Non-destructive X-ray Diffraction Research Articles

Contribution to X-ray analysis of carbo-nitrided steel layers

The non-destructive X-ray diffraction method is used to analyse carbo-nitrided steel layers after wear testing. These measurements are carried out on the two major phases of the material,i.e.the martensite and the retained austenite. Such measurements are particularly difficult for three reasons. First, strong gradients exist across the wear track. Second, the diffraction peaks obtained for the martensite are broadened, as a result of the overlap of different reflections of the tetragonal structure. Third, the studied material is multiphase. Its major phases are martensite and austenite, but it also contains carbide and nitride clusters, which lead to incoherent scattering of X-rays. A new quantitative phase analysis method is thus proposed to define the volume fractions of these different constituents of the material. This method accounts for the evolution of the background level during wear. A micro-mechanical model is then developed to process the diffraction peak positions obtained for the martensite and the retained austenite. This model defines the `true' stress and carbon content of both phases. It also allows separation of the reflections of the martensite. The true widths of the diffraction peaks, which characterize the plastic deformation, can thus be quantified. Results for wear-test specimens show a strong plastic deformation of the retained austenite during contact fatigue. This leads to a partial transformation of this phase into martensite. In the martensite, on the contrary, the plastic deformation remains low but the carbon content decreases. This is caused by a stress-induced precipitation of carbides.

X-ray diffraction microtomography using synchrotron radiation

The X-ray diffraction computed tomography technique is based on the interference phenomena of the coherent scatter. For low-momentum transfer, it is most probable that the scattering interaction will be coherent. A selective discrimination of a given element in a scanned specimen can be realized by fixing the Bragg angle which produces an interference peak and then, to carry out the computed tomography in the standard mode. The image reconstructed exalts the presence of this element with respect to other ones in a sample. This work reports the feasibility of a non-destructive synchrotron radiation X-ray diffraction imaging technique. This research was performed at the X-ray Diffraction beam line of the National Synchrotron Light Laboratory (LNLS) in Brazil. The coherent scattering properties of different tissue and bone substitute materials were evaluated. Furthermore, diffraction patterns of some polycrystalline solids were studied due to industrial and environmental human exposure to these metals. The obtained diffraction patterns form the basis of a selective tomography technique. Preliminary images are presented.

The application of white radiation to residual stress analysis in the intermediate zone between surface and volume

Mechanical surface processing is known to give rise to complex residual stress fields in the near surface region of polycrystalline materials. Consequently, their analysis by means of non-destructive X-ray and neutron diffraction methods has become an important topic in materials science. However, there remains a gap with respect to the accessible near surface zone, which concerns a range between about 10 μm and 1 mm, where the conventional X-ray methods are no longer and the neutron methods are not yet sensitive. In order to achieve the necessary penetration depth τ to perform residual stress analysis (RSA) in this region, advantageous use can be made of energy dispersive X-ray diffraction of synchrotron radiation (15–60 keV) in the reflection mode. Besides an example concerning the adaptation of methods applied so far in the angle dispersive RSA to the energy dispersive case, the concept of a new materials science beamline at BESSY II for residual stress and texture analysis is presented.

Angle-dispersive diffraction with synchrotron radiation at Laboratório Nacional de Luz Sı́ncrotron (Brazil): potential for use in biomedical imaging

At low angles the scattering of X-rays in the diagnostic energy range (low-momentum transfer), it is probable that the scattering interaction will be coherent. This coherence gives rise to interference effects resulting in X-ray diffraction patterns that are characteristic of the scattering material. The usefulness of coherent scattering is not limited to crystallography. It can provide information about biological material as well. The interatomic and intermolecular co-operative effects which modify the free-atom coherent scattering process are well known for highly ordered structures such as crystalline materials but are important for amorphous solids and liquids where short-range ordering occurs. X-ray diffraction using synchrotron radiation has became a well established technique. This work introduces a non-destructive synchrotron radiation X-ray diffraction imaging technique. The feasibility of the X-ray diffraction computed microtomography using synchrotron radiation has been investigated. This research was carried out at the X-ray diffraction beam line of the National Synchrotron Light Laboratory supported by the National Council for Scientific and Technological Development (LNLS/CNPq) in Brazil. These experimental patterns were carried out with a 500 μm slit in front of the detector and an 11.101 keV beam ( λ=1.117 Å) monochromatic beam from the double crystal monochromator. The diffracted beam was detected by a fast scintillation detector (10 6 counts s −1) designed specifically to meet the needs of high quality X-ray diffraction and synchrotron radiation experiments. The data were recorded at rates of one second per degree of 2 θ (angular steps equal to 0.05±0.01°) and registered by a multichannel analyzer. These experimental data could be used to evaluate the scattering properties of different tissue-substitute (water, lucite, nylon, plastic and polystyrene) and bone-substitute (hydroxyapatite and aluminum) materials. The data are in good agreement with those obtained by other authors, indicating the feasibility of the imaging technique.

