High-energy Synchrotron Radiation Research Articles

Evolution of microstructure and crystallographic texture of Ni-Mn-Ga melt-spun ribbons exhibiting 1.15% magnetic field-induced strain

The microstructure and texture evolution of 10M Ni-Mn-Ga melt-spun ribbons were thoroughly evaluated by high-energy synchrotron radiation and electron backscatter diffraction. The as-spun ribbons were subjected to annealing treatment in order to tailor microstructure, atomic order degree, and crystallographic texture. The optimum annealing treatment at 1173 K for 72 h produced a homogenous <100> fiber texture and induced grain growth to the size that spans the entire ribbon thickness. This in turn reduced microstructural constraints for twin variant reorientation in the direction perpendicular to the ribbon surface. On the other hand, a homogenous radial microstructure ensured in-plane stress/strain compatibility giving rise to strain accommodation during variant reorientation. Particular attention was also given to the evaluation of atomic order, which to the largest extent controls the characteristic transformation temperatures. It also lowered the twinning stress to a level sufficiently low for martensitic variant reorientation under magnetic field. As a result, 1.15% magnetic field-induced strain without the aid of mechanical training in the self-accommodated state was achieved.

An In Situ Synchrotron Dilatometry and Atomistic Study of Martensite and Carbide Formation during Partitioning and Tempering.

Precipitation hardened and tempered martensitic-ferritic steels (TMFSs) are used in many areas of our daily lives as tools, components in power generation industries, or in the oil and gas (O&G) industry for creep and corrosion resistance. In addition to the metallurgical and forging processes, the unique properties of the materials in service are determined by the quality heat treatment (HT). By performing a quenching and partitioning HT during an in situ high energy synchrotron radiation experiment in a dilatometer, the evolution of retained austenite, martensite laths, dislocations, and carbides was characterized in detail. Atomic-scale studies on a specimen with the same HT subjected to a laser scanning confocal microscope show how dislocations facilitate cloud formation around carbides. These clouds have a discrete build-up, and thermodynamic calculations and density functional theory explain their stability.

Internal Strain Distribution of Laser Lap Joints in Steel under Loading Studied by High-Energy Synchrotron Radiation X-rays

The automotive industries employ laser beam welding because it realizes a high energy density without generating irradiation marks on the opposite side of the irradiated surface. Typical measurement techniques such as strain gauges and tube X-rays cannot assess the localized strain at a joint weld. Herein high-energy synchrotron radiation X-ray diffraction was used to study the internal strain distribution of laser lap joint PNC-FMS steels (2- and 5-mm thick) under loading at a high temperature. As the tensile load increased, the local tensile and compressive strains increased near the interface. These changes agreed well with the finite element analysis results. However, it is essential to complementarily utilize internal defect observations by X-ray transmission imaging because the results depend on the defects generated by laser processing.

Elliptical plasma-filled waveguide as a new standard short-period undulator.

Undulators as the sources of high-brilliance synchrotron radiation are of widespread interest in new generations of light sources and free-electron lasers. Microwave propagation in a plasma-filled elliptical waveguide can be studied as a standard short-period undulator. This structure as a lucrative insertion device can be installed in the storage ring of third- and fourth-generation light sources to produce high-energy and high-brilliance synchrotron radiation. In this article, the propagation of the transverse electric modes in a plasma-filled waveguide with an elliptical cross-section is investigated, and the field components, the cut-off frequencies and the electron beam trajectory are calculated. With due consideration of the electron beam dynamics and in order to achieve a standard short-period undulator, parameters such as the dimensions of the waveguide elliptical cross-section, the microwave frequency and the plasma density are calculated.

Probing the Electronic Band Gap of Solid Hydrogen by Inelastic X-Ray Scattering up to 90GPa.

