Compositional design and synergistic deformation mechanisms of a lightweight Ti-Al-V-Cr-Zr-Mo medium-entropy alloy

Abstract

A new non-equiatomic Ti-based medium-entropy alloy with the composition of Ti₆₈Al₁₀V₁₀Cr₆Zr₄Mo₂ was developed based on thermodynamic calculations and the electronic structure-guided B_o−M_d approach. This alloy exhibits a yield strength of ∼826.3 MPa in the as-cast state, which increases to ∼1370 MPa after thermomechanical processing, while retaining substantial ductility. The high alloying content not only induces significant solid solution strengthening, but also leads to the formation of short-range order (SRO). The atomic resolution image and correlated chemical mapping revealed the presence of B2-type SRO with preferential elemental pairs between small atoms (Cr, V, and Mo) and large atoms (Ti, Al, and Zr). This SRO promotes planar dislocation slip during early deformation, enabling Taylor lattice formation that enhances strain hardening and delays necking. In the later stages of plastic deformation, kink bands emerge and further improve the alloy’s ductility. Thus, rather than merely applying the medium-entropy alloy concept, this work leverages multi-level deformation mechanisms activated by high alloying to achieve superior mechanical properties. This work provides new insights into SRO-driven deformation mechanisms in Ti-based MEAs and offers a viable pathway for designing next-generation lightweight structural materials.