Time-of-flight Neutron Diffraction Research Articles

A Mechanism on Multiscale Heterogenous Deformation of Nickel-Based Single Crystal Superalloys Unraveled by Time-of-Flight Neutron Diffraction Technology

Time-of-flight (TOF) neutron diffraction technology is a powerful tool for acquiring rich diffraction information on the multiscale microstructures and stresses of nickel-based single crystal superalloys. In this study, the tensile deformation behaviors of DD426 superalloy at 760°C were investigated by TOF neutron diffraction. Combined with electron backscatter diffraction technology, the multiscale deformation heterogeneity between γ/γ' phases and dendritic/interdendritic regions was simultaneously characterized for the first time. Our experiments revealed a significant misorientation difference and the existence of a long-range stress field in the adjacent area between the dendritic and interdendritic regions after tensile deformation at 760°C. The misorientation angles of crystal planes along the loading direction between the dendritic and interdendritic regions in the deformed alloy was approximately 1.6±0.6°. This misorientation can be attributed to the geometrically necessary dislocations (GNDs) concentrated in the adjacent area between the two regions with densities of approximately 1014 m-2. In addition, the lattice strains of both γ' and γ showed a compressive–tensile transition from the dendritic to interdendritic regions, balanced with a long-range stress field. The pile-up GNDs in the adjacent area between the two regions contributed to the existence of long-range stress fields. This study highlights that TOF neutron diffraction technology may reveal well the heterogeneous deformation mechanisms via the formation of both GNDs and pile-up in the adjacent interdendritic/dendritic area of single crystal superalloys.

Neutron diffraction analysis of microstructural evolution and mechanical behavior in an additively manufactured multiphase alloy

Abstract Additive manufacturing (AM) involves an unprecedented thermal history during solidification and post-melt high-temperature exposure, leading to unique microstructural evolution. In this study, we employed neutron-diffraction-based microstructural analysis to better understand the microstructural evolution and mechanical behavior of AM alloys, with a particular focus on multiphase alloys. Samples of Ti−6Al−4V alloy used as a model material were prepared using electron beam powder bed fusion (EB-PBF) under varying building conditions. Time-of-flight neutron diffraction (TOF-ND) measurements were performed using an iMATERIA (BL20), J-PARC, Japan. Using Rietveld texture analysis (RTA), we revealed the textural evolution during hierarchical microstructural development from solidification to solid-state phase transformations in the EB-PBF process. The effects of building conditions on the textures in the as-built states and their evolution during subsequent tensile loading were analyzed.

The Vittoria Alata from Brescia: a combined neutron techniques and SEM-EDS approach to the study of the alloy of a bronze Roman statue

The “Vittoria Alata” (Winged Victory) from Brescia, dated around the 1st Century BCE, is one of the most well-known Roman bronzes discovered in Italy. The statue has recently undergone a restoration coordinated by the Opificio delle Pietre Dure di Firenze (OPD) that offered a unique opportunity for a thorough investigation on its manufacturing methods and previous non-documented repair/restauration interventions. In this paper, we present the results of the study of the metal alloy, obtained by neutron techniques and Scanning Electron Microscope analysis (SEM-EDS), on 24 samples of mm-size from various parts of the statue and on a cm-size feather fragment, believed to have detached from the right wing. Time of Flight Neutron Diffraction (ToF-ND) and Neutron Imaging (NI) measurements were performed at the ISIS neutron and muon source, Rutherford Appleton Laboratory, UK; SEM-EDS analysis were carried out at the OPD Scientific Laboratory, Florence, IT. The representativeness of ToF-ND on millimetric samples was confirmed by comparing the results obtained on several large, irradiated areas (few cm2) of an entire bronze frame fragment from the same excavation context with the ones on a millimetric sample taken from the same frame. This investigation led to the characterization of the alloys used for the different parts of the statue and to identify meaningful details on the manufacturing method.

