engleski

Study of innovative AlSi7MgCu alloy with improved properties

Aluminium alloys have expanded its application as a lightweight material in transport industry due to downsizing effect and therefore reducing the CO2 emissions. Safety loaded aluminium alloy castings have been exposed to high market demands related to material and properties quality. The quality of aluminium components mainly depends from casting process and parameters, but also from chemical composition which significantly affects the mechanical properties. Therefore, the innovative development of high strength aluminium alloys becomes significant for structural components in transport industry. Conventional AlSi7Mg alloy is a frequent selection for complex geometry castings with high mechanical properties due to extraordinary castability and favorable relation between strength and weight, especially in the heat-treated state. An innovative approach in this study was reflected in new design of special chemical composition of an AlSi7Mg alloy with the aim of tensile mechanical properties improvement. With this purpose, an extra addition of Cu (up to 1.435 wt.%) as a secondary alloying element was added. Designing of innovative AlSi7MgCu alloy reveals a wide range of complex reactions and possible intermetallic phases due to the interaction with other alloying and trace elements (Fe, Mn, Mg). Determination of their interactions in solidification process was performed by modeling of equilibrium phase diagram, simultaneous thermal analysis and metallographic investigations. Beside common intermetallic Al5SiFe, modified Chinese script phase Al15(FeMn)3(SiCu)2 also appears. Copper influence resulted in formation of compact complex intermetallic phases Al5Cu2Mg8Si6 and Al8FeMg3Si6. Solidification ended with secondary eutectic phases Mg2Si and Al2Cu. Wide spectra of favorable intermetallic phases comprehend to tensile mechanical properties development. Comparison of yield and tensile strength indicate significant increase of investigated properties for innovative AlSi7MgCu alloy in as- cast state.

AlSi7MgCu alloy ; copper ; microstructure ; mechanical properties

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