An Investigation of Relationship Between Corrosion Behaviour- Fe Tolerance Limit in AZ91 Mg Alloys

Abstract

In this study, relationship between Corrosion Behaviour-Tolerance Limit of Fe content (0.025, 0.05, 0.1 wt. %) in AZ91 Mg alloys, cast under similar chemical composition and cooling rate, were investigated. The microstructures of Mg alloys were analysed by Scanning Electron Microscopy (SEM) and X Ray Diffractometry (XRD). The corrosion behaviours were evaluated by immersion tests and electrochemical polarization measurements in 3.5 wt. % NaCl solution. Microstructure analysis revealed that the increase of Fe content increased the “partially divorced” or “lamella eutectic” type β phase morphologies in the microstructure. Results indicated that the limit content value of Fe in AZ91 alloys was ~0.05 wt. % above which the corrosion loss had increased abruptly.

Keywords

• AZ91 Mg alloys,Microstructure,Corrosion

AZ91 Mg ALAŞIMLARINDA KOROZYON DAVRANIŞI-Fe TOLERANS SINIRI ARASINDAKİ İLİŞKİNİN ARAŞTIRILMASI

Abstract

Bu çalışmada, aynı şartlarda üretilmiş (benzer katılaşma hızı ve benzer kimyasal bileşimde) farklı Fe içeriğine (% ağ. 0.025, 0.05, 0.1) sahip AZ91 Mg alaşımlarının korozyon davranışları-Fe tolerans limit değeri arasındaki ilişki değerlendirilmiştir. Numunelerin mikro yapı analizleri Taramalı Elektron Mikroskobu (SEM) ve X Işını Difraktometre (XRD) kullanılarak yapılmıştır. Korozyon davranışları %3,5 NaCl çözeltisinde, ağırlık kaybı ve potansiyodinamik polarizasyon test yöntemleri kullanılarak araştırılmıştır. Mikroyapı analizlerinde, Fe içeriğinin artması ile yapıdaki “kısmen ayrışmış” veya “lameller ötektik” tipi β fazı morfolojilerinde artış eğiliminin daha fazla olduğu gözlenmiştir. Sonuçlar, AZ91 alaşımı Fe tolerans limit değerinin ~%0.05 olduğunu bu değerden sonra korozyon kaybının eksponansiyel olarak arttığını göstermiştir.

Keywords

• AZ91 Mg alaşımı,Mikro yapı,Korozyon

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