Particle Collisions and Inclusion Removal in Molten Aluminium: A Numerical Simulation

Gudmundsson, Throstur; Sigfusson, T. I.; McCartney, D.G.; Wuilloud, E.; Fisher, P. A.

doi:10.4028/www.scientific.net/msf.217-222.159

Cited by 4 publications

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“…The single-humped form of solution is seen to persist for small times, with the position of the hump staying almost static, the distribution becoming smaller in amplitude as mass is lost from the system, and much broader as aggregation creates clusters of larger sizes. This is in agreement with the numerical results of Gudmundsson for a system modelling the evolution under agglomeration of an initially single-humped distribution of TiB 2 particles in molten aluminium [12,18].…”

Section: Discussionsupporting

confidence: 80%

“…The exact solutions given in Section 2 did not have the form observed in the numerical simulations of Gudmundsson (see Gudmundsson [12] and Gudmundsson et al [18]). One reason for this may be the differences in the kernel used; in numerical work, Gudmundsson used the more accurate kernel a i,j = 2 + (i/j) 1/3 + (j/i) 1/3 for Brownian coagulation, whereas the theory of Section 2 considered the simpler kernels a i,j = a, a i,j = a(i + j).…”

Section: Match To Experimental Resultsmentioning

confidence: 85%

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Coagulation equations with mass loss

Wattis

McCartney

Gudmundsson³

2004

Journal of Engineering Mathematics

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We derive and solve models for coagulation with mass loss arising, for example, from industrial processes in which growing inclusions are lost from the melt by colliding with the wall of the vessel. We consider a variety of loss laws and a variety of coagulation kernels, deriving exact results where possible, and more generally reducing the equations to similarity solutions valid in the large-time limit. One notable result is the effect that mass removal has on gelation: for small loss rates, gelation is delayed, whilst above a critical threshold, gelation is completely prevented. Finally, by forming an exact explicit solution for a more general initial cluster size distribution function, we illustrate how numerical results from earlier work can be interpreted in the light of the theory presented herein.

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Section: Discussionsupporting

confidence: 80%

Section: Match To Experimental Resultsmentioning

confidence: 85%

Coagulation equations with mass loss

Wattis

McCartney

Gudmundsson³

2004

Journal of Engineering Mathematics

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“…Individual particles of TiB 2 have typically a size between 0.5 and 2 lm but some reach 10 lm. Agglomeration of particles increases with increasing residence time in the melt and worsens in the presence of halide salt traces [16,17] although recent studies have shown that Mg additions reduce the agglomeration and increase nucleation efficiency in Al-Si alloys. [18] The coarse TiB 2 particles and agglomerates are a serious concern and can cause surface defects, especially if the aluminum is to be rolled in thin foils.…”

Section: Introductionmentioning

confidence: 99%

Behavior of Boron in Molten Aluminum and its Grain Refinement Mechanism

Alamdari

Dubé

Tessier

2012

Metall Mater Trans A

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The mechanism of heterogeneous grain refining of aluminum by ultrafine elemental boron particles was investigated. In order to facilitate the observation of the boron-aluminum interface, a boron filament was introduced in a melt at 1013 K (740°C) containing different levels of Ti. The Al/B interface was studied using transmission electron microscopy and different phases were identified using the electron diffraction method. The experimental results showed that boron is dissolved in pure aluminum while its dissolution is inhibited in presence of titanium solute. A thin layer of TiB 2 formed at the surface of boron thickens with residence time in the melt. The mechanisms by which aluminum is crystallized on boron are discussed.

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“…Boron content measurement, assuming it corresponds to the level of TiB 2 , showed a~30 pct reduction after 8 minutes of degassing. Gudmundsson [5,8] and Chu [4] also reported loss of TiB 2 during degassing. However, Ar-Cl 2 gas was used in their experiments, and both suggested that Cl led to the formation of TiB 2 agglomerates and thus a loss of refinement.…”

Section: Introductionmentioning

confidence: 93%

“…The grain refiner is normally added to the melt immediately prior to or during degassing, because the stirring motion helps to distribute the grain refining particles throughout the melt. However, it has been reported in the literature [4][5][6][7] that grain refining particles are removed during degassing. Khorasani [6] investigated the effect of degassing with Ar, N, or a mixture of the two on A356 grain refined with an Al-5 wt pct-1 wt pct B master alloy.…”

Section: Introductionmentioning

confidence: 99%

The Effect of Degassing on Grain Refinement in Commercial Purity Aluminum

Schaffer

Dahle

2009

Metall Mater Trans A

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Degassing of molten aluminum is used to remove dissolved hydrogen and impurity particles prior to casting. The most common method, rotary degassing, gives a small bubble size and distributes the bubbles throughout the melt by means of vigorous stirring. Although this is an efficient method for hydrogen removal, the purge gas may also inadvertently remove grain refining particles and thus reduce refinement efficiency. During degassing, particle removal occurs by physical attachment to the degassing bubbles and flotation, by turbulent transport due to the flow field generated by stirring, or by sedimentation. The experiments reported here were undertaken using a static graphite degassing lance (i.e., nonrotating) in order to prevent the formation of strong flow fields and to quantify the rate of grain refiner loss due to bubble attachment and floatation. By varying either (a) gas flow rate, (b) grain refiner addition level, or (c) type of grain refiner, it was found that, although grain size increased with time, the increase was predominantly due to particle sedimentation and not caused by attachment.

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Particle Collisions and Inclusion Removal in Molten Aluminium: A Numerical Simulation

Cited by 4 publications

References 0 publications

Coagulation equations with mass loss

Coagulation equations with mass loss

Behavior of Boron in Molten Aluminum and its Grain Refinement Mechanism

The Effect of Degassing on Grain Refinement in Commercial Purity Aluminum

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