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Pressure‐induced swelling has been reported earlier for several hydrophilic layered materials. MXene Ti3C2Tx is also a hydrophilic layered material composed by 2D sheets but so far pressure‐induced swelling is reported for this material only under conditions of shear stress at MPa pressures. Here, high‐pressure experiments are performed with MXenes prepared by two methods known to provide "clay‐like" materials. MXene synthesized by etching MAX phase with HCl+LiF demonstrates the effect of pressure‐induced swelling at 0.2 GPa with the insertion of additional water layer. The transition is incomplete with two swollen phases (ambient with d(001) = 16.7Å and pressure‐induced with d(001) = 19.2Å at 0.2 GPa) co‐existing up to the pressure point of water solidification. Therefore, the swelling transition corresponds to change from two‐layer water intercalation (2L‐phase) to a never previously observed three‐layer water intercalation (3L‐phase) of MXene. Experiments with MXene prepared by LiCl+HF etching have not revealed pressure‐induced swelling in liquid water. Both MXenes also show no anomalous compressibility in liquid methanol. The presence of pressure‐induced swelling only in one of the MXenes indicates that the HCl+LiF synthesis method is likely to result in higher abundance of hydrophilic functional groups terminating 2D titanium carbide. [ABSTRACT FROM AUTHOR]

The formation of martensite (ε and α ′ ) in metastable austenitic Fe-18Cr-(10-11.5)Ni alloys was investigated in-situ during cooling. High-energy X-rays were used to study the bulk of the alloys. Both grain-averaged and single-grain data was acquired. ε played an important role in the formation of α ′ with an indistinguishable difference in the martensite start temperature. The single-grain data indicated that stacking faults appear as precursors to ε. An analogy can be made with deformation-induced martensitic transformation, where the generation of nucleation sites would significantly lower the driving force required to overcome the energy barrier in low stacking fault energy Fe-Cr-Ni alloys. [ABSTRACT FROM AUTHOR]

In situ high-energy X-ray diffraction during tensile loading has been used to investigate the evolution of lattice strains and the accompanying strain-induced martensitic transformation in cold-rolled sheets of a metastable stainless steel. At high applied strains the transformation to α-martensite occurs in stepwise bursts. These stepwise transformation events are correlated with stepwise increased lattice strains and peak broadening in the austenite phase. The stepwise transformation arises from growth of α-martensite embryos by autocatalytic transformation. [Copyright &y& Elsevier]

Abstract: The (hcp) ε-martensite formation and the elastic strain evolution of individual (fcc) austenite grains in metastable austenitic stainless steel AISI 301 has been investigated during in situ tensile loading up to 5% applied strain. The experiment was conducted using high-energy X-rays and the 3DXRD technique, enabling studies of individual grains embedded in the bulk of the steel. Out of the 47 probed austenite grains, one could be coupled with the formation of ε-martensite, using the reported orientation relationship between the two phases. The formation of ε-martensite occurred in the austenite grain with the highest Schmid factor for the active {111}<12¯1> slip system. [Copyright &y& Elsevier]

The magnesium alloy AZ31, which has undergone high-pressure torsion processing, was subjected to in situ annealing microbeam synchrotron high-energy X-ray diffraction and compared to the as-received rolled sheet material that was investigated through in situ neutron diffraction. While the latter only exhibits thermal expansion and minor recovery, the nanostructured specimen displays a complex evolution, including recovery, strong recrystallization, phase transformations, and various regimes of grain growth. Nanometer-scale grain sizes, determined using Williamson–Hall analysis, exhibit seamless growth, aligning with the transition to larger grains, as assessed through the occupancy of single-grain reflections on the diffraction rings. The study uncovers strain anomalies resulting from thermal expansion, segregation of Al atoms, and the kinetics of vacancy creation and annihilation. Notably, a substantial number of excess vacancies were generated through high-pressure torsion and maintained for driving the recrystallization and forming highly activated volumes for diffusion and phase precipitation during heating. The unsystematic scatter observed in the Williamson–Hall plot indicates high dislocation densities following severe plastic deformation, which significantly decrease during recrystallization. Subsequently, dislocations reappear during grain growth, likely in response to torque gradients in larger grains. It is worth noting that the characteristics of unsystematic scatter differ for dislocations created at high and low temperatures, underscoring the strong temperature dependence of slip system activation. [ABSTRACT FROM AUTHOR]

The development of a sample environment for in situ x-ray characterization during metal Electron Beam Powder Bed Fusion (PBF-EB), called MiniMelt, is presented. The design considerations, the features of the equipment, and its implementation at the synchrotron facility PETRA III at Deutsches Elektronen-Synchrotron, Hamburg, Germany, are described. The equipment is based on the commercially available Freemelt ONE PBF-EB system but has been customized with a unique process chamber to enable real-time synchrotron measurements during the additive manufacturing process. Furthermore, a new unconfined powder bed design to replicate the conditions of the full-scale PBF-EB process is introduced. The first radiography (15 kHz) and diffraction (1 kHz) measurements of PBF-EB with a hot-work tool steel and a Ni-base superalloy, as well as bulk metal melting with the CMSX-4 alloy, using the sample environment are presented. MiniMelt enables time-resolved investigations of the dynamic phenomena taking place during multi-layer PBF-EB, facilitating process understanding and development of advanced process strategies and materials for PBF-EB. [ABSTRACT FROM AUTHOR]

