrystalline materials. Use of irradiated single crystals to study the effect of dislocation strain on diffraction line profiles eliminates this problem. The diffraction line profiles of single crystals of Zr were measured before and after irradiation in a nuclear reactor. The irradiation produces damage in the material in the form of dislocation loops. Using the original material as a standard the deconvoluted diffraction peak represents the broadened peak profile that is due to the dislocation loops only. Fourier analysis of the deconvoluted peak using the method of Warren and Averbach shows that the magnitude of the micro-strain component is consistent with the dislocation density measured by transmis-sion electron microscopy with some allowance for reduction of the lattice strain due to loop alignment (polygonisation). The Fourier analysis also gives a value for the coherent diffrac-tion domain size that is consistent with the mean spacing between the dislocations. These results are discussed in terms of the effect of the lattice strain induced by dislocation loops on the diffraction line profile.