Investigation of the Effect of Various Ca Content on Microstructure and Mechanical Properties of As-cast ZK60 Magnesium Alloys

Öz

The effect of various Ca content on microstructure and mechanical properties of as-cast Mg-6Zn-0.5Zr (wt.%) Mg alloys with hot tensile testing at 345°C were investigated. The alloy was produced with the LPDC method [1]. Microstructural characterization as-cast alloy demonstrated that wt.% Ca content increase, grain size decreases till wt.% 0.8Ca, the further increase affects gradual change in grain size to ~60 µm at 345°C. Therefore, increase in Ca ratio from 0.4 wt% forming to strip-like Mg-Zn intermetallics at grain boundaries, Ca-Mg-Zn ternary phase at grain boundary corners. Dramatical decrease in yield and tensile strength at wt% 1.6Ca addition is 37.6 MPa and 39.7 MPa respectively which is relatively low at 345°C due to the absence of retarded DRX’ed small particles prohibited the grain growth after the TMT process. Conversely, elongation-to-fracture increases were observed as 1.26 at 345°C showing the temperature-dependent texture softening results in improvement of mechanical properties. Wear rate is also affected from wt.% Ca addition so the gradual increase up to 1.2 wt% Ca is 3.70 x 10-3 mm3/m. Similarly, a gradual increase in hardness values was obtained with Ca addition in ZK60 alloy. In this study, the effect of temperature-dependent Ca addition (wt %) on gradual enhancement in mechanical properties was observed at as-cast magnesium alloys.

Anahtar Kelimeler

• ZK60 Alloy
• Ca addition
• Microstructure
• Hot Tensile Testing
• Mechanical Properties

Proje Numarası

2018/047

Farklı Oranlarda Ca Katkısının Döküm ZK60 Mg Alaşımlarının Mikroyapı ve Mekanik Özellikler Üzerindeki Etkisinin İncelenmesi

Öz

Ağırlıkça farklı Ca (%) oranlarında katılarak elde edilen olarak bilinen döküm Mg-6Zn-0.5Zr (ağ. %) ZK60 Mg alaşımının 345°C’de sıcak çekme testleriyle mikroyapı ve mekanik özellikleri incelenmiştir. Deneysel bu çalışmada, alaşım düşük basınçlı kokil döküm (LPDC) yöntemiyle üretilmiştir. Döküm alaşımının mikroyapı karakterizasyonunda ağ.% 0.8Ca oranına kadar tane boyutu küçülmüş, Ca oranı yavaş yavaş arttırıldıkça tane boyutu da 345°C sıcaklıkta yaklaşık ~60 µm boyutuna ulaştığı gözlemlenmiştir. Sonuç olarak, ağ.% 0.4Ca oranına bağlı olarak tane sınırlarında şerit benzeri Mg-Zn intermetalik yapıyı tane köşelerinde ise kabalaşmış üçlü Ca-Mg-Zn intermetalik yapısını oluştururlar. ağ.% 1.6Ca ilavesinde akma ve çekme mukavemetleri mukayese edilebilecek şekilde 345°C sıcaklıkta sırasıyla 37.6 Mpa ve 39.7 MPa değerlerine düştüğü görülmüştür. Kopma uzaması ise, bunların tam tersine sıcaklığa bağlı tekstür yumuşaması neticesi mekanik özelliklerdeki artışına bağlı olarak, ağ.% 1.6Ca oranında 1.26 % olarak ölçülmüştür. Aşınma oranı ağ.% Ca oranından etkilenmiştir ağ.% 1.2Ca oranında aşınma hızı 3.70 x10-3 mm3/m olarak ölçülmüştür. Benzer şekilde ZK60 Magnezyum alaşımı sertlik değerlerinde de Ca içeriğine bağlı artışlar grafiklerde gösterilmiştir. Bu çalışmada döküm ZK60 magnezyum alaşımlarına % ağ. Ca katkısıyla sıcaklığa bağlı etkisinin mekanik özellikleri geliştirdiği gözlemlenmiştir.

Anahtar Kelimeler

• ZK60 Alaşımı
• Ca ilavesi
• Mikroyapı
• Sıcak Çekme Testi
• Mekanik Özellikler

Destekleyen Kurum

Kocaeli Üniversitesi Bilimsel Araştırma Projeleri (BAP) Koordinasyon Birimi

Proje Numarası

2018/047

Teşekkür

Yazarlar Kocaeli Üniversitesi Bilimsel Araştırma Projeleri (BAP) Koordinasyon Birimi'ne bu projeye sağlamış oldukları finansal hakkı nedeniyle teşekkürlerini sunar.

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