Al hypereutectic alloys are characterized by high solute content. The chemistry must be higher than 12.0wt%Si. The commercial alloys like A390 are recognized as those which are the most used in order to produce automobile parts such as pistons, engine blocks and manifolds. Although the effects of eutectic and primary silicon modifiers such as Na, Ca, Sr, Sb and P on microstructure of these alloys are relatively well known, the impacts of cooling rate and composition on the form, size and distribution of the primary Si particles is already to be investigated according with literature. Other than, the consequences provided by these features on the mechanical properties of the hypereutectic Al-Si are an issue to be accomplished. The foundry processes envisage the manufacture of reliable components. This means to produce parts which can be able to attain the demands of a project. In the case of Al-Si alloys such demands include mainly mechanical properties and wear resistance, which should be enough for a certain specification. For instance, in automotive applications, the quality of an engine block, for instance, depends on the microstructures and the grains structures homogeneity. Severe requirements are thus imposed by the potential users and the knowledge of interrelations between the cooling rate and the microstructure of hypereutectic Al-Si alloys would therefore certainly be valuable assets for the practicians. The present purpose aims to provide experimental methods which can lead to a better comprehension of the microstructure evolution in non-modified hypereutectic Al-Si directionally solidified alloys under unsteady-state heat flow conditions.
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