Tackling Fe-rich Intermetallics in Al-Si Alloy: A Critical Review

Iron-rich intermetallics in Al-Si alloys pose a major challenge in aluminum recycling. Virgin Al-Si alloys typically contain a minimal iron concentration which enhances properties like tensile strength and conductivity. Although aluminum is a recycling friendly metal, Fe impurity increases due to scrap contaminations, coatings and rust, which eventually leads to the evolution and growth of detrimental Fe-rich intermetallics. These Fe-rich particles exhibit platelet or needle-like morphologies, and their aspect ratios grow with higher Si and Fe concentrations. Among the identified βphases, β-Al5FeSi is predominantly known for its fragility and negative impact on the mechanical properties of the alloy. Two potential solutions to this problem are, removing Fe from Al-Si alloys or suppressing the formation of β-Al5FeSi. While the method of alloying additions is much more viable for industry scale. Current study is a critical review of morphological modification of Fe-rich intermetallics through alloying additions to Al-Si alloys. The independent mechanism(s) of suppression of β-Al5FeSi phase by Mn, Mo, V and Cr additions is discussed along with the challenges and future scope of this work are discussed in detail.