Laser shock peening (LSP) is an advanced surface enhancement technique used to enhance the fatigue strength of metal parts by imparting deep compressive residual stresses. In the present study, LSP was performed on IN718 SPF alloy, a fine grained nickel-based superalloy, with three different power densities and depth resolved residual strain and stress characterization was conducted using high energy synchrotron x-ray diffraction in beam line 1-ID-C at the Advanced Photon Source at the Argonne National laboratory. A fine probe size and conical slits were used to non-destructively obtain data from specific gauge volumes in the samples, allowing for high-resolution strain measurements. The results show that LSP introduces deep compressive residual stresses and the magnitude and depth of these stresses depend on the energy density of the laser. The LSP induced residual stresses were also simulated using three-dimensional nonlinear finite element analysis, with employment of the Johnson-Cook model for describing the nonlinear materials constitutive behavior. Good agreement between the experimental and simulated data was obtained. These various results are presented and discussed. [ABSTRACT FROM AUTHOR]

The electrochemical growth of Au nanowires in a template of nanoporous anodic aluminum oxide was investigated in situ by means of grazing-incidence transmission small- and wide-angle x-ray scattering (GTSAXS and GTWAXS), x-ray fluorescence (XRF), and two-dimensional surface optical reflectance. The XRF and the overall intensity of the GTWAXS patterns as a function of time were used to monitor the progress of the electrodeposition. Furthermore, we extracted powder diffraction patterns in the direction of growth and in the direction of confinement to follow the evolution of the direction-dependent strain. Quite rapidly after the beginning of the electrodeposition, the strain became tensile in the vertical direction and compressive in the horizontal direction, which showed that the lattice deformation of the nanostructures can be artificially varied by an appropriate choice of the deposition time. By alternating sequences of electrodeposition with sequences of rest, we observed fluctuations of the lattice parameter in the direction of growth, attributed to stress caused by electromigration. Furthermore, the porous domain size calculated from the GTSAXS patterns was used to monitor how homogeneously the pores were filled. [ABSTRACT FROM AUTHOR]

This work introduces the high‐energy surface X‐ray diffraction analysis toolkit (HAT), an open‐source cross‐platform software package written in Python to allow the extraction and processing of high‐energy surface X‐ray diffraction (HESXRD) data sets. Thousands of large‐area detector images are collected in a single HESXRD scan, corresponding to billions of pixels and hence reciprocal space positions. HAT is an optimized reciprocal space binner that implements a graphical user interface to allow the easy and interactive exploration of HESXRD data sets. Regions of reciprocal space can be selected with movable and resizable masks in multiple views and are projected onto different axes to allow the creation of reciprocal space maps and the extraction of crystal truncation rods. Current and future versions of HAT can be downloaded and used free of charge. [ABSTRACT FROM AUTHOR]

Radiotherapy is an important component in the treatment of lung cancer, one of the most common cancers worldwide, frequently resulting in death within only a few years of diagnosis. In order to evaluate new therapeutic approaches and compare their efficiency with regard to tumour control at a pre-clinical stage, it is important to develop standardized samples which can serve as inter-institutional outcome controls, independent of differences in local technical parameters or specific techniques. Recent developments in 3D bioprinting techniques could provide a sophisticated solution to this challenge. We have conducted a pilot project to evaluate the suitability of standardized samples generated from 3D printed human lung cancer cells in radiotherapy studies. The samples were irradiated at high dose rates using both broad beam and microbeam techniques. We found the 3D printed constructs to be sufficiently mechanically stable for use in microbeam studies with peak doses up to 400 Gy to test for cytotoxicity, DNA damage, and cancer cell death in vitro. The results of this study show how 3D structures generated from human lung cancer cells in an additive printing process can be used to study the effects of radiotherapy in a standardized manner. [ABSTRACT FROM AUTHOR]

Metallic material concepts associated with the sustainable and efficient use of resources are currently the subject of intensive research. Al addition to steel offers advantages in view of lightweight, durability, and efficient use of high-Fe scrap from the Al industry. In the present work, Al was added to Fe-12Cr-(9,12)Ni-3Mn-0.3C-xAl (x = 0.1–6) (wt.%) stainless steels to assess its influence on microstructure and mechanical properties. According to density measurements based on Archimedes' principle, densities were between 7.70 and 7.08 g/cm3. High-energy X-ray diffraction estimations of the lattice parameter indicated that nearly 31% of density reduction was caused by the lattice expansion associated with Al addition. Depending on Al concentration, austenitic and duplex matrix microstructures were obtained at room temperature. In the presence of up to 3 wt.% Al, the microstructure remained austenitic. At the same time, strength and hardness were slightly enhanced. Al addition in higher quantities resulted in the formation of duplex matrix microstructures with enhanced yield strength but reduced ductility compared to the austenitic alloys. Due to the ready formation of B2-(Ni,Fe)Al intermetallics in the ferrite phase of the present alloy system, the increase in strength due to the presence of ferrite was more pronounced compared to standard duplex stainless steels. The occurrence of B2 intermetallics was implied by dilatometry measurements and confirmed by electron microscopy examinations and high-energy X-ray diffraction measurements. [ABSTRACT FROM AUTHOR]

