CoB Ön Alaşımlarının Alüminotermik Redüksiyon Yöntemiyle Üretilmesi ve Termokimyasal Modellenmesi

Öz

Bu çalışmada CoB ön alaşımlarının metalotermik (alüminotermik) redüksiyon yöntemi ile üretim parametrelerinin belirlenmesi üzerine çalışılmıştır. Çalışmada redüktan olarak aluminyum kullanılmış ve redüktan stokiyometrisindeki değişimin ürünler üzerindeki etkisi incelenmiştir. Redüksiyon sistemi FactSage 7.1 programıyla termokimyasal olarak modellenmiş, deneysel sonuçlar ile tutarlı bulgulara ulaşılmıştır. Deneysel çalışmalar sonunda elde edilen ürünler, X-ışınları difraksiyon spektrometrisi (XRD), optik mikroskobi, taramalı elektron mikroskobisi (SEM-EDS) ve mikro-vickers sertlik ölçüm yöntemleri ile karakterize edilmiştir. Karakterizasyon sonuçları incelendiğinde metal oluşum miktarının artan aluminyum stokiyometrisi ile yükseldiği gözlenirken, hedef alaşıma en yakın kompozisyonun Al stokiyometrisinin en düşük olduğu %100’lük oranda elde edildiği görülmüştür. Ürünlerin sertlik değişimi incelendiğinde, hedef alaşıma en yakın kompozisyonda olan %100 stokiyometrik aluminyum içeren deneyde 950 HV1’lik değer ile en yüksek sertliğe ulaşıldığı belirlenmiş, yapıya giren Co-Al fazının alaşımın sertlik değerini olumsuz etkilediği görülmüştür. Optik mikroskop incelemeleri sonucunda açık ve koyu renkten oluşan iki faz görülmüş, koyu renkli fazın Co-Al bileşiminden oluşan yapı olduğu sonucuna varılmıştır. Artan Al miktarıyla koyu renkli bu fazın miktarının da arttığı görülmüş, gerek kompozisyondaki farklılıkların, gerekse sertlikteki düşüşlerin bu sebeple oluştuğu düşünülmektedir. Termokimyasal incelemeler ve deneysel çalışmalar sonucunda bu alaşımın alüminotermik redüksiyon ile üretilebileceği ve yapılabilecek ilaveler ile istenilen kompozisyonda alaşım üretiminin mümkün olabileceği sonucuna varılmıştır. Gerçekleştirilen literatür taramasında CoB alaşımlarının alüminotermik olarak üretimine ilişkin çalışma bulunmamış ve bu çalışmanın ilgili ön alaşımın metalotermik üretimi üzerine gelecek çalışmalara yön gösterici olacağı kanaati oluşmuştur.

Anahtar Kelimeler

• CoB,Metalotermik redüksiyon,Pirometalurji

Production and Thermochemical Modelling of CoB Pre-Alloys through Aluminothermic Reduction Method

Öz

In the present study, experiments were carried out to determine the production parameters of CoB pre-alloys through metallothermic (aluminothermic) reduction method. The aluminium was used as reductant in this study and, effects of Al stoichiometry on product properties were investigated. Reduction system was modelled by using FactSage 7.1 thermochemical simulation program and, results were consistent with experimental results. Experimental products were characterized by means of X-rays diffraction spectrometry (XRD), optical microscopy, scanning electron microscopy (SEM-EDS) and micro-vickers hardness testing methods. When characterization results were investigated, it was understood that the amount of reduced metal increased with the increase in aluminium stoichiometry whilst the closest composition to the target alloy was obtained in the experiment with the lowest Al stoichiometry as 100%. In hardness results, the highest value was measured as 950 HV1 for the sample produced with 100% Al stoichiometry. On the other hand, the increase in Al stoichiometry caused the increase in CoAl formation in microstructures and, therefore hardness values decreased. In optical microscopy micrographs, two phases, dark and bright, were observed in microstructures and, it was anticipated that dark phases were CoAl. The ratio of dark CoAl phase increased with the increase in aluminium stoichiometry and, it was predicted that it was the reason of either composition change and fall in hardness values. As a result of thermochemical investigations and experiments, it was thought that the alloy can be produced by using aluminothermic reduction method and, it is possible to produce almost pure samples with some basic modifications. There are no accounts in the literature on the aluminothermic reduction of CoB pre-alloys and, it was predicted that the present study will help further studies in this area.

Anahtar Kelimeler

• CoB,Metallothermic Reduction

Kaynakça

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