Infiltration and solidification/remelting of a binary hypoeutectic alloy (Al-4.5 wt pct Cu) in a porous preform is numerically modeled in this paper. The infiltration of the alloy in the porous preform is made possible by means of a constant external applied pressure difference. The initial temperature of the porous preform is kept at a lower temperature than the liquidus line of the alloy in order to minimize the chemical interactions between the molten alloy and preform material, therefore, a partial fraction of the alloy will solidify in the preform during the infiltration process. At the same time, the inlet molten alloy will remelt some of the previously solidified alloy due to the superheat of the inlet molten alloy. This solidification/remelting process influence not only the infiltration dynamics due to the change of the preform permeability, but also the temperature and the solute distribution in the porous preform. A nonuniform distribution of the solute, called macrosegregation, occurs in the infiltrated composite casting. The objective of this paper is to study the relationship between the macrosegregation phenomenon and the operating variables, namely: pressure difference, preform temperature and alloy inlet temperature, as well as preform porosity. Darcy's law is assumed to be valid for modeling the metal flow in the preform. The two moving fronts-infiltration front, and the remelting front, are immobilized by the appropriate coordinate transformations. The temperature, solidification volume fraction, as well as the solute concentration are calculated by solving the governing equations for representative parameters. Comparison with experimental results are also made to validate our numerical model. The current numerical code can be used to analyze and predict the temperature and solute evolution in the unidirectional infiltration fabrication of metal-matrix composites.
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