Short-wavelength X-ray Research Articles

Numerical and experimental study of residual stress in multi-pass laser welded 5A06 alloy ultra-thick plate

The laser welding technology of ultra-thick plates has been widely applied in many crucial engineering structures, where its safety and stability still suffer from the residual stress brought by the welding temperature. In this work, experimental and numerical studies are carried out to reveal the evolution and distribution of the residual stress. A 5A06 aluminum alloy plate with 30 mm thickness is used to conduct the laser welding experiment, and the short-wavelength X-ray diffractometer (SWXRD) is employed to measure the residual stress. Furthermore, a multi-pass laser welding numerical model is developed to predict the residual stress during the welding process. The simulation results of the weld pool geometry and residual stress agree well with the experimental data, which gives a good validation of the numerical model. Based on the proposed numerical model, the influence of the welding parameters, including inter-pass cooling time and welding rate are also investigated. It is discovered that the reduction of the inter-pass cooling time results in weakness effect of the temperature gradient, which hinders the generation of plastic deformation and leads to a lower residual stress value. Meanwhile, the simulation results also show that the increase in welding rate promotes the generation of thermal stress, which brings a higher residual stress value appeared in the structure.

Multi-focal Shack–Hartmann wavefront sensing with self-interference Chinese Taiji-lenslet array

Shack–Hartmann wavefront sensor (SHWS) is a traditional method of obtaining the phase information of the incident light. As a classical method, SHWS has the merit of simple structure, good usability, real-time monitoring and wide waveband. Traditional SHWS depends mainly on a lenslet array which can split the incident wavefront and produce an array of distorted foci, which reflect the change of wavefront curvature under test. Compared to the mono-focal lenslet in SHWS, here self-interference Chinese Taiji lenslet have been introduced into the wavefront sensing in order to improve the precision of the centroid position by means of multiple foci. Wavefront sensing experiments on self-interference Taiji-lenslet array with bi- and quad-foci were sequentially carried out to verify the validity of our proposed method. More foci-splitter would bring more accuracy. Taiji lens can also be designed with amplitude modulation such as Taiji sieve, which is very suitable for wavefront measurement in the region of short wavelength, especially EUV and soft X-ray.

Diffraction gratings with two-orders-of-magnitude-enhanced dispersion rates for sub-meV resolution soft X-ray spectroscopy.

Diffraction gratings with large angular dispersion rates are central to obtaining high spectral resolution in grating spectrometers operating over a broad spectral range from infrared to soft X-ray domains. The greatest challenge is of course to achieve large dispersion rates in the short-wavelength X-ray domain. Here it isshown that crystals in non-coplanar asymmetric X-ray Bragg diffraction can function as high-reflectance broadband soft X-ray diffraction gratings with dispersion rates that are at least two orders of magnitude larger than those thatare possible with state-of-the-art man-made gratings. This opens new opportunities to design and implement soft X-ray resonant inelastic scattering (RIXS) spectrometers with spectral resolutions that are up to two orders of magnitude higher than what is currently possible, to further advance a very dynamic field of RIXS spectroscopy, and to make it competitive with inelastic neutron scattering. Examples of large-dispersion-rate crystal diffraction gratings operating near the 930 eV L3 absorption edge in Cu and of the 2.838 keV L3-edge in Ru are presented.

Effect of homogenization annealing on internal residual stress distribution and texture in ME21 magnesium alloy extruded plates

Abstract The distribution of residual stresses through thickness of 5 mm-thick ME21 magnesium alloy extruded plates was analyzed non-destructively using short-wavelength X-ray diffraction (SWXRD), and the effect of homogenization annealing before extrusion on the residual stress was discussed. The classic d0 method with an annealed stress-free reference specimen was employed to determine the residual stress of the extruded plates. The residual stress results showed that the gradient of residual stress in the transverse direction was larger than that of the extrusion direction. The homogenization process prior to extrusion weaken the formed sample's texture. The maximum residual stress of the as-extruded plate was reduced, and the residual stress distribution was homogenized.

