I15-1-X-ray Pair Distribution Function (XPDF)
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Mohamed. A.
Ali
,
Wessel M. W.
Winters
,
Moushira A.
Mohamed
,
Dezhi
Tan
,
Guojun
Zheng
,
Rasmus S. K.
Madsen
,
Oxana V.
Magdysyuk
,
Maria
Diaz-Lopez
,
Biao
Cai
,
Nan
Gong
,
Yijue
Xu
,
Ivan
Hung
,
Zhehong
Gan
,
Sabyasachi
Sen
,
Hong-Tao
Sun
,
Thomas D.
Bennett
,
Xiaofeng
Liu
,
Yuanzheng
Yue
,
Jianrong
Qiu
Diamond Proposal Number(s):
[30401]
Abstract: Glassy metal coordination compounds (MCC) [e.g., metal-organic framework (MOF), coordination polymer, and metal inorganic-organic complex (MIOC)] are emerging members of the hybrid glass family. So far, a limited number of crystalline MCCs can be converted into glasses by the melt-quenching. Here, we report a universal wet-chemistry method, by which the super-sized supramolecular MIOC glasses can be synthesized from non-meltable MOFs. Alcohol and acid were used as agents to inhibit crystallization. The MIOC glasses demonstrate unique features including high transparency, shaping capability, and anisotropic network. Directional photoluminescence with a large polarization ratio (~47%) was observed from samples doped with organic dyes. This crystallization-suppressing approach enables fabrication of MCC glasses, which cannot be achieved by conventional vitrification methods, and thus allows for exploring new MCC glasses possessing photonic functionalities.
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Feb 2023
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Abstract: Manufacturing austenitic stainless steels (ASSs) using additive manufacturing is of great interest for cryogenic applications. Here, the mechanical and microstructural responses of a 316L ASS built by laser powder bed fusion were revealed by performing in situ neutron diffraction tensile tests at the low-temperature range (from 373 to 10 K). The stacking fault energy almost linearly decreased from 29.2 ± 3.1 mJm−2 at 373 K to 7.5 ± 1.7 mJm−2 at 10 K, with a slope of 0.06 mJm−2K−1, leading to the transition of the dominant deformation mechanism from strain-induced twinning to martensite formation. As a result, excellent combinations of strength and ductility were achieved at the low-temperature range.
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Sep 2022
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I12-JEEP: Joint Engineering, Environmental and Processing
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Diamond Proposal Number(s):
[19251]
Abstract: Vanadium base alloys represent potentially promising candidate structural materials for use in nuclear fusion reactors due to vanadium's low activity, high thermal strength, and good swelling resistance. In this work, the mechanical properties of the current frontrunner vanadium base alloy, V-4Cr-4Ti, have been interrogated using in-situ high energy X-ray diffraction (XRD) tensile testing at varying temperatures. The single crystal elastic constants of the samples were determined from the in-situ XRD data and used to evaluate results from density functional theory calculations. Polycrystalline elastic properties and Zener anisotropy were calculated from the single crystal elastic constants produced, revealing the effect of elevated temperature on the alloy's elastic properties. These results characterise important thermomechanical properties, valuable in mechanical modelling, that will allow further and improved analysis of the structural suitability of V-4Cr-4Ti ahead of alloy adoption in the mainstream.
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Jul 2022
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I12-JEEP: Joint Engineering, Environmental and Processing
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Diamond Proposal Number(s):
[21103]
Abstract: The effect of Strain Path Changes (SPCs) on the mechanical properties and crystal-level features of deformation for a single phase, ferritic steel has been investigated. SPCs were applied via a two-step deformation process, which included pre-straining via cold rolling, followed by uniaxial tension. The pre-strain magnitude and direction, as well as the tensile direction, varied between the specimens. The role of texture and micromechanics were examined in-situ, via Synchrotron X-ray Diffraction (SXRD), and ex-situ, via Electron Backscatter Diffraction (EBSD). Abrupt strain paths (i.e. strain paths where the pre-strain and the subsequent loading directions differ; here they are orthogonal) result in a significant ductility reduction, becoming more prevalent for high pre-strain magnitudes. The macroscopic response, as well as the texture configuration were greatly dependent on the pre-strain direction but were insensitive to the direction of uniaxial tension. Increasing pre-strain magnitudes resulted in a stagnation of lattice strain hardening rates in all macroscopic directions and in a significant increase in the Geometrically Necessary Dislocation (GND) densities. This was vastly increased for specimens rolled perpendicular to the as-received prior rolling direction. No correlation was found between the GND density and the grain orientation, eliminating this as a controlling ductility factor for BCC ferrite. Instead, the initial texture and the texture developed in a subsequent pre-strain influences the density of dislocations accumulated in all grains, and ultimately determines ductility.
