Production of Ti-W alloys from mixed oxide precursors via the FFC Cambridge process

摘要

Ti-10 wt % W alloys were produced via the electrochemical deoxidation of mixed TiO2+WO3 sintered precursors in a molten CaCl2 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)O-2 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 WO3 to a fine W-Ti particulate. TiO2 then proceeded to reduce sequentially through the lower oxides, with concurrent formation of Ca(Ti,W)O-3. Between 1 and 3 h of reduction the sample is believed to be composed of Ca(Ti,W)O-3 and TiO. A comproportionation reaction between these two phases is then observed, resulting in the formation of W-Ti and CaTi2O4. However homogenization between the product titanium and W-Ti does not take place until the titanium is sufficiently deoxidized; thus, beta-Ti forms late in the reduction process. It is believed that the late formation of beta-Ti in the reduction process, coupled with the lack of a conductive metal oxide network, accounts for the relatively slow reduction time.