Hydrogen-Related Properties of the Pd71.5Cu12Si16.5 Metallic Glass

The Pd71.5Cu12Si16.5 metallic glass was synthesized as wide ribbons by arc melting and copper roller spinning. The structures were determined by X-ray diffraction patterns using the conventional X-ray diffractometer and short wavelength X-ray stress analyzer, and the fully glassy state of the ribbons is confirmed. Multiple hydrogen absorption and desorption cycles at room temperature under 100 kPa were carried out on the samples. No destruction after more than 10 cycles is observed, which demonstrates good hydrogen embrittlement resistance. The hydrogen permeation properties of the Pd71.5Cu12Si16.5 metallic glass and its crystallized counterpart were further tested using a direct permeation method. In the supercooled liquid region, the hydrogen permeation rate is obviously higher for the metallic glass form, which could be explained by the increasing free volumes introduced during isothermal stage in this range.

Research progress of residual stress determination in magnesium alloys

Abstract With the research development of the magnesium alloys, the deformation or stress corrosion induced by residual stress (RS) attracted extensive interests in industry and research efforts extensive. However, there are relatively few studies on the RS of magnesium alloys in the world. The generation cause of RS in magnesium alloys was analyzed at first. Several methods of determinate the RS, including destructive methods (drilling hole, crack compliance, layer exfoliation etc.) and non-destructive methods (X-ray Diffraction, Neutron Diffraction, Short Wavelength X-ray Diffraction) were summarized. The factors that influence the measuring accuracy of XRD method were emphasized. The research trends of RS in magnesium alloys were put forward.

Translational and rotational averaging of nonlocal response tensors for nano-shaped light

Orientational averaging of response tensors is an essential operation in calculating optical signals in randomly oriented liquid or gas phase molecular ensembles. When expanded in multipoles, rotational averaging can be performed simply through contraction with isotropic tensors. Alternatively, the multipolar expansion can be avoided and all multipoles may be naturally and implicitly incorporated via nonlocal response tensors which are fields and may not be rotationally averaged in a simple manner. The nonlocal response is useful when the light beam variation across the system is non negligible. Examples are nano-sculpted or short wavelength x-ray field. We derive exact expressions which recast optical signals as a convolution of a nonlocal response function of matter with a nonlocal intrinsic property of the electromagnetic field. The approach involves a gauge invariant calculation based on the minimal coupling Hamiltonian.

The preparation and hydrogen brittleness resistance of Pd71.5Cu12Si16.5 metallic glass ribbons

Pd71.5Cu12Si16.5 metallic glass ribbons as wide as 10mm were prepared by splat quenching. Structure was identified with X-ray diffraction (XRD) spectrums from the conventional X-ray diffractometer and also short wavelength X-ray stress analyzer. The results confirm fully amorphous structure of the ribbons. Multiple H2 adsorption and desorption cycles under a pressure of 100kPa were carried out in the metallic glass ribbon and also pure palladium membrane for comparison. The former didn’t show any cracks after more than 10 cycles, and thermal desorption spectroscopy (TDS) measurement confirms that hydrogen was adsorbed abundantly in the metallic glass ribbon. Pd71.5Cu12Si16.5 metallic glass ribbons demonstrate excellent hydrogen brittleness resistance.

