Twin related silicon crystals in Al–Si alloys and their growth mechanism

Wang, Ru-yao; Lu, Weihua; Hogan, L.M.

doi:10.1179/026708395790165183

Cited by 8 publications

(18 citation statements)

References 5 publications

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“…By etching sections of primary silicon crystals in the alloys, intermittent traces of solute pileup in front of the growing interface revealed the existence of cores without any faceting and, consequently, a spherical morphology at the beginning of crystal growth. [14,15] Spherical, nonfaceted growth corresponds to normal growth of an atomically rough solid/liquid interface, such as is usual for metals. However, the solidification mode of silicon is usually strongly faceted, as already seen, for example, in Figure 4.…”

Section: B Crystal Morphology At Initiation Of Growthmentioning

confidence: 99%

“…[23] Furthermore, an octahedral morphology has also been inferred in Al-Si alloy castings. [14,15,16] If crystals of silicon, bounded by {111} planes, are not distorted, for instance, by twins, they will exhibit an octahedral morphology at equilibrium. This is most likely to be found in the most slowly cooled part of the contact surface, i.e., at the outer edge.…”

Section: Octahedral and Other Polyhedral Morphologiesmentioning

confidence: 99%

“…In contrast, traces of the growth morphology in pure silicon are more difficult to detect. Patterns on etched cross sections of bulk silicon suggest a strong trend toward predominance of octahedral crystals bounded by {111} facets, [13][14][15][16] but no direct evidence has been presented for this morphology.…”

Section: Introductionmentioning

confidence: 95%

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Morphologies of silicon crystals solidified on a chill plate

Liu

Herlach

Vandyoussefi

et al. 2004

Metall Mater Trans A

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Electromagnetically levitated liquid droplets of pure Si or a Si-Ge alloy were cooled to different temperatures and then dropped onto a chill plate of Cu. Droplet oscillations mark the solid/liquid interface during solidification and permit the different crystal morphologies of silicon to be observed on the quenched surface by scanning electron microscopy (SEM). A spherical morphology found on the quenched surface represents the initial stage of crystal growth. Further growth leads to octahedral crystals bounded by {111} faces near equilibrium and to other polyhedra or even faceted dendrites further from equilibrium. The spherical growth can be observed only when the initial melt undercooling is moderately high. The critical size at which spherical crystals start to develop dendritic growth is much bigger than that calculated from the Mullins and Sekerka model, and is bigger than the Coriell and Parker model when kinetic undercooling is taken into account.

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Section: B Crystal Morphology At Initiation Of Growthmentioning

confidence: 99%

Section: Octahedral and Other Polyhedral Morphologiesmentioning

confidence: 99%

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Morphologies of silicon crystals solidified on a chill plate

Liu

Herlach

Vandyoussefi

et al. 2004

Metall Mater Trans A

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“…[40] Numerous primary Si morphologies have been observed experimentally earlier. [37][38][39] Nonetheless, no unbiased quantitative 3D data could be extracted, because the past observations were mostly either on 2D sections or on deep-etched structures using SEM that only yields projected images.…”

Section: D Visualization and Characterization Of Primary Si Partimentioning

confidence: 99%

“…On the one hand, octahedral primary Si can form by repeated generation of {111} planes on the octahedral facets. [39] On the other hand, the plate-like morphology of eutectic Si is caused by the well-known twin plane re-entrant edge (TPRE) growth mechanism. [40] Numerous primary Si morphologies have been observed experimentally earlier.…”

Section: D Visualization and Characterization Of Primary Si Partimentioning

confidence: 99%

Reconstruction and Quantitative Characterization of Multiphase, Multiscale Three-Dimensional Microstructure of a Cast Al-Si Base Alloy

Singh

Gokhale

Mao

et al. 2009

Metall Mater Trans B

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The serial sectioning technique is well known for the reconstruction of three-dimensional (3D) microstructures of opaque materials. In recent years, techniques also have been developed for the reconstruction of high-fidelity, large-volume segments of 3D microstructures that use montage serial sections and robot-assisted automated acquisitions of montage serial sections. This article reports the reconstruction of the multiphase, multiscale 3D microstructure of a permanent mold cast unmodified Al-12 wt pct Si-1 wt pct Ni base alloy that contains eutectic Si platelets, coarse primary polyhedral Si particles, Fe-rich script intermetallic particles, and pores. These constituents are segmented, reconstructed, rendered, and characterized in three dimensions. The estimated 3D microstrucutral attributes include the distribution of eutectic platelet thickness; the mean volume, mean surface area, and mean thickness of the eutectic Si platelets; the mean volume and the mean surface area of the polyhedral primary Si particles; and the mean number of faces, edges, and corners on the polyhedral primary Si particles.

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Revealing the nucleation kinetics of primary Si particles in hypereutectic Al–Si alloys under the influence of P inoculation

Deng

Casari

et al. 2020

J Mater Sci

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A quantitative study on the kinetics of nucleation of primary Si particles (PSPs), especially under the effect of P inoculation, during isothermal melt solidification of hypereutectic Al-Si(-Cu) alloys has been realized for the first time by using a unique micro-focus in situ X-radiography method, which is impossible by synchrotron X-radiography or tomography methods. The nucleation undercooling and nucleation rate of PSPs have been measured. Besides, TP-1 type solidification test has been carried out. It is found that nucleation undercooling of PSPs is reduced, while nucleation rate and number density of PSPs is increased significantly by P inoculation. Moreover, the influence of cooling rate on the nucleation kinetics of PSPs in the P inoculated alloy was investigated in situ. It is observed that higher cooling rate has the influence of increasing the peak nucleation rate and extending the nucleation temperature ranges of PSPs, in terms of earlier nucleation at lower undercooling and nucleation stopping at higher undercooling, which results in higher number density of PSPs. The decrease in minimum nucleation undercooling with increasing cooling rate in the P inoculated alloy is unexpected, which has been attributed to the extremely slow growth rate of faceted Si crystal on AlP substrates under low undercooling.

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Twin related silicon crystals in Al–Si alloys and their growth mechanism

Cited by 8 publications

References 5 publications

Morphologies of silicon crystals solidified on a chill plate

Morphologies of silicon crystals solidified on a chill plate

Reconstruction and Quantitative Characterization of Multiphase, Multiscale Three-Dimensional Microstructure of a Cast Al-Si Base Alloy

Revealing the nucleation kinetics of primary Si particles in hypereutectic Al–Si alloys under the influence of P inoculation

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