Materials with heterogeneous microstructures have been reported to have an attractive combination of strength and ductility. This is attributed to synergistic strengthening effects from the difference in strength of fine- and coarse-grained regions. Understanding the interaction of the regions is crucial for further optimization of the microstructures. In this work, we fabricated nickel of harmonic structure (HS) and a reference with homogenous coarse grains. The HS constitutes of an interconnected fine-grained network that surrounds regions of coarse grains. The interplay of the regions was studied by monitoring Bragg reflections from individual grains in situ during tensile deformation until approximately 2 % strain through synchrotron X-ray diffraction. The technique allows grain-level assessment of the degree of plastic deformation. Two grains were followed in the reference and two small grains (fine-grained region) and two large grains (coarse-grained region) in the HS. Three deformation regimes were identified: elastic deformation, onset of plastic deformation and significant plastic deformation. Our results reveal that the large grains in the harmonic structure onset plastic deformation during the macroscopic elastic stage. With increasing applied stress, the small grains yield plastically also and once a large fraction of the fine-grained network deforms plastically the large grains undergo significant plastic deformation. Notably, the onset of significant plastic deformation of large grains in the HS occurs at approximately 100 MPa higher applied stress than in the grains in the reference. This shows that fine grains constrain the large grains from deforming plastically in the HS. [Display omitted] [ABSTRACT FROM AUTHOR]

High-energy synchrotron X-rays are well suited to study engineering (structural) materials due to their small wavelength, adjustable energy and beam size, high flux, and ability to penetrate bulk polycrystalline samples up to centimeters in thickness. Recent advances in the use of high-speed, high-resolution detectors are making it possible to characterize microstructures at both the single grain and ensemble levels and to characterize the micromechanical responses of polycrystalline aggregates in three dimensions. These capabilities open new avenues of “in-situ” research that augments traditional forensic evidence with real-time data on functioning, evolving systems. X-ray scattering data are extremely rich, but taking the best advantage requires a continued refinement of experimental methods and analysis and a closer coupling of material models to detected intensities. [ABSTRACT FROM AUTHOR]

Abstract: The lattice strain tensor evolution for single bulk grains of austenite and ferrite in a duplex stainless steel during tensile loading to 0.02 applied strain has been investigated using in situ high-energy X-ray measurements and finite-element modeling. Single-grain X-ray diffraction lattice strain data for the eight austenite and seven ferrite grains measured show a large variation of residual lattice strains, which evolves upon deformation to the point where some grains with comparable crystallographic orientations have lattice strains different by 1.5×10−3, corresponding to a stress of ∼300MPa. The finite-element simulations of the 15 measured grains in three different spatial arrangements confirmed the complex deformation constraint and importance of local grain environment. [Copyright &y& Elsevier]

Abstract: A novel synchrotron-based technique “high angular resolution 3DXRD” is presented in detail, and applied to the characterization of oxygen-free, high-conductivity copper at a tensile deformation of 2%. The position and shape in reciprocal space of 14 peaks originating from deeply embedded individual subgrains is reported. From this dataset the density of redundant dislocations in the individual subgrains is inferred to be below 12×1012 m−2 on average. It is found that the subgrains on average experience a reduction in strain of 0.9×10−4 with respect to the mean elastic strain of the full grain, a rather wide distribution of the strain difference between the subgrains (twice the standard deviation is 2.9×10−4), and a narrow internal strain distribution (upper limit is 2.4×10−4 full width at half maximum). [Copyright &y& Elsevier]

During plastic deformation of metals and alloys, dislocations arrange in ordered patterns. How and when these self-organization processes take place have remained elusive, because in situ observations have not been feasible. We present an x-ray diffraction method that provided data on the dynamics of individual, deeply embedded dislocation structures. During tensile deformation of pure copper, dislocation-free regions were identified. They showed an unexpected intermittent dynamics, for example, appearing and disappearing with proceeding deformation and even displaying transient splitting behavior. Insight into these processes is relevant for an understanding of the strength and work-hardening of deformed materials. [ABSTRACT FROM AUTHOR]

We report on the microstructural features associated with the formation of incipient spall and damage in a fully recrystallized, high purity copper sample. Before and after ballistic shock loading, approximately 0.8mm3 of the sample's crystal lattice orientation field is mapped using non-destructive near-field High Energy Diffraction Microscopy. Absorption contrast tomography is used to image voids after loading. This non-destructive interrogation of damage initiation allows for novel characterization of spall points vis-a-vis microstructural features and a fully 3D examination of microstructural topology and its influence on incipient damage. The spalled region is registered with and mapped back onto the pre-shock orientation field. As expected, the great majority of voids occur at grain boundaries and higher order microstructural features; however, we find no statistical preference for particular grain boundary types. The damaged region contains a large volume of Σ-3 (60°(111)) connected domains with a large area fraction of incoherent Σ-3 boundaries. [ABSTRACT FROM AUTHOR]

