Gábor Csiszár

Dislocation density and Burgers vector population in fiber-textured Ni thin films determined by high- resolution X-ray line profile analysis

Nanocrystalline Ni thin films have been produced by direct current electrodeposition with different additives and current density in order to obtain 〈100〉, 〈111〉 and 〈211〉 major fiber textures. The dislocation density, the Burgers vector population and the coherently scattering domain size distribution are determined by high-resolution X-ray diffraction line profile analysis. The substructure parameters are correlated with the strength of the films by using the combined Taylor and Hall–Petch relations. The convolutional multiple whole profile method is used to obtain the substructure parameters in the different coexisting texture components. A strong variation of the dislocation density is observed as a function of the deposition conditions.

The dislocation density and twin-boundary frequency determined by X-ray peak profile analysis in cold rolled magnetron-sputter deposited nanotwinned copper

The dislocation density and the average twin boundary frequency is determined quantitatively in as-deposited and cold-rolled nanotwinned Cu thin films by high-resolution X-ray line profile analysis. After cold-rolling the dislocation density increases considerably, whereas the twin boundary frequency decreases only slightly. The physical parameters of the substructure provided by the quantitative X-ray analysis are in agreement with earlier transmission electron microscopy observations. The flow stress of the as-deposited and the cold-rolled films is directly correlated with the average thickness of twin lamellae and the dislocation density by taking into account the Hall-Petch and Taylor type strengthening mechanisms.

Resolving ensembled microstructural information of bulk-metallic-glass- matrix composites using synchrotron x-ray diffraction

The microstructural characterization of the Zr60.0Ti14.7Nb5.3Cu5.6Ni4.4Be10.0 bulk-metallic-glass-matrix composites is investigated using high-energy synchrotron x-ray diffraction. The convoluted diffraction-intensity distribution in the azimuthal direction is naturally yielded from the spatial arrangements of the crystalline dendrites and their amorphous matrix. We facilitate the area selection and the intensity integration of the diffraction collected from a two-dimensional detector to characterize the diffraction intensity of the amorphous matrix. The results enable us to apply the modified Williamson–Hall plots for using the peak width to study the microstrain and micromechanism of the deformation of the crystalline phase.

Dislocation densities and prevailing slip-system types determined by X-ray line profile analysis in a textured AZ31 magnesium alloy deformed at different temperatures

Tension experiments were carried out at room temperature, 473 K and 673 K on AZ31-type extruded magnesium alloy samples. The tensile deformation has almost no effect on the typical extrusion texture at any of the investigated temperatures. X-ray diffraction patterns provided by a high-angular-resolution diffractometer were analyzed for the dislocation density and slip activity after deformation to fracture. The diffraction peaks were sorted into two groups corresponding either to the major or to the random texture components in the specimen. The two groups of reflections were evaluated simultaneously as if the two texture components were two different phases. The dislocation densities in the major texture components are found to be always larger than those in the randomly oriented grain populations. The overwhelming fraction of dislocations prevailing in the samples is found to be of type, with a smaller fraction of -type dislocations. The fraction of -type dislocations is always obtained to be zero within experimental error.

Dislocation structure in different texture components determined by neutron diffraction line profile analysis in a highly textured Zircaloy-2 rolled plate

A novel diffraction-based method has been developed to determine the substructure in terms of the fraction of prevailing slip systems and dislocation densities in multiple individual texture components of strongly textured materials. The method was applied to a strongly textured cold-rolled Zircaloy-2 sample, compressed along the normal direction of the rolled plate. Fourteen diffraction patterns were collected by time-of-flight neutron diffraction experiments at seven different purposely selected sample orientations. The diffraction peaks corresponding only to one single texture component out of the four prevailing components were identified and used to construct texture-specific diffraction patterns. The best five such patterns were evaluated by the convolutional multiple whole profile procedure of line profile analysis for the fractions of the prevailing 〈a〉-, 〈c + a〉- and 〈c〉-type slip systems and the corresponding dislocation densities. It is found that in the three texture components with the c axis not parallel to the normal direction of rolling the average dislocation densities and fractions of slip-system types are the same. However, in the texture component with the c axis parallel to the normal direction of rolling the fraction of the 〈a〉-type slip system is somewhat smaller than in the other components and that of the 〈c〉-type slip system is somewhat larger than zero. The fractions of the prevailing slip systems are in good correlation with literature data of self-consistent polycrystal plasticity modeling of Zircaloy-2.

Hydrogen permeability with dislocation in low carbon, aluminium-killed, enamel-grade steels

Abstract The role of dislocations on hydrogen permeation time of Al-killed, unalloyed low-carbon steels was investigated using a special high-resolution double crystal diffractometer operated at a rotating copper anode with fine focus. Information about dislocation character and Burgers vector populations are given by strain anisotropy. Generally, the hydrogen permeability increases or decreases with dislocation densities but hydrogen accumulation proved to be less favourable near a screw dislocation than an edge dislocation.

Planar defects, dislocations, and coherently scattering-size in GdBa2Cu3O7−x high-Tc thin films determined by high resolution X-ray diffraction

The frequency of planar defects, the average dislocation densities, and coherent domain size in epitaxial GdBa2Cu3O7−x high Tc thin films, with altering CuO2 and CuO planes, are measured by fitting full widths at half maximum values of 00l type reflections using a model function based on intensity distribution configurations in reciprocal space. The reduction of the dislocation density during oxygenation seems to be an unavoidable condition to obtain superconductivity in GdBa2Cu3O7−x thin films.