I12-JEEP: Joint Engineering, Environmental and Processing
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Diamond Proposal Number(s):
[28804]
Open Access
Abstract: Melt flow is critical to build quality during additive manufacturing (AM). When an external magnetic field is applied, it causes forces that alter the flow through the thermoelectric magnetohydrodynamic (TEMHD) effect, potentially altering the final microstructure. However, the extent of TEMHD forces and their underlying mechanisms, remain unclear. We trace the flow of tungsten particles using in situ high-speed synchrotron X-ray radiography and ex situ tomography to reveal the structure of TEMHD-induced flow during directed energy deposition AM (DED-AM). When no magnetic field is imposed, Marangoni convection dominates the flow, leading to a relatively even particle distribution. With a magnetic field parallel to the scan direction, TEMHD flow is induced, circulating in the cross-sectional plane, causing particle segregation to the bottom and side of the pool. Further, a downward magnetic field causes horizontal circulation, segregating particles to the other side. Our results demonstrate that TEMHD can disrupt melt pool flow during DED-AM.
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Jun 2023
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I12-JEEP: Joint Engineering, Environmental and Processing
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Diamond Proposal Number(s):
[28804]
Open Access
Abstract: Directed energy deposition (DED) is a promising additive manufacturing technique for repair; however, DED is prone to surface waviness (humping) in thin-walled sections, which increases residual stresses and crack susceptibility, and lowers fatigue performance. Currently, the crack formation mechanism in DED is not well understood due to a lack of operando monitoring methods with high spatiotemporal resolution. Here, we use inline coherent imaging (ICI) to optically monitor surface topology and detect cracking in situ, coupled with synchrotron X-ray imaging for observing sub-surface crack healing and growth. For the first time, ICI was aligned off-axis (24° relative to laser), enabling integration into a DED machine with no alterations to the laser delivery optics. We achieved accurate registration laterally (<10 µm) and in depth (<3 µm) between ICI measurements and the laser beam position using a single-element MEMS scanner and a custom calibration plate. ICI surface topology is verified with corresponding radiographs (correlation >0.93), directly tracking surface roughness and waviness. We intentionally seed humping into thin-wall builds of nickel super-alloy CM247LC, locally inducing cracking in surface valleys. Crack openings as small as 7 µm were observed in situ using ICI, including sub-surface signal. By quantifying both humping and cracking, we demonstrate that ICI is a viable tool for in situ crack detection.
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Apr 2023
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I12-JEEP: Joint Engineering, Environmental and Processing
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Diamond Proposal Number(s):
[20096]
Open Access
Abstract: Laser additive manufacturing is transforming several industrial sectors, especially the directed energy deposition process. A key challenge in the widespread uptake of this emerging technology is the formation of undesirable microstructural features such as pores, cracks, and large epitaxial grains. The trial and error approach to establish the relationship between process parameters and material properties is problematic due to the transient nature of the process and the number of parameters involved. In this work, the relationship between process parameters, melt pool geometry and quality of build measures, using directed energy deposition additive manufacturing for IN718, is quantified using neural networks as generalised regressors in a statistically robust manner. The data was acquired using in-situ synchrotron x-ray imaging providing unique and accurate measurements for our analysis. An analysis of the variations across repeated measurements show heteroscedastic error characteristics that are accounted for using a principled nonlinear data transformation method. The results of the analysis show that surface roughness correlates with melt pool geometry while the track height directly correlates with process parameters indicating a potential to directly control efficiency and layer thickness while independently minimising surface roughness.
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Mar 2023
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I13-2-Diamond Manchester Imaging
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Diamond Proposal Number(s):
[19322]
Abstract: In-line phase contrast synchrotron tomography combined with in situ mechanical loading enables the characterisation of soft tissue micromechanics via digital volume correlation (DVC) within whole organs. Optimising scan time is important for reducing radiation dose from multiple scans and to limit sample movement during acquisition. Also, although contrasted edges provided by in-line phase contrast tomography of soft tissues are useful for DVC, the effect of phase contrast imaging on its accuracy has yet to be investigated. Due to limited time at synchrotron facilities, scan parameters are often decided during imaging and their effect on DVC accuracy is not fully understood. Here, we used previously published data of intervertebral disc phase contrast tomography to evaluate the influence of i) fibrous image texture, ii) number of projections, iii) tomographic reconstruction method, and iv) phase contrast propagation distance on DVC results. A greater understanding of how image texture influences optimal DVC tracking was obtained by visualising objective function mapping, enabling tracking inaccuracies to be identified. When reducing the number of projections, DVC was minimally affected by image high frequency noise but with a compromise in accuracy. Iterative reconstruction methods improved image signal-to-noise and consequently significantly lowered DVC displacement uncertainty. Propagation distance was shown to affect DVC accuracy. Consistent DVC results were achieved within a propagation distance range which provided contrast to the smallest scale features, where; too short a distance provided insufficient features to track, whereas too long led to edge effect inconsistencies, particularly at greater deformations. Although limited to a single sample type and image setup, this study provides general guidelines for future investigations when optimising image quality and scan times for in situ phase contrast x-ray tomography of fibrous connective tissues.