Time-of-flight neutron diffraction applied to the identification of crystalline phases in historical mosaic glasses

We present a completely non-destructive study of the crystalline phases present in the vitreous matrix of ancient mosaic glass tesserae, based on the application of the time-of-flight neutron diffraction (ToF-ND) technique. In contrast, standard phase analysis techniques may involve a sample preparation step, which is not compatible with the requirement of damage prevention of archaeological artefacts. Moreover, superficial or spot investigation by standard methods may not provide a complete description of the samples, especially in the case of inhomogeneous materials such as mosaic glasses, whereas ToF-ND can investigate the whole glass composition at the centimetre scale. The present study aims to obtain a bulk characterization of the glasses in terms of their mineralogical phase composition. Six glass specimens of ancient mosaic glass tesserae, that had been previously analysed with other non-destructive techniques to obtain their chemical and phase composition, were investigated by ToF-ND. These tesserae come from archaeological excavations or mosaics under restoration from different archaeological sites and geographical areas (Italy, Greece, and Syria) and date from the 1st to the 11th century AD. Several crystalline phases based on Ca, Sb, Sn, Cu and Pb minerals were identified, confirming the mineralogical phases identified with Raman spectroscopy in previous analyses. In addition, several other phases were identified for five of the samples. It is concluded that ToF-ND is an extremely important complementary tool for non-destructive bulk investigations of mosaic glass tesserae, which can overcome the heterogeneity of this kind of archaeological material.

Low-background gamma spectrometry and neutron diffraction in the study of stony meteorites

Non-destructive characterisation of meteorites is here performed on a stony meteorite. The identification of the sample is performed by low-background γ-ray spectrometry in order to determine the presence of certain cosmogenic radionuclides, whereas a mineralogical phase quantitative analysis is carried out by Time-of-Flight Neutron Diffraction (ToF-ND) on the sample as-it-is. The protocol is then validated by applying micro-Raman Spectroscopy (μRS) and Energy Dispersive X-ray Spectroscopy (EDS). This paper is focused on γ-ray spectrometry, proving the meteoric origin of the sample, and it also presents some preliminary results of ToF-ND.

Dislocation Density of Electron Beam Powder Bed Fusion Ti–6Al–4V Alloys Determined via Time-Of-Flight Neutron Diffraction Line-Profile Analysis

Ti–6Al–4V alloys undergo a multiple phase transformation sequence during electron beam powder bed fusion (EB-PBF) additive manufacturing, forming unique dislocation substructures. Thus, determining the dislocation density is crucial for comprehensively understanding the strengthening mechanisms and deformation behavior. This study performed time-of-flight neutron diffraction (TOF-ND) measurements of Ti–6Al–4V alloys prepared via EB-PBF and examined the dislocation density in the as-built and post-processed states using convolutional multiple whole profile (CMWP) fitting. The present TOF-ND/CMWP approach successfully determined the bulk-averaged dislocation density (6.8 × 1013 m−2) in the as-built state for the α-matrix, suggesting a non-negligible contribution of dislocation hardening. The obtained dislocation density values were comparable to those obtained by conventional and synchrotron X-ray diffraction (XRD) measurements, confirming the reliability of the analysis, and indicating that the dislocations in the α-matrix were homogeneously distributed throughout the as-built specimen. However, the negative and positive neutron scattering lengths of Ti and Al, respectively, lowered the diffraction intensity for the Ti–6Al–4V alloys, thereby decreasing the lower limit of the measurable dislocation density and making the analysis difficult.

Evolution of the Microstructure and Phase Composition of the Products Formed in the Reaction between Iridium and W2B.

In the present study, we perform a systematic examination of the products formed by mixing and heating of tungsten boride and iridium powders at different ratios in a broad temperature range using qualitative and quantitative X-ray analysis and time-of-flight neutron diffraction (TOF-ND), in combination with scanning electron microscopy/energy-dispersive spectroscopy (SEM/EDS) performed at different accelerating voltages. The well-known and unknown ternary W-Ir-B phases were detected. The Vickers microhardness value for the new ternary W2Ir5B2 boride was measured. Based on these findings, the ternary W2Ir5B2 boride can be considered hard.

