Achieving exceptional high-temperature strength and oxidation resistance in an additively manufactured refractory high-entropy alloy via strategic elemental substitutions

The AlMo _0.5NbTa _0.5TiZr alloy are promising for high-temperature applications due to the high specific strength at 1000°C, but poor oxidation resistance limits its further development. To solve this problem, a strategic element substitution strategy was proposed by replacing Mo with Ta here. The designed alloy, AlNbTaTiZr, was prepared by laser-directed energy deposition (L-DED) and the oxidation resistance and strength at 1000°C were measured. The results showed that AlNbTaTiZr alloy had an obviously higher oxidation resistance than AlMo _0.5NbTa _0.5TiZr alloy but same strength at at 1000°C. The oxide sacle thickness of AlNbTaTiZr was only 4.6 % of that of AlMo _0.5NbTa _0.5TiZr. The improvement of oxidation resistance was thanks to the replacement of MoO ₃ by Ta ₂O ₅, thus a more stable oxide layer was formed.