Metallization of hydrogen as a key problem in modern physics is the pressure-induced evolution of the hydrogen electronic band from a wide-gap insulator to a closed gap metal. However, due to its remarkably high energy, the electronic band gap of insulating hydrogen has never before been directly observed under pressure. Using high-brilliance, high-energy synchrotron radiation, we developed an inelastic x-ray probe to yield the hydrogen electronic band information insitu under high pressures in a diamond-anvil cell. The dynamic structure factor of hydrogen was measured over a large energy range of 45eV. The electronic band gap was found to decrease linearly from 10.9 to 6.57eV, with an 8.6 times densification (ρ/ρ_{0}∼8.6) from zero pressure up to 90GPa.

Current Status of the VEPP-4 Accelerator Facility

At the VEPP-4 accelerator complex experiments on high energy physics, nuclear physics, synchrotron radiation and hard X-ray are carried out. The paper presents the current status of the complex and its experimental programs. The development of the resonance depolarization method for the absolute beam energy measurement using a laser polarimeter is discussed. The results of observing the azimuthal difference of the orbits of electron and positron beams, which is a consequence of energy losses due to synchrotron radiation, are presented.

In-Situ GI-XRD of Electrochemically Formed Thin Gold-Oxide Layers

In-situ XRD analysis is a valuable tool to maximize understanding of complex (electro-)chemical reactions while eliminating errors or changes in the structure when instable compounds or materials that react with air are analysed ex-situ. Surface analysis has been a key aspect in the basic research of metal corrosion. Nevertheless, there is more work to be done to achieve complete understanding which is in part because of the lack of proper in-situ analyses. Unfortunately, previous setups for in-situ XRD analysis come along with their own set of problems. In these constructions a low signal/noise ratio can be seen as the beam has to penetrate the electrolyte. High energy synchrotron radiation and long exposure is needed to get information of surface reactions which makes it very laborous and hard to get high quality data. Various researchers like M. Fleischmann et al [1] introduced new XRD cells in which electrolyte layer thickness was minimized to reduce the energy loss and get more accurate XRD information. However, due to issues with current density distribution and other restrictions like depletion of electroactive species or unfavorable reference electrode position electrochemical processes with high reaction rates cannot be investigated accurately in this setup.In a new setup S. Reither et al [2] introduced a XRD cell where copper is sputtered on a XRD-transmittable polyimide foil as a working electrode. The XRD beam is directed through the polyimide and the thin metal film where the reaction happens without passing the electrolyte underneath. A normal electrochemical cell can be used at the side of the working electrode with inlets for counter- and reference electrode. Depending on the reaction rate the setup also includes an in- and outlet to circulate electrolyte if required. Gracing incidence XRD geometry allows for improvement of the signal intensity of thin-film surface reactions.To demonstrate the strength of the setup the oxidation of polycrystalline gold was investigated. Gold is used as the surface reactions are unique compared to other metals due to its stability against oxide formation. L D Burke et al [3] have tried to investigate the reactions taking place at high voltages to create monolayers and thick oxide layers under different conditions. While normal metal oxidation occurs at the surface, gold oxidation occurs beneath a monolayer of adsorbed hydroxy-ions and is catalysed by repulsion triggered ion exchanges at the surface, increasing the influence of conditions and reaction time as well as the current. Our goal is to use the novel in-situ-XRD system to better understand how gold behaves in various electrolytes using both cyclic and constant voltages to create oxide films. It is suspected that gold oxides have porous or amorphous structure. Therefore, a direct XRD-analysis might be difficult. On the other hand, the correlation of electrochemical data with XRD-data allows the indirect categorization between amorphous and crystalline phases at different conditions as pH and temperature.The details of the in-situ XRD-cell as well as its contribution to analysing gold oxide are presented in this contribution.Image explanation:1 .. counter electrode2 .. polymer window with working electrode3 .. reference electrode4, 5 .. solution in- and outlet[1] M. Fleischmann, A. Oliver, and J. Robinson, ‘In Situ X-ray diffraction studies ofelectrode solution interfaces’, Electrochimica Acta, vol. 31, no. 8, pp. 899–906, (1986)[2] S. Reither, W. Artner, A. Eder, S. Larisegger, M. Nelhiebel, C. Eisenmenger-Sittner, G.Fafilek, ‘On the In-Situ Grazing Incidence X-Ray Diffraction of Electrochemically FormedThin Films’, ECS Transactions, 80 (10) 1231-1238, (2017) 10.1149/08010.1231ecst[3] L.D. Burke and P.E Nugent, Electrochim. Acta, 42, 399, (1997) Figure 1

