Integrated X-ray substructure analysis of plastically deformed beryllium single crystals

The X-ray double-crystal technique was applied for arm integrated analysis of substructures in plastically deformed beryllium single crystals, using both radial intensity distributions I(2 theta) and rocking curves I(omega) of the reflections 0002, <10(1)over bar 0> and <11(2)over bar 0>. Scanning of the surroundings of selected points of the reciprocal lattice (reciprocal space mapping) in two dimensions gives comprehensive information about the lattice disorder due to the dislocation structure. From the line broadening of the intensity distributions 1(2 theta), which is caused by the local lattice strains of the irradiated specimen, mean total dislocation densities rho can be estimated via Fourier analysis of the peak shape. The line broadening of the rocking curves I(omega) is mainly related to the local lattice disorientations and allows, therefore, the estimation of the excess density be of edge dislocations of same sign introduced by the plastic bending of the crystals, Using the kinematical approach of Krivoglaz for dislocation-induced diffraction line broadening, total dislocation densities rho approximate to 10(13) m(-2) were obtained from the radial intensity distributions. The evaluation of the rocking curves led to excess dislocation densities in the range Delta rho = 10(10) m(-2). These values are in good agreement with a calculation of the density of geometrically necessary dislocations for the plastic bending.