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Nov 2022
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I13-2-Diamond Manchester Imaging
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Maximilian
Ackermann
,
Jan C.
Kamp
,
Christopher
Werlein
,
Claire L.
Walsh
,
Helge
Stark
,
Verena
Prade
,
Rambabu
Surabattula
,
Willi
Wagner
,
Catherine
Disney
,
Andrew J.
Bodey
,
Thomas
Illig
,
Diana J.
Leeming
,
Morten A.
Karsdal
,
Alexandar
Tzankov
,
Peter
Boor
,
Mark P.
Kuhnel
,
Florian P.
Länger
,
Stijn E.
Verleden
,
Hans M.
Kvasnicka
,
Hans H.
Kreipe
,
Axel
Haverich
,
Stephen M.
Black
,
Axel
Walch
,
Paul
Tafforeau
,
Peter D.
Lee
,
Marius M.
Hoeper
,
Tobias
Welte
,
Benjamin
Seeliger
,
Sascha
David
,
Detlef
Schuppan
,
Steven J.
Mentzer
,
Danny D.
Jonigk
Diamond Proposal Number(s):
[27025, 27094]
Open Access
Abstract: Background: COVID-19 is characterized by a heterogeneous clinical presentation, ranging from mild symptoms to severe courses of disease. 9–20% of hospitalized patients with severe lung disease die from COVID-19 and a substantial number of survivors develop long-COVID. Our objective was to provide comprehensive insights into the pathophysiology of severe COVID-19 and to identify liquid biomarkers for disease severity and therapy response. Methods: We studied a total of 85 lungs (n = 31 COVID autopsy samples; n = 7 influenza A autopsy samples; n = 18 interstitial lung disease explants; n = 24 healthy controls) using the highest resolution Synchrotron radiation-based hierarchical phase-contrast tomography, scanning electron microscopy of microvascular corrosion casts, immunohistochemistry, matrix-assisted laser desorption ionization mass spectrometry imaging, and analysis of mRNA expression and biological pathways. Plasma samples from all disease groups were used for liquid biomarker determination using ELISA. The anatomic/molecular data were analyzed as a function of patients’ hospitalization time. Findings: The observed patchy/mosaic appearance of COVID-19 in conventional lung imaging resulted from microvascular occlusion and secondary lobular ischemia. The length of hospitalization was associated with increased intussusceptive angiogenesis. This was associated with enhanced angiogenic, and fibrotic gene expression demonstrated by molecular profiling and metabolomic analysis. Increased plasma fibrosis markers correlated with their pulmonary tissue transcript levels and predicted disease severity. Plasma analysis confirmed distinct fibrosis biomarkers (TSP2, GDF15, IGFBP7, Pro-C3) that predicted the fatal trajectory in COVID-19. Interpretation: Pulmonary severe COVID-19 is a consequence of secondary lobular microischemia and fibrotic remodelling, resulting in a distinctive form of fibrotic interstitial lung disease that contributes to long-COVID.
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Nov 2022
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I12-JEEP: Joint Engineering, Environmental and Processing
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Diamond Proposal Number(s):
[16214]
Open Access
Abstract: Laser powder bed fusion (LPBF) can produce high-value metallic components for many industries; however, its adoption for safety-critical applications is hampered by the presence of imperfections. The interdependency between imperfections and processing parameters remains unclear. Here, the evolution of porosity and humps during LPBF using X-ray and electron imaging, and a high-fidelity multiphase process simulation, is quantified. The pore and keyhole formation mechanisms are driven by the mixing of high temperatures and high metal vapor concentrations in the keyhole is revealed. The irregular pores are formed via keyhole collapse, pore coalescence, and then pore entrapment by the solidification front. The mixing of the fast-moving vapor plume and molten pool induces a Kelvin–Helmholtz instability at the melt track surface, forming humps. X-ray imaging and a high-fidelity model are used to quantify the pore evolution kinetics, pore size distribution, waviness, surface roughness, and melt volume under single layer conditions. This work provides insights on key criteria that govern the formation of imperfections in LPBF and suggest ways to improve process reliability.
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Oct 2022
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I13-2-Diamond Manchester Imaging
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Lorenzo
Massimi
,
Samuel J.
Clark
,
Sebastian
Marussi
,
Adam
Doherty
,
Saurabh M.