Quantifying the dislocation structures of additively manufactured Ti–6Al–4V alloys using X-ray diffraction line profile analysis

Abstract Ti–6Al–4V alloy is widely used in aerospace and biomedical industries, and its preparation using additive manufacturing techniques has recently attracted considerable attention. Herein, the dislocation structures developed during electron beam and laser beam powder-bed fusion (EB-PBF and LB-PBF, respectively) of the Ti–6Al–4V alloy were quantitatively examined via X-ray diffraction (XRD) line profile analysis. The microstructures of both as-built samples were characterized, revealing fine acicular microstructures attributable to a β → α' martensitic transformation. While a fully α'-martensite matrix with a high dislocation density was formed and preserved during the LB-PBF process, the decomposition of the α'-martensite toward the thermodynamically stable α + β microstructure occurred during EB-PBF as a result of post-solidification exposure to high temperatures. Accordingly, a higher dislocation density and finer crystallite size were observed at the top cross-section from the XRD line profile analysis, suggesting that the extent of phase decomposition depended on the duration of the exposure to the elevated temperature. Nonetheless, the saturated dislocation density was as high as 1014 m−2, where dislocation strengthening affected the overall strength of the EB-PBF specimen. Diffraction peaks of sufficient intensity that enabled the analysis of the dislocation structures in both the α (α')-matrix and the nanosized β-phase precipitates at the α (α')-laths were obtained under high-energy synchrotron radiation; this revealed that the β-phase had a much higher dislocation density than the surrounding α (α')-matrix. The enhanced dislocation accumulation in the nanosized β-phase precipitates probably reflects the elemental partitioning that occurred during post-solidification cooling. The valuable insights provided in this study are expected to promote further development of alloy preparation using additive manufacturing processes.

Effect of B addition on the superelasticity in FeNiCoAlTa single crystals

The study focuses on the superelastic effect in single-crystalline boron-doped Fe-based shape memory alloys. The homogenized and quenched single crystals were subjected to a heat treatment at 973 K for variable aging times. As a result, small and coherent nanometer-sized γ′ (Ni3Al-type) precipitates were formed. It was established that Fe-28Ni-17Co-11.5Al-2.5Ta-0.05B single crystals oriented along [001] direction exhibit the fully reversible superelastic behavior up to 14.3% compression strain at 77 K reaching the maximum theoretical value. The boron addition suppressed completely the formation of the brittle β phase and reduced the average precipitate size of the γ′ precipitates. Using high-energy synchrotron radiation and high-resolution transmission electron microscopy analysis the volume fraction and precipitate size of γ′ were determined indicating that both factors are critical in obtaining the largest superelastic reversibility. Boron addition counters the initial effect of mechanical stabilization which was detected in single crystals without boron. Unlike the thermally induced martensitic transformation, applied stresses produce a different austenite/martensite interface composed of interchanging austenite and martensite variants. It is also demonstrated that upon loading/unloading cycles the moving transformation front divides the material into three district regions i.e. single variant of austenite, austenite intermixed with martensite and single variant of martensite.

On the role of atomic shuffling in the 4O, 4M and 8M martensite structures in Ni-Mn-Sn single crystal

The crystal structure of a four-layered martensite phase in Ni50Mn37.5Sn12.5 single crystal following various modes of training procedure was examined by high energy synchrotron radiation and high-resolution transmission electron microscopy. Three distinct types of unit cell i.e. 4O, 4M, and 8M were unveiled, depending on the mechanical history of the specimen. The most stable phase turned out to be the 4M martensite. Analysis of the intensity of modulation reflections allowed for defining a periodic atomic displacement of 0.3497 Å. The results support the concept of a periodic atomic shuffling as opposed to the adaptive nanotwining approach.

