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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Diamond Proposal Number(s):
[26307]
Open Access
Abstract: X-ray computed tomography (XCT) is regularly employed in geomechanics to non-destructively measure the solid and pore fractions of soil and rock from reconstructed 3D images. With the increasing availability of high-resolution XCT imaging systems, researchers now seek to measure microfabric parameters such as the number and area of interparticle contacts, which can then be used to inform soil behaviour modelling techniques. However, recent research has evidenced that conventional image processing methods consistently overestimate the number and area of interparticle contacts, mainly due to acquisition-driven image artefacts. The present study seeks to address this issue by systematically assessing the role of XCT acquisition parameters in the accurate detection of interparticle contacts. To this end, synchrotron XCT has been applied to a hexagonal close-packed arrangement of glass pellets with and without a prescribed separation between lattice layers. Different values for the number of projections, exposure time, and rotation range have been evaluated. Conventional global grey value thresholding and novel U-Net segmentation methods have been assessed, followed by local refinements at the presumptive contacts, as per recently proposed contact detection routines. The effect of the different acquisition set-ups and segmentation techniques on contact detection performance is presented and discussed, and optimised workflows are proposed.
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May 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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I12-JEEP: Joint Engineering, Environmental and Processing
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Abstract: Zero carbon energy generation from renewable sources can reduce climate change by mitigating carbon emissions. A major challenge of renewable energy generation is the imbalance between supply and demand. To overcome the energy imbalances, subsurface storage of hydrogen in porous mediais suggested as a large-scale and economic solution, yet its mechanisms are not fully understood. Important unknowns are the effect of the high migration potential of the small and mobile hydrogen molecule and the volume of recoverable hydrogen.
We conducted non-steady state, cyclic hydrogen and brine injection experiments at 2-7 MPa and flow rates of 2-80 µl min-1 using water-wet Clashach sandstone cylinders of 4.7 mm diameter and 53-57 mm length (Clashach composition: ~96 wt.% quartz, 2% K-feldspar, 1% calcite, 1% ankerite). Two sets of experiments were performed using our new transparent flow-cell designed for x-ray computed microtomography: 1) Experiments using a laboratory x-ray source (University of Edinburgh) imaged the flow, displacement and capillary trapping of hydrogen by brine as a function of saturation after primary drainage and secondary imbibition. 2) Experiments using synchrotron radiation (Diamond Light Source, I12-JEEP tomography beamline) captured time-resolved hydrogen and brine flow and displacement processes. Pressure and mass flow measurements across the experimental apparatus complemented the microtomography volumes in both sets of experiments.
Results from a water-wet rock show that hydrogen behaves as a non-wetting phase and sits in the centre of the pore bodies, while residual brine sits in corners and pore throats. Hydrogen saturation in the pore volume is independent of the injection pressure and increases with increasing hydrogen/brine injection ratio up to ~50% saturation at 100 % hydrogen. Capillary trapping of hydrogen during brine imbibition occurs via snap off and is greatest at higher brine injection pressures, with 10 %, 12% and 21% hydrogen trapped at 2, 5 and 7 MPa, respectively. Higher brine flow rates reduce capillary trapping and increase hydrogen recovery at any given injection pressure. Based on these results, future hydrogen storage operations should inject 100% hydrogen and manage the reservoir pressure to avoid high pressures and minimize capillary trapping of hydrogen during brine reinjection.
Ongoing analysis of time-resolved experimental data will provide further insight into the critical pore-scale processes that ultimately influence the potential for geological hydrogen storage and recovery.
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Mar 2022
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I12-JEEP: Joint Engineering, Environmental and Processing
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Diamond Proposal Number(s):
[20096]
Open Access
Abstract: To prevent oxygen contamination, additive manufacturing (AM) techniques normally operate in an inert gas chamber (GC). An alternative method, useful for large builds and components repair, is the application of localised shielding gas (LSG). The effect of oxygen contamination on Ti6242 during directed energy deposition (DED) AM using an inert GC compared to LSG was investigated by in situ synchrotron X-ray experiments. When processing in LSG mode, the amount of oxygen absorbed from the atmosphere was sufficient to reverse the Marangoni flow leading to an alteration of the molten pool geometry and strongly influencing defect formation. Microstructural analysis reveals that, at high oxygen levels, the commonly developed α' martensitic microstructure was completely suppressed, forming precipitation of a tetra modal microstructure of α phase consisting of globular, primary and secondary lamellae (in colonies) and basketweave structure. These results help elucidate the influence of oxygen contamination in additively manufactured Ti alloys, potentially enabling improved industrial practices for AM of titanium alloy.
