A conical slit for three-dimensional XRD mapping

Abstract

Traditionally, depth resolution in diffraction experiments is obtained by inserting pinholes in both the incoming and diffracted beam. For materials science investigations of local strain and texture properties this leads to very slow data-acquisition rates, especially when characterization is performed on the level of the individual grains. To circumvent this problem a conical slit has been manufactured by wire-electrodischarge machining. The conical slit has six 25 microm-thick conically shaped openings matching six of the Debye-Scherrer cones from a face-centred-cubic powder. By combining the slit with a microfocused incoming beam of hard X-rays, an embedded gauge volume is defined. Using a two-dimensional detector, fast and complete information can be obtained regarding the texture and strain properties of the material within this particular gauge volume. The average machining and assemblage errors of the conical slit are found both to be of the order of 5 microm. An algorithm for alignment of the slit is established, and the potential of the technique is illustrated with an example of grain mapping in a 4.5 mm-thick Cu sample.

Measuring Stress Distributions in Ti-6Al-4V Using Synchrotron X-Ray Diffraction

“…Experimental techniques have been developed toward this end, to observe both ''bulk'' populations [1][2][3] and individual embedded grains. [4][5][6][7] The data from such experiments can provide an unparalleled level of detail regarding the evolution of micromechanical states during deformation processes.…”

Quantifying Three-Dimensional Residual Stress Distributions Using Spatially-Resolved Diffraction Measurements and Finite Element Based Data Reduction

“…Quantifying the residual stress field within a component using lab source x-rays relies on removing layers of materials from the surface and investigating the newly exposed layers [39], [32], which introduces a significant uncertainty to the stress solution. Penetration through moderate thicknesses (mm-cm) of metallic samples combined with the advantages of high speed area detectors and short collection times have enabled a new generation of high energy synchrotron x-ray diffraction experiments [34], [48], [30], [49], [13], [33], [23], [5]. This large number of lattice strain measurements can be assembled into lattice strain pole figures [15], [46], [36], [33], which can be "inverted" to calculate the orientation-dependent strain and stress tensors within the polycrystalline diffraction volume [3], [47], [6].…”

“…The sample and laboratory coordinate systems employed in this work were chosen carefully to illustrate the attributes of the experimental method and our results. While the incident monochromatic x-ray beam illuminates the entire volume of material in its beam path, a diffraction volume located at a particular point, p S , inside the sample is isolated using an x-ray optical device referred to as conical slit [34]. For a particular {hkl} and scattering vector, q, all lattice planes in a diffraction volume and satisfying Bragg's law will diffract.…”

“…It is a standard equipment at the 1-ID-C beam line of the Advanced Photon Source where this experimental work was performed. The readers are referred to Lienert et al [27] and Nielsen et al [34] for a more detailed description of the conical slits. The following are the key features of the conical slits used in this work.…”

Depth-Resolved Residual Stress Analysis with Conical Slits for High-Energy X-Rays

“…The CSC has several concentric slits that are focussed on a spot within the sample by their conical shape [4]. With a CSC, complete diffraction rings can be measured with depth resolution, except for small regions where material is required for the mechanical stability of the slits.…”