The Effect of Iron Content on Microstructure and Porosity of Secondary AlSi7Mg0.3 Cast Alloy

Abstract

In the present study, microstructure and porosity of AlSi7Mg0.3 cast alloy including various amounts (0.123; 0.454 and 0.655 wt. %) of iron were investigated. The alloys were produced as secondary (scrap-based - recycled). Iron leads to the formation of complex intermetallic phases during solidification, and how these phases can adversely affect mechanical properties, especially ductility, and also lead to the formation of excessive shrinkage porosity defects in castings. In order to determine the effect of iron addition to AlSi7Mg0.3 alloy, optical and SEM microscopy with EDX were used for microstructural examinations. Image analysis was conducted in order to determine effect of the Fe content on phases and porosity. It was found that increasing Fe content from 0.123 to 0.655 wt. % has no effect on SDAS but the morphology of Al-Si eutectic became finer. From EDX examinations, different Fe-based intermetallic phases (β-Al5FeSi and α-Al15(FeMg)3Si2) were observed. It was also observed that as Fe content increased, α-Al15(FeMg)3Si2 phases was transformed into Al5FeSi and the size and the number of Al5FeSi phases increases. The image analysis results revealed that porosity values were by increasing Fe content increased too. We can to predict, that with the increasing amount of Fe decreasing the mechanical properties (first of all) ductility (through long β-Al5FeSi intermetallic and high porosity).