The Failure Degradation of Recycled Aluminium Alloys with High Content of β-Al5FeSi Intermetallic Phases

Abstract

In this study, the effect of the β-Al5FeSi phases on fracture surfaces in secondary AlSi7Mg0.3 cast alloys with common and higher amount of iron was investigated. Iron addition caused the formation of different Fe-rich intermetallic phases in aluminium alloys. Components made of secondary aluminium alloys commonly have a higher amount of such phases. Sharp needles as β-Al5FeSi phase lead to initiate stress tension, thereby contributing to increased risk of micro-cracks formation on the fracture surfaces. To determine the effect of β-Al5FeSi to fracture surfaces of AlSi7Mg0.3 cast alloy, SEM microscopy with energy-dispersive X-ray spectroscopy (EDX) was used to study the amount of needles phases, their morphology and violation wave. It was found that increasing Fe content increased the size and the number of Al5FeSi phases. The fractographic analysis of fracture surfaces shows an increasing amount of cleavage fracture in materials with a higher amount of iron, too.