Biyoçözünür magnezyum alaşımlarının korozyona bağlı mekanik davranışlarının araştırılması
Küçük Resim Yok
Tarih
2013
Yazarlar
Dergi Başlığı
Dergi ISSN
Cilt Başlığı
Yayıncı
Karabük Üniversitesi
Erişim Hakkı
info:eu-repo/semantics/openAccess
Özet
Bu çalışmada, Al ve Zn (ağ. %0 - 3,0) içeren Magnezyum alaşımlarının yapay vücut sıvısı (SBF) ortamında korozyona bağlı mekanik davranışları araştırılmıştır. Mekanik test sonuçları; mikroyapı, sertlik ve çekme deneyleri ile, korozyon davranışları; daldırma deneyi (1 ve 7 gün) ve elektrokimyasal ölçümleri ile değerlendirilmiştir. Korozyon testleri 37oC'de ve pH=7 ortamında gerçekleştirilmiştir. Korozyon ilerlemesi Taramalı Elektron Mikroskop (SEM) kullanılarak numunelerin kesit görüntülerinden değerlendirilmiştir. Sonuçlar, mikroyapıda Zn ve Al miktarının her ikisinin artışı ile Mg'nin tane boyutunun inceldiğini göstermiştir. Matriste Al oranının %3,0 civarı ve Zn'nin %1,0 ve üzerinde beraber olduğu durumlarda Mg17Al12 (ß) fazının ortaya çıktığı gözlenmiştir. Her bir alaşım için hem Zn miktarının, hem de Al miktarının artışı ile birlikte sertlik, çekme ve akma dayanımlarında doğrusal olarak artış gözlenirken, % uzamalarda doğrusal azalma meydana gelmiştir. Polarizasyon deneyleri, Al içermeyen Mg-Zn alaşımlarında korozyon akım yoğunluğunun Zn oranının artışına bağlı olarak azaldığını göstermiştir. Mg-Al-Zn üçlü alaşımlarında ise Al oranının artışı ile (%3,0 Zn hariç) korozyon akım yoğunluğu azalmıştır. %3 Zn içeren alaşımlarda ise matriste %0,5 - 2,0 aralığında Al bulunması durumunda korozyon akım yoğunluğu kayda değer oranda artmıştır. En düşük korozyon akım yoğunluğu matriste %3,0 oranında Al ve Zn'nin beraber olduğu üçlü alaşımlarda elde edilmiştir. Daldırma deneyi sonrası kesit SEM analizleri; korozyonun yüzeyden iç kısımlara ilerlediğini, Al oranının artışının korozyon ilerlemesindeki rolünün Zn'ye nazaran çok daha etkili olduğunu göstermiştir. Daldırma deneyi sonrası mekanik dayanımlar, orijinal numunelere nazaran tüm alaşımlar için düşüş gösterirken, bu düşüş 7 günlük testlerde çok daha belirginleşmiştir. 1 günlük daldırma testlerinde korozyona uğramış numuneler kendi aralarında kıyaslandığında; %1'e kadar Al içeren (%1 dahil) alaşımların Zn miktarının artışıyla mekanik dayanımlarının arttığı, Al miktarının %1'den fazla olması durumunda ise Zn miktarının artışıyla dayanımların azalma eğilimine girdiği gözlenmiştir. 7 günlük daldırma sonrası dayanımlarda, 1 günlük dayanımların tersine, Zn miktarının artmasıyla oransal düşüş gözlenmiştir. Diğer taraftan, Al oranı arttıkça çekme dayanımında düşük Zn oranlarında artış gözlenirken, yüksek Al ve Zn oranlarında (%3 Al - %3 Zn) dayanımının tamamını kaybetmiş ve malzeme çekme testine girmeden kopmuştur.
