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Synthesis and characterization of Ti-based bulk amorphous/naocrystalline alloys for engineering applications

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2004
Abdelal, Ali
Amorphous and bulk amorphous metallic alloys are an intriguing class of structural materials and possess a range of interesting properties, including near theoretical strength, high hardness, extremely low damping characteristics, excellent wear properties, high corrosion resistance, low shrinkage during cooling and almost perfect as-cast surfaces with good potential for forming and shaping. In this study, new Ti-based bulk amorphous alloys are tried to be modeled and synthesized. For that purpose, electronic theory of alloys in the pseudo potential approximation was used as a tool for understanding the theory lying beneath the bulk glass forming ability (BGFA). The results from this approach were evaluated both separately and together with the other theories supposed by our colleagues. Glass forming parameters of ordering energy, ?HM, viscosity, mismatch entropy, Rc was calculated for various Ti-based binary and ternary and the change in these parameters in both cases was evaluated. The results of the theoretical calculations of glass forming parameters has shown good relation with the literature data that the predicted alloying elements, i.e. Mo, Hf, Zr, B, Fe, Sn, and Be, to increase GFA for Ti2Ni binary system were generally used in the production of Ti-based bulk amorphous alloys. In the second part of this thesis, new Ti-based compositions with high GFA were tried to be synthesized with light of these results and encouraging conclusions were drawn. The production of these alloys were made with centrifugal casting method which is relatively a new technique for producing such alloys and the characterization of these alloys were made with metallographic, X-ray and thermal means.