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Effect of the cooling rate on distribution of transition elements in the intermetallic Al-Mn- Fe-Si phase in AlSi9MgMn alloy

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 produced by high pressure die casting process. Characteristics of this technology favourably affect the microstructure development through evolution of intermetallic AlxMnyFezSiu phase in globular manner and thus enhance mechanical properties of castings such as elasticity and toughness. Correlation of investigated microstructure features reveals different morphologies of intermetallic AlxMnyFezSiu phase due to different kinetic factors. Kinetic factors were controlled by characteristic cooling rates. Performed microstructural investigations also indicate significant differences in relationship between Mn and Fe as variable constituents of AlxMnyFezSiu phase. Rapid cooling promotes an increase of total amount of (Mn+Fe) due to fast and independent nucleation of AlxMnyFezSiu phase in globular manner. The highest cooling rate is also attributed to the smallest Mn:Fe ratio, due to narrowing of the solidification interval and therefore restricted possibilities for Mn ↔ Fe replacement.

AlSi9MgMn alloy ; microstructure development ; Al-Mn-Fe-Si phase ; cooling rate

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