Shah
,
Joachim
Schulz
,
Shashidhara
Marathe
,
Christoph
Rau
,
Marco
Endrizzi
,
Peter D.
Lee
,
Alessandro
Olivo
Diamond Proposal Number(s):
[23760]
Open Access
Abstract: In this work, the application of a time resolved multi-contrast beam tracking technique to the investigation of the melting and solidification process in metals is presented. The use of such a technique allows retrieval of three contrast channels, transmission, refraction and dark-field, with millisecond time resolution. We investigated different melting conditions to characterize, at a proof-of-concept level, the features visible in each of the contrast channels. We found that the phase contrast channel provides a superior visibility of the density variations, allowing the liquid metal pool to be clearly distinguished. Refraction and dark-field were found to highlight surface roughness formed during solidification. This work demonstrates that the availability of the additional contrast channels provided by multi-contrast X-ray imaging delivers additional information, also when imaging high atomic number specimens with a significant absorption.
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Jul 2022
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I12-JEEP: Joint Engineering, Environmental and Processing
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Fabio
Arzilli
,
Margherita
Polacci
,
Giuseppe
La Spina
,
Nolwenn
Le Gall
,
Edward W.
Llewellin
,
Richard A.
Brooker
,
Rafael
Torres-Orozco
,
Danilo
Di Genova
,
David A.
Neave
,
Margaret E.
Hartley
,
Heidy M.
Mader
,
Daniele
Giordano
,
Robert
Atwood
,
Peter D.
Lee
,
Florian
Heidelbach
,
Mike R.
Burton
Diamond Proposal Number(s):
[16188]
Open Access
Abstract: The majority of basaltic magmas stall in the Earth’s crust as a result of the rheological evolution caused by crystallization during transport. However, the relationships between crystallinity, rheology and eruptibility remain uncertain because it is difficult to observe dynamic magma crystallization in real time. Here, we present in-situ 4D data for crystal growth kinetics and the textural evolution of pyroxene during crystallization of trachybasaltic magmas in high-temperature experiments under water-saturated conditions at crustal pressures. We observe dendritic growth of pyroxene on initially euhedral cores, and a surprisingly rapid increase in crystal fraction and aspect ratio at undercooling ≥30 °C. Rapid dendritic crystallization favours a rheological transition from Newtonian to non-Newtonian behaviour within minutes. We use a numerical model to quantify the impact of rapid dendritic crystallization on basaltic dike propagation, and demonstrate its dramatic effect on magma mobility and eruptibility. Our results provide insights into the processes that control whether intrusions lead to eruption or not.
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Jun 2022
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I12-JEEP: Joint Engineering, Environmental and Processing
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Lorna
Sinclair
,
Yunhui
Chen
,
Samuel J.
Clark
,
Sebastian
Marussi
,
Saurabh
Shah
,
Oxana
Magdysyuk
,
Robert
Atwood
,
Gavin J.
Baxter
,
Martyn
Jones
,
Graham
Mccartney
,
Chu Lun Alex
Leung
,
Peter D.
Lee
Diamond Proposal Number(s):
[20096]
Open Access
Abstract: During directed energy deposition (DED) additive manufacturing, powder agglomeration and sintering can occur outside of the melt pool when using titanium alloy powders. Using in situ synchrotron radiography we investigate the mechanisms by which sintering of Ti6242 powder occurs around the pool, performing a parametric study to determine the influence of laser power and stage traverse speed on sinter build-up. The results reveal that detrimental sinter can be reduced using a high laser power or increased stage traverse speed, although the latter also reduces deposition layer thickness. The mechanism of sinter formation during DED was determined to be in-flight heating of the powder particles in the laser beam. Calculations of particle heating under the processing conditions explored in this study confirm that powder particles can reasonably exceed 700 °C, the threshold for Ti surface oxide dissolution, and thus the powder is prone to sintering if not incorporated into the melt pool. The build-up of sinter powder layer on deposit surfaces led to lack of fusion pores. To mitigate sinter formation and its detrimental effects on DED component quality, it is essential that the powder delivery spot area is smaller than the melt pool, ensuring most powder lands in the melt pool.
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Apr 2022
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I13-2-Diamond Manchester Imaging
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Maximilian
Ackermann
,
Paul
Tafforeau
,
Willi
Wagner
,
Claire
Walsh
,
Christopher
Werlein
,
Mark P.
Kuhnel
,
Florian P.
Länger
,
Catherine
Disney
,
Andrew
Bodey
,
Alexandre
Bellier
,
Stijn E.
Verleden
,
Peter D.
Lee
,
Steven J
Mentzer
,
Danny D.
Jonigk
Diamond Proposal Number(s):
[27025, 27094]
Open Access
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Nov 2021
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