The rigidity threshold in a two-phase soft-rigid material is linked to the formation of networks of the rigid phase, which supports a substantial fraction of overall load. Metal filled particulate polymer composites were used to characterize rigidity transition experimentally, as metals and polymers have contrasting mechanical properties enabling easy detection of the rigidity transition. A detailed analysis of the load transferring mechanisms was performed using in-situ synchrotron X-ray diffraction to directly verify the compressive loading of the rigid metal particles at a microscopic scale. Elastic buckling of the force chains was attributed to the non-affine deformation at the rigidity threshold at room temperature, using digital image correlation (DIC) technique at a mesoscopic length scale. However, beyond the glass transition temperature of the polymer, the deformation was homogeneous due to the low viscosity and high compressibility of the polymer and the absence of buckling of force chains. Macroscopically, an increasing Poisson ratio was observed as a function of elastic strains, which is quite unique for these composites. The criteria for having increasing Poisson ratio is discussed based on elastic buckling of force chains and polymer incompressibility, and a link is proposed between deformation at microscopic, mesoscopic and macroscopic scale for the composite. [ABSTRACT FROM AUTHOR]

A correction to the article "High Spatial Resolution, High Energy Synchrotron X-Ray Diffraction Characterization of Residual Strains and Stresses in Laser Shock Peened Inconel 718SPF Alloy," which appeared in a 2012 issue is presented.

• Origins of anisotropic ductility in AM IN718 with weak texture was revealed with the help of HEXRD. • Negative stress triaxiality factor of {220} grains in vertical sample and elongated grain structure result anisotropic ductility. • Anisotropic ductility was first revealed to be associated with the stress triaxiality factor of {220} grains. • δ-phase alignment and grain boundary orientation were proved to have a pronounced impact on the anisotropic ductility. • Positive effect of {220} grains on ductility is marginally over others, contributing to the excellent ductility exceeding 12%. Anisotropic ductility in additively manufactured (AM) alloys, namely better ductility along the building direction (BD) has been extensively studied and traditionally attributed to the crystallographic texture. However, recent studies have shown significant ductility anisotropy in weakly or non-textured AM alloys, indicating that other factors may also play critical roles. To explore this, AM Inconel 718 with weak crystallographic texture was selected as the model material, and the in-situ high-energy X-ray diffraction tests together with multiscale microstructural characterization techniques were performed to explore the deformation micromechanisms. The results of this study, for the first time, revealed that the better ductility in the vertical specimen (loading parallel to BD) was partially due to the negative stress triaxiality factor (TF) of the {220} grains during plastic deformation, which results in the shrinkage or even healing of the microvoids. Furthermore, the δ-phase alignment in conjunction with grain boundary orientation were also proved to have a pronounced impact on the anisotropic ductility of AM alloys. On the other hand, though in the overall weak-textured microstructure, the proportion of 〈101〉 grains were marginally over other grains. Thus, the positive effect of {220} grains on ductility was stronger than the negative effect of {200} and {311} grains, contributing to the excellent failure elongation exceeding 12% for both samples. The findings of this study shed new light on the mechanisms underlying the anisotropic ductility of AM alloys and provide insight into strategies for enhancing their performance. [ABSTRACT FROM AUTHOR]

Transformation-induced plasticity (TRIP) assisted duplex stainless steels, with three different stabilities of the austenite phase, were investigated by synchrotron x-ray diffraction characterization during in situ uniaxial tensile loading. The micromechanics and the deformation-induced martensitic transformation (DIMT) in the bulk of the steels were investigated in situ . Furthermore, scanning electron microscopy supplemented the in situ analysis by providing information about the microstructure of annealed and deformed specimens. The dependence of deformation structure on austenite stability is similar to that of single-phase austenitic steels with shear bands and bcc -martensite ( α′ ) generally observed, and blocky α′ is only frequent when the austenite stability is low. These microstructural features, i.e. defect structure and deformation-induced martensite, are correlated with the micro- and macro-mechanics of the steels with elastoplastic load transfer from the weaker phases to the stronger α′ , in particular this occurs close to the point of maximum rate of α′ formation. A clear strain-hardening effect from α′ is seen in the most unstable austenite leading to a pronounced TRIP effect. [ABSTRACT FROM AUTHOR]

The aim of this work is to characterize the precipitation kinetics in Haynes® 282® superalloys using in-situ high-energy Small Angle X-ray Scattering (SAXS) together with Wide Angle X-ray Scattering (WAXS). The phases identified by WAXS include γ (matrix), γ ′ (hardening precipitates), MC (metallic carbides), and M 23 C 6 /M 6 C (secondary metallic carbides). The γ ’ -precipitates are spheroids with a diameter of several nanometres, depending on the temperature and ageing time. From the SAXS data, quantitative parameters such as volume fraction, number density and inter-particle distance were determined and correlated with ex-situ Vickers microhardness measurements. The strengthening components associated with precipitates and solid solutions are differentiated using the measured Vickers microhardness and SAXS model parameters. A square root dependence between strengthening attributable to the precipitates and the product of volume fraction and mean precipitate radius is found. The solid solution strengthening component correlates with the total volume fraction of precipitates. [ABSTRACT FROM AUTHOR]

