The preparation of hafnium-tantalum alloy by carbide-oxide reaction

Abstract

The direct preparation of Hf-Ta alloys (40-50% Ta) by reaction between HfC and Ta₂O₅ has been investigated. By progressive heat soaking of the pelletised charge up to 2000°C under a dynamic vacuum, followed by electron-beam melting, Hf-Ta alloys containing 0.29% carbon and 0.021% oxygen have been prepared. The influence of different process parameters, such as the initial oxygen: carbon ratio in the charge, temperature, and time of heat soak, on the final purity of the alloy, has been examined. The thermodynamics of the reaction are discussed. The overall material balance for the reaction indicates removal of oxygen both through carbothermic reduction (as CO) and through sacrificial deoxidation (as HfO). No tantalum loss was observed during the reaction.