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.

Effect of the Fe/Mn Ratio on the Microstructural Evolution of the AA6063 Alloy with Homogenization Heat Treatment Interruption

“…This is particularly true for the formation of needle-shaped β-Al 5 FeSi intermetallics during solidification, which can compromise mechanical properties, including ductility and fatigue strength. As such, careful attention is necessary to ensure that these high iron levels are appropriately managed to maintain the desired quality of the alloy [4,5].…”

Effects of Mn addittion, cooling rate and holding temperature on the modification and purification of iron-rich compounds in AlSi10MnMg(Fe) alloy

“…According to this work, the most common phases in Al–Fe–Si systems are ternary α-AlFeSi (α-Fe) and β-AlFeSi (β-Fe) phases [ 13 ]. Among these, the β-Fe phase is considered the most harmful phase to the mechanical properties of the alloy due to its brittleness and morphology [ 18 , [20] , [21] , [22] , [23] ]. This phase presents a needle-like morphology when observed in a two-dimensional micrography, even though the β-Fe phase has a platelet-like morphology in three dimensions [ 15 ].…”