DÖKÜM Al-10Mg2Si İN-SİTÜ KOMPOZİTLERİN KOROZYON DİRENCİNE KATILAŞMA HIZININ ETKİSİ

Al-6.3Mg-3.7Si (ağ.%) alaşımı olarak da adlandırılan hipoötektik Al-10Mg2Si (ağ.%) kompozitleri, farklı katılaşma oranlarının elde edildiği bir kademeli çelik kalıba dökülmüştür. Mikroyapısal karakterizasyonlar optik mikroskop ve XRD ile yapılmıştır. Korozyon performansları %3.5 NaCl çözeltisinde daldırma ve elektrokimyasal korozyon testleri ile ölçülmüştür. Mikroyapı analizleri, tüm alaşımlarda a-Al, Çin yazısı şekilli Mg2Si ve iğnemsi Al5FeSi fazlarının oluştuğunu göstermiştir. Katılaşma hızındaki artış, Çin yazısı şekilli ötektik Mg2Si fazlarının önemli derece küçülmesine neden olmuştur. Korozyon testleri sonucunda artan katılaşma hızının Al-10Mg2Si kompozitlerinin korozyon direncini arttırdığı görülmüştür ve bu da Mg2Si fazlarının daha düzgün dağılımı ve numune yüzeyindeki koruyucu oksit filmlerinin daha kararlı hale gelmesi ile meydana gelmiştir.

Anahtar Kelimeler:

Alüminyum alaşımları, katılaşma, döküm, mikroyapı, korozyon

EFFECT OF SOLIDIFICATION RATE ON CORROSION RESISTANCE OF CAST Al-10Mg2Si IN-SITU COMPOSITES

The hypoeutectic Al-10Mg2Si (wt%) composites, also denoted as Al-6.3Mg-3.7Si (wt%) alloy, were cast in a steel step mould, in which different solidification rates were obtained. The microstructural characterizations were made by optical microscope and XRD. Corrosion performances were measured by immersion and electrochemical corrosion tests in 3.5% NaCl solution. Microstructure analysis showed that all the alloys consisted of a-Al, Chinese script type Mg2Si and needle-like Al5FeSi phases. Increasing solidification rate resulted in a remarkable refinement of Chinese script-like eutectic Mg2Si phases. Corrosion tests revealed that increasing solidification rate improved the corrosion resistance of Al-10Mg2Si composites due to the more uniform distribution of Mg2Si phases and the stabilization of protective oxide films on the sample surface.

Keywords:

Aluminum alloys, solidification, casting, microstructure, corrosion,

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