In situ X-ray diffraction was employed to gain insight into the tensile deformation behavior of harmonic structure (HS) nickel. HS consists of a continuous network of fine grains encompassing islands of coarse grains. With the aid of a newly developed separation algorithm, the X-ray diffraction signals from coarse and fine grains were analyzed separately. Using line profile analysis, the evolution of local stresses and microstrains in the respective grain fractions were examined. Several stages were identified during yielding and the onset of plastic deformation in HS nickel. The mechanical behavior of the individual fractions was related to the macroscopic behavior of the HS and compared to that of homogeneous counterparts with similar average grain sizes as the grain fractions. The analysis reveals that the stress partitions between the grain fractions and that the plastic deformation of coarse grains within the HS are constrained by the network of fine grains. [Display omitted] [ABSTRACT FROM AUTHOR]

High energy x-ray characterization methods hold great potential for gaining insight into the behavior of materials and providing comparison datasets for the validation and development of mesoscale modeling tools. A suite of techniques have been developed by the x-ray community for characterizing the 3D structure and micromechanical state of polycrystalline materials; however, combining these techniques with in situ mechanical testing under well characterized and controlled boundary conditions has been challenging due to experimental design requirements, which demand new high-precision hardware as well as access to high-energy x-ray beamlines. We describe the design and performance of a load frame insert with a rotational and axial motion system that has been developed to meet these requirements. An example dataset from a deforming titanium alloy demonstrates the new capability. [ABSTRACT FROM AUTHOR]

An important advance in understanding the mechanics of solids over the last 50 years has been development of a suite of models that describe the performance of engineering materials while accounting for internal fluctuations and anisotropies (ex., anisotropic response of grains) over a hierarchy of length scales. Only limited engineering adoption of these tools has occurred, however, because of the lack of measured material responses at the length scales where the models are cast. Here, we demonstrate an integrated experimental capability utilizing high energy X-rays that provides an in situ , micrometer-scale probe for tracking evolving microstructure and intergranular stresses during quasi-static mechanical testing. We present first-of-a-kind results that show an unexpected evolution of the intergranular stresses in a titanium alloy undergoing creep deformation. We also discuss the expectation of new discoveries regarding the underlying mechanisms of strength and damage resistance afforded by this rapidly developing X-ray microscopy technique. [ABSTRACT FROM AUTHOR]

Crystals with a hexagonal close-packed (HCP) structure are inherently anisotropic, and have a limited number of independent slip systems, which leads to strong deformation textures and reduced formability in polycrystalline products. Tension along the c-axis of the crystal ideally activates extension twinning as a deformation mode due to the lack of easy-slip systems. In this work, experiments were devised to study extension twinning in a polycrystalline Mg alloy AZ31B with a strong basal rolling texture by tensile deformation parallel to the plate normal. Three-dimensional synchrotron X-ray diffraction (3DXRD) was used to map the center-of-mass positions, volumes, orientations, elastic strains, and stress tensors of over 1400 grains in-situ up to a true strain of 1.4%. More than 700 tensile twins were observed to form in the mapped volume under deformation. The measured center-of-mass positions and grain volumes are used to construct various 3D microstructures and model them with a Crystal Plasticity Finite Element (CPFE) code. It is observed that the average grain-resolved stress did not always select the highest ranked Schmid factor twin variant. In fact, the contribution of lower ranked variants was non-negligible. The CPFE simulation indicates that there is a small variation in the stress within each grain in the elastic regime, which increases drastically upon the onset of plasticity. One of the significant outcomes of this work is the new statistical information on the interaction between twin and parent grain. It is shown that, on average, there is a small difference between the stress normal to the twin habit plane in the parent and twin, but that this is not the case for the shear acting on the habit plane. [ABSTRACT FROM AUTHOR]

• Normalization of the photoelectron intensity increases quantitative accuracy of XPS. • Combination of synchrotron XPS and XRR allowed reliable quantitative analysis. • Results revealed a 13 Å thick oxide film and a 3 Å thick hydroxide layer on top. • The oxide was enriched in Nb, Mo and Cr while underlying alloy layer enriched in Ni. • Alloy element contribution to the oxide was correlated to their oxidation enthalpy. [Display omitted] The surface chemistry and thickness of the native oxide, hydroxide, and modified sub-surface layer of three Ni superalloys (alloy 59, 625, and 718) were determined by synchrotron X-ray Photoelectron Spectroscopy (XPS) and X-ray Reflectivity (XRR). Taking advantage of the synchrotron radiation techniques, a procedure for normalizing the photoelectron intensity was employed, which allowed for accurate quantitative analysis revealing a total oxide thickness for all samples of 12–13 Å, a hydroxide layer of 2–3 Å, and a thickness of the sub-surface alloy layer of 20–35 Å. The thickness results were compared to structural atomic models suggesting that the oxide thickness corresponds to four planes of metal cations in the oxide matrix. The XPS data revealed that the native oxides were enriched in Cr3+, Mo(4,5,6)+, and Nb5+, while no Ni oxide was detected. The hydroxide layer mainly contained Ni2+ and Cr3+ hydroxide. The sub-surface layer was enriched in Ni and depleted in Cr, Fe, Mo, and Nb. The obtained oxide composition can be explained using thermodynamics, and it was found that the oxide composition correlates with the enthalpy of oxide formation for the metal elements in the alloys. Finally, the advantages of synchrotron radiation for composition and thickness determination are discussed. [ABSTRACT FROM AUTHOR]

