Materials Science. Non-Equilibrium Phase Transformations.
Vol. 11 (2025), Issue 1, pg(s) 30-33

Effect of chromium on the microstructure of AlSi7Mg alloy with increased iron content

  • 1 Silesian University of Technology, Poland
  • 2 Superior Industries Production Poland Sp. z o.o., Poland
  • 3 Superior Industries Production, Mexico

Abstract

The need to protect the environment by reducing the energy intensity of production, the amount of waste, and reducing greenhouse gas emissions, as well as shrinking bauxite resources, means that secondary raw materials are playing an increasingly important role in aluminum alloy smelting. However, the increase in the proportion of scrap results in a higher content of various impurities, the worst of which is iron in the group of metallic ones. It is well known that manganese is one of the most commonly used additives to neutralize morphologically unfavorable β-Al5FeSi phases. However, there is little information about the effects of other transition elements, such as chromium. Accordingly, the study’s results concern the effect of chromium on the microstructure of AlSi7Mg alloy with increased iron content (from 0.4wt.% to 1.4wt.%, in 0.2% increments). Based on SEM/EDX and XRD studies, it was found that the addition of chromium causes the transformation of the lamellar-needle phase β-Al5FeSi into the α-Al13(Fe,Cr)4Si4 phase with a dendritic morphology (so-called “Chinese script”). However, care should be taken not to exceed the permissible value of the chromium/iron quotient (Cr/Fe ~ about 1/3). Otherwise, the morphology of the α-Al13(Fe,Cr)4Si4 phase changes from more “fluffy” to massive polygons. This is accompanied by an unfavorable increase in the slime ratio from about 1.6 to more than 3.0%.

Keywords

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