Electric-field-induced structural changes for cubic system of lead-free and lead-based perovskite-type oxides

Changes in crystal structures of lead-free BaTiO3 (BT) and lead-based 0.70Pb(Mg1/3Nb2/3)–0.30PbTiO3 (PMN–PT) single crystals with a perovskite-type structure have been investigated under applied electric field by analyzing the high-energy synchrotron radiation X-ray diffraction data. The experiment is performed within the cubic phase in the phase diagram with the range of temperatures and electric fields where no electric field-induced phase transition is caused. The crystal structure analysis demonstrates that the crystal system is change to a tetragonal system by electrostriction when the electric field is applied along the crystal axis. The atomic arrangement in BT corresponds to the displacement pattern attributed to the Slater mode where Ti and O ions are mutually shifted in the opposite directions along the electric field, while that in PMN–PT is of the Last mode where Pb ions and (Mg, Nb)O6 oxygen octahedra are mutually shifted. The electron charge density study demonstrates that the Ba–O bonding in BT is ionic, whereas the Pb–O bonding in PMN–PT is highly covalent in the cubic structure. PMN–PT is revealed to have a characteristic Pb–O covalent bond which induces the atomic displacement attributed to the Last mode under applied electric field within the cubic phase despite no phase transition.

Thermal decomposition of Yttrium 2-methylbutyrate in argon

The thermal decomposition of yttrium 2-methylbutyrate (Y(C4H9CO2)3) under argon gas flow has been investigated by means of simultaneous thermogravimetry and differential thermal analysis, FTIR-spectroscopy (solid residue and evolved gas analysis), mass spectrometry, hot-stage optical microscopy and X-ray diffraction with a standard laboratory Cu-tube source as well as with a high-energy synchrotron radiation source. At least one structural transition occurs in the solid state between 100 °C and 160 °C. The decomposition of the Y 2-methylbutyrate salt takes place above 400 °C. A first stage results in the formation of Y2O2CO3 between 400 °C and 490 °C. This decomposition step is accompanied by the release of CO2, a symmetrical ketone (3,5-dimethyl-4-heptanone), as well as probably a terminal alkyne, which could not be unambiguously identified. At higher temperature, Y2O2CO3 is slowly converted to Y2O3 with release of CO2, while some carbonaceous residue is eliminated via combustion. The TG trace reaches the final plateau at about 1200 °C.

Design of control algorithm for accelerator magnet power supply with large time constant load

High Energy Photon Source-Test Facility (HEPS-TF) is a pre-research project for the construction of high energy synchrotron radiation source in the 12th five-year plan period. The purpose is to research the key technology and develop the key equipment of high energy synchrotron radiation source. Superconducting 3W1 magnet is the first self-developed superconducting wiggler magnet in China, and it is also one of the key research topics of HEPS. The author has completed a new digital closed-loop control algorithm for the superconducting 3W1 magnet with large load time constant and the nonlinear characteristics of inductance increasing with current, namely three-branch structure algorithm. In the face of the rapid development of high energy accelerator technology, the application of intelligent technology has become an inevitable development trend in the field of accelerator magnet power supply technology. Although the digital control of accelerator magnet power supply has been widely used, it is the first time to apply the new closed-loop control algorithm to realize fast adjustment and precision tracking in accelerator superconducting magnet power supply in China. According to the nonlinear characteristics of inductance and output current of superconducting magnet, a new digital closed-loop control algorithm for the load of superconducting magnet power supply with large time constant is proposed. This algorithm is quite different from the traditional algorithm and can attain the independent tracking and adjustment of the control target. Finally, by testing the ripple, error and stability of superconducting 3W1 magnet power supply, the correctness, practicability and reliability of power supply system as well as the digital control algorithm are verified. The results provide a new idea for the control of accelerator magnet power supply.