Contribution to residual-stress evaluation in high-stress-gradient zones by X-ray diffraction

The non-destructive X-ray diffraction method is usually employed to evaluate stress states at the near surface of materials. In specific zones with high-stress gradients parallel to the surface, like welding joins, areas affected by lasers, or ball-bearing raceways, the classical measurement method is not particularly well suited, as the irradiation spot covers regions of varying stress according to its size. This leads to inaccurate stress evaluations. A new X-ray diffraction measurement and data treatment method is therefore proposed. It is based on longitudinal step-by-step scanning in a fixed direction of the surface. As the acquired data results from the convolution of local diffraction peaks with the incident-beam intensity, an accurate model of the true two-dimensional intensity distribution inside the spot has been developed. Firstly, the true shape and size of the irradiation area is defined. The distribution of the intensity received by the sample surface is then computed. The true local strains and stresses along the scanning direction are finally determined from the acquired peaks using an optimization through a least-squares fitting by a nonlinear function.

Analysis of the Defect Structure of Epitaxial GaN

The type and density of threading dislocations in GaN epitaxial layers grown on c-plane sapphire have been analyzed by using nondestructive high resolution X-ray diffraction. The highly distorted GaN layers were described as mosaic crystals characterized by a mean tilt and twist angle between the mosaic blocks which are correlated with the densities of screw and edge type threading dislocations, respectively. Triple axis rocking curves of (00l) reflections for varying l-indices were used to determine the tilt angle, while the twist was extrapolated from ω-scans for (hkl) Bragg reflections with h or k nonzero, measured in skew symmetric diffraction geometry. This defect analysis was applied to selected GaN layers grown by molecular beam epitaxy (MBE) and metalorganic chemical vapour deposition (MOCVD) revealing clear differences between both sample types.

Investigation of inhomogeneous structures of near-surface-layers in ion-implanted silicon

The ion implantation as a subject of investigations attracts increasing interest because of its technological applications. For example, the ion implantation and the adequate thermal treatment are the basic processes for fabrication of a new so-called delta-BSF solar cell. In this silicon solar cell, the continuous sub-structure of modified material (planar amorphous-like layer of nanometric thickness with very thin transition zones) is inserted into the single-crystal emitter. From earlier high resolution electron microscopy studies, it is evident that these two Si phases coexist in the form of well-defined layers separated by sharp heterointerfaces [Z.T. Kuznicki, J. Thibault, F. Chautain-Mathys, S. De Unamuno, Towards ion beam processed single-crystal Si solar cells with a very high efficiency, E-MRS Spring Meeting, Strasbourg, France, First Polish–Ukrainian Symposium, New Photovoltaic Materials for Solar Cells, October 21–22, Kraków, Poland, 1996.]. The aim of this paper is the further structural characterisation of silicon single crystal with buried `amorphous' layer. The non-destructive X-ray diffraction methods as well as the transmission electron microscopy were used to investigate the quality of the a-Si/c-Si heterointerfaces, structural homogeneity of the layers and distribution of the stress field. The measurements were carried out on an initial, as-implanted and annealed material. The 〈100〉-oriented Si single crystals were implanted with 180 keV energy P ions at room temperature.

A Review of Recent Developments and Applications in the Field of X-Ray Diffraction for Residual Stress Studies

Much research effort has been conducted recently in the field of residual stresses. This presentation is a review of different studies carried out during the last few years on the X-ray diffraction technique. The first part of this paper presents an introduction to the residual stresses and the different techniques of measurement. The second part of this paper is focused on the X-ray diffraction technique. Then the different factors that affect the measurement results are discussed and some examples shown for different applications of the X-ray method. The last part of the work deals with the residual stress measurement techniques and the overall necessity to combine destructive (incremental hole drilling) and non-destructive (X-ray and neutron diffraction) methods in order to evaluate precisely the residual stress distribution.

Fabrication of Ag-Sheathed Bi-2223 tapes using powders produced by aerosol spray pyrolysis

Bi-2223 tapes were manufactured from a fine “two-powder” product produced by using an aerosol spray pyrolysis technique. Critical current density of 22000 A/ cm2 at 77K and 0 T was achieved. Nondestructive transmission x-ray diffraction study indicated good alignment of the superconducting grains. The texturing process of the superconducting phase was found to be nearly complete after the first 24 h of heat treatment for the samples studied. Pressing was found to play little role in the texturing process. The texturing can be enhanced by Ag-doping. Jc, however, was not found to be improved significantly, presumably due to the reduced effective cross-sectional area. A new phase, Bi-4435, was identified which may play a significant role in the formation of 2223.

