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Study of low pressure die casting AlSi11 alloy solidification

Aluminium alloys possess an excellent mechanical, physically-chemical and technological properties which have found an extensive application in the automotive industry. Alloy AlSi11 belongs to a group of eutectic alloys, which are characterized by high castability, low pouring temperature and narrow solidification interval which makes it suitable for low pressure casting technology (LPDC). In addition to chemical composition, the structural and mechanical properties of alloys depend on many factors that act during solidification. Study of AlSi11 alloy solidification sequence has been accompanied by calculation of equilibrium phase diagram, and simultaneous thermal analysis, all in correlation to microstructure development. Thermodynamic calculation revealed solidification sequence with corresponded temperatures in equilibrium state. Differential scanning calorimetry enables determination of exact temperatures of phases’ transformations. Metallographic investigation comprehends fractography, as well as optical and scanning electron microscopy. Microstructural examination performed on scanning electron microscope equipped by EDS revealed development of following constituents: primary aluminum (αAl), high temperature intermetallic phases on the iron basis (Al5FeSi and/or Al15(Fe, Mn)3Si2), binary eutectic (αAl+βSi) and secondary eutectic (Mg2Si and Al5Mg8FeSi6) as a last solidifying phases’. Synergy of performed thermodynamic and microstructural investigation, as well as obtained mechanical properties enables an evaluation of material quality and management of solidification process.

AlSi11 alloy, solidification sequence, mechanical properties, microstructure.

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