Production of Ti–W Alloys from Mixed Oxide Precursors via the FFC Cambridge Process

Abstract

Ti-10 wt % W alloys were produced via the electrochemical deoxidation of mixed TiO2 +W O3 sintered precursors in a molten Ca Cl2 electrolyte at 1173 K. Fully metallic samples were retrieved after 15 h of reduction. This reduction time was longer than that observed for metallization of (Ti,Mo)O2 sintered precursors. This was believed to occur as a result of significant differences in the reduction pathway, despite tungsten and molybdenum possessing similar interactions with titanium. It was found that the reduction initiated with the rapid reduction of W O3 to a fine W-Ti particulate. TiO2 then proceeded to reduce sequentially through the lower oxides, with concurrent formation of Ca (Ti,W) O3. Between 1 and 3 h of reduction the sample is believed to be composed of Ca (Ti,W) O3 and TiO. A comproportionation reaction between these two phases is then observed, resulting in the formation of W-Ti and Ca Ti2 O4. However homogenization between the product titanium and W-Ti does not take place until the titanium is sufficiently deoxidized; thus, Β-Ti forms late in the reduction process. It is believed that the late formation of Β-Ti in the reduction process, coupled with the lack of a conductive metal oxide network, accounts for the relatively slow reduction time. © 2008 The Electrochemical Society.