Real-time observation of grain nucleation and growth during solidification of aluminium alloys

Iqbal, Naveed; Dijk, N.H. van; Offerman, S.E.; Moret, Mona P.; Katgerman, L.; Kearley, Gordon J.

doi:10.1016/j.actamat.2005.02.045

Cited by 116 publications

(65 citation statements)

References 13 publications

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“…These correspond well to two neighbor separations in the D0 22 Al 3 Ti structure (2.72, and 3.85 Å), which might explain the apparent presence of Al 3 Ti in the experimental X-ray spectra [10][11][12] .…”

Section: Results and Discussion A Tib 2 Substratesupporting

confidence: 73%

“…Recently, Inqbal et al [10][11][12] carried out in situ x-ray diffraction experiments on pure Al with different volume fractions of TiB 2 inoculants and Ti solute concentrations using a synchrotron x-ray source. They successfully identified the formation of a metastable phase prior to the formation of solid α-Al, which they identified as Al 3 Ti on the TiB 2 .…”

Section: Introductionmentioning

confidence: 99%

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Heterogeneous nucleation of solid Al from the melt byTiB2andAl3Ti: Anab initiomolecular dynamics study

et al. 2010

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The nucleation of solid Al from the melt by TiB 2 is well established and is believed to involve the formation of Al 3 Ti. Since the atomic scale mechanisms involved are not fully understood, we look to computer simulation to provide insight. As there is an absence of suitable potentials for all of this complex system we have performed large scale density functional theory molecular dynamics simulations of the nucleation of solid Al from the melt on TiB 2 and Al 3 Ti substrates at undercoolings of around 2K. Using periodic boundary conditions, we find limited ordering and no signs of incipient growth in the liquid Al close to the B-terminated surface of TiB 2 . By contrast, we see fcc-like ordering near the Ti-terminated surface, with growth being frustrated by the lattice mismatch between bulk Al and the TiB 2 substrate. The Al interatomic distances at the Ti-terminated surface are similar to distances found in Al 3 Ti; we suggest that the layer encasing TiB 2 observed experimentally may be strained Al on a Ti-terminated surface rather than Al 3 Ti. For the Al 3 Ti substrate, fcc-like structures are observed on both sides which extend rapidly into the melt. Periodic boundaries introduce unphysical stresses which we removed by introducing a vacuum region to separate the liquid from the solid at one of the interfaces. We see ordering in the Al on both the B-terminated (0001) surface of TiB 2 , and on Al 3 Ti(112), with the ordering able to be stronger on the Al 3 Ti substrate.However, we cannot draw strong conclusions as these simulations need more time to allow long ranged fluctuations in the liquid Al to dampen out. The huge computational cost restricted the range and duration of simulations that was possible.

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Section: Results and Discussion A Tib 2 Substratesupporting

confidence: 73%

Section: Introductionmentioning

confidence: 99%

Heterogeneous nucleation of solid Al from the melt byTiB2andAl3Ti: Anab initiomolecular dynamics study

et al. 2010

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“…Several mechanisms might be suggested: (1) Al 3 Zr particles provide substrates for the formation of metastable Al 3 Ti layer similar to what has been found in metallic glass experiments [23] and observed by neutron diffraction in the Al-Ti-B system; [24] (2) Al 3 Zr particles are fragmented by ultrasonic treatment and become active solidification sites; and (3) aluminum grains formed at the active Al 3 Zr particles are restricted in growth by titanium present in the melt. To check these hypotheses, we studied the morphology and composition of the primary Al 3 Zr intermetallics in a commercial 7075 alloy.…”

Section: B Treatment In the Liquid Statementioning

confidence: 58%

Criteria of Grain Refinement Induced by Ultrasonic Melt Treatment of Aluminum Alloys Containing Zr and Ti

Atamanenko

Eskin

Zhang

et al. 2010

Metall Mater Trans A

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237

162

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It is well known that ultrasonic melt treatment (UST) promotes grain refinement in aluminum alloys. Cavitation-aided grain refinement has been studied for many years; however, it is still not being applied commercially. The current article summarizes the results of experimental work performed on various alloying systems at different stages of solidification. The influence of UST parameters and solidification conditions on the final grain structure is analyzed. It was found that small additions of zirconium and titanium can significantly increase the efficiency of UST, under the stipulation that grain refinement is performed in the temperature range of primary solidification of Al 3 Zr. The possible mechanisms for this effect are discussed.

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“…Recent advances in materials characterization can be attributed to developments in three-dimensional visual-ization using computerized serial sectioning, X-ray microtomography, and focused ion beam (FIB) techniques, and this type of characterization is increasingly applied in studies on nucleation, [11] growth, [12] coarsening, [13] deformations, [14] and phase formation. [15] Only a few tomographic investigations have been performed on the b phases in concentrated AlSi alloys (i.e., the studies by Terzi, [16] Dinnis, [17] Timpel [18] and Puncreobutr [19] ).…”

Section: Introductionmentioning

confidence: 99%

Interplay Between Melt Flow and the 3D Distribution and Morphology of Fe-Rich Phases in AlSi Alloys

Mikołajczak

Ratke

2014

Metall Mater Trans A

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The presence of Fe aids in establishing the mechanical and physical properties of AlSi alloys and is also one of the main impurities leading to formation of b-Al 5 FeSi intermetallics. This study aims to understand the effect of fluid flow on the dendritic microstructure with intermetallics in Al-5/7/9 wt pct Si-0.2/0.5/1.0 wt pct Fe alloys that are directionally solidified under defined thermal and fluid flow conditions. We made extensive use of 3D X-ray tomography to obtain a better insight into the morphology and formation of the intermetallics. Three-dimensional (3-D) distribution of intermetallics presented here shows that the growth of large b-Al 5 FeSi due to forced flow occurs in the eutectic specimen center and together with an increase in the number density of b precipitates. The 3D reconstructions have verified the b shaped to be curved, bent with twining, branched, and to have imprints, holes, and propeller-shaped platelets. The 3D views showed that hole-shaped b arose from the lateral growth around a-Al dendrites. These views also confirmed the phenomenon of shortening of b as an effect of flow in the dendritic region, where b could be fragmented or completely remelted, and ultimately resulting in microstructures with shorter b-Al 5 FeSi and increases in number density. The analysis revealed an interaction between melt flow, 3D distribution, and the morphology of b-Al 5 FeSi. The growth of a large and complex group of b intermetallics can reduce the melt flow between dendrites and strengthen pore nucleation and eutectic colonies nucleation, leading to lower permeability of the mushy zone and increased porosity in the castings.

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Real-time observation of grain nucleation and growth during solidification of aluminium alloys

Cited by 116 publications

References 13 publications

Heterogeneous nucleation of solid Al from the melt byTiB2andAl3Ti: Anab initiomolecular dynamics study

Heterogeneous nucleation of solid Al from the melt byTiB2andAl3Ti: Anab initiomolecular dynamics study

Criteria of Grain Refinement Induced by Ultrasonic Melt Treatment of Aluminum Alloys Containing Zr and Ti

Interplay Between Melt Flow and the 3D Distribution and Morphology of Fe-Rich Phases in AlSi Alloys

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