Comparison of residual stress determination using different crystal planes by short-wavelength X-ray diffraction in a friction-stir-welded aluminum alloy plate

A friction-stir-welded (FSW) AA7050-T7451 pre-stretched plate was investigated nondestructively using the short-wavelength X-ray diffraction method to study the distribution of internal residual stress. During the investigation, anomalous deviation of the diffraction peak with crystal plane Al (111) was observed causing large testing errors. The relationship between texture of the material and the anomalous deviation peaks of (111), (200) and (311) and the method to eliminate their effect on residual stress determination were investigated. In addition, the comparison of the average d 0 method and the in situ d 0 method was performed using the three crystal planes to solve the problem caused by gradient in weld structure. Results showed that the anomalous deviations of different crystal planes were different from each other in the directions deflected from the maximum pole density direction. The method of residual stress determination performed in the directions of maximum pole density proved to be helpful to reduce the effect of anomalous deviations. The values and profiles of the residual stress tested by this method using (111), (200) and (311) were identical. The results suggest that in situ d 0 method could be used to eliminate the influence of the difference in lattice spacing among different areas of the FSW plate. The errors of residual stress determination decreased with the increase in the diffracting plane crystal indices.

A new nondestructive instrument for bulk residual stress measurement using tungsten kα1 X-ray.

We describe an experimental instrument used for measuring nondestructively the residual stress using short wavelength X-ray, tungsten kα1. By introducing a photon energy screening technology, the monochromatic X-ray diffraction of tungsten kα1 was realized using a CdTe detector. A high precision Huber goniometer is utilized in order to reduce the error in residual stress measurement. This paper summarizes the main performance of this instrument, measurement depth, stress error, as opposed to the neutron diffraction measurements of residual stress. Here, we demonstrate an application on the determination of residual stress in an aluminum alloy welded by the friction stir welding.

Using portable X-ray fluorescence (pXRF) to determine fecal concentrations of non-absorbable digesta kinetic and digestibility markers in sheep and cattle

Concentration of indigestible markers in feces is routinely used to estimate the digestibility or rate of passage of feed through the gut. Current procedure for measuring fecal marker concentrations is an acid digest before analysis using inductively coupled plasma optical emission spectroscopy (ICP). Portable X-ray fluorescence (pXRF) spectroscopy uses short wavelength X-rays to excite sample material and generate characteristic elemental emissions proportional to the concentration of the element present in ground fecal material. The aim of this study was to measure fecal concentrations of Co, Cr, Ti, and Yb digesta marker by both ICP and pXRF and determine any correlation between the two methods, thereby assessing the potential of using pXRF as a marker analysis method. Silica (Si) concentrations in fecal and feed samples were also measured using both methods. Cattle and sheep feces and various feed samples collect from four separate studies were analyzed for concentrations of Co (CoEDTA), Cr (Cr mordanted fibre), Ti (TiO2), Yb (Yb(III)acetate), and Si using ICP and pXRF. Regression analysis used to assess the relationship between ICP and pXRF determined fecal concentrations indicated strong linear relationships (P<0.01) between pXRF and ICP estimates of Co (r2=1.00), Cr (r2=0.95), Ti (r2=0.97), Yb (r2=0.94), and Si (r2=0.88). All curves were validated using a second set of independent fecal samples. A full set of total collection fecal samples for six sheep were also analyzed by pXRF for Co and Cr (digesta kinetics), and Si (digestion) marker concentrations. These fecal Co and Cr concentrations were used to estimate digesta mean retention times (MRT) and compared to estimated digesta MRT from the same sheep using Co and Cr marker concentrations determined by ICP analysis. No differences in estimated MRT were found when using either analytical method. Silica concentrations from the same fecal samples as determined by pXRF were used to determine the rate of DMD for each animal. When compared to apparent DMD for the same animals as determined using feed DM intake and fecal DM output collected during the total collection, no differences were again found using either analytical method. The results indicate that pXRF can be used as an alternative to standard ICP procedure, obviating the need for acid digestion, reducing cost and time; and may also offer an alternative analytical method for determining livestock DM digestibility.