Transformations of Metal Supply during the Bronze Age in the Carpathian Basin

This paper presents recent research questions which have been raised and methods which have been used in the study of Bronze Age metallurgy in connection with available natural resources (ores) in and around the Carpathian Basin. This topic fits in the most current trends in the research on European prehistoric archaeology. Given the lack of written sources, copper and bronze artifacts discovered in settlement and cemetery excavations and prehistoric mining sites provide the primary sources on which the studies in question are based. The aim of compositional and isotope analysis of copper and tin ores, metal tools, ornaments, and weapons is to determine the provenience of the raw materials and further an understanding of the chaine operatiore of prehistoric metal production. The Momentum Mobility Research Group of the Institute of Archaeology, Research Centre for the Humanities studies these metal artifacts using archaeological and scientific methods. It has focused on the first thousand years of the Bronze Age (2500–1500 BC). Multidisciplinary research include non-destructive XRF, PGAA (promptgamma activation), TOF-ND (time-of-flight neutron diffraction) analyses and neutron radiography, as well as destructive methods, e.g. metal sampling for compositional and lead isotope testing, alongside archaeological analysis. Microstructure studies are also efficient methods for determining the raw material and production techniques. The results suggest the use of regional ore sources and interregional connections, as well as several transformations in the exchange network of the prehistoric communities living in the Carpathian Basin.

Evolution of phase stresses in Al/SiCp composite during thermal cycling and compression test studied using diffraction and self-consistent models

In this work, the evolutions of stresses in both phases of the Al/SiCp composite subjected to thermal cycling during in situ compression test were measured using Time of Flight neutron diffraction. It was confirmed that inter-phase stresses in the studied composite can be caused by differences in the coefficient of thermal expansion for the reinforcement and matrix, leading to a different variation of phase volumes during sample heating or cooling. The results of the diffraction experiment during thermal cycling were well predicted by the Thermo-Mechanical Self-Consistent model. The experimental study of elastic-plastic deformation was carried out in situ on a unique diffractometer EPSILON-MDS (JINR in Dubna, Russia) with nine detector banks measuring interplanar spacings simultaneously in 9 orientations of scattering vector. For the first time, the performed analysis of experimental data allowed to study the evolution of full stress tensor in both phases of the composite and to consider the decomposition of this tensor into deviatoric and hydrostatic components. It was found that the novel Developed Thermo-Mechanical Self-Consistent model correctly predicted stress evolution during compressive loading, taking into account the relaxation of thermal origin hydrostatic stresses. The comparison of this model with experimental data at the macroscopic level and the level of phases showed that strengthening of the Al/SiCp composite is caused by stress transfer from the plastically deformed Al2124 matrix to the elastic SiCp reinforcement, while thermal stresses relaxation does not significantly affect the overall composite properties.

Time-of-Flight Neutron Diffraction (TOF-ND) Analyses of the Composition and Minting of Ancient Judaean "Biblical" Coins.

TOF-ND elastic scattering of thermal neutrons offers some important advantages over X-ray diffraction (XRD), X-ray fluorescence (XRF), and metallography for the study of archaeological and numismatic problems. Traditional analytical methods are usually destructive and often probe only the surface. Neutrons deeply penetrate samples, simultaneously giving nondestructive bulk information about the crystal structure, composition, and texture (alignment of crystallites) from which thermomechanical manufacturing processes (e.g., cast, struck, or rolled) may be inferred. An analysis of the metal composition and minting processes used for making ancient Judaean bronze and leaded bronze coins from first century BCE and CE is used as a case study. One of the first ND analyses of the temperature used for striking bronze coins is also presented.

