Abstract
Abstract Iron exists as a common impurity element in AlSi foundry alloys. The main consequence of the presence or adding of iron to AlSi alloys is the formation Fe-rich intermetallics with especially deleterious β-Al5FeSi. This work aims to identify the role of fluid flow on the microstructure and intermetallics in Al-9 wt.% Si-0.2/0.5/1.0 wt.% Fe alloys directionally solidified under defined thermal and fluid flow conditions and extensively uses 3D x-ray tomography to get a better insight into their morphology and formation. The results have revealed the growth of larger and more dense β-Al5FeSi intermetallics in the specimen centre as an effect of forced flow. The reconstructions confirmed that the course of number density at the specimen cross section increases from the specimen edge to its centre.
Highlights
Aluminum alloys are characterized by good thermal and electrical conductivity, excellent corrosion resistance, sound castability and high specific strength
In particular areas in Fig. 2 one can observe a qualitative increase in number density and size of precipitated iron intermetallics along with the increase in the Fe content regarding the Al-9 wt.% Si-0.2 wt.% Fe and Al-9 wt.% Si-0.5/1.0 wt.% Fe alloys
For the Al-9 wt.% Si-0.5/1.0 wt.% Fe alloys intermetallics take the shape of platelets (Figs. 2 h, k and l)
Summary
Aluminum alloys are characterized by good thermal and electrical conductivity, excellent corrosion resistance, sound castability and high specific strength. They are replacing traditional materials in the areas of electrical conductors, construction, transportation, packaging, aerospace and machinery to achieve greater weight reduction. Hard and brittle β-Al5FeSi (labelled β-AlFeSi, β, platelets, needles, β precipitates) have detrimental influence on the alloy properties. These phases cause porosity [3], lower fluidity [4], act as stress concentrators [5] and promote crack initiation and lower fatigue life. These phases cause porosity [3], lower fluidity [4], act as stress concentrators [5] and promote crack initiation and lower fatigue life. β-Al5FeSi intermetallics increase hardness, reduce impact strength, machinability, but lower soldering of the casting in permanent molds and high pressure die casting
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