Influence of Intermetallic Phase’s on the Fracture Surfaces in Secondary Aluminium Cast Alloy

Abstract

The contribution describes changes of the character of fracture surfaces depending on the morphology of intermetallic phases in secondary aluminium cast alloy. Morphology changes of intermetallic phases in recycled (secondary) aluminium cast alloy were depended on agehardening. For study was used age-hardening. The age hardening consist of solution treatment at temperature 515°C with holding time 4 hours, water quenching at 40°C and artificial aging by different temperature 130°C, 170°C and 210°C with different holding time 2, 4, 8, 16 and 32 hours. Recycled (secondary) aluminium cast alloys containing more of additional elements that form various intermetallic phases in microstructure. It is therefore necessary to study structure of recycled aluminium alloy and influence of intermetallic phases. Intermetallic phases were observed by using of combination different analytical techniques (scanning electron microscopy -SEM upon black-white etching, deep etching and energy dispersive X-ray analysis -EDX) in microstructure. Heat treatment led to gradual disintegration, shortening and thinning of Fe-rich intermetallic phases, the dissolution of precipitates and the precipitation of finer hardening phase (Al 2 Cu). The changes of the morphology of intermetallic phases led to changes of fracture surface in recycled (secondary) aluminium cast alloy.Keywords: microscopy and microanalysis techniques, aluminium alloys, microstructure, Scanning Electron Microscopy (SEM), fracture surface IntroductionAluminium alloys are use in applications in the industries of aerospace, automotive and even commercial products. In particular, the automotive industry demands both low weight and low cost materials in order to reduce fuel emissions and improve fuel economy at affordable prices [1]. The need for aluminium alloys having a good toughness, high strength, adequate damage tolerance capability, good fatigue resistance and good corrosion resistance for use in industries led to study of the properties and the structure these materials [2]. Today an increasing amount of the aluminium going into producing new aluminium alloy products is coming from recycled products. The increase in recycled metal becoming available is a positive trend, as secondary metal produced from recycled metal requires only about 2.8 kWh/kg of metal produced while primary aluminium production requires about 45 kWh/kg of metal produced. It is to the aluminium industry's advantage to maximize the amount of recycled metal, for both the energy-

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