Non-destructive Depth Profiling of a Nano Surface by High-energy Synchrotron Radiation XPS

Non-destructive Depth Profiling of a Nano Surface by High-energy Synchrotron Radiation XPS

Origins of superparamagnetism in self-accommodated and trained Ni50Mn37.5Sn12.5 single crystal

The low temperature magnetic state of martensite in the shape memory Ni50Mn37.5Sn12.5 single crystal was confirmed from DC and AC magnetization measurements. At temperatures below the martensite finish and above the Curie temperature of martensite the martensite phase shows superparamagnetic behavior. On cooling growing superparamagnetic clusters manifest a strong interaction and develop, below the freezing temperature (~200 K), into a nonconventional spin glass state. The amount of retained austenite evaluated by high-energy synchrotron radiation was estimated at the level of 1.5 – 2%. Subsequent training procedure cleansed martensite from any retained austenite fraction. The evaluated cluster magnetic moment decreased following training (~9.5%). It is demonstrated that the retained austenite effectively subsidizes but not warrants the superparamagnetic exchange in martensite, which descends from alterations in interatomic spacing inflicted by martensitic transformation.

A laser powder bed fusion system for in situ x-ray diffraction with high-energy synchrotron radiation.

In Laser Powder Bed Fusion (LPBF), the highly localized energy input by the laser leads to high-temperature gradients. Combined with the inherent cycles of re-melting and solidification of the material, they can result in high mechanical stresses. These stresses can cause distortion and cracking within the component. In situ diffraction experiments with high-energy synchrotron radiation allow an analysis of the lattice spacing during the LPBF process and provide insight into the dynamics of stress generation and texture evolution. In this work, an LPBF system for the purpose of synchrotron x-ray diffraction experiments during the manufacturing process of multi-layer components with simple geometries is described. Moreover, results from diffraction experiments at the HEMS beamline P07 at PETRA III, DESY, Hamburg, Germany, are presented. Components with a length of ls = 20 mm and a width of ws = 2.5 mm consisting of 100 layers with a layer thickness of Δz = 50 µm were produced using the nickel-base alloy Inconel 625 as the powder material. Diffraction experiments were carried out in situ at sampling rates of f = 10 Hz with a synchrotron radiation beam size of 750 × 70 µm2. The presented experimental setup allows for the observation of arbitrary measuring positions in the sample in the transmission mode while gathering full diffraction rings. Thus, new possibilities for the observation of the dynamic evolution of strains, stresses, and textures during the LPBF process are provided.

Fast-current-heating devices to study in situ phase formation in metallic glasses by using high-energy synchrotron radiation.

Details of fast-resistive-heating setups, controlled heating ranging from ∼101 K s-1 to ∼103 K s-1, to study in situ phase transformations (on heating and on cooling) in metallic glasses by high-energy synchrotron x-ray diffraction are discussed. Both setups were designed and custom built at the Leibniz Institute for Solid State and Materials Research Dresden (IFW Dresden) and have been implemented at the P02.1 Powder Diffraction and Total Scattering Beamline and the P21.1 Swedish Materials Science Beamline at PETRA III storage ring, DESY, Hamburg. The devices are interchangeable at both beamlines. Joule heating is triggered automatically and is timed with the incident beam and detector. The crystallization process can be controlled via a feedback circuit by monitoring the change in the time-dependent resistivity and temperature of glasses. Different ambient atmospheres, such as vacuum and inert gases (He and Ar), can be used to control oxidation and cooling. The main focus of these devices is on understanding the crystallization mechanism and kinetics in metallic glasses, which are brittle and for which fast heating gives defined glass-crystal composites with enhanced plasticity. As an example, phase-transformation sequence(s) in a prototyped Cu-Zr-based metallic glass is described on heating, and a crystalline phase beneficial to the plasticity is identified.

Comparing CALPHAD predictions with high energy synchrotron radiation X-ray diffraction measurements during in situ annealing of Al0.3CoCrFeNi high entropy alloy

