Computational design of ductility and phase stability in W-Ti-V-Cr refractory multiprincipal element alloys for fusion applications.

Refractory multiprincipal element alloys (rMPEAs) are potential materials for the plasma-facing components in future fusion reactors due to their high melting point, strength and irradiation resistance. However, the concurrent optimization of ductility and high-temperature properties remains a significant challenge due to the complex interdependence between alloy chemistry, mechanical behavior, and thermodynamic stability. In this work, we develop models for fast and accurate exploration of compositional space of bcc rMPEAs in W-Ti-V-Cr system, and evaluate three critical design properties: melting (solidus) temperature, [Formula: see text], [Formula: see text]transus temperature, [Formula: see text], and ductility (quantified by peak true strain, [Formula: see text]). Thermal properties, [Formula: see text] and [Formula: see text], are initially computed on a coarse compositional grid using CALPHAD approach, and interpolated using machine learning models. For ductility prediction, we adopt the framework established by Borges et al. [Sci. Adv. 10 (2024) eadp7670], where bonding state depletion, a descriptor derived from the electronic density of states, is shown to correlate with [Formula: see text] in bcc high-entropy alloys. In our system, we discover a strong linear correlation between bonding state depletion and valence electron concentration across the compositional space, enabling an efficient mapping of ductility directly from composition. This approach allows for rapid screening of alloys that simultaneously optimizes [Formula: see text], [Formula: see text], and [Formula: see text], providing a computationally accelerated pathway for the design of ductile, high-temperature alloys for extreme environments. We find that the intersecting region lies within a narrow compositional window that balances opposing thermodynamic and mechanical trends. While W and Cr increase the solidus temperature, they decrease the ductility. Cr poses an additional challenge of increasing [Formula: see text]. On the other hand, Ti increases ductility and [Formula: see text]. Finally, we find that at a constant W. at.%, sufficient Ti and V are needed to lower [Formula: see text] and enhance ductility, but still retain enough Cr to maintain high melting temperatures. The compositional space of interest is near the V-rich region for 35 at.% W and gradually moves towards Ti-rich region as W content is increased to 60 at.%.