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

Artikel i vetenskaplig tidskrift, 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.