Modeling Macrosegregation during Direct-Chill Casting of Multicomponent Aluminum Alloys

Du, Qiang; Eskin, Dmitry; Katgerman, L.

doi:10.1007/s11661-006-9042-0

Cited by 67 publications

(44 citation statements)

References 24 publications

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“…Some implications of forced convection are considered in Section 3.4. Thermal-solutal convection is initiated due to the temperature and concentration gradients and its buoyancy term in the momentum equation is related to the temperature and average concentration by [34]:…”

Section: Flow Patterns In DC Cast Billetsmentioning

confidence: 99%

“…2a). Inherent to the DC casting are the temperature differences between the centre and the surface of the billet, which lead to density differences in the alloy, the addition of Mg to the binary Al-Cu alloy influences the final macrosegregation pattern by its opposite contribution to the solutal buoyancy in comparison with Cu [91]. As a result, Fig.…”

Section: Thermo-solutal and Forced Convectionmentioning

confidence: 99%

“…From modelling perspective, this is very important [91]. Experimental work under identical conditions on a 2024 alloy and an equivalent binary Al-Cu alloy indicated that the presence of Mg influence the segregation of Cu [74].…”

Section: Macrosegregation -Influence Of Process Parameters and Structurementioning

confidence: 99%

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Macrosegregation in direct-chill casting of aluminium alloys

Nadella

Eskin

et al. 2008

Progress in Materials Science

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251

148

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Semi-continuous direct-chill (DC) casting holds a prominent position in commercial aluminium alloy processing, especially in production of large sized ingots.Macrosegregation, which is the non-uniform chemical composition over the length scale of a casting, is one of the major defects that occur during this process. The fact that macrosegregation is essentially unaffected by subsequent heat treatment (hence constitutes an irreversible defect) leaves us with little choice but to control it during the casting stage. Despite over a century of research in the phenomenon of macrosegregation in castings and good understanding of underlying mechanisms, the contributions of these mechanisms in the overall macrosegregation picture; and interplay between these mechanisms and the structure formation during solidification are still unclear. This review attempts to fill this gap based on the published data and own results. The following features make this review unique: results of computer simulations are used in order to separate the effects of different macrosegregation mechanisms. The issue of grain refining is specifically discussed in relation to macrosegregation. This report is structured as follows. Macrosegregation as a phenomenon is defined in the Introduction. In Part 2, direct-chill casting, the role of process parameters and the evolution of structural features in the as-cast billets are described. In Part 3, macrosegregation mechanisms are elucidated in a historical perspective and the correlation with DC casting process parameters and structural features are made. The issue of how to control macrosegregation in direct-chill casting is also dealt with in Part 3. In Part 4, the effect of grain refining on macrosegregation is introduced, the current understanding is described and the contentious issues are outlined. The review is finished with conclusion remarks and outline for the future research.

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Section: Flow Patterns In DC Cast Billetsmentioning

confidence: 99%

Section: Thermo-solutal and Forced Convectionmentioning

confidence: 99%

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Macrosegregation in direct-chill casting of aluminium alloys

Nadella

Eskin

et al. 2008

Progress in Materials Science

Self Cite

251

148

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“…In our previous papers we discussed the effects of convective and shrinkage-induced flows on macrosegregation during direct-chill casting of aluminum alloys [1,2,3]. The relevant review of literature is given in these papers.…”

Section: Introductionmentioning

confidence: 99%

Effect of different grain structures on centerline macrosegregation during direct-chill casting

2008

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Duplex grain structure consisting of coarse-cell and fine-cell dendritic grains is frequently found in the central portion of direct-chill cast billets and ingots. Coarse-cell grains are usually considered as free-floating grains settled to the bottom of the billet sump. These grains are assumed to be solute-lean and contribute to the negative centerline segregation. In this paper the contribution of coarse-cell and fine-cell grains to macrosegregation is for the first time studied experimentally by direct measurements of their composition. It is shown that the coarse-cell, floating grains are depleted of solute and the areas of their accumulation contribute to the negative macrosegregation. The areas of fine-cell grains can be either enriched in solute or be close to the nominal composition. It is argued that their composition results from the interplay between thermo-solutal and shrinkage-induced flows. The roles of casting speed and grain refining are also under scrutiny in this paper.

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“…1(a)]: by the melt flow induced by thermosolutal natural convection, shrinkage, and pouring, and by the transport of solute-lean free-floating grains. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] A commonly observed, surface-to-surface distribution of alloying elements at a transverse cross-section of a DC cast ingot is shown in Figure 1(b), revealing distinct regions of positive (solute-rich) and negative (solute-depleted) segregation. [1,3,17,18] A solute-depleted region is present in the ingot center, adjoined by a positive segregation zone spreading into the outward radial direction, an adjacent thin negative segregation zone and another positive segregation layer at the surface.…”

mentioning

confidence: 99%

Influence of Transport Mechanisms on Macrosegregation Formation in Direct Chill Cast Industrial Scale Aluminum Alloy Ingots

et al. 2011

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The phenomena responsible for the formation of macrosegregations and grain structures during solidification are closely related. We present a model study of macrosegregation formation in an industrial sized (350 mm thick) direct chill (DC) cast aluminum alloy slab. The modeling of these phenomena in DC casting is a challenging problem mainly due to the size of the products, the variety of the phenomena to be accounted for, and the nonlinearities involved. We used a volume‐averaged two‐phase multiscale model that describes nucleation on grain refiner particles and grain growth, fully coupled with macroscopic transport: fluid flow driven by natural convection and shrinkage, transport of free‐floating equiaxed grains, heat transfer, and solute transport. The individual and combined roles of shrinkage, natural convection, and grain motion on the sump profile and macrosegregation formation are analyzed. The formation and evolution of grains are discussed. We show that it is important to account for all the named transport mechanisms to be able to explain the macrosegregation pattern observed experimentally in DC cast ingots.

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Modeling Macrosegregation during Direct-Chill Casting of Multicomponent Aluminum Alloys

Cited by 67 publications

References 24 publications

Macrosegregation in direct-chill casting of aluminium alloys

Macrosegregation in direct-chill casting of aluminium alloys

Effect of different grain structures on centerline macrosegregation during direct-chill casting

Influence of Transport Mechanisms on Macrosegregation Formation in Direct Chill Cast Industrial Scale Aluminum Alloy Ingots

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