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Solidification sequence of AlSi11 alloy

The automotive industry is forced to apply advanced materials and technologies in order to overcome the mutual competition, but also for compliance with environmental regulations requiring reduction of emissions, and fuel consumption. One of main component for achieving this goal is weight saving by downsizing of components using advanced materials and production technologies. The widest production of automotive aluminium component refers to wheels produced by low pressure die casting. Complex geometry of thin wall wheel casting indicates application of AlSi11 alloy (EN AC 44000). An AlSi11 alloy (EN AC 44000) belongs to the group of “eutectic alloys” and is characterized with relatively low melting point and narrow solidification interval which both brought to the uniformly distributed eutectic microstructure indicating superior mechanical and technological properties. This is the reason for this alloy to be widely used for high and low pressure die casting production. Silicon is one of the most important alloying elements which comprehend to good castability of aluminium alloys. Addition of silicon improves resistance to hot cracks and feeding capability. Synergy of influenced alloying and trace elements effect comprehend to different intermetallic phase evolution. The content of secondary alloying elements (Mg, Cu) and trace elements (Fe, Mn, Cr, Zn) was minor in investigated AlSi11 alloy. Also thin wall casting geometry using low pressure die casting technology ensures rapid cooling with minimal available time for significant number of intermetallic phases development. Metallographic analysis resulted in following microstructural constituents: primary aluminium αAl, main eutectic αAl + βSi, high temperature iron phase Al5FeSi, intermetallic phases in form of secondary eutectic Mg2Si and Al8FeMg3Si6. Correlation of established microstructural constituents with thermodynamic modelling and differential scanning calorimetry indicates exact solidification sequence for this particular chemical composition.

AlSi11, automotive industry, thermodynamic modelling, microstructure, solidification

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