Alloy design and microstructure of AlxMoV medium-entropy alloys

Incorporating light elements into refractory high-entropy alloys (RHEAs) has been extensively studied to reduce density while maintaining strength. The equiatomic MoV alloy, composed of common RHEA constituents, is promising for forming an isomorphous solid solution and avoiding brittle intermetallic compounds. This study investigates the effects of Al on the equiatomic MoV alloy by fabricating and analyzing MoV, Al₁₅MoV, Al₃₃MoV, and Al₅₀MoV alloys. The crystal structures of MoV, Al₁₅MoV, and Al₃₃MoV were body-centered cubic, while secondary phases were observed in Al₅₀MoV. The Al₁₅MoV and Al₃₃MoV alloys demonstrated higher yield strengths than MoV, despite the addition of soft Al. Notably, the Al₁₅MoV alloy exhibited the best combination of strength and ductility among designed alloys, with a compressive strength of ~1273 MPa and a ductility of ~13%. The primary strengthening mechanism was solid solution strengthening, induced by the significant shear modulus misfit of Al atoms with Mo and V. These novel Al-Mo-V medium-entropy alloys represent a significant advancement in developing lighter RHEAs without compromising mechanical properties, offering a new direction for future RHEA design.