Non-destructive microstructural characterization of a bronze boat model from Vetulonia

In this paper, we present the results of the archaeometric analysis performed on a nuragic bronze statuette, representing a boat model decorated with zoomorphic figurines, made in Sardinia during the early Iron Age. The bronze boat model was found in the Etruscan tomb of the Duce located in Vetulonia (Italy) and dated no later than the second half of the seventh century bc. The Vetulonia boat model represents an extraordinary example of this type of objects, exhibiting a high level of complexity from the manufacturing point of view and an unusual choice of the subjects represented by the figurines. The study was performed by means of Time of Flight Neutron Diffraction, a non-destructive method able to give us quantitative information on phase composition and microstructure.

Special Section on Texture and Microstructure

The International Materials Research Congress (IMRC) is organized yearly at Cancun, Mexico, by the Sociedad Mexicana de Materiales (SMM) and the Materials Research Society (MRS). The conference is structured in plenary sessions, poster sessions and specialized symposia. In 2016, the XXVth IMRC conference included a topical symposium devoted to “Texture and Microstructure”. It is worth underlining that this was the very first conference ever organized in Latin America on a topic related to crystallographic texture. This symposium ran over 2 days. The first day was comprised of presentations on Recrystallization, Deformation, and Substructure. The second day continued on Deformation & Substructure, Unique Applications, and Data Acquisition & Processing. Thirteen invited and seventeen regular lectures were presented as well as 3 posters. The symposium co-organizers are pleased that many of the symposium participants have accepted the invitation to submit their work for a Special Section of Advanced Engineering Materials entitled “Texture and Microstructure”. Fifteen papers were submitted for review, eleven of which were accepted for publication. In addition to contributions from the symposium, several articles were invited to complement the research presented in Cancun and we also are pleased that the authors of six additional relevant papers submitted directly to Advanced Engineering Materials accepted our invitation for being included in this Special Section. The study of crystallographic textures was developed to a semi-quantitative theory by the pioneering work of Guenter Wasserman and Johanna Grewen, “Texturen Metallischer Werkstoffe” (Springer-Verlag, 1962), who studied mainly industrial relevant problems by means of the analysis of two-dimensional pole figures. Later, the reference book of Hans Bunge, “Texture Analysis in Materials Science − Mathematical Methods”, offered a rigorous and complete methodology to determine crystallographic textures by means of a statistical Orientation Distribution Function ODF, calculated by pole-figure inversion methods in the frame of spherical harmonic series. Bunge also developed a systematic method to calculate physical properties of textured polycrystals, as a weighted average of the single crystal properties, the weighting function being the ODF. The next milestone was the determination of individual orientations with Electron Backscattered Diffraction EBSD, where David Dingley made much of the pioneering work. After Brent Adams’ team (including his PhD student Stuart Wright) developed the first fully automated EBSD system they coined the term “Orientation Imaging Microscopy” to describe the technique. Dingley and Adams founded the start-up TSL to provide the first commercial OIM systems. Several companies currently offer automated EBSD systems capable of measuring the local orientation of the grains, the distribution and characteristics of the grain boundaries, the various phases, the local deformation, etc. However, the scientists interested in texture analysis should keep in mind that the statistical population sampled by EBSD is not the same as that by X-rays, since the penetration depth of X-rays is at least hundred times larger than that of electrons. But conversely, the electrons offer much better local resolution enabling the texture to be linked directly to the microstructure. The topic “textures” enjoys special attention from AEM. After the Special Issue “Texture and Microscopy” in 2003, the Special Issue “Texture and Anisotropy” in honor of Prof. Richard Penelle, University Orsay Paris Sud in 2010, with this Special Section “Texture and Microstructure”, all scientists interested in this topic will have in their hand a collection of papers offering a broad and actual covering of the topic. The Special Section opens with two review papers, one on fine-grained magnesium alloys by SPD, the other on electromagnetic coupling, followed by a communication on fatigue cracking resistance of bimodal Ti-6Al-4V alloys. Then, the reader will find 19 full papers covering all measurement techniques, neutron diffraction and Time of Flight neutron diffraction, X-ray diffraction and EBSD, including EBSD coupled with XEDS. The papers cover a broad variety of processing techniques, rolling, wire drawing, hot temperature extrusion, various techniques of Severe Plastic Deformation, e.g. Accumulated Roll Bonding, hot rectangular extrusion, ECASD. The reader will also find information on heat treatment and on epitaxial deposition of thin films. The materials studied are steel, aluminum composites, titanium alloys, magnesium alloys, and the currently widely studied Multi-Component Alloys (NiCoAlFeCu(Cr,Ti) in this Special Section). We are confident that with the papers included in this Special Section and the many references offered in the literature quoted, the reader will find useful information and inspiration for his own research work on “Texture and Microstructure”. Finally, this Special Section could not have been achieved without the constant, efficient and generous help of Sandra Kalveram, Editor-in-Chief at AEM. We express to her our deepest gratitude for her gigantesque help.