Residual stress distribution and microstructure in the friction stir weld of 7075 aluminum alloy

In order to study the relationship between residual stress (RS) and the microstructure of friction stir weld (FSW), RS profiles through thickness in the un-welded aluminum alloy 7075 plate and in middle layer of its FSW joint were determined nondestructively by the short-wavelength X-ray diffraction (SWXRD) and neutron diffraction. Microstructure and mechanical properties of the FSW joint were also studied by optical microscopic analysis, and microhardness and tensile strength measurements. RS profiles measured by the two methods had the same distribution trend. The maximum tensile RS tested by SWXRD and neutron diffraction in transverse and longitudinal direction occurred in the weld nugget. Microhardness in the direction perpendicular to the weld line showed a “W” shape distribution. Position of the local maximal extremum of RS in thermo-mechanically affected zone corresponded to that of minimal microhardness. The grain-refined strengthening caused by the recrystallization in the weld nugget kept the joint from fracturing at this region notwithstanding the maximum tensile RS. And the tensile fracture occurred near the boundary of welding zone and thermo-mechanically affected zone where minimum of hardness and maximum of RS appear at the same position.

Coherence filtering and revivals in x-ray waveguides: a communication-modes approach.

Waveguides for short-wavelength x-rays have been successfully employed for microbeam and nanobeam production and microscopy experiments. The coherence of hard x-ray sources is generally poor, and therefore the spatial coherence filtering characteristics of waveguides have been attractive for high-resolution microscopy experiments. To quantify the spatial coherence filtering properties of a waveguide, we here report a theoretical study of the propagation of a partially coherent beam in a waveguide in the paraxial approximation. By propagating the cross-spectral density function associated with the partially coherent field, we quantify in detail the evolution of the spatial coherence as the beam proceeds along the waveguide. The propagation is efficiently accomplished using the communication-modes formalism. The generality of the approach makes it suitable to study more complex phenomena such as the second-order Talbot self-imaging effect and coherence revivals in waveguides. Numerical results are shown for waveguides illuminated by partially coherent hard x-rays.

Residual Stresses Comparison Determined by Short-Wavelength X-Ray Diffraction and Neutron Diffraction for 7075 Aluminum Alloy

High strength Al alloy 7075 is widely used in aeronautic and space domains. However, when the thick plate of 7075 alloy is quenched improperly, large residual stress (RS) will be produced which leads to the loss of performance in resistance corrosion, fatigue and fracture. It is necessary to get the detailed information about residual stress distribution in the quenched plate. Conventional X-ray diffraction, a viable residual stress test method, can only reveal the RS state near surface layer due to limited penetrated depth. RS in the bulk components now can usually be analyzed by neutron diffraction or hard X-ray diffraction of high energy synchrotron in non-destructive way. Here a novel non-destructive method using short-wavelength characteristic X-ray diffraction meter (SWXRD) with the X-ray tube of tungsten anode target to determine the RS within the materials is developed in China. This paper revealed the RS distribution in a 20 mm thick plate of 7075 Al alloy determined by SWXRD and typical neutron diffraction (in LLB laboratory of France). The RS distribution through the thickness of Al plate shows a good agreement with the result determined by SWXRD compared with neutron diffraction.

A multi purpose source chamber at the PLEIADES beamline at SOLEIL for spectroscopic studies of isolated species: Cold molecules, clusters, and nanoparticles

This paper describes the philosophy and design goals regarding the construction of a versatile sample environment: a source capable of producing beams of atoms, molecules, clusters, and nanoparticles in view of studying their interaction with short wavelength (vacuum ultraviolet and x-ray) synchrotron radiation. In the design, specific care has been taken of (a) the use standard components, (b) ensuring modularity, i.e., that swiftly switching between different experimental configurations was possible. To demonstrate the efficiency of the design, proof-of-principle experiments have been conducted by recording x-ray absorption and photoelectron spectra from isolated nanoparticles (SiO2) and free mixed clusters (Ar/Xe). The results from those experiments are showcased and briefly discussed.