Bone structure studies with holographic interferometric nondestructive testing and x-ray methods

Changes in the biomechanics and in the molecular texture and structure of isolated radioulnar bones of subadult European moose (Alces alces L.) collected in various environmentally polluted areas of Finland were investigated by means of holographic interferometric nondestructive testing (HNDT), radiological, morphometrical, and x-ray diffraction methods. By means of small caudal-cranial bending forces, the surface movements of the lower end (distal epiphysis) of the radial bone were recorded with the HNDT method. To study bone molecular texture and structure changes under external compressing forces, the samples for x-ray diffraction analysis were taken from the upper end of the ulnar bone (olecranon tip). Results showed that the bones obtained from the Harjavalta area and those of North Karelian moose showing malnutrition and healing femoral fractures produced different HNDT pictures compared with the four normally developed North Karelian moose. In the x-ray diffraction, the Harjavalta samples showed changes in molecular texture and structure compared with the samples from the apparently normal North Karelian animals.

Non-Destructive X-Ray Diffraction with 30-Micron Spatial Resolution: Some Examples

ABSTRACTWe have been measuring x-ray diffraction spectra of small samples of layers in cross-sections using a Micro X-ray diffractometer (PSPC/MDG) system since 1988. In measuring with xray diffractometry, the position sensitive proportional counter (PSPC) covers 150 degrees of x-ray diffraction, continuously. The data are accumulated by the multichannel analyser (MCA) and monitored on a CRT during the measurement period. Mounted samples can rotate around three axes. The XRD spectra are very like those from a wide angle goniometer used in powder diffraction. Normally the spatial limits are around 30 microns in diameter, as we have found experimentallly in our samples. We feel this system is very feasible for art and archaeological studies. Some case studies are presented.

Non-Destructive X-Ray Diffraction Analysis of the Under-Film Corrosion Processes in Zinc-Coated Steel Sheets by Synchrotron Radiation

ABSTRACTA highly brilliant x-ray beam from a synchrotron radiation source is a powerful tool to perform non-destructive x-ray diffraction analysis of an under-film corroded region of zinc-coated steel sheets. Investigations to identify corrosion products under the outdoor salt-spray test condition and to reveal their one-dimensional distribution were carried out Simonkolleite (ZnCl2•4Zn(OH)2 ) was identified for the first time at the tip of the under-film corroded region. By the one-dimensional analysis, it was shown that the x-ray diffraction intensity of simonkolleite increased, where that of metal zinc decreased. It was suggested that simonkolleite was formed as the first corrosion product under the outdoor salt-spray test condition.

The determination of three-dimensional stress tensors on multilayer thin films

The three-dimensional residual stress condition of copper sputtered on Kapton™ films was studied by two nondestructive x-ray diffraction techniques. Four samples were evaluated—one “control sample,” and three heat-treated samples. Because of concerns about steep stress gradients normal to the specimen surface, an experimental technique described by Dolle(1) was used to obtain the residual strain tensors in the near surface region. The resulting stress tensors were compared to data obtained through a modification of the technique described by Dolle, referred to as the differential method.(2)

Measurement of residual stresses by X-ray diffraction in a [formula omitted] system obtained by high temperature oxidation

The resistance of metallic materials to high temperature oxidation is strongly linked with the adherence of the oxide layers developed on its surface and thus with the internal stresses of the metal-oxide system. The study of these stresses is delicate and the measurements are, more often than not, indirect. By using the non-destructive and superficial X-ray diffraction measurement, we have analysed the evolution of residual stresses (after returning to ambient temperature) in the Ni NiO system. The oxidation has been performed in air, at 900°C. After perfecting the experimental conditions of the analysis, we have calculated and measured the Radiocrystallographic Elastic Constants required for stress calculation. In NiO, the stresses are compressive. They may reach −600 MPa. This value increases at first and then diminishes when the thickness of the oxide layer increases. The maximum position depends on the Ni substrate thickness. The weaker the initial substrate roughness, the higher the stresses in the oxide (−400 to −600 MPa for polished samples, −100 to −300 MPa for shot-peened samples). The width of the diffraction peaks, index of the quantity of defects in NiO, is small. It diminishes when NiO thickness increases. This may be explained by the gradient of ponctuai defects and dislocations in NiO. Residual stresses in Ni-substrate, in the layers near the interface, are almost zero.

Fast Thickness Measurement of Thin Crystalline Layers by Relative Intensities in XRPD Method

In this work a continuous wave CO2 laser was used for melting a layer of amorphous alumina obtained by anodizing 6061 aluminum plates. Melting the surface of the anodized plates led to the formation of a new uniform corundum layer at the expense of some of the amorphous coating, resulting in a double layer coating of crysta11ine on amorphous.The characterization of the corundum layer is essential for process optimization study. Among the non-destructive methods X-ray diffraction is useful, because it provides us with selected data on the crystalline layer.