Neutron based archaeometallurgical investigation of Picenan and Roman age metal objects from the Academia Georgica Treiensis collection (Italy)

ABSTRACTNon-destructive prompt gamma activation analysis (PGAA), neutron radiography (NR) and high resolution time-of-flight neutron diffraction (TOF-ND) have been applied to investigate metal archaeological artefacts belonging to the Academia Georgica Treiensis (AGT) collection. 8 archaeological items have been analysed, by using the facilities of the Budapest Neutron Centre (BNC). Some of these objects mostly dating back probably to the VI-IV century B.C. and presumed to be discovered in the Marche Region, Italy. The primary goal of the analyses was to advance the correct technological and material description of the objects, providing scientific data for further and more comprehensive comparative analyses also covering the find material from the close archaeological sites.The neutron investigations allowed determining the bulk composition, also providing either a qualitative and quantitative assessment of the phase composition and the structural properties of the constituents, or radiographic images, which would finally help to identify possible manufacturing techniques.Additional examinations, carried out by external milli-beam particle induced X-ray emission spectroscopy (PIXE), provided quantitative analyses of major and trace elements (e.g., Fe, Pb and As) in order to recognize the constitutive alloys and to supply information on the near-surface elemental composition, complementary to the data characteristic for the bulk.The obtained results, thought to be useful to set up a classification according to the chemical composition, and this way allow achieving important information related to the possible provenance of the objects.

Calculation of full-pattern neutron time-of-flight (TOF) powder diffraction patterns

The ICDD has implemented an option in Powder Diffraction File (PDF)-4 products to calculate time-of-flight (TOF) neutron powder diffraction patterns using atomic coordinates and structure information (the PDF-4+ 2016 has 271 499 entries that contain atomic coordinates and structure data). The calculated pattern data are used to populate PDF data cells and entries that contain d-spaces and neutron intensities, and are also available for calculated on-the-fly fully digitized patterns. To extend this on-the-fly capability, we include size and strain effects that affect the profile shapes. For specific application to TOF neutron diffraction full pattern analyses, a method was developed for calculating a background function. This method treats incoherent scattering and a zeroth order approximation to thermal diffuse scattering. The results are compared with experimental data from SRM 640C (Si), SRM 676 (Al2O3 corundum), SRM 660C (LaB6), and NAC (Na2La3Al2F14) instrument standards. Finally, a comparison of the calculated total patterns (Bragg scattering plus background) scattering contrast between Nd2Ni2InD7.52 and Nd2Ni2InH7.52 shows the value of neutron scattering simulation for planning experiments.

Elastoplastic Deformation and Damage Process in Duplex Steel Studied Using Synchrotron and Neutron Diffraction

In the present work, the mechanical behavior of phases in duplex steel during tensile test was studied. Special interest was taken in the analysis of damage process just before failure. In this aim two diffraction methods: in-situ time of flight neutron diffraction and X-ray synchrotron diffraction were applied. Using diffraction data, the slip mechanism on crystallographic planes during plastic deformation was investigated. In the case of aged UR45N steel, it was found that significant softening caused by damage process was initiated in the ferritic phase. The lattice strains measured in situ by two above mentioned diffraction methods were compared with prediction of the self-consistent model.