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Apr 2022
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I12-JEEP: Joint Engineering, Environmental and Processing
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Diamond Proposal Number(s):
[19216]
Open Access
Abstract: This study usedhigh-speed synchrotron X-ray tomography to image the growth of Al2Cu intermetallic compoundsin 4D (3D plus time) during solidification of Al-45wt%Cu alloy. Two categories of growth patterns (basic units and dendrites) are identified. Basic unitsare elongated rods whose cross-section areL, U orhollow-rectangularshapes. The transition from L pattern to U and finally to hollow-rectangularshaped morphologywas observed. Faceted dendritic patterns include equiaxed prism and columnar dendrites. Self-repeated layer-by-layer stacking of the basic units (such as L shaped particles) is proposed as a governing mechanism for the growth of Al2Cu faceted dendrites. The growth orientation and morphologies of these patterns are strongly influenced by solidification conditions (temperature gradients, cooling rates and external magnetic fields). Another finding is that when rotating Al-45wt%Cu during upwards directional solidification,under a transverse magnetic field of 0.5T, highly refined and well aligned Al2Cu intermetallic compounds are obtained, much finer than those without the imposition of the magnetic field. This is attributed to a rotational stirring flow that modulates and regulates the temperature and solute distribution.The developed experimental findings provide a physical understanding of the formation of faceted intermetallic compounds during solidification.
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Mar 2022
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B16-Test Beamline
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Diamond Proposal Number(s):
[20251]
Abstract: Microdefects in the rust layer of conventional steel and weathering steel were investigated by synchrotron X-ray micro tomography to understand the effect of defects on corrosion resistance. The rust layer of the weathering steel contained fewer and smaller defects than that of the conventional steel. A good correlation existed between the volume of defects and ion permeation of the rust layer obtained by EIS. In comparison with the conventional steel, the tomography results indicated that a protective layer formed on the weathering steel.
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Feb 2022
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I12-JEEP: Joint Engineering, Environmental and Processing
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Diamond Proposal Number(s):
[22506]
Open Access
Abstract: Isotropy in microstructure and mechanical properties remains a challenge for laser powder bed fusion (LPBF) processed materials due to the epitaxial growth and rapid cooling in LPBF. In this study, a high-strength TiB2/Al-Cu composite with random texture was successfully fabricated by laser powder bed fusion (LPBF) using pre-doped TiB2/Al-Cu composite powder. A series of advanced characterisation techniques, including synchrotron X-ray tomography, correlative focussed ion beam–scanning electron microscopy (FIB-SEM), scanning transmission electron microscopy (STEM), and synchrotron in situ X-ray diffraction, were applied to investigate the defects and microstructure of the as-fabricated TiB2/Al-Cu composite across multiple length scales. The study showed ultra-fine grains with an average grain size of about 0.86 μm, and a random texture was formed in the as-fabricated condition due to rapid solidification and the TiB2 particles promoting heterogeneous nucleation. The yield strength and total elongation of the as-fabricated composite were 317 MPa and 10%, respectively. The contributions of fine grains, solid solutions, dislocations, particles, and Guinier–Preston (GP) zones were calculated. Failure was found to be initiated from the largest lack-of-fusion pore, as revealed by in situ synchrotron tomography during tensile loading. In situ synchrotron diffraction was used to characterise the lattice strain evolution during tensile loading, providing important data for the development of crystal-plasticity models.
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Sep 2021
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I12-JEEP: Joint Engineering, Environmental and Processing
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Nolwenn
Le Gall
,
Fabio
Arzilli
,
Giuseppe
La Spina
,
Margherita
Polacci
,
Biao
Cai
,
Margaret E.
Hartley
,
Nghia T.
