Change in the Oxide Structure of Al-12Si Melts in the Presence of Sr

Abstract

Bifilm defects are the surface entrained double oxide films that are introduced into melts during turbulence and disturbance to the surface of the melt. These defects lead to porosity formation if they are not cleaned from the melt. Thus, the characterisation of the dross that is formed on the surface of the melt becomes a key parameter. In this work, Sr containing Al12Si alloy was used. For the modification process, 100, 200 and 300 ppm Sr was added to the alloy. The oxidation tests were carried out in liquid state at 700, 750 and 800 °C for holding durations of 12, 24, 36 and 48 hours. The structure was characterised by optical microscopy, Scanning Electron Microscopy, X-Ray Diffraction and X-ray photoelectron spectroscopy techniques. It was found that after 12 hours of holding, spinel oxides were formed on the surface mainly SrO.Al2O3 and MgO.Al2O3.

Keywords

• Strontium modification
• Al-12Si
• oxide films
• XPS

Al-12Si Alaşımlarında Yüzey Oksit Uapısının Sr Varlığında Değişimi

Abstract

Alüminyum alaşımlarının döküm proseslerinde yüzeyden sıvı metale karışan bifilm hataları en önemli hatalardan biri olarak değerlendirilirler. Bu yüzden, ergitme prosesleri sırasında yüzeyde oluşan oksit yapılarının karakterizasyonu çok önemlidir. Bu çalışmanın amacı Sr içeren Al12Si alaşımlarında farklı sıcaklık ve bekleme sürelerinde yüzeyde oluşan oksit yapısının karakterize edilmesidir. 100, 200 ve 300 ppm seviyelerinde Sr ilave edilen Al12Si alaşıma 700, 750 ve 800 oC’lerde 12, 24, 36 ve 48 saat boyunca bekleme sürelerinde oksit yapısındaki değişim incelenmiştir. Optik mikroskop, taramalı elektron mikroskobu, XRD ve XPS analizleri ile yüzeyde oluşan oksitler karakterize edilmiştir. 12 saat bekleme süreleri sonrasında yüzey oksit yapısının SrO.Al2O3 ve MgO.Al2O3 yapılarından oluşmaya başladığı tespit edilmiştir.

Keywords

• Sr modifikasyonu
• Al12Si alaşımı
• oksit oluşumu
• XPS

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