Evolution of microstructure of niobium carbide NbC0.77 powders

The microstructural evolution of annealed nonstoichiometric niobium carbide NbC0.77 powders subjected to high‐energy ball milling has been investigated by time‐of‐flight (TOF) high resolution neutron diffraction. The diffraction patterns have been collected with the high resolution Fourier diffractometer HRFD by using the TOF mode of data acquisition. The nanocrystalline powders produced by high‐energy milling have an inhomogeneous microstructure, in which two fractions with different particle size and composition can be identified. The average sizes of the coherent scattering regions and microstrains in nanocrystallites with allowance for the anisotropy of the deformation distortions have been estimated. It is shown that TOF neutron diffraction patterns can provide the very accurate data for microstructure analysis of nanocrystalline powders. No superstructure has been observed in the annealed NbC0.77 carbide.

New neutron time-of-flight (TOF) capability in PDF-4+ relational databases: digitized diffraction patterns and I/Ic for quantitative phases analysis

The PDF-4+ 2016 contains 271 449 entries with atomic coordinates that can be used to calculate neutron time-of-flight (TOF) powder diffraction patterns. These diffraction patterns can all be calculated on-the-fly. Three TOF results can be realized: the live calculation of on-the fly diffraction patterns, the population of static PDF® entries, and data for search/match tables for phase identification. In connection with search/match, we have extended the development of the I/Ic formalism to include both constant wavelength (CW) and TOF neutron diffraction data. It is shown that the wavelength dependence of X-ray and CW neutron data must be factored into the behavior of I/Ic, whereas this dependence is directly incorporated into TOF data.

Elastoplastic deformation and damage process in duplex stainless steels studied using synchrotron and neutron diffractions in comparison with a self-consistent model

In situ time of flight neutron diffraction and X-ray synchrotron diffraction methods were applied to measure lattice strains in duplex steels during a tensile test. The experimental results were used to study slips on crystallographic planes and the mechanical effects of damage occurring during plastic deformation. For this purpose the prediction of an elastoplastic self-consistent model was compared with the experimental data. The used methodology allowed to determine the elastic limits and parameters describing work hardening in both phases of studied polycrystalline materials.In the second part of this work the developed elastoplastic model was applied to study damage occurring in the ferritic phase. The theoretical results showed a significant reduction of stresses localized in the damaged phase (ferrite) and confirmed the evolution of the lattice strains measured in the ferritic and austenitic phases.

The birth of time‐of‐flight (TOF) neutron powder diffraction at pulsed neutron source (invited)

Behind every improvement there is a story.The early history of the TOF neutron powder diffraction technique is presented. Successes and problems in the application of this technique in material science are reported. Powder diffraction technique is very useful when materials, in a single crystal form, reveal complicated electric and magnetic domain structures. Finding and describing the magnetic structure of multiferroics is the great success of ultra‐high resolution TOF neutron diffraction. This unique role of the TOF method in discovery of the modulated magnetic structure of BiFeO3 is presented. To date, the TOF powder neutron diffraction technique gives the richest information on the long period modulated magnetic structure of BiFeO3 and its solid solutions. Determination of magnetic moment direction in a crystal lattice is the unique area of application of the TOF technique. The current status and perspectives of the application of the TOF neutron powder diffraction technique in material science are presented in the review.

Design and performance of high-pressure PLANET beamline at pulsed neutron source at J-PARC

PLANET is a time-of-flight (ToF) neutron beamline dedicated to high-pressure and high-temperature experiments. The large six-axis multi-anvil high-pressure press designed for ToF neutron diffraction experiments enables routine data collection at high pressures and high temperatures up to 10GPa and 2000K, respectively. To obtain clean data, the beamline is equipped with the incident slits and receiving collimators to eliminate parasitic scattering from the high-pressure cell assembly. The high performance of the diffractometer for the resolution (Δd/d~0.6%) and the accessible d-spacing range (0.2–8.4Å) together with low-parasitic scattering characteristics enables precise structure determination of crystals and liquids under high pressure and temperature conditions.