Design of refractory multi-principal-element alloys for high-temperature applications

Refractory multi-principal-element alloys (RMPEAs) exhibit high specific strength at elevated temperatures (T). However, current RMPEAs lack a balance of room-temperature (RT) ductility, high-T strength, and high-T creep resistance. Using density-functional theory methods, we scanned composition space using four criteria: (1) formation energies for operational stability: -150≤ E_f − 150 ≤ E f ≤ +70 meV per atom; (2) higher strength found via interstitial electron density with Young’s moduli E > 250 GPa; (3) inverse Pugh ratio for ductility: G/B < 0.57; and (4) high melting points: Tm > 2500 °C. Using rapid bulk alloy synthesis and characterization, we validated theory and down-selected promising alloy compositions and discovered Mo72.3W12.8Ta10.0Ti2.5Zr2.5 having well-balanced RT and high-T mechanical properties. This alloy has comparable high-T compressive strength to well-known MoNbTaW but is more ductile and more creep resistant. It is also superior to a commercial Mo-based refractory alloy and a nickel-based superalloy (Haynes-282) with improved high-T tensile strength and creep resistance.