Numerical study on directional solidification of AlSi alloys with rotating magnetic fields under microgravity conditions

Hainke, Marc; Friеdrich, J.; Müller, G.

doi:10.1023/b:jmsc.0000017762.16763.2b

Cited by 38 publications

(33 citation statements)

References 20 publications

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“…In [16], stirring was weaker, caused by a rotating electromagnetic field of 3 mT, while, in [25], and, in the current study, the RMF was 6 mT. According to [28], the flow in the axial direction may constrain the mushy zone length to 12 mm in a temperature gradient of 4 K/mm and with electromagnetic field strength 3 mT. However, that is much less than the observed lengths of the mushy zones reported in [25] and current study (Figures 9-13).…”

Section: Discussionmentioning

confidence: 59%

“…However, that is much less than the observed lengths of the mushy zones reported in [25] and current study (Figures 9-13). The simulated flow velocities [28] in the axial direction are 2.5 mm/s for strength 3 mT and 10.5 mm/s for 6 mT. There is no information that increased flow velocities due to increased field strength may point on the longer area with included flow.…”

Section: Discussionmentioning

confidence: 97%

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Mushy Zone Morphology Calculation with Application of CALPHAD Technique

Mikołajczak

Genau

Ratke

2017

Metals

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Mushy zone morphology in AlSiMn alloys was studied using directional solidification, and the CALPHAD (Computer Coupling of Phase Diagrams and Thermochemistry) technique was applied for thermodynamic calculations. The specimens solidified with forced convection presented segregation across the sample diameter, and the measured compositions were located on the Al-Si-Mn phase diagram. Scheil-Gulliver calculations for measured compositions were used to determine various solidification paths that may occur in specimens. Property diagrams and solidification paths presented the segregation effect on the characteristic temperatures, mushy zone length and the sequence of occurring phases whilst 2D maps enabled visualization of the mushy zone during directional solidification. Melt stirring was found to change solidification range, as well as mushy zone length and shape, and the dendrite tips formed a rough profile across the specimens. The study revealed mushy zones with dense dendritic structure and liquid channels empty of Mn phases, where intermetallics had no possibility to flow in the liquid, whilst in other samples with channels filled with Al 15 Si 2 Mn 4 , Mn-precipitates also flowed above the α-Al. The melt flow may lead to a mainly dendritic mushy zone or to a mushy zone with dendrites reaching only lower half of mushy length with intermetallics forming and freely flowing above dendrites in the liquid upper half.

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Section: Discussionmentioning

confidence: 59%

Section: Discussionmentioning

confidence: 97%

Mushy Zone Morphology Calculation with Application of CALPHAD Technique

Mikołajczak

Genau

Ratke

2017

Metals

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“…Convection may originate from thermosolutal buoyancy forces [6][7][8] as well as from any forced-melt flows (e.g., electromagnetic stirring [9] or volume changes caused by the shrinkage). It has been shown both experimentally and numerically that fluid flow (especially electromagnetically driven flows) can produce macrosegregations [10][11][12][13] and change the structure. [13] Furthermore, special design of the flow field can be used to control the segregation pattern [9,10] and even to suppress segregation when stirring is pulsated or periodically reversed.…”

Section: Introductionmentioning

confidence: 99%

Influence of Forced/Natural Convection on Segregation During the Directional Solidification of Al-Based Binary Alloys

Noeppel

Ciobanas

Wang

et al. 2009

Metall Mater Trans B

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We analyzed the columnar solidification of a binary alloy under the influence of an electromagnetic forced convection of various types and investigated the influence of a rotating magnetic field on segregation during directional solidification of Al-Si alloy as well as the influence of a travelling magnetic field on segregation during solidification of Al-Ni alloy through directional solidification experiments and numerical modeling of macrosegregation. The numerical model is capable of predicting fluid flow, heat transfer, solute concentration field, and columnar solidification and takes into account the existence of a mushy zone. Fluid flows are created by both natural convection as well as electromagnetic body forces. Both the experiments and the numerical modeling, which were achieved in axisymmetric geometry, show that the forced-flow configuration changes the segregation pattern. The change is a result of the coupling between the liquid flow and the top of the mushy zone via the pressure distribution along the solidification front. In a forced flow, the pressure difference along the front drives a mush flow that transports the solute within the mushy region. The channel forms at the junction of two meridional vortices in the liquid zone where the fluid leaves the front. The latter phenomenon is observed for both the rotating magnetic field (RMF) and traveling magnetic field (TMF) cases. The liquid enrichment in the segregated channel is strong enough that the local solute concentration may reach the eutectic composition.

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“…The dendritic area is about 20 mm (575-635 • C) long for all specimens, but the whole predicted mushy zone differs according to Fe and Mn content. According to [39], the flow by rotating electromagnetic field 3 mT in axial direction may enclose the mushy length on 12 mm and flow velocities in axial direction 2.5 mm/s, while in the current experiment the applied field of 6 mT may cause a velocity of 10.5 mm/s. It seems that these velocities concern only about 12 mm area, but the flow generated by the field also propagates outside it and may cause stirring in that region.…”

Section: Discussionmentioning

confidence: 61%

Thermo-Calc Prediction of Mushy Zone in AlSiFeMn Alloys

Mikołajczak

Genau

Janiszewski

et al. 2017

Metals

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Convection forces can cause significant segregation within the liquid during directional solidification, influencing the structure of the mushy zone and the type and distribution of phases present in the solidified alloy. The solidification behavior of AlSiFeMn alloys with strong convection was investigated via experimental results combined with thermodynamic calculations. Experimental specimens were processed in a directional solidification facility with forced melt flow, resulting in high levels of elemental segregation across samples. The resulting local compositions were located on phase diagrams Al-Si-Fe, Al-Si-Mn and Al-Fe-Mn for prediction of the variation in solidification behavior. Phase mass fraction diagrams created in Thermo-Calc showed the effect of segregation on the characteristic temperatures, mushy zone length and the order of occurring phases precipitating across specimens. These findings were used to create 2D maps for visualization of the mushy zone, mass fraction of α-Al dendrites, β-Al 5 FeSi, Al 15 Si 2 Mn 4 and their spatial location. The specimen centers showed enrichment in AlSi-eutectic but for β-Al 5 FeSi and Al 15 Si 2 Mn 4 results are ambiguous. Fe-phases start to grow mainly behind the dendrites tips and in general may flow between them. Mn-rich phases start to precipitate at higher temperatures than β and in many places before α-Al and in this way may flow in the melt above the mushy zone.

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Numerical study on directional solidification of AlSi alloys with rotating magnetic fields under microgravity conditions

Cited by 38 publications

References 20 publications

Mushy Zone Morphology Calculation with Application of CALPHAD Technique

Mushy Zone Morphology Calculation with Application of CALPHAD Technique

Influence of Forced/Natural Convection on Segregation During the Directional Solidification of Al-Based Binary Alloys

Thermo-Calc Prediction of Mushy Zone in AlSiFeMn Alloys

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