Concurrent model for sharp and progressive columnar to equiaxed transitions validated by directional solidification experiments processed in microgravity conditions

Mooney, Robin P.; Sturz, Laszlo; Zimmermann, G.; Mangelinck-Noel, N.; Nguyen-Thi, Henri; Li, Yuze; Browne, David J.; McFadden, Shaun

doi:10.1016/j.commatsci.2022.111436

Cited by 9 publications

(3 citation statements)

References 49 publications

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“…To apply the estimated dendrite-tip undercoolings predicted by the KGT model in the Hunt model, the critical activation undercooling and heterogeneous nucleation site density are required, which are difficult to obtain directly and these parameters are normally fitted through matching simulated grain structures to experiments (e.g., References 28,70,71). In Ti alloys, the nucleation site efficiency and density are particularly poorly known as there are no artificial inoculants.…”

Section: B Cet Predictionsmentioning

confidence: 99%

Achieving a Columnar-to-Equiaxed Transition Through Dendrite Twinning in High Deposition Rate Additively Manufactured Titanium Alloys

Davis,

Wainwright,

Sahu

et al. 2024

Metall Mater Trans A

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The coarse β-grain structures typically found in titanium alloys like Ti–6Al–4V (wt pct, Ti64) and Ti–6Al–2Sn–4Zr–2Mo–0.1Si (Ti6242), produced by high deposition rate additive manufacturing (AM) processes, are detrimental to mechanical performance. Certain modified processing conditions have been shown to lead to a more refined grain structure, which has generally been attributed to a change in the solidification conditions with respect to the experimental Hunt diagram proposed by Semiatin and Kobryn. It is shown that with Wire Arc AM (WAAM) increasing the wire feed speed (WFS) is effective in promoting a columnar-equiaxed transition (CET). Conversely, estimates of the dendrite-tip undercooling using the KGT model suggest that this will be too small for free nucleation without the addition of artificial nucleants, due to the very low solute partitioning in Ti alloys. It is also shown that it is difficult to promote a CET with plasma transferred arc WAAM as computational fluid dynamics (CFD) melt-pool simulations indicate that the solidification parameters remain within the columnar region on the Semiatin-Kobryn Hunt map, within the constraints of a stable process. However, a high fraction of twin boundaries was observed in the refined β-grain structures seen at high WFS. This has been attributed to departure of $$\left\langle {001} \right\rangle _{\beta }$$ 001 β alignment from the direction of maximum thermal gradient, caused by the curvature of the fusion boundary, stimulating dendrite twinning during solidification. In addition, it is shown that increasing the WFS leads to a change in melt-pool geometry and a reduction of remelt depth, which promoted dendrite twinning and grain refinement.

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Section: B Cet Predictionsmentioning

confidence: 99%

Achieving a Columnar-to-Equiaxed Transition Through Dendrite Twinning in High Deposition Rate Additively Manufactured Titanium Alloys

Davis,

Wainwright,

Sahu

et al. 2024

Metall Mater Trans A

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“…Studies on CET in microgravity have been performed previously using metallic alloys 97 , where it was shown that a CET can occur either as a sharp or a progressive phenomenon. Modeling suggested that a progressive CET occurs by simultaneous columnar and equiaxed growth, the nucleation rate of equiaxed dendrites being an important factor.…”

Section: Reviewmentioning

confidence: 99%

Microgravity studies of solidification patterns in model transparent alloys onboard the International Space Station

Akamatsu,

Bottin-Rousseau,

Witusiewicz

et al. 2023

npj Microgravity

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We review recent in situ solidification experiments using nonfaceted model transparent alloys in science-in-microgravity facilities onboard the International Space Station (ISS), namely the Transparent Alloys (TA) apparatus and the Directional Solidification Insert of the DEvice for the study of Critical Liquids and Crystallization (DECLIC-DSI). These directional-solidification devices use innovative optical videomicroscopy imaging techniques to observe the spatiotemporal dynamics of solidification patterns in real time in large samples. In contrast to laboratory conditions on ground, microgravity guarantees the absence or a reduction of convective motion in the liquid, thus ensuring a purely diffusion-controlled growth of the crystalline solid(s). This makes it possible to perform a direct theoretical analysis of the formation process of solidification microstructures with comparisons to quantitative numerical simulations. Important questions that concern multiphase growth patterns in eutectic and peritectic alloys on the one hand and single-phased, cellular and dendritic structures on the other hand have been addressed, and unprecedented results have been obtained. Complex self-organizing phenomena during steady-state and transient coupled growth in eutectics and peritectics, interfacial-anisotropy effects in cellular arrays, and promising insights into the columnar-to-equiaxed transition are highlighted.

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“…Nucleation and growth of equiaxed crystals occur in sufficient numbers and then block the columnar front, causing the CET. Recent investigations have shown that the CET can be sharp or progressive [7][8][9]. In a sharp CET, equiaxed growth occurs in sufficient numbers to cause an abrupt transition from aligned columnar crystals to randomly oriented equiaxed crystals with an aspect ratio close to unity.…”

Section: Introductionmentioning

confidence: 99%

Competitive growth during directional solidification experiments of 〈1 1 1〉 Dendrites

Hughes

Robinson

McFadden

2022

Journal of Crystal Growth

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Concurrent model for sharp and progressive columnar to equiaxed transitions validated by directional solidification experiments processed in microgravity conditions

Cited by 9 publications

References 49 publications

Achieving a Columnar-to-Equiaxed Transition Through Dendrite Twinning in High Deposition Rate Additively Manufactured Titanium Alloys

Achieving a Columnar-to-Equiaxed Transition Through Dendrite Twinning in High Deposition Rate Additively Manufactured Titanium Alloys

Microgravity studies of solidification patterns in model transparent alloys onboard the International Space Station

Competitive growth during directional solidification experiments of 〈1 1 1〉 Dendrites

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