Phase Stability and Alloy Performance—The Role of CALPHAD and VASP in Fusion Power Material Development

Fusion power plants are a top candidate for clean, renewable energy. However, the nature of the fusion process still holds many challenges including those pertaining to the materials being used for the power plants. Materials that can be used for fusion power plants are constantly in development. The materials need to be able to withstand the extreme heat present during the fusion process as well as the radiation damage that occurs as most tend to become too brittle or degrade quickly. Vanadium-chromium-titanium (V-Cr-Ti) alloys in particular have proven to be promising candidates due to the properties they exhibit. This study builds upon the framework established by Samuel McAlpine in his work on predicting single-phase stability and segregation in alloys, confirming the robustness of simulation-based approaches for material property prediction [1]. This research investigates whether the Computation of Phase Diagrams (CALPHAD) and Vienna ab-initio Simulation Package (VASP) can accurately predict phase stability and thermomechanical properties for V-Cr-Ti alloys. The focus will be on alloys containing 85 at% vanadium (V85%), 92 at% V (V92%), and other highly concentrated alloys in the V-Cr-Ti space. These compositions serve as a validation step for our phase stability predictions prior to tackling V-Cr-Ti-W-Zr alloys in the future. Once our predictions are established we will move on to the V-Cr-Ti-W-Zr system as high alloyed vanadium alloys are likely to suffer from phase instability due to prevalence of Laves Phases between each element in our system [2]. Key findings include the identification of single-phase stability regions critical for ensuring the material's performance in fusion environments. These results validate the effectiveness of integrating CALPHAD and VASP simulations for the predictive modeling of alloy properties. For the broader scientific community, including the aerospace, energy, and nuclear communities, this research has direct implications on the design of concentrated alloys in the BCC refractory space. These findings provide a pathway for the systematic design and optimization of advanced materials, which supports the realization of efficient and durable fusion reactors. The integration of CALPHAD and VASP simulations proves to be a powerful tool in predicting phase stability and thermomechanical properties of V-Cr-Ti alloys, specifically V85% and V92%.<br/><br/>[1] McAlpine, Samuel W., Julie V. Logan, and Michael P. Short. 2021. “Predicting Single Phase Stability and Segregation in the NbMoTaTi–(W,V) High Entropy Alloy System with the Vacancy Exchange Potential.” <i>Scripta Materialia </i>191 (January):29–33. https://doi.org/10.1016/j.scriptamat.2020.08.043.<br/>[2] King, D. J. M., A. J. Knowles, D. Bowden, M. R. Wenman, S. Capp, M. Gorley, J. Shimwell, L. Packer, M. R. Gilbert, and A. Harte. 2022. “High Temperature Zirconium Alloys for Fusion Energy.” <i>Journal of Nuclear Materials</i> 559 (February):153431. https://doi.org/10.1016/j.jnucmat.2021.153431.