Melt characteristics and solidification growth direction with respect to gravity affecting the interfacial heat transfer coefficient of chill castings

Cheung, Noé; Ferreira, Itamar; Pariona, Moisés Meza; Quaresma, José M.V.; Garcia, Amauri

doi:10.1016/j.matdes.2009.02.025

Cited by 41 publications

(22 citation statements)

References 22 publications

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“…Moreover, it has been frequently used by other authors in researching unidirectional solidification in downward vertical 12,[33][34][35] , horizontal [32][33][34]36 and rotary systems 37 , which produce melt convection effects.…”

Section: Methodsmentioning

confidence: 99%

The columnar to equiaxed transition of horizontal unsteady-state directionally solidified Al-Si alloys

et al. 2014

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Experiments were conducted to investigate the influence of thermal parameters on the columnar to equiaxed transition during the horizontal unsteady-state directional solidification of Al-Si alloys. The parameters analyzed include the heat transfer coefficients, growth rates, cooling rates, temperature gradients and composition. A combined theoretical and experimental approach is developed to determine the solidification thermal variables considered. The increasing solute content in Al-Si alloys was not found to affect significantly the experimental position of the CET which occurred for cooling rates in the range between 0.35 and 0.64 K/s for any of three alloy compositions examined. A comparative analysis between the results of this work and those from the literature proposed to analyze the CET during upward vertical solidification of Al-Si alloys is reported and the results have shown that the end of the columnar region during horizontal directional solidification is abbreviated as a result of about six times higher thermal gradient than that verified during upward unidirectional solidification of alloys investigated.

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Section: Methodsmentioning

confidence: 99%

The columnar to equiaxed transition of horizontal unsteady-state directionally solidified Al-Si alloys

et al. 2014

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“…Although the numerical model 40,41 employed for h i theoretical estimation does not take effects on convection in liquid into account, it was selected from the literature as the most appropriate model for representing the solidification conditions considered in this study. Moreover, it has been frequently used by other authors in researching unidirectional solidification in horizontal 41 , downward vertical 40,42,43 and rotary systems 44 , which produce melt convection effects.…”

Section: Methodsmentioning

confidence: 99%

Characterization of the Al-3wt.%Si alloy in unsteady-state horizontal directional solidification

et al. 2013

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The main purpose of this paper is to investigate both the columnar to equiaxed transition and primary dendritic arm spacings of Al-3wt.%Si alloy during the horizontal directional solidification. The transient heat transfer coefficient at the metal-mold interface is calculated based on comparisons between the experimental thermal profiles in castings and the simulations provided by a finite difference heat flow program. Simulated curve of the interfacial heat transfer coefficient was used in another numerical solidification model to determine theoretical values of tip growth rates, cooling rates and thermal gradients that are associated with both columnar to equiaxed transition and primary dendritic arm spacings. A good agreement was observed between the experimental values of these thermal variables and those numerically simulated for the alloy examined. A comparative analysis is carried out between the experimental data of this work and theoretical models from the literature that have been proposed to predict the primary dendritic spacings. In this context, this study may contribute to the understanding of how to manage solidification operational parameters aiming at designing the microstructure of Al-Si alloys.

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“…This gap contributes to the heat extraction inefficiency during unsteady-state solidification. Some studies in literature [20,21] also reported that such decrease in thermal contact during downward solidification, is conducive to lower and constant interfacial heat transfer coefficients. Indeed, during solidification of immiscible Al-Pb alloys in this study, the growth rates profiles along the castings lengths for both alloys solidified downwards are lower than those experimentally determined for the upward cases [22].…”

Section: Resultsmentioning

confidence: 94%

On the growth of the minority phase during downward transient directional solidification of hypomonotectic and monotectic Al–Pb alloys

et al. 2012

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Al-Pb alloys were solidified under non steady heat flow conditions using a casting assembly in order to promote vertical downward directional solidification. The downward configuration enables the effects of gravitydriven convection on the final microstructure to be evaluated since the collective movement of Pb-rich particles downwards is favored, due to density differences between the two coexisting liquid phases. Investigations have been made of the obtained solidification structures. Growth rates (v) and cooling rates (T Á ) of the Al-Pb alloys solidified downwards were experimentally determined by the cooling curves recorded along the casting length. The monotectic structure was characterized by metallography and a microstructural transition has been observed in all cases. The microstructure was characterized by well-distributed Pb-rich droplets in the aluminum-rich matrix from the casting cooled surface up to a certain position in the casting, followed by a mixture of fibers and strings of pearls from this point to the bottom of the casting. The increase in alloy lead content delays the formation of fibers for alloys solidified downwards, which occurs for v \ 0.48 mm/s and v \ 0.15 mm/s for Al-0.9 wt%Pb and Al-1.2 wt%Pb alloys, respectively. Experimental power laws relating the interphase spacing, k, to v and characterized by -2.0 and -6.5 exponents, were found to represent the growth of droplets and fibers, respectively, for both alloys solidified downwards.

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Melt characteristics and solidification growth direction with respect to gravity affecting the interfacial heat transfer coefficient of chill castings

Cited by 41 publications

References 22 publications

The columnar to equiaxed transition of horizontal unsteady-state directionally solidified Al-Si alloys

The columnar to equiaxed transition of horizontal unsteady-state directionally solidified Al-Si alloys

Characterization of the Al-3wt.%Si alloy in unsteady-state horizontal directional solidification

On the growth of the minority phase during downward transient directional solidification of hypomonotectic and monotectic Al–Pb alloys

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