From research to cost effective directional solidification and single crystal production - an integrated approach - part C

The integrated approach to automated production technologies has required work in three broad areas. 1. Process Development 2. Material Development 3. Quality Assurance It necessitates bringing together a multidisciplined task force with specialists in metallurgy, ceramics, a non-destructive testing, x-ray diffraction, plant and equipment design, control systems and manufacturing engineering. The result of these programmes has been to develop and prove an automated technology for the production of high quality cost effective Directionally Solidified (DS) and Single Crystal (SC) Castings and in the latter case has led to the use of the seeding technique which, though technically more difficult, allows greater flexibility. As a result of carefully optimised furnace design, enhanced thermal gradients are achieved resulting in improved casting quality coupled with a greater flexibility for the alloy developer. This has led to the development of a series of three alloys to meet specific turbine applications. The need to provide rapid, accurate and audited measurement of single crystal orientation has been met by the development of SCORPIO which is a real time rapid orientation measurement system for the production environment. In the continual search to raise the quality and reliability of the product much development work has been carried out to match process capability with component design intent leading to development of new methods, processes and production control techniques for dimensional control, cleanliness, solution treatment and orientation control. The enabling factor has been the deliberate bringing together of the component design team, the manufacturing engineers and metallurgists into one team for the earliest design stages right through to the production mature process. The success of the integrated approach is best judged by the precise measurement of labour times and material costs for the identical blade made on production by equiaxed, DS and SC casting process and by the complexity and quality of the casting that can be achieved.

Eignung von Tiefenprofilanalysen zur Charakterisierung von Oxidschichten an Hochtemperaturlegierungen

The characterization of oxide scales by their composition and structure is necessary in order to predict their protective behaviour for the high temperature alloys in various corrosive media. For this purpose information obtained by classical methods, such as metallography, X-ray diffraction and microprobe analysis can be supplemented by depth profiles determined by various spectroscopical methods. In this paper, HASTELLOY X und INCONEL 617 were oxidized for relatively short times in two different atmospheres. Depth profiles were determined by GDOS (Glow Discharge Optical Spectroscopy), SNMS (Secondary Neutral Mass Spectrometry) and SIMS (Secondary Ion Mass Spectrometry). The measured profiles were compared with the results of non-destructive X-ray diffraction analysis to characterize the scales and the oxide-metal interface.

A review of selected non-destructive methods for residual stress measurement

The roll of residual stresses in the failure of metallic components has long been recognized. However, the most commonly employed methods for its measurement are destructive or at least partially so. This has led to an active interest in non-destructive methods for residual stress measurement. This review describes the essence of the principles of a semi-destructive (hole drilling) and three non-destructive (X-ray diffraction, ultrasonic velocity, and Barkhausen noise analysis) residual stress measurement methods. The review also describes selected applications of these four methods to residual stress and related property measurements, as well as discussing their limitations and some sources of measurement errors. Conclusions as to the general applicability of the methods to practical residual stress measurements are drawn and a prognosis for the future development of each is offered.

Optical Properties of Semiconductor Superlattices Grown by MBE

GaAs-AlAs superlattices were grown by molecular beam epitaxy with various widths of the GaAs quantum well. A non-destructive X-ray diffraction technique was shown to be a practical method to measure the GaAs quantum well width Lz with an accuracy of 10%. Photoluminescence measurements showed the main carrier recombination process to be from the n=1 electron quantum level to the n=1 heavy hole level. Optical absorption spectra exhibited the sharply peaked structure assocated with excitons at room temperature. MQW laser diodes with GaAs-Asx Ga1-xAs superlattice active layers had lower threshold current density than in conventional DH laser diodes. This illustrated the good optical quality of the superlattices.

X-ray diffraction investigation of bimetallic diffusion zones in the Cu-Pd system

A nondestructive X-ray diffraction technique was used to investigate the diffusion of 8β thick deposits of Pd into [100] oriented single crystals of Cu. The concentration profiles produced by isothermal diffusion at 900°C were determined by mathematical analyses of two diffracted intensity bands. The Boltzmann-Matano analysis was used to determine concentration dependent diffusion coefficients which were found to compare favorably with previously reported values. Also, X-ray rocking curves were made on selected compositions to determine the degree of diffusion-generated subgrain misorientation increase in the diffusion zones. These rocking curves were Gaussian in shape and indicated that the distribution of subgrain misorientations was Gaussian. The widths of the Gaussian misorientation functions were found to be directly related to the lattice parameter gradient existing in the specimen after diffusion. The results of this investigation are compared with those obtained from a previous examination of nearly identically prepared Cu-Ni specimens.