Suppression of Microbunching Instability Using Bending Magnets in Free-Electron-Laser Linacs

The microbunching instability driven by collective effects of the beam inside an accelerator can significantly degrade the final electron beam quality for free electron laser (FEL) radiation. In this Letter, we propose an inexpensive scheme to suppress such an instability in accelerators for next generation FEL light sources. Instead of using an expensive device such as a laser heater or RF deflecting cavities, this scheme uses longitudinal mixing associated with the transverse spread of the beam through bending magnets inside the accelerator transport system to suppress the instability. The final uncorrelated energy spread increases roughly by the current compression factor, which is important in seeded FEL schemes in order to achieve high harmonic short-wavelength x-ray radiation.

Internal Residual Stresses in the Friction Stir Weldment of 2024-T351 Al Alloy Determined by Short Wavelength X-ray Diffraction

In order to optimize the process of friction stir welding(FSW) and supply the information to the further machine,it is significant to measure the residual stress distribution in the FSW weldment of Al alloy.A domestic invented short wavelength X-ray diffractometer(SWXRD) is employed to determine the internal residual stresses in 2024-T351 Al alloy FSW weldment using both d0 mode and sin2ψ mode.The residual stress distribution results which obtained using SWXRD,neutron diffraction and high energy synchrotron respectively are compared and analyzed.Meanwhile the microstructure in the weldment is observed and the hardness in the center layer of plate is measured.The results show that the internal residual stress in Al alloy FSW can be determined by SWXRD.As for 2024-T351 Al alloy weldment,there are three tensile stress peaks,two tensile peaks located in the heat affected zone(HAZ) and another on the weld line.The result of d0 mode is identical with results of other methods such as neutron diffraction and synchrotron diffraction.The stress distribute in the weld nugget zone(WNZ) of the FSW weldment determined using sin2ψ mode fit well with the result of d0 mode.However the sin2ψ mode can not used to measure the stress distribution in the other zone such as thermal-mechanically affected zone(TMAZ),HAZ and base material zone(BMZ) due to strong texture.It is an applicable method to determine internal residual stresses combined sin2ψ and d0 mode together by SWXRD.

Short wavelength X-ray emission generated by highly excited cluster beams

X-ray radiation is studied for large clusters consisting of 107–1010 atoms and irradiated by an intense laser pulse with an intensity ranged from (1014 up to 1018 W/cm2). The model is developed for such a laser plasma that includes the radiative transitions and the processes of excitation and quenching of multicharged ions of this plasma by electron impact. Due to interaction of a radiating multicharged ion with a surrounding plasma, spectral lines of emission are broaden and neighboring spectral lines are overlapped. As a result, the spectrum of radiation of multicharged ions is transformed into a continuous spectral band. The model under consideration includes important plasma processes including dielectronic recombination, spontaneous radiation, excitation, quenching and ionization of multicharged ions by electron impact. On the basis of the model developed the X-ray spectrum and spectral power are evaluated. In the range of laser intensities under consideration a laser plasma formed contains multicharged ions with charges Z = 26−36 that corresponds to the 3d-electron shell in the xenon case.

短波長軟Ｘ線域の多層膜技術と顕微鏡応用の新展開

短波長軟Ｘ線域の多層膜技術と顕微鏡応用の新展開

Electron charge distribution of CaAl 2−xZn x: Maximum entropy method combined with Rietveld analysis of high-resolution-synchrotron X-ray powder diffraction data

Using short wavelength X-rays from synchrotron radiation (SPring-8), high-resolution powder diffraction patterns were collected. In order to study both the structural relationship and the mechanism of stability in the CaAl 2− x Zn x system, among the Laves phases (MgCu 2 and MgNi 2 type) and KHg 2-type structures, the charge density distribution of CaAl 2− x Zn x as a function of x was obtained from the diffraction data by Rietveld analysis combined with the maximum entropy method (MEM). In the MEM charge density maps overlapping electron densities were clearly observed, especially in the Kagomé nets of the Laves phases. In order to clarify the charge redistribution in the system, the deformation charge densities from the densities formed by the constituent free atoms are discussed. In the ternary MgNi 2-type phase, partial ordering of Al and Zn atoms is observed, a finding that is supported by ab-initio total energy calculations.