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Using polychromatic microbeam synchrotron diffraction together with electron and optical microscopy, we studied dislocation structure changes of Ni—based single crystal superalloy during impulse heating up to the melting temperature. It is shown that the distribution of the thermal gradient is not monotonic. The maximum value of the thermal gradient is observed in the heat affected zone near the fusion line. Depending on the temperature, the formation of dislocation is accompanied by the partial or complete dissolution of γ′ particles in the matrix. Dislocations form and multiply due to thermal gradients, and their arrangement correlates with temperature gradient field and with the dissolution and reprecipitation of γ′ particles.

This article describes how unpaired dislocations alter white-beam Laue patterns for either isolated dislocations, dislocation walls, or combinations of dislocation walls and isolated dislocations. The intensity distribution of Laue diffraction is analyzed as a function of local misorientation. We show how to quantitatively determine the dislocation structure of single crystals and polycrystals with plastic deformation. The technique is applied to interpret the complicated plastic–elastic field in an iridium weld sample.

A differential coating method is described for fabricating high-performance x-ray microfocusing mirrors. With this method, the figure of ultrasmooth spherical mirrors can be modified to produce elliptical surfaces with low roughness and low figure errors. Submicron focusing is demonstrated with prototype mirrors. The differential deposition method creates stiff monolithic mirrors which are compact, robust, and easy to cool and align. Prototype mirrors have demonstrated gains of more than 104 in beam intensity while maintaining submilliradian divergence on the sample. This method of producing elliptical mirrors is well matched to the requirements of an x-ray microdiffraction Kirkpatrick–Baez focusing system.

We describe the design, construction, and performance of the MHATT-CAT microdiffraction x-ray monochromator. This monochromator is specially engineered for x-ray microdiffraction experiments with a high brilliance undulator source. The monochromator passes a small emittance beam, suitable for focusing to submicron size with submilliradian divergence. Over its energy range of 8–22 keV the absolute energy calibration is better than 2 eV and scans of ± 1 keV show no measurable hysterisis. The monochromator operates with a simple water-cooled first crystal and shows no measurable warm-up time. Horizontal linear bearings allow the monochromator crystals to be rapidly inserted or removed from the beam. Slits before and after the monochromator work to pass broad bandpass or monochromatic x-ray beams at the same vertical height. The monochromatic beam direction is adjusted so the monochromatic and broad bandpass beams are coaxial. The design and performance of the monochromator allows efficient collection of microdiffraction data when coupled to a nondispersive Kirkpatrick–Baez focusing mirror pair.

Methods are derived for measuring local strain, stress, and crystallographic texture (orientation) in polycrystalline samples when 1–10 grains are simultaneously illuminated by an energy scanable or broad-bandpass x-ray beam. The orientation and unit-cell shape for each illuminated grain can be determined from the diffracted directions of four Bragg reflections. The unit-cell volume is determined by measuring the energy (wavelength) of one reflection. The methods derived include an algorithm for simultaneously indexing the reflections from overlapping crystal Laue patterns and for determining the average strain and stress tensor of each grain. This approach allows measurements of the local strain and stress tensors which are impractical with traditional techniques.

We have performed X-ray synchrotron micro-diffraction measurements to study the processes controlling the formation of hillocks and whiskers in Sn layers on Cu. The studies were done in real-time on Sn layers that were electro-deposited immediately before the X-raymeasurements were started. This enabled a region of the sample to be monitored from the as-deposited state until after a hillock feature formed. In addition to measuring the grain orientation and deviatoric strain (via Laue diffraction), the X-ray fluorescence was monitored to quantify the evolution of the Sn surface morphology and the formation of intermetallic compound (IMC) at the Sn-Cu interface. The results capture the simultaneous growth of the feature and the corresponding film stress, grain orientation, and IMC formation. The observations are compared with proposed mechanisms for whisker/hillock growth and nucleation.

A scanning-monochromatic form of differential-aperture x-ray microscopy (DAXM) has been developed that provides micron-resolution depth-resolved dilatational strain measurements. This scanning-monochromatic DAXM technique is applied to measurements of Poisson dilatational strain in 25-μm-thick Si bent into an arch with an apex radius of R=3 mm. Poisson strain measurements agree with anisotropic linear elasticity calculations for a Searle parameter as large as β=1009. Local anticlastic bend radii were shown to oscillate across the arch and reach the R/ν limit for distances less than the plate thickness from the edges, where ν is the anisotropic Poisson’s ratio.

