The influence of the Nb:Ta ratio on the microstructural evolution in refractory metal superalloy systems

Abstract

Refractory metal superalloys have the potential to facilitate a significant increase in gas turbine operating temperatures that would enhance efficiency and reduce emissions. However, fulfilling this potential requires a much more detailed understanding of the underlying metallurgy and how it is influenced by alloying additions. Here, the influence of systematically varying the Nb:Ta ratio in a series of Ti-Zr-Nb-Ta alloys has been studied and compared to thermodynamic predictions. The experimental results show that higher Nb:Ta ratios suppress phase separation but lower the inter-phase misfit. As such, optimizing these alloys for specific applications will require careful balancing of these effects.