Abstract: A novel X-ray diffraction-based technique for grain-by-grain assessment of dislocation density within polycrystals is applied. The technique discriminates dislocation densities of different slip modes, slip systems and dislocation character. Data which was formerly confined to the transmission electron microscope (TEM) is now available from X-ray diffraction (XRD). In addition, there is a profound statistical advantage of the XRD approach over the traditional TEM-based approach. Over 130 grains were analyzed for one sample of CoTi, which would be a Herculean task on the TEM, requiring dozens of samples as well as numerous hours on the microscope and analysis of the images generated for each sample. The present experiments were performed in about 30h per sample and the analysis is semi-automated, involving a Monte-Carlo-type algorithm to determine the dislocation structure best representing the single crystal diffraction peak profiles in a polycrystalline aggregate. Conclusive confirmation of a previously suggested explanation for the anomalous ductility of two CsCl structured intermetallic compounds, CoTi and CoZr, is provided: namely, that hard dislocation modes, with b =〈110〉 and 〈111〉, rarely observed in single crystal experiments, are active in nearly every grain. The results call into question the value of employing single crystal deformation experiments alone to understand the deformation behavior of polycrystalline materials. Further, the results re-emphasize that the uniform stress assumption implicit in Schmid factor analysis is a poor one for materials which are highly anisotropic at the single crystal level. [Copyright &y& Elsevier]

Abstract: The deformation behavior of silica sand particles under one-dimensional (1D) loading compression was investigated using nondestructive 3D synchrotron micro-computed tomography (SMT) and three dimensional X-ray diffraction (3DXRD). High-resolution SMT images were used to monitor particle-to-particle interactions, and the onset and propagation of fracture mechanism in a column composed of three silica sand particles. Particle-averaged lattice strain tensors within individual sand particles were measured using the 3DXRD technique and were then used to calculate the stress tensor components via the general elastic stress–strain relationship. The normal stress component in the axial direction (σ zz) exhibited a nearly linear increasing trend in all sand particles. Shear stress components were in general small relative to the normal stress components and displayed no systematic trend. Knowing lattice strains, stresses, and particle kinematic behavior, one can formulate and develop a micromechanics-based constitutive model to fully characterize strength properties and deformation characteristics of granular materials. [Copyright &y& Elsevier]

The three-dimensional X-ray diffraction (3DXRD) nondestructive technique was used to measure lattice strains within individual sand particles subjected to compressive loading. Three experiments were conducted on similar single columns of silica sand particles with particle sizes between 0.595 and 0.841 mm. In each experiment, three sand particles were placed inside an acrylic mold with an inner diameter of 1 mm. Multiple in situ 3DXRD scans were acquired for each sand column as compressive load was increased. The volume-averaged lattice strain tensor was calculated for each sand particle. In addition, particle orientation and volumetric strain were calculated for individual sand particles. The axial normal strain $$\upvarepsilon _\mathrm{zz}$$ ε zz exhibited a linear response in the range of 0 to $$10^{-3}$$ 10 − 3 when the applied compressive axial load (F) increased from 0 to $$\sim $$ ∼ 30 N when one particle in the sand column fractured. Stress tensor of individual particles was calculated from the acquired lattice strain measurements and elastic constants of silica sand that were reported in the literature. To the best of our knowledge, there have been no reported experimental measurements of the lattice strain tensor measurements within individual silica sand particles. The quantitative measurements reported in this paper at the particle level are very valuable for developing, validating or calibrating micromechanics-based finite element and discrete element models to predict the constitutive behavior of granular materials. 3DXRD represents an exciting new non-destructive technique to directly measure constitutive behavior at the scale of individual particles. [ABSTRACT FROM AUTHOR]

Abstract: High-energy X-ray diffraction microscopy is a non-destructive materials characterization technique that is capable of tracking the evolution of three-dimensional microstructures as they respond to external stimuli. We present measurements of the annealing response of high-purity aluminum using the near-field variant of this technique. The data are analyzed with the forward modeling method which produces orientation maps that exhibit complex intragranular structures. Analysis and verification of results use both reconstructed sample space maps and detector space intensity patterns. Sensitivity to the ordering of the microstructure through both recovery and recrystallization is demonstrated. Sharpening of diffraction peaks and a corresponding reduction in intragranular orientation variations signal recovery processes. The emergence of a new bulk grain (recrystallization) is observed in a disordered region of the microstructure; the new grain has an orientation with no obvious relation to those of grains surrounding the disordered region. [Copyright &y& Elsevier]