A Monte Carlo ray-tracing program was developed to analyze the geometrical defects and alignment errors on the shape of the x-ray beam image and focusing efficiency of a conical sagittal-focusing monochromator. The geometrical defects and alignment errors were represented with measurable and controllable parameters so that their effects can be analyzed quantitatively. The programmed analysis can be used as a guide to find the precision needed for an optimal sagittal-focusing optical system in terms of flux and focus for large horizontal divergences.

The measurement of dislocation structures on mesoscopic length scales is a particularly important application of white-beam Laue microdiffraction. Near a Bragg reflection the intensity distribution in reciprocal space is sensitive to the organization of the dislocations, which occurs at several structural levels. Unpaired geometrically necessary dislocations (GND) and geometrically necessary boundaries (GNB) result in elongated streaks in the Laue image. The direction of the streaks depends on the average orientation of the dislocation arrays and the diffraction vectors. Laue images collected using synchrotron x-ray microbeams are sensitive to the detailed hierarchical distribution of dislocations and can be used to study the orientation and density of individual GNDs and GNBs.

We present a general description of white-beam (Laue) scattering from grains with dislocations. This approach is applied to examples with equal numbers of positive and negative Burger’s vectors (paired) and with unpaired dislocations of one sign (geometrically necessary). We find that streaking of the Laue reflections is sensitive to both long-range geometrical rotations introduced by unpaired edge dislocations and to local rotation fluctuations introduced by the total number of dislocations (paired and unpaired). We demonstrate the technique by analyzing the dislocation distribution in a nanoindented Cu single crystal.

We have used submicron-resolution synchrotron x-ray beams to study the size, type, and depth distribution of ion-implantation-induced defect clusters in Si. A 0.65 μm resolution x-ray beam, generated using Fresnel zone plate focusing optics, was used to study (001)-oriented Si implanted at 300 °C with 10 MeV Si ions. Diffuse scattering measurements were made near the (220) Bragg reflection, as a function of depth on a (110) cross-sectioned sample, with a 0.65 μm depth resolution. The microbeam focusing optics and the depth-resolved scattering measurements are discussed, and an analysis of the intensity and lineshape of the diffuse scattering is presented in terms of existing models of vacancy and interstitial clusters in Si.

Spatially resolved strain distributions in the NiAl matrix and the ∼550–1000 nm Mo fibers of a NiAl–Mo eutectic were investigated by microbeam x-ray diffraction. Position sensitive d-spacings for the individual phases were obtained from spatially resolved and energy-resolved Laue patterns. For embedded Mo fibers, the measured elastic strain is consistent with the predicted thermal mismatch strain between the NiAl and Mo phases. However, when the NiAl matrix is etched back to expose Mo micropillars, the d-spacing increases to that of unconstrained Mo, indicating release of the compressive residual strain in the Mo fibers.

The spatial distribution of strain, misfit and threading dislocations, and crystallographic orientation in uncoalesced GaN layers grown on Si(111) substrates by maskless cantilever epitaxy was studied by polychromatic x-ray microdiffraction, high resolution monochromatic x-ray diffraction, and scanning electron microscopy. Tilt boundaries formed at the column/wing interface depending on the growth conditions. A higher lateral to vertical growth ratio suppressed sidewall deposition and was found to produce larger lattice tilts in the GaN films. Two kinds of crystallographic tilts are observed in the films. The measurements revealed that the free-hanging wings are tilted upward at room temperature in the direction perpendicular to the stripes. Finite element simulations of the thermally induced part of the wing tilt are presented. Moreover, a misorientation between the GaN(0001) and the Si(111) planes is observed in the parallel to the stripe direction. Its origin is discussed with respect to the strain of the epitaxial GaN on a miscut Si(111) surface and misfit dislocations formed at the interface.

We describe progress in the fabrication of short-focal-length total-external-reflection Kirkpatrick-Baez x-ray mirrors with ultralow figure errors. The short focal length optics produce nanoscale beams (

Polychromatic x-ray microdiffraction, high-resolution monochromatic x-ray diffraction, and finite element simulations have been used to determine the distribution of strain, defects, and crystallographic tilt in uncoalesced GaN layers grown by maskless pendeo-epitaxy. An important materials parameter was the width-to-height ratio of the etched columns of GaN from which occurred the lateral growth of the wings. Tilt boundaries formed at the column/wing interface for samples with a large ratio. Formation of the tilt boundary can be avoided by using smaller ratios. The strain and tilt across the stripe increased with the width-to-height ratio. The wings were tilted upward at room temperature.