Direct Production of Ti-29Nb-13Ta-4.6Zr Biomedical Alloy from Oxide Mixture in Molten CaCl2

概要

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A process based on the principle of the Ono-Suzuki process involving electrolysis and the calciothermic coreduction of an oxide mixture consisting of TiO2, Nb2O5, Ta2O5, and ZrO2 for producing Ti-29Nb-23Ta-4.6Zr (TNTZ) was proposed. Ca was produced by the electrolysis of CaO in molten CaCl2 by applying a voltage of 3.2 V between a carbon anode and Ti cathode at 1173 K. The residual oxygen concentration in the obtained powder decreased monotonically with an increase in the supplied electric charge. An oxygen concentration of 0.19 mass % was attained by supplying the electrical charge around 3 times larger than that necessary to generate the stoichiometrically required amount of Ca. This sample consisted of a Ti-based body-centered cubic solid solution and a small amount of hexagonal close-packed (hcp) solid solution. The inhomogeneity in the composition was suppressed to a relatively low level so that it could be easily improved by heat-treatment. After sintering at 1300 K for 54 ks, for example, the Ti- and Zr-rich hcp phase disappeared and the composition achieved the targeted value. The results of this study indicate that the OS process can be applied to directly produce TNTZ alloy from an oxide mixture.
2010-06-03