Abstract: The stress field around a notch in a coarse grained Mg AZ31 sample has been measured under tensile load using the individual grains as probes in an in situ high energy synchrotron diffraction experiment. The experimental set-up, a variant of three-dimensional X-ray diffraction microscopy, allows the position, orientation and full stress tensor of each illuminated grain to be determined and, hence, enables the study of evolving stress fields in coarse grained materials with a spatial resolution equal to the grain size. Grain resolved information like this is vital for understanding what happens when the traditional continuum mechanics approach breaks down and fracture is governed by local heterogeneities (e.g. phase or stress differences) between grains. As a first approximation the results obtained were averaged through the thickness of the sample and compared with an elastic–plastic continuum finite element simulation. It was found that a full three-dimensional simulation was required to account for the measured transition from the overall plane stress case away from the notch to the essentially plane strain case observed near the notch tip. The measured and simulated stress contours were shown to be in good agreement except at the highest applied load, at which stress relaxation at the notch tip was observed in the experimental data. This stress relaxation is attributed to the initiation and propagation of a crack. Finally, it was demonstrated that the measured lattice rotations could be used as a qualitative measure of the shape and extent of the plastic deformation zone. [Copyright &y& Elsevier]

A GE Revolution 41RT flat-panel detector (GE 41RT) from GE Healthcare (GE) has been in operation at the Advanced Photon Source for over two years. The detector has an active area of 41 cm × 41 cm with 200 µm × 200 µm pixel size. The nominal working photon energy is around 80 keV. The physical set-up and utility software of the detector system are discussed in this article. The linearity of the detector response was measured at 80.7 keV. The memory effect of the detector element, called lag, was also measured at different exposure times and gain settings. The modulation transfer function was measured in terms of the line-spread function using a 25 µm × 1 cm tungsten slit. The background (dark) signal, the signal that the detector will carry without exposure to X-rays, was measured at three different gain settings and with exposure times of 1 ms to 15 s. The radial geometric flatness of the sensor panel was measured using the diffraction pattern from a CeO2 powder standard. The large active area and fast data-capturing rate, i.e. 8 frames s-1 in radiography mode, 30 frames s-1 in fluoroscopy mode, make the GE 41RT one of a kind and very versatile in synchrotron diffraction. The loading behavior of a Cu/Nb multilayer material is used to demonstrate the use of the detector in a strain-stress experiment. Data from the measurement of various samples, amorphous SiO2 in particular, are presented to show the detector effectiveness in pair distribution function measurements. [ABSTRACT FROM AUTHOR]

Quantitative strain analysis (QSA) provides a means for assessing the orientation- dependent micromechanical stress states in bulk polycrystalline materials. When combined with quantitative texture analysis, it facilitates tracking the evolution of micromechanical states associated with selected texture components for specimens deformed in situ. To demonstrate this ability, a sheet specimen of rolled and recrystallized oxygen-free high conductivity Cu was subject to tensile deformation at APS 1-ID-C. Strain pole figures (SPFs) were measured at a series of applied loads, both below and above the onset of macroscopic yielding. From these data, a lattice strain distribution function (LSDF) was calculated for each applied load. Due to the tensorial nature of the LSDF the full orientation-dependent stress tensor fields can be calculated unambiguously from the single-crystal elastic moduli. The orientation distribution function (ODF) is used to calculate volume-weighted average stress states over tubular volumes centered on the (100)11 [100], (311)11 [100], and (111)11 [100] fibers-accounting for ~50% of the total volume-are shown as functions of the applied load along [100]. Corresponding weighted standard deviations are calculated as well. Different multiaxial stress states are observed to develop in the crystal subpopulations despite the uniaxial nature of the applied stress. The evolution of the orientation-dependent elastic strain energy density is also examined. The effects of applying stress bound constraints on the SPF inversion are discussed, as are extensions of QSA to examine defect nucleation and propagation. [ABSTRACT FROM AUTHOR]

Abstract: Non-180° domain switching leads to fracture toughness enhancement in ferroelastic materials. Using a high-energy synchrotron X-ray source and a two-dimensional detector in transmission geometry, non-180° domain switching and crystallographic lattice strains were measured in situ around a crack tip in a soft tetragonal lead zirconate titanate ceramic. At K I =0.71MPam1/2 and below the initiation toughness, the process zone size, spatial distribution of preferred domain orientations, and lattice strains near the crack tip are a strong function of direction within the plane of the compact tension specimen. Deviatoric stresses and strains calculated using a finite element model and projected to the same directions measured in diffraction correlate with the measured spatial distributions and directional dependencies. Some preferred orientations remain in the crack wake after the crack has propagated; within the crack wake, the tetragonal 001 axis has a preferred orientation both perpendicular to the crack face and toward the crack front. [Copyright &y& Elsevier]