In this study, corrosion dependant mechanical behaviours of Mg alloys, containing Al and Zn (0 - 3,0 wt.%), in simulated body fluid (SBF) were investigated. Mechanical behaviours were evaluated by taking into account of microstructure, hardness and tensile tests while corrosion behaviours were evaluated by immersion tests (1 and 7 days) and electrochemical measurements. Corrosion tests were carried out at 37oC and pH=7 environment. Investigation of corrosion progress through the cross section of the matrix was analysed by using scanning electron microscopy (SEM). Results showed that grains of the Mg matrix transformed into finer grains as both Al and Zn content were increased. It was observed that Mg17Al12 (ß) has been appeared as Al content was around 3,0 wt.% together with the content of Zn was above 1,0 wt.% in the matrix. Both increase in Zn and Al content of the each alloy investigated; hardness, tensile and yield strengths were increased proportionally while elongation was decreased proportionally. Polarisation tests showed that corrosion current density was decreased as Zn content is incresed in non-Al containing alloys. On the other hand, corrosion current density was also decreased as Al content is increased in Mg-Al-Zn ternary alloys (except 3,0 wt.% Zn) whereas in 3,0 wt.% Zn containing alloy, corrosion current density was increased considerably in 0,5 to 2,0 wt.% Al containing alloys. The lowest corrosion current density was obtained in 3,0 wt.% Al and Zn containing alloy. Cross sectional SEM analysis of the samples, after the immersion tests, showed that the corrosion has propagated from the surface to the inner part of the samples and the role of Al was more pronounced compared to Zn content. Mechanical strenghts of the samples were reduced after the immersion tests for all the samples, however; they were more apparent in 7 days immersion tests. Among the corroded samples, after 1 day immersion tests, mechanical properties were increased up to 1,0 wt.% Al content (including 1,0 wt.%) with increasing Zn content, however; the mechanical properties were tend to decrease with increasing Zn content in the alloys containing Al content above 1,0 wt.%. Unlike 1 day immersion tests, proportional reduction has been observed in the tensile properties as Zn content is increased in the matrix for 7 days immersion tests. On the other hand, increased tensile properties were observed as increased Al content of lower Zn containing alloys whereas complete rupture had been occurred in the highest Al and Zn containing alloys (i.e 3,0 wt.% Al and Zn).
In this study, corrosion dependant mechanical behaviours of Mg alloys, containing Al and Zn (0 - 3,0 wt.%), in simulated body fluid (SBF) were investigated. Mechanical behaviours were evaluated by taking into account of microstructure, hardness and tensile tests while corrosion behaviours were evaluated by immersion tests (1 and 7 days) and electrochemical measurements. Corrosion tests were carried out at 37oC and pH=7 environment. Investigation of corrosion progress through the cross section of the matrix was analysed by using scanning electron microscopy (SEM). Results showed that grains of the Mg matrix transformed into finer grains as both Al and Zn content were increased. It was observed that Mg17Al12 (ß) has been appeared as Al content was around 3,0 wt.% together with the content of Zn was above 1,0 wt.% in the matrix. Both increase in Zn and Al content of the each alloy investigated; hardness, tensile and yield strengths were increased proportionally while elongation was decreased proportionally. Polarisation tests showed that corrosion current density was decreased as Zn content is incresed in non-Al containing alloys. On the other hand, corrosion current density was also decreased as Al content is increased in Mg-Al-Zn ternary alloys (except 3,0 wt.% Zn) whereas in 3,0 wt.% Zn containing alloy, corrosion current density was increased considerably in 0,5 to 2,0 wt.% Al containing alloys. The lowest corrosion current density was obtained in 3,0 wt.% Al and Zn containing alloy. Cross sectional SEM analysis of the samples, after the immersion tests, showed that the corrosion has propagated from the surface to the inner part of the samples and the role of Al was more pronounced compared to Zn content. Mechanical strenghts of the samples were reduced after the immersion tests for all the samples, however; they were more apparent in 7 days immersion tests. Among the corroded samples, after 1 day immersion tests, mechanical properties were increased up to 1,0 wt.% Al content (including 1,0 wt.%) with increasing Zn content, however; the mechanical properties were tend to decrease with increasing Zn content in the alloys containing Al content above 1,0 wt.%. Unlike 1 day immersion tests, proportional reduction has been observed in the tensile properties as Zn content is increased in the matrix for 7 days immersion tests. On the other hand, increased tensile properties were observed as increased Al content of lower Zn containing alloys whereas complete rupture had been occurred in the highest Al and Zn containing alloys (i.e 3,0 wt.% Al and Zn).
Açıklama
Fen Bilimleri Enstitüsü, Metal Eğitimi Ana Bilim Dalı
Anahtar Kelimeler
Mühendislik Bilimleri, Engineering Sciences