Vo
,
Robert C.
Atwood
,
Danilo
Di Genova
,
Sara
Nonni
,
Edward W.
Llewellin
,
Mike R.
Burton
,
Peter D.
Lee
Diamond Proposal Number(s):
[12392]
Abstract: Crystallisation is a complex process that significantly affects the rheology of magma, and thus the flow dynamics during a volcanic eruption. For example, the evolution of crystal fraction, size and shape has a strong impact on the surface crust formation of a lava flow, and accessing such information is essential for accurate modelling of lava flow dynamics. To investigate the role of crystallisation kinetics on lava flow behaviour, we performed real-time, in situ synchrotron X-ray microtomography, studying the influence of temperature-time paths on the nucleation and growth of clinopyroxene and plagioclase in an oxidised, nominally anhydrous basaltic magma. Crystallisation experiments were performed at atmospheric pressure in air and temperatures from 1250 °C to 1100 °C, using a bespoke high-temperature resistance furnace. Depending on the cooling regime (single step versus continuous), two different crystal phases (either clinopyroxene or plagioclase) were produced, and we quantified their growth from both global and individual 3D texture analyses. The textural evolution of charges suggests that suppression of crystal nucleation is due to changes in the melt composition with increasing undercooling and time. Using existing viscosity models, we inferred the effect of crystals on the viscosity evolution of our crystal-bearing samples to trace changes in rheological behaviour during lava emplacement. We observe that under continuous cooling, both the onsets of the pāhoehoe-‘a‘ā transition and of non-Newtonian behaviour occur within a shorter time frame. With varying both temperature and time, we also either reproduced or approached the clinopyroxene and plagioclase phenocryst abundances and compositions of the Etna lava used as starting material, demonstrating that real-time synchrotron X-ray tomography is an ideal approach to unravel the final solidification history of basaltic lavas. This imaging technology has indeed the potential to provide input into lava flow models and hence our ability to forecast volcanic hazards.
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Aug 2021
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I12-JEEP: Joint Engineering, Environmental and Processing
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Diamond Proposal Number(s):
[19216]
Abstract: High-speed synchrotron tomography was used to investigate the nucleation and growth dynamics of Al13Fe4 intermetallic during solidification of an Al-5wt%Fe alloy, providing new insights into its formation process. The majority of Al13Fe4 intermetallics nucleated near the surface oxide of the specimen and a few nucleated at Al13Fe4 phase. Al13Fe4 crystals grew into a variety of shapes, including plate-like, hexagonal tabular, stair-like and V-shaped, which can be attributed to the crystal structure of this compound and its susceptibility to twinning. Hole-like defects filled with aluminium melt were observed within the intermetallics. Oriented particle attachment mechanism was proposed to explain the formation of the Al13Fe4 intermetallic, which needs further experiments and simulation to confirm.
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Apr 2021
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I12-JEEP: Joint Engineering, Environmental and Processing
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Diamond Proposal Number(s):
[12631, 13764, 19216]
Abstract: A key technique for controlling solidification microstructures is magneto-hydrodynamics (MHD), resulting from imposing a magnetic field to solidifying metals and alloys. Applications range from bulk stirring to flow control and turbulence damping via the induced Lorentz force. Over the past two decades the Lorentz force caused by the interaction of thermoelectric currents and the magnetic field, a MHD phenomenon known as Thermoelectric Magnetohydrodynamics (TEMHD), was also shown to drive inter-dendritic flow altering microstructural evolution. In this contribution, high-speed synchrotron X-ray tomography and computational simulation are coupled to reveal the evolution, dynamics and mechanisms of solidification within a magnetic field, resolving the complex interplay and competing flow effects arising from Lorentz forces of different origins. The study enabled us to reveal the mechanisms disrupting the traditional columnar dendritic solidification microstructure, ranging from an Archimedes screw-like structure, to one with a highly refined dendritic primary array. We also demonstrate that alloy composition can be tailored to increase or decrease the influence of MHD depending on the Seebeck coefficient and relative density of the primary phase and interdendritic liquid. This work paves the way towards novel computational and experimental methods of exploiting and optimising the application of MHD in solidification processes, together with the calculated design of novel alloys that utilise these forces.
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Jun 2020
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