Fueled by pressures to reduce scrap and tooling costs, the modeling and prediction of springback has become a major focus of interest in sheet metal forming. Finite element codes and packages are being developed or improved but face the demand for higher predictive accuracy which, in turn, requires accurate property data and a more complete understanding of the stresses that are responsible for the elastic part of the springback. In order to provide experimental data for these calculations, synchrotron X-ray diffraction measurements were carried out in order to determine the through-thickness distribution of axial and tangential residual stresses in an Al6022 deep drawn cup. The technique is able to provide true spatial resolutions of 0.05 mm for a strain measurement on a cup with 0.92 mm wall thickness. It is found that both axial and tangential stresses exhibit non-linear gradients through thickness and both exhibit a pronounced dependency on the axial position. The springback measured on a split ring cut from the cup agrees within 3% accuracy with the value predicted from the average of measured through-thickness stresses. [Copyright &y& Elsevier]

Demands for designing prime reliant, energy-efficient, and high-performance thermal barrier coatings (TBCs) in gas turbines have led to a growing interest toward comprehensive microstructural characterization. Here we investigate the novel use of high-energy X-rays for small-angle X-ray scattering (SAXS), together with wide-angle scattering and radiography, for the depth-resolved characterization of TBCs grown by electron beam physical vapor deposition (EB-PVD). The coating microstructure is found to consist of columns perpendicular to the substrate, extending through the thickness, with a [001] growth texture and significant intercolumnar porosity. In addition, overshadowing effects during deposition together with gas entrapment give rise to nanoscale intracolumnar porosity consisting of featherlike and globular pores. Radiography showed an increase in the total porosity, from 15% near the substrate to 25% near the coating surface, which is ascribed to an increase in the intercolumnar spacing at the top of the coating. By contrast, the small-angle scattering studies, which are sensitive to fine features, showed the pore internal surface area to be greatest near the substrate. [ABSTRACT FROM AUTHOR]

Local damage evolution in a composite is the primary micromechanical process determining its fracture toughness, strength, and lifetime. In this study, high energy X-ray microdiffraction was used to measure the lattice strains of both phases in a Ti–SiC fiber composite laminate. The data provided in situ load transfer information under applied tensile stress at the scale of the microstructure. To better understand damage evolution, predictions of a modified shear lag model were compared to the strain data. This comparison (1) demonstrated the importance of accounting for the matrix axial and shear stiffness, (2) optimized the stiffness ratio for load transfer, and (3) improved the interpretation of the ideal planar geometry commonly used in micromechanical composite models. In addition, the results proved the matrix within and around the damage zone sustained substantial axial load and locally yielded. It was also shown that an area detector is essential in such a diffraction study as it provides multi-axial strain data and helps eliminate the “graininess” problem. [Copyright &y& Elsevier]

• Synchrotron high-energy XRD and DFT calculation were used to study degradation of Cu exposed to S-containing groundwater. • XRD revealed heterogeneous lattice deformation and lattice expansion in near-surface regions after two-month exposure. • DFT calculations suggest spontaneous adsorption of H, H_S and H_S_H on Cu surface, and S promotes H adsorption on Cu. • Water causes surface reconstruction and promotes H insertion, occurring via interstitial sites next to vacancies leading to lattice dilation and metal bond weakening. • H infusion in the presence of S caused lattice degradation, indicating a risk for H-induced corrosion cracking. Synchrotron high-energy XRD measurements and ab-initio DFT calculations were employed to investigate microstructural degradation of copper upon exposure to sulfide-containing anoxic groundwater simulating nuclear waste repository. After two-month exposure, the high-energy XRD measurements revealed heterogeneous lattice deformation in the microstructure and lattice expansion in near-surface regions. The DFT calculations show that sulfur promotes hydrogen adsorption on copper. Water causes surface reconstruction and promotes hydrogen insertion into the microstructure, occurring via interstitial sites next to vacancies leading to lattice dilation and metal bond weakening. Hydrogen infusion in the presence of sulfur caused lattice degradation, indicating a risk for H-induced cracking. [ABSTRACT FROM AUTHOR]

• Infusing hydrogen leads to higher strains in the austenite than the ferrite. • The strains perpendicular to the surface are highest and tensile. • Hydrogen-induced lattice strain development is heterogeneous. • Most lattice strain evolution occurs at the near surface. • The austenite supports the ferrite against hydrogen embrittlement. Local strain development in the microstructure of a commercial 25Cr-7Ni super duplex stainless steel was mapped using high-energy x-ray diffraction during cathodic hydrogen charging under constant uniaxial load. The infusion of hydrogen resulted in tensile strains in austenite grains, one order of magnitude larger than those in the ferrite. Most strain evolution occurred at the near-surface, with compensating compressive forces developed in underlying regions, with up to two-times more compression occurring in the ferrite than the austenite. The strains along the loading axis were more pronounced than in the transverse direction, in which mostly compressive strains developed in the ferrite. [ABSTRACT FROM AUTHOR]

The investigation of the lattice strain development in three Ni-Fe alloys suggests that the lattice strain evolution behaviour depends on the deformation mechanism. When the plastic deformation is governed by the dislocation, the lattice strain exhibited pronounced nonlinear behaviour around the elastic limit. When the grain boundary sliding dominates the deformation, there is no obvious shift in the lattice strain evolution as soon as plastic deformation occurs. [ABSTRACT FROM AUTHOR]