I12-JEEP: Joint Engineering, Environmental and Processing
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Barbara
Bonechi
,
Margherita
Polacci
,
Fabio
Arzilli
,
Giuseppe
La Spina
,
Jean-Louis
Hazemann
,
Richard A.
Brooker
,
Robert
Atwood
,
Sebastian
Marussi
,
Peter D.
Lee
,
Roy A.
Wogelius
,
Jonathan
Fellowes
,
Mike R.
Burton
Diamond Proposal Number(s):
[28538]
Open Access
Abstract: Transitions in eruptive style during volcanic eruptions strongly depend on how easily gas and magma decouple during ascent. Stronger gas-melt coupling favors highly explosive eruptions, whereas weaker coupling promotes lava fountaining and lava flows. The mechanisms producing these transitions are still poorly understood because of a lack of direct observations of bubble dynamics under natural magmatic conditions. Here, we combine x-ray radiography with a novel high-pressure/high-temperature apparatus to observe and quantify in real-time bubble growth and coalescence in basaltic magmas from 100 megapascals to surface. For low-viscosity magmas, bubbles coalesce and recover a spherical shape within 3 seconds, implying that, for lava fountaining activity, gas and melt remain coupled during the ascent up to the last hundred meters of the conduit. For higher-viscosity magmas, recovery times become longer, promoting connected bubble pathways. This apparatus opens frontiers in unraveling magmatic/volcanic processes, leading to improved hazard assessment and risk mitigation.
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Aug 2024
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I12-JEEP: Joint Engineering, Environmental and Processing
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Kai
Zhang
,
Tim
Wigger
,
Rosa
Pineda
,
Simon A.
Hunt
,
Ben
Thomas
,
Thomas
Kwok
,
David
Dye
,
Gorka
Plata
,
Jokin
Lozares
,
Inaki
Hurtado
,
Stefan
Michalik
,
Michael
Preuss
,
Peter D.
Lee
,
Mohammed A.
Azeem
Diamond Proposal Number(s):
[23749]
Abstract: Microstructure evolution during high-strain rate and high-temperature thermo-mechanical processing of a 44MnSiV6 microalloyed steel is investigated using in situ synchrotron high-energy powder X-ray diffraction. The conditions selected replicate a newly developed near solidus high-strain rate process designed for reducing raw material use during the hot processing of steels. High temperatures (exceeding 1300 °C) and high strain rate
= 9 s-1 processing regimes are explored. The lattice strains and dislocation activity estimated from diffraction observations reveal that the microstructure evolution is primarily driven by dynamic recrystallisation. A steady-state stress regime is observed during deformation, which develops due to intermittent and competing work hardening and recovery processes. The texture evolution during the heating, tension, shear deformation and cooling stages is systematically investigated. The direct observation of phase evolution at high-temperature and high-strain rate deformation enables a comprehensive understanding of new manufacturing processes and provides deep insights for the development of constitutive models for face-centred cubic alloys.
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Aug 2024
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I12-JEEP: Joint Engineering, Environmental and Processing
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Lorna
Sinclair
,
Oliver
Hatt
,
Samuel J.
Clark
,
Sebastian
Marussi
,
Elena
Ruckh
,
Robert C.
Atwood
,
Martyn
Jones
,
Gavin J.
Baxter
,
Chu Lun Alex
Leung
,
Iain
Todd
,
Peter D.
Lee
Diamond Proposal Number(s):
[20096]
Open Access
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Jul 2024
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I12-JEEP: Joint Engineering, Environmental and Processing
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Diamond Proposal Number(s):
[20096]
Open Access
Abstract: The columnar grains in additively manufactured alloys increase tendency to form solidification cracks and cause anisotropy. Studying the effect of process parameters on microstructure development helps to guide the manufacturing of the equiaxed grain microstructure. We firstly studied the effect of process condition on the melt pool dimensions using in-situ synchrotron X-ray imaging; and thermal profile and solidification condition using finite element simulation and calculation of thermodynamics phase diagrams of CrMnFeCoNi High-Entropy Alloy (HEA) fabricated by directed energy deposition (DED). Increasing the laser power reduced the thermal gradient to solidification rate ratio, pushing the solidification closer to the columnar-equiaxed transition. Nevertheless, the simulations still indicated the columnar microstructure for all scan conditions in contrast to experimental observation that showed single-wall samples built at 200 W consisted of dominantly equiaxed grains, whereas columnar grains were dominant in samples built at 100 W. It was believed that in addition to the effect of thermal gradient and solidification rate, the chemical segregation (Mn and Ni) during solidification might promote dendrite detachment, hence assisting the transition to equiaxed grains. The multi-track deposition results in more solid beneath a new melt pool, increasing the thermal gradient that promotes more columnar grains in comparison to single-tracks.
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Jun 2024
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I12-JEEP: Joint Engineering, Environmental and Processing
I13-2-Diamond Manchester Imaging
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Diamond Proposal Number(s):
[22053, 30735, 31855]
Open Access
Abstract: Synchrotron X-ray imaging has been utilised to detect the dynamic behaviour of molten pools during the metal additive manufacturing (AM) process, where a substantial amount of imaging data is generated. Here, we develop an efficient and robust deep learning model, AM-SegNet, for segmenting and quantifying high-resolution X-ray images and prepare a large-scale database consisting of over 10,000 pixel-labelled images for model training and testing. AM-SegNet incorporates a lightweight convolution block and a customised attention mechanism, capable of performing semantic segmentation with high accuracy (∼96%) and processing speed (< 4 ms per frame). The segmentation results can be used for quantification and multi-modal correlation analysis of critical features (e.g. keyholes and pores). Additionally, the application of AM-SegNet to other advanced manufacturing processes is demonstrated. The proposed method will enable end-users in the manufacturing and imaging domains to accelerate data processing from collection to analytics, and provide insights into the processes’ governing physics.
