TiNb-esaslı ?-Ti Alaşımlarının Kristal Yapı, Mikroyapı ve Dönüşüm Sıcaklıklarına Tantal Katkısının Etkileri

β-tipi Ti-esaslı alaşımlar yüksek sıcaklıktaki dayanıklılığı ve biyo-uyumluluğu sayesinde uzay teknolojisi ve medikal alanlarda kullanımı yaygın olan materyallerdir. Nb ve Ta gibi düşük yoğunluklu, üstün korozyon direnci ve toksik olmayan özelliklere sahip elementler ile takviye edilmesi, β-tipi Ti-esaslı alaşımları daha da çekici hale getirmiştir. Hazırlanan TiNb(24,5-x)Ta(x=0,1,2,3,4) (at. %) alaşımlarının kristalografik özellikleri, mikroyapısı ve dönüşüm sıcaklıkları incelendi. DSC analizlerinden 5,5 oC ile 41,1 oC aralığında sadece ? → ? ters dönüşümü gözlenmiştir. Oda sıcaklığında yapılan XRD analizleri ile DSC sonuçlarının uyumlu olduğu görülmüştür. Baskın ? fazlarına karşın ? fazlarının küçük miktarlar da olduğu tespit edilmiştir. ? fazının baskın olması Ta ve Nb elementlerinin fazını kararlı hale getirdiği göstermiştir. Optik mikroskop görüntülerinden, Ta ilavesi ile tane yapıları içerisindeki ? fazının ve bu fazın tane sınırlarının belirginleştiği görülmüştür. ? fazının, SEM-EDX görüntülerinden alınan sonuçlara göre çökelti fazı olduğu görülmüştür. Ayrıca EDX sonuçları ile Ta element konsatrasyonunun tane sınırlarında arttığı bulunmuştur. Alaşımların değerlik elektron sayısı (??⁄?) ve ortalama değerlik elektron konsantrasyonu oranları (??) [(??⁄?

The Effects of Tantalum Additive on the Crystal Structure, Microstructure and Transformation Temperatures of TiNb-based β-Ti Alloys

β-type Ti-based alloys are materials which widely used in the aerospace technology and medical fields because it has a sufficient biocompatibility and high temperature resistance. Reinforcement with low-density, high corrosion resistance and non-toxic elements, such as Nb and Ta alloying with β-type of Ti-based alloys even more attractive. The crystallographic properties, microstructure and transformation temperatures of TiNb (24,5-x) Ta (x = 0,1,2,3,4) (at.%) alloys were investigated. The DSC analysis showed only ? → ? reverse transformation for the temperature range of 5,5 oC to 41,1 oC. DSC results were found to be compatible with X-ray analysis taken at room temperature. It was found that ? phases were in small amounts despite dominant ? phases. The dominance of the ? phase has shown that the Ta and Nb elements are good stabilizer. It was observed from optical microscope images that the phase within the grain structures and the grain boundaries of this phase became clear with the addition of Ta. According to the results obtained from SEM-EDX images, the ? phase was found to be the precipitate phase. Additionally, the EDX results showed that Ta elements concentration increased in the grain boundaries. The number of valance electrons (??⁄?) and average concentration of valance electron (??) values (??⁄?

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