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Characterization of innovative high pressure die casting AlSi9MgMn alloy properties

Novel multicomponent AlSi9MgMn alloy has been investigated due to unusual chemical composition. An AlSi9MgMn alloy is the first aluminum alloy with low iron and intentionally high manganese content developed for structural automotive casting parts and sets produced by high pressure die casting process. This alloy has been characterised by enhanced mechanical properties of castings such as ductility and toughness at high cooling rates due to evolution of intermetallic AlxMnyFezSiu phase in globular manner. Characterization of novel multicomponent AlSi9MgMn alloy at high cooling rate related to high pressure die casting indicates evolution of fine intermetallic phases with globular morphology which directly influence on development of enhanced mechanical properties. Investigation revealed evolution of characteristic microstructural constituents on the base of their morphology and chemical composition: primary aluminum (aAl) with mixed dendrite and globular morphology, complex intermetallic phase AlxMnyFezSiu in globular / polyhedron morphology, main eutectic in interdendritic spaces (aAl + bSi). Complex intermetallic phase AlxMnyFezSiu evaluated at high cooling rate reveals globular or polyhedron morphology which indicate independently evolution in early stages of solidification, due to both local undercooling and liquid composition which allow direct nucleation of the equilibrium phase in the liquid by individual nucleation and growth or by increase in thickness of that originated previously, that have been transported mainly by diffusion in the liquid. Eutectic posses mixed lamellar and fibrous morphology. Obtained mechanical properties were very high when compared to common aluminium automotive alloys. A significant differentiation has been established due to increasing of cooling / solidification rate obtained by several sample diameters. Test samples exposed to higher cooling rate due to their geometry (smaller diameter) show increase in yield and tensile strength and elongation due to finer microstructure, prominent globular microstructure of primary aluminium, intermetallic AlxMnyFezSiu phase and completely modified fibrous eutectic. Characterization of novel multicomponent AlSi9MgMn alloy indicates applicability of this material for safety automotive parts due to obtained high values of mechanical properties.

AlSi9MgMn alloy ; microstructure development ; mechanical properties ; high pressure die casting

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