Effect of Grain Refinement on Structure Evolution, “Floating” Grains, and Centerline Macrosegregation in Direct-Chill Cast AA2024 Alloy Billets

Nadella, Ravi Kumar; Eskin, Dmitry; Katgerman, L.

doi:10.1007/s11661-007-9423-z

Cited by 40 publications

(31 citation statements)

References 15 publications

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“…A detailed analysis of the structure is reported elsewhere [15], here only some relevant data are given. Addition of a grain refiner resulted in significant decrease in the grain size as illustrated in Fig.…”

Section: Resultsmentioning

confidence: 99%

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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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Section: Resultsmentioning

confidence: 99%

“…The line scans were made through the selected grains with coarse and fine dendrite branches and the examples of such scans are given elsewhere [15]. In this paper we will focus on the analysis of results that can be extracted from the compositional profiles like those shown in Fig.…”

Section: Resultsmentioning

confidence: 99%

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

2008

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“…Generally, higher casting speed and lower casting temperature result in a finer microstructure, [3][4][5] while cooling water-flow rate has relatively minor effect on grain structure. [6,7] The distribution of structure parameters in the horizontal section of a DC casting billet (along the radius or diameter) is of great importance since it determines the homogeneity of technological properties during downstream processing.…”

Section: Introductionmentioning

confidence: 99%

Influence of Melt Feeding Scheme and Casting Parameters During Direct-Chill Casting on Microstructure of an AA7050 Billet

Zhang

Eskin

Miroux

et al. 2012

Metall Mater Trans B

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Direct-chill (DC) casting billets of an AA7050 alloy produced with different melt feeding schemes and casting speeds were examined in order to reveal the effect of these factors on the evolution of microstructure. Experimental results show that grain size is strongly influenced by the casting speed. In addition, the distribution of grain sizes across the billet diameter is mostly determined by melt feeding scheme. Grains tend to coarsen towards the center of a billet cast with the semi-horizontal melt feeding, while upon vertical melt feeding the minimum grain size was observed in the center of the billet. Computer simulations were preformed to reveal sump profiles and flow patterns during casting under different melt feeding schemes and casting speeds. The results show that solidification front and velocity distribution of the melt in the liquid and slurry zones are very different under different melt feeding scheme. The final grain structure and the grain size distribution in a DC casting billet is a result of a combination of fragmentation effects in the slurry zone and the cooling rate in the solidification range.

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“…However, contrary to Mg, Mn shows negative segregation at the surface of the ingot. This phenomenon has not been seen before as Eskin et al [24], and Nadella et al [25] found positive segregation of Mn in DC cast ingots, while Dons et al [26] observed that manganese resists macrosegregation in DC cast Al-Si alloys. Finally Cr shows a positive segregation at the center, no segregation at the middle and negative segregation at the surface of the ingot.…”

Section: Segregationmentioning

confidence: 88%

Microstructure, Macrosegregation, and Thermal Analysis of Direct Chill Cast AA5182 Aluminum Alloy

Jamaly

Haghdadi

Phillion

2015

J. of Materi Eng and Perform

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The variation in microstructure, macrosegregation, and solidification behavior during aluminum alloy Direct Chill casting is investigated with respect to geometry. Optical microscopy, energy dispersive analysis and differential scanning calorimetry were employed to study the grain size evolution, distribution of alloying elements and solidification sequence across the cross-section of DC cast AA5182 aluminum alloy. The results show: (1)

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Effect of Grain Refinement on Structure Evolution, “Floating” Grains, and Centerline Macrosegregation in Direct-Chill Cast AA2024 Alloy Billets

Cited by 40 publications

References 15 publications

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

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

Influence of Melt Feeding Scheme and Casting Parameters During Direct-Chill Casting on Microstructure of an AA7050 Billet

Microstructure, Macrosegregation, and Thermal Analysis of Direct Chill Cast AA5182 Aluminum Alloy

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