Superior tensile ductility in an annealed Ti-rich high entropy alloy with unexpected high specific strength

Journal article, 2025

Ti alloys are known for their high specific strength (SS) at the expense of low tensile ductility (tensile elongation, TE) in the as-fabricated state. Metastable Ti alloy design using the high entropy approach and multi-step thermomechanical processing is found to overcome this TE limitation partially, but at the expense of cost and density. To address these issues, this work presents a lightweight (density (ρ) = 5.31 g/cc) Ti50V16Nb16Al15Mo3 (at%) high entropy alloy (L-HEA) with excellent total tensile ductility (TE = 37 %) while having a high SS of 217 N·m/kg with no thermo-mechanical processing. The excellent SS is attributed to annealing-induced grain refinement and the formation of heterophase (β1 and β2) domains in the microstructure. The remarkable TE results from the hetero-deformation tendency in these dual phases in the early stage of deformation, followed by activation of multiple slip systems in the β1 phase and planar slip limited to a single slip system in the β2 phase in later stages of deformation. Thus, this unique SS and TE combination makes L-HEA a potential candidate for further property evaluation related to future space and defence applications to achieve good fuel efficiency.