Capturing Marangoni flow via synchrotron imaging of selective laser melting

Clark, Samuel J.; Leung, Chu Lun Alex; Chen, Yunhui; Sinclair, Lorna; Marussi, Sebastian; Lee, P D

doi:10.1088/1757-899x/861/1/012010

Cited by 24 publications

(14 citation statements)

References 14 publications

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“…4b (regime II) moves at 2.4 ± 0.7 m/s. In regime III with high AED, the pore migration speed of 1.0 m/s agrees well with our previous measurements of the Marangoni flow speed with tungsten carbide particles (0.97 m/s under the same AED) 60 , while we assume that a strong viscous drag force is responsible for the higher initial speed of bubbles initiated at the RKW in regime II at lower AED.…”

Section: Keyhole-induced Bubble Lifetime Dynamics In Lpbfsupporting

confidence: 90%

Keyhole fluctuation and pore formation mechanisms during laser powder bed fusion additive manufacturing

Huang

Fleming

Clark

et al. 2021

Preprint

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Keyhole porosity is a key concern in laser powder-bed fusion (LPBF), potentially impacting component fatigue life. However, the dynamics of keyhole porosity formation, i.e., keyhole fluctuation, collapse and bubble growth and shrinkage, remain unclear. Using synchrotron X-ray imaging we reveal keyhole and bubble behaviours, quantifying their formation mechanisms. The findings support the hypotheses that: (i) keyhole porosity can initiate not only in unstable, but also transition keyhole regimes, created by high laser power-velocity conditions, causing fast radial keyhole fluctuations (~ 10 kHz); (ii) transition regime collapse tends to occur part way up the rear-wall; and (iii) immediately after keyhole collapse, the bubble grows as pressure equilibrates then shrinks due to metal-vapour condensation. Concurrent with condensation, hydrogen diffusion into the bubble slows the shrinkage and stabilises the bubble size. The physics revealed here can guide the development of real-time monitoring and control systems for keyhole porosity.

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Section: Keyhole-induced Bubble Lifetime Dynamics In Lpbfsupporting

confidence: 90%

Keyhole fluctuation and pore formation mechanisms during laser powder bed fusion additive manufacturing

Huang

Fleming

Clark

et al. 2021

Preprint

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“…Notably, their reported average melt flow velocity of the entire melt pool was 1.1 ± 0.5 m s −1 and very similar to prior work [ 58 , 161 , 163 ]. The aforementioned studies showed that most flow patterns followed a centrifugal Marangoni convection owing to the negative temperature dependant coefficient of surface tension in metallic systems [ 58 , 162 , 163 , 164 , 165 ]; however, the Marangoni convection can be reversed when there is an increase in oxygen content within the molten pool, i.e., centripetal Marangoni convection [ 152 ], resulting in a deeper molten pool, larger pore size distribution, and more frequent spatter ejection. These new insights provided detailed information regarding the influence of powder chemistry on the melt flow and defect dynamics under a wide range of processing regimes which can be used for developing a reliable high-fidelity simulation model to predict the formation of undesirable features during LAM.…”

Section: The Future? In Situ Imaging For Ultra-fast Solidification Processing Additive Manufacturingsupporting

confidence: 87%

Progress on In Situ and Operando X-ray Imaging of Solidification Processes

2021

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In this review, we present an overview of significant developments in the field of in situ and operando (ISO) X-ray imaging of solidification processes. The objective of this review is to emphasize the key challenges in developing and performing in situ X-ray imaging of solidification processes, as well as to highlight important contributions that have significantly advanced the understanding of various mechanisms pertaining to microstructural evolution, defects, and semi-solid deformation of metallic alloy systems. Likewise, some of the process modifications such as electromagnetic and ultra-sound melt treatments have also been described. Finally, a discussion on the recent breakthroughs in the emerging technology of additive manufacturing, and the challenges thereof, are presented.

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“…One may suggest that the temperature-induced Marangoni convection may disperse the clustered oxide layer in the high energy beam-powder interaction. According to the oxide agglomeration model [34] and the Marangoni flow characterization, [35] the turbulence kinetic energy is~0.35 m 2 /s 2 by assuming turbulence intensity is 50 pct of the mean flow rate, which is still lower than the energy required to disperse the oxides agglomerate smaller than 100 lm (0.75 m 2 /s 2 ). The oxide agglomeration may well exist in the fusion process from the steel powder with excessive oxygen pick-up during its service life.…”

Section: A Oxide Evolution During the Solidification Of 316l Stainless Steelmentioning

confidence: 99%

Oxide Evolution During the Solidification of 316L Stainless Steel from Additive Manufacturing Powders with Different Oxygen Contents

Yang

Tang

Hao³

et al. 2021

Metall Mater Trans B

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The oxide evolution during the solidification of 316L stainless steel from additive manufacturing powders with different oxygen contents is studied by in situ observation of the melting and solidification of the powder materials, advanced characterization of the solidified materials, and non-equilibrium thermodynamic analysis. An oxide evolution map is established for the 316L powders with different oxygen contents. It reveals the relationship between the surface oxidation in the reused powder and its expected oxide species and morphology in the as-solidified component. For the 316L powder with oxygen content higher than ~ 0.039 pct, the liquid oxide formed first from the steel melt and then crystallized to certain oxide phases during solidification, while for the powder with lower oxygen, oxide phases are suggested to directly form from the steel melt. The oxide species in the as-solidified sample was predicted by the Scheil–Gulliver cooling calculation and verified by the TEM-based phase identification. The oxides formed in the melt of low O 316L alloy (0.0355 pct O) are predicted to be (Mn, Cr)Cr2O4 spinel and SiO2 oxide. In the high O (0.4814 pct O) 316L melt solidification, the final oxides formed are (Mn, Cr)Cr2O4 spinel, SiO2 oxide, and Cr2O3 corundum. As an important characteristic of powder materials, the oxygen pick-up due to the powder surface oxidation significantly influences the inclusion evolution in the powder fusion process.

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Capturing Marangoni flow via synchrotron imaging of selective laser melting

Cited by 24 publications

References 14 publications

Keyhole fluctuation and pore formation mechanisms during laser powder bed fusion additive manufacturing

Keyhole fluctuation and pore formation mechanisms during laser powder bed fusion additive manufacturing

Progress on In Situ and Operando X-ray Imaging of Solidification Processes

Oxide Evolution During the Solidification of 316L Stainless Steel from Additive Manufacturing Powders with Different Oxygen Contents

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