Lightweight Multiprincipal Element Alloys with Excellent Mechanical Properties at Room and Cryogenic Temperatures

Lightweight multiprincipal element alloys (MPEAs) are promising candidates for potential application as engineering materials due to their high strength and low density. In this work, lightweight Ti₇₀Al₁₅V₁₅ and Ti₈₀Al₁₀V₁₀ MPEAs were fabricated via vacuum arc melting. The phases of the Ti₇₀Al₁₅V₁₅ alloys consisted of a BCC phase and a small amount of B2 phase while the Ti₈₀Al₁₀V₁₀ alloys displayed a dual-phase structure with BCC and HCP phases. The different phase compositions led to differences in their mechanical properties. When the temperature changed from 298 K to 77 K, the strength of the alloys further increased and maintained a certain plasticity. This is attributed to the increasing lattice friction stress at cryogenic temperature. TEM observation demonstrated that dislocation played a crucial role in plastic deformation for both the Ti₇₀Al₁₅V₁₅ and Ti₈₀Al₁₀V₁₀ alloys. In addition, Ti₈₀Al₁₀V₁₀ exhibited significant work-hardening capabilities. By analyzing the strengthening mechanism of the alloys, the theoretical yield strength was calculated, and the results agreed with the experimental values. The present results provide new insight into developing lightweight MPEAs containing Ti and Al.