Computational exploration and experimental validation of reduced- multi-principal element alloys with stable BCC phases and superior mechanical properties

Abstract

Structural materials for fusion reactors must possess exceptional mechanical strength to withstand extreme high-temperature and irradiation conditions. Multi-principal element alloys (MPEAs) have emerged as promising candidates due to their exceptional irradiation resistance and high-temperature mechanical properties. The reduced-activation type MPEAs (RAMPEAs) are particularly noted for mitigating the effects of radioactivation and contributing to the safe operation of fusion reactors and waste management. This study systematically explored the compositional regimes of ternary, quaternary, and quinary RAMPEAs composed of nine low-activation elements. Using a yield strength prediction model, we performed phase diagram calculations and employed the valence electron concentration as a ductility index, screening a total of 625,518 compositions. As a result, 83 promising chemical compositions were identified on the Pareto front based on three objective functions: yield strength at 1000 K, valence electron concentration, and phase stability. Among them, Ti₄₀V₂₀Cr₃₀W₁₀, Ti₄₀V₁₅Fe₁₀Zr₃₅, and Ti₄₀Fe₂₅Zr₃₅ were experimentally evaluated for their predicted superior balance of yield strength, ductility, and phase stability. The computational framework was validated through compression tests and microstructure analysis, achieving a yield strength of 1.39 GPa and a fracture elongation of 16.5 % for Ti₄₀V₂₀Cr₃₀W₁₀ at room temperature, surpassing most RAMPEAs reported in previous studies. This study provides valuable insights into the RAMPEA design and highlights promising chemical compositions for nuclear fusion reactor applications