High-entropy alloys (HEAs) offer the unique ability to tailor microstructures through thermal processing techniques. One family of alloys of interest is AlxCoCrFeNi, where x varies from 0.0 to 2.0 molar fraction which allows for a transition from face-centered cubic (FCC) to body-centered cubic (BCC) crystal structure, as well as the formation of various secondary phases, such as B2, sigma, and L12. In this study, we focus on the Al0.3CoCrFeNi HEA. Based on CALPHAD simulations, the Al0.3CoCrFeNi HEA consists of the following phases from highest to lowest temperature: a) FCC at high temperature, followed by b) B2 precipitation in an FCC matrix, c) then B2 and σ phase co-precipitation in an FCC matrix, d) then B2, σ phase, and L12 phase in an FCC matrix, and finally e) B2, σ phase, and L12 phase in a BCC matrix at low temperature. The purpose of our study is to compare phases observed using high-energy synchrotron radiation X-ray diffraction measurements during in situ annealing with the equilibrium phases predicted using CALPHAD. Phase evolution and dissolution are discussed and compared with the CALPHAD simulation predictions. Our experimental results matched well with the CALPHAD predictions of the phase evolution for the B2 phase, however, the phase dissolution of L12 and σ phases was incomplete, which is likely only observable using high resolution synchrotron radiation X-ray diffraction. Better CALPHAD models are needed as well as longer annealing times due to the complexity of achieving phase equilibrium in multi-phase HEAs.

Static and dynamic structural features of single pellets determine the release behaviors of metoprolol succinate sustained-release tablets

The multiple-unit sustained-release (MUSR) dosage forms containing numerous sustained-release subunits present a reliable choice for oral formulation of controlled release systems. As a typical MUSR, the metoprolol succinate sustained-release tablet is an advanced system with limited researches devoted to relating its structure to the drug release phase other than the preparation process and modulation to the release behaviors. This research details a three-dimension method to image the internal structure and detail drug release features of commercial metoprolol succinate sustained-release tablets and component individual single pellets. As such, a new perspective for MUSR dosage form is provided. Using high energy synchrotron radiation X-ray microcomputed tomography (SR-μCT), the in-situ structure parameters were obtained nondestructively. It was demonstrated that the average number of spherical pellets in a tablet was 853 ± 12 (n = 3). The average volume of the pellets was 0.09 ± 0.01 mm3, the diameter was 0.55 ± 0.03 mm, and the sphericity was 0.87 ± 0.06. These data reflected the numerical features of pellets in MUSR tablets, which were helpful for reverse engineering to MUSR. Based on the three dimensional model generated by image processing and analysis software, the pellet structures were divided into three layers of typical depot sustained release system: pellet core, drug-containing layer and outer film. The dynamic structural features determined refer to the changes of structures in pellets during in vitro drug release, with evidence that the coating layer on the pellets maintained a spherical morphology whilst numerous valleys appeared on the surface. The material constitution and distribution in coating layer were evaluated by synchrotron radiation-based Fourier transform infrared mapping and results indicated a composition of hydroxypropyl methylcellulose dispersed in ethyl cellulose. Knowledge of these structural characteristics confirmed that the mechanism of sustained drug release was membrane controlled and consistent with the drug release profiles. In conclusion, the structural investigation provided knowledge of the intrinsic quality of metoprolol succinate sustained-release tablets and offers guidance for reverse engineering of MUSR.

Studies on the Two-Step Aging Process of Fe-Based Shape Memory Single Crystals.

Fe50Ni28Co17Al11.5Ta2.5 single crystals oriented along the [001] direction were investigated in order to establish the influence of two-step aging conditions on superelastic properties. The homogenized and quenched single crystalline material was subjected to a combination of high-temperature and low-temperature heat treatment at 973 K for 0.5 h and at 723 K for various aging times, respectively. As a result, fine and coherent γ’ precipitates were formed. Using diffraction of high energy synchrotron radiation, the volume fraction of γ’ precipitates was computed while their size was determined by high resolution TEM analysis. Compared with one-step heat treatment, the two-step aging process enables control of the precipitate size in a more accurate way. Moreover, it allows one to obtain a higher volume fraction of precipitates without increasing their size significantly. The obtained coherent γ’ precipitates ranged in size from 5 to 8 nm; that considerably improved mechanical properties. The highest superelastic response was obtained for single crystals aged at 973 K for 0.5 h followed by aging at 723 K for 3 h. The single crystals treated with such conditions exhibited a superelastic strain of 15% in which the mechanical martensite stabilization was substantially suppressed.