The design of materials through the selection of the chemical composition, thermodynamic modelling, melt treatment by alloying, correctly developed casting tehnology followed by adequate heat treatment could improve casting properties. Due to castings complex geometry adn customer properties, casting manufacturers are forced to adopt production process with additional steps such as heat treatment. Rigorous regime with reatively high temperaure and long holding time indicates the microstructural changes in the material, thus indirectly affects the mechanical properties of the material. An importaint aspect for further improvement and application is to developed a better understanding of the microstructural constituent changes due to performed heat treatment and consequently improved mechanical properties. Heat treatment is accompanied with increased costs and longer time for total production, which cause lower competitiveness of casting producer per produced casting. In addition, manufacturers must comply with environmental and energy legislation that aims for sustainable developent. Conventional EN AC-43500 alloy represents a frequent selection for complex geometry castings production. Designing of new chemical composition of EN AC-43500 alloy represents a challenge in order to achieve advanced mechanical properties already in as-cast state. A wide range of complex reactions and intermetallic phases occurs due to numerous alloying (silicium, magnesium, copper) and trace elements (iron, manganese) interaction. Performed heat treatment influences on iron bearing phases morphology change, refining of microstructural constituents and enrichment of metal matrix on secondary alloying elements such as Cu and Mg. Exact determination of alloy behaviour was performed by modelling of equilibrium phase diagram, simultaneous thermal analysis and metallographic investigations.
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