An experimental study with an A356-AlSiMgFe alloy was developed to evaluate the microhardness performance in the microstructure resulting of an unsteady-state horizontal solidification process. The Al-7wt%Si-0.3wt%Mg-0.15wt%Fe alloy was elaborated and directionally solidified in a water-cooled horizontal solidification device. In order to experimentally determine the cooling and growth rates (V L and T R , respectively), a thermal analysis was also conducted during solidification. Microstructural characterization by optical microscopy, SEM/EDS elemental mapping and microanalysis of the punctual EDS compositions allowed to observe the presence of an Al-rich dendritic phase (Al (α)) with interdendritic phases second composed of an eutectic mixture: Al (α-eutectic) + Si + Al 8 Mg 3 FeSi 6(π) + Mg 2 Si (θ). Furthermore, the dendritic microstructure was characterized by measuring the secondary dendritic spacings (λ 2) along the horizontally solidified ingot. Higher HV values were observed within the eutectic mixture.
In this work, a study on the interrelationship between the solidi cation and heat-treatment processes parameters with tensile properties and fracture feature was performed with an automotive AlSiMg alloy. For that, samples of the horizontally solidi ed Al7Si0.3Mg (wt.%) alloy were subjected to the T6-heat treatment as well as tensile tests were performed on both investigated samples, under conditions established from the literature. The solidi cation conditions such as growth and cooling rates and the secondary dendritic spacing (V L and T R and λ 2 , respectively) and their effects on the ultimate tensile strength (σ UTS ) and elongation (E%) were evaluated. It was observed higher σ UTS values in the heat-treated samples and ner microstructures have inherited a better E% performance. Analysis by SEM/EDS fractography on both samples showed a mix between brittle and ductile fractures, constituted by cleavage facets, secondary cracks, facets covered with micro-voids, tear ridges and dimples. It has allowed deducing on the occurrence of a transition from ductile to brittle fracture along the solidi ed ingot as well as the predominance of brittle fracture in the heat-treated samples.
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