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Nov 2021
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I12-JEEP: Joint Engineering, Environmental and Processing
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Diamond Proposal Number(s):
[22627]
Abstract: Ductile cast irons (DCIs) are of increasing importance in the renewable energy and transportation sectors. The distribution and morphology of the graphite nodules, in particular the formation of degenerate features during solidification, dictate the mechanical performance of DCIs. In situ high-speed synchrotron X-ray tomography was used to capture the evolution of graphite nodules during solidification of DCI, including degenerate features and the effect of the carbon concentration field. The degeneration of nodules is observed to increase with re-melting cycles, which is attributed to Mg-loss. The dendritic primary austenite and carbon concentration gradients in the surrounding liquid phase were found to control nodule morphology by locally restricting and promoting growth.
A coupled diffusion-mechanical model was developed, confirming the experimentally informed hypothesis that protrusions form through liquation cracking of the austenite shell and subsequent localised growth. These results provide valuable insights into the solidification kinetics of cast irons, supporting the design of advanced alloys.
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Oct 2021
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I12-JEEP: Joint Engineering, Environmental and Processing
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Chaoling
Xu
,
Tim
Wigger
,
Mohammed
Azeem
,
Tito
Andriollo
,
Søren
Fæster
,
Samuel
Clark
,
Zhixuan
Gong
,
Robert
Atwood
,
Jean-Claude
Grivel
,
Jesper H.
Hattel
,
Peter D.
Lee
,
Niels S.
Tiedje
Diamond Proposal Number(s):
[22627]
Open Access
Abstract: In spite of many years of research, the physical phenomena leading to the evolution of compacted graphite (CG) during solidification is still not fully understood. In particular, it is unknown how highly branched CG aggregates form and evolve in the semi-solid, and how local microstructural variations at micrometer length scale affect this growth process. We present here the first time-resolved synchrotron tomography combined with a bespoke high-temperature environmental cell that allows direct observation of the evolution of CG and relates this dynamic process to the local surrounding microstructures in a cast iron sample during repeated melting and solidification. Distinct processes are identified for the formation of CG involving the nucleation, growth, development of branches and interconnection of graphite particles, ultimately evolving into highly branched graphite aggregates with large sizes and low sphericities. CG is found to nucleate with a spheroidal or a plate-like shape, developing branches induced by high carbon concentration, e.g. thin melt channels. Additionally, CG grows much faster than spheroidal graphite during subsequent cooling in solid state. The direct visualization of the dynamic solidification process provides unprecedented new insights into formation mechanisms of CG and correlating factors such as local microstructural variations, and guides the development of CG iron solidification 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):
[22109, 24740, 14033, 19526, 21999]
Open Access
Abstract: Parallel-beam tomography systems at synchrotron facilities have limited field of view (FOV) determined by the available beam size and detector system coverage. Scanning the full size of samples bigger than the FOV requires various data acquisition schemes such as grid scan, 360-degree scan with offset center-of-rotation (COR), helical scan, or combinations of these schemes. Though straightforward to implement, these scanning techniques have not often been used due to the lack of software and methods to process such types of data in an easy and automated fashion. The ease of use and automation is critical at synchrotron facilities where using visual inspection in data processing steps such as image stitching, COR determination, or helical data conversion is impractical due to the large size of datasets. Here, we provide methods and their implementations in a Python package, named Algotom, for not only processing such data types but also with the highest quality possible. The efficiency and ease of use of these tools can help to extend applications of parallel-beam tomography systems.
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May 2021
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I12-JEEP: Joint Engineering, Environmental and Processing
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Yunhui
Chen
,
Samuel J.
Clark
,
David M.
Collins
,
Sebastian
Marussi
,
Simon A.
Hunt
,
Danielle
Fenech
,
Thomas
Connolley
,
Robert C.
Atwood
,
Oxana V.
Magdysyuk
,
Gavin J.
Baxter
,
Martyn A.
Jones
,
Chu Lun Alex
Leung
,
Peter D.
Lee
Diamond Proposal Number(s):
[20096]
Abstract: The governing mechanistic behaviour of Directed Energy Deposition Additive Manufacturing (DED-AM) is revealed by a combined in situ and operando synchrotron X-ray imaging and diffraction study of a nickel-base superalloy, IN718. Using a unique DAE-AM process replicator, real-space imaging enables quantification of the melt-pool boundary and flow dynamics during solidification. This imaging knowledge was also used to informed precise diffraction measurements of temporally resolved microstructural phases during transformation and stress development with a spatial resolution of 100 µm. The diffraction quantified thermal gradient enabled a dendritic solidification microstructure to be predicted and coupled to the stress orientation and magnitude. The fast cooling rate entirely suppressed the formation of secondary phases or recrystallisation in the solid-state. Upon solidification, the stresses rapidly increase to the yield strength during cooling. This insight, combined with the large solidification range of IN718 suggests that the accumulated plasticity exhausts the ductility of the alloy, causing liquation cracking. This study has revealed additional fundamental mechanisms governing the formation of highly non-equilibrium microstructures during DED-AM.
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Mar 2021
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