Effects of solutes on grain refinement of selected wrought aluminium alloys

Kearns, Martin; Cooper, P. S.

doi:10.1179/026708397790286006

Cited by 13 publications

(16 citation statements)

References 6 publications

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“…For ternary and higher-component systems (e.g. commercial Al alloys), an approximate value of Q can be obtained [114] by treating the individual solute effects additively {∑ m L (K i -1)C 0 i }, provided the amount of alloying elements is limited (below any eutectic or peritectic reaction) and there are no phases formed during the early stages of solidification process between the solutes. Table 6 lists estimated values of GRF for some commercial alloys.…”

Section: Structure Formation and Permeability In Grain Refined Al Alloysmentioning

confidence: 99%

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Macrosegregation in direct-chill casting of aluminium alloys

Nadella

Eskin

et al. 2008

Progress in Materials Science

236

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: Structure Formation and Permeability In Grain Refined Al Alloysmentioning

confidence: 99%

“…According to this, grain refinement becomes progressively easier in the series 1xxx, 3xxx≈6xxx, 5xxx, 2xxx≈7xxxx Al alloys, providing there is no poisoning effect (e.g. by Zr in 7xxx series alloys) [67,108,114,115].…”

Section: Structure Formation and Permeability In Grain Refined Al Alloysmentioning

confidence: 99%

Macrosegregation in direct-chill casting of aluminium alloys

Nadella

Eskin

et al. 2008

Progress in Materials Science

236

148

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“…It was found that the experimental data were better interpreted in terms of Q [17]. Empirically, the average grain size l can be described as a linear function of 1/Q for various Al [4,[10][11][12][13][14]18,19], Mg [1,20] and Ti alloys [21]: Q b a l (3) where a and b are empirical constants. By further analysis of the experimental data, it is believed that a is related to the number density of active nucleating particles and b is related to the efficiency of the nucleating particles [22].…”

Section: Introductionmentioning

confidence: 99%

Effects of solute content on grain refinement in an isothermal melt

2011

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It is well accepted in the literature that for effective grain refinement some solute is required in the melt to restrict the growth of the solid even if potent nucleating particles with a favourable physical nature are present. In this paper, we investigate the effect of solute on grain initiation in an isothermal melt, and an analytical model is developed to account for the effect of solute elements on the grain size. This study revealed that the solute elements in the liquid ahead of the growing crystals reduce the growth velocity of the nucleated crystals, and increase the maximum undercooling achievable before recalescence. This allows for more particles to be active for nucleation, and consequently increases the number density of active particles, giving rise to a finer grain size. The analytical model shows that the final grain size can be related to the maximum undercooling, average growth velocity and solid fraction at the moment of the recalescence. Further analysis using the free growth model and experimental data in the literature revealed that for a given alloy system solidified under similar conditions the grain size can be empirically related to 1/Q (Q is the growth restriction factor) to a power of 1/3, which is considerably different from the empirical linear relationship in the literature. It is demonstrated that the 1/3 power law can describe the experimental data more accurately than a linear relationship.

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“…Experimental studies have produced a large amount of data relating grain size with various solute based parameters 27,30,[32][33][34][44][45][46][47][48][49][50][51][52][53] . It is fortunate that what is a complex relationship between grain size and alloy composition 36,38,54 can be in the first instance related to some simple parameters.…”

Section: Constitutional Supercooling and The Supercooling Parametmentioning

confidence: 99%

Grain Refinement of Al-Si Hypoeutectic Alloys by Al3Ti1B Master Alloy and Ultrasonic Treatment

Gui

Wang

Prasad

et al. 2016

Shape Casting: 6th International Symposium

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The concept of constitutional supercooling (CS) including the term itself was first described and discussed qualitatively by in order to understand the formation of cellular structures during the solidification of tin, and then quantified by Tiller, Jackson, Rutter, and Chalmers (1953). On that basis, Winegard and Chalmers (1954) further considered 'supercooling and dendritic freezing of alloys' where they described how CS promotes the heterogeneous nucleation of new crystals and the formation of an equiaxed zone. Since then the importance of CS in promoting the formation of equiaxed microstructures in both grain refined and unrefined alloys has been clearly revealed and quantified. This paper describes our current understanding of the role of CS in promoting nucleation and grain formation. It also highlights that CS, on the one hand, develops a nucleation-free zone surrounding each nucleated and growing grain and, on the other hand, protects this grain from readily remelting when temperature fluctuations occur due to convection. Further, due to the importance of the diffusion field that generates CS recent analytical models are evaluated and compared with a numerical model. A comprehensive description of the mechanisms affecting nucleation and grain formation and the prediction of grain size is presented with reference to the influence of the casting conditions applied during the practical casting of an alloy.

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Effects of solutes on grain refinement of selected wrought aluminium alloys

Cited by 13 publications

References 6 publications

Macrosegregation in direct-chill casting of aluminium alloys

Macrosegregation in direct-chill casting of aluminium alloys

Effects of solute content on grain refinement in an isothermal melt

Grain Refinement of Al-Si Hypoeutectic Alloys by Al3Ti1B Master Alloy and Ultrasonic Treatment

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