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Mar 2024
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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
,
Mike R.
Burton
Open Access
Abstract: The mobility and the rheological behaviour of magma within the Earth’s crust is controlled by magma viscosity. Crystallization and crystal morphology strongly affect viscosity, and thus mobility and eruptibility of magma, by locking it at depth or enabling its ascent towards the surface. However, the relationships between crystallinity, rheology and eruptibility remain uncertain because it is difficult to observe dynamic magma crystallization in real time.
Here we show the results of in situ 3D time-dependent, high temperature, moderate pressure experiments performed under water-saturated conditions to investigate crystallization kinetics in a basaltic magma. 4D crystallization experiments with in situ view were performed using synchrotron X-ray microtomography, which provides unique quantitative information on the growth kinetics and textural evolution of pyroxene crystallization in basaltic magmas. Crystallization kinetics obtained with 4D experiments were combined with a numerical model to investigate the impact of rapid dendritic crystallization on basaltic dike propagation, and demonstrate its dramatic effect on magma mobility and eruptibility.
We observe dendritic growth of pyroxene on initially euhedral cores, and a sur- prisingly 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. Modelling results show that dendritic crystallization at moderate undercooling (30-50 °C) can strongly affect magma rheology during magma ascent within a dike with important implications for the mobility of basaltic magmas within the crust. Our results provide insights into the processes that control whether magma ascent within the crust leads to eruption or not.
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Mar 2024
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Kai
Zhang
,
Yunhui
Chen
,
Sebastian
Marussi
,
Xianqiang
Fan
,
Maureen
Fitzpatrick
,
Shishira
Bhagavath
,
Marta
Majkut
,
Bratislav
Lukic
,
Kudakwashe
Jakata
,
Alexander
Rack
,
Martyn A.
Jones
,
Junji
Shinjo
,
Chinnapat
Panwisawas
,
Chu Lun Alex
Leung
,
Peter D.
Lee
Open Access
Abstract: Porosity in directed energy deposition (DED) deteriorates mechanical performances of components, limiting safety-critical applications. However, how pores arise and evolve in DED remains unclear. Here, we reveal pore evolution mechanisms during DED using in situ X-ray imaging and multi-physics modelling. We quantify five mechanisms contributing to pore formation, migration, pushing, growth, removal and entrapment: (i) bubbles from gas atomised powder enter the melt pool, and then migrate circularly or laterally; (ii) small bubbles can escape from the pool surface, or coalesce into larger bubbles, or be entrapped by solidification fronts; (iii) larger coalesced bubbles can remain in the pool for long periods, pushed by the solid/liquid interface; (iv) Marangoni surface shear flow overcomes buoyancy, keeping larger bubbles from popping out; and (v) once large bubbles reach critical sizes they escape from the pool surface or are trapped in DED tracks. These mechanisms can guide the development of pore minimisation strategies.
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Feb 2024
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I12-JEEP: Joint Engineering, Environmental and Processing
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Diamond Proposal Number(s):
[2370]
Open Access
Abstract: Surface roughness controls the mechanical performance and durability (e.g., wear and corrosion resistance) of laser powder bed fusion (LPBF) components. The evolution mechanisms of surface roughness during LPBF are not well understood due to a lack of in situ characterisation methods. Here, we quantified key processes and defect dynamics using synchrotron X-ray imaging and ex situ optical imaging and explained the evolution mechanisms of side-skin and top-skin roughness during multi-layer LPBF of Ti-6AI-4V (where down-skin roughness was out of the project scope). We found that the average surface roughness alone is not an accurate representation of surface topology of an LPBF component and that the surface topology is multimodal (e.g., containing both roughness and waviness) and multiscale (e.g., from 25 µm sintered powder features to 250 µm molten pool wavelength). Both roughness and topology are significantly affected by the formation of pre-layer humping, spatter, and rippling defects. We developed a surface topology matrix that accurately describes surface features by combining 8 different metrics: average roughness, root mean square roughness, maximum profile peak height, maximum profile valley height, mean height, mean width, skewness, and melt pool size ratio. This matrix provides a guide to determine the appropriate linear energy density to achieve the optimum surface finish of Ti-6AI-4V thin-wall builds. This work lays a foundation for surface texture control which is critical for build design, metrology, and performance in LPBF.
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Oct 2023
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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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I13-2-Diamond Manchester Imaging
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Diamond Proposal Number(s):
[19354, 22976]
Open Access
Abstract: Laser powder bed fusion (LPBF) additive manufacturing of 2XXX series Al alloys could be used for low volume specialist aerospace components, however, such alloys exhibit hot cracking susceptibility that can lead to component failure. In this study, we show two approaches to suppress the formation of hot cracks by controlling solidification behaviour using: (1) TiB2 additions; and (2) optimisation of LPBF process parameters. Using high-speed synchrotron X-ray radiography, we monitored LPBF of Al-2139 in situ, with and without TiB2 under a range of process conditions. In situ X-ray radiography results captured the crack growth over 1.0 ms at a rate of ca. 110 mm s-1, as well as pore evolution, wetting behaviour and build height. High-resolution synchrotron X-ray computed tomography (sCT) was used to measure the volume fraction of defects, e.g. hydrogen pores and microcracks, in the as-built LPBF samples. Our results show adding TiB2 in Al-2139 reduces the volume of cracks by up to 79 % under a volume energy density of 1000 to 5000 J mm-3, as well as reducing the average length, breadth, and surface area of cracks.
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Jun 2023
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