Achieving excellent strength-ductility synergy of Ti6Al4V alloy produced by powder metallurgy and thermo-mechanical treatment

This study aimed to enhance the mechanical properties of Ti6Al4V alloy through powder metallurgy and thermo-mechanical treatment (TMT). By engineering a fine primary α phase (α_p) and heterogeneous martensite (α′) microstructure, comprising fine martensite laths (FMLs) and coarse martensite laths (CMLs), we achieved an exceptional combination of strength σ_b∼1148.15 MPa and ductility ϵ_f∼24.32%. Detailed TEM analysis revealed variations in nanohardness between α_p and α′ regions, strain partitioning between the two constituents, and a strain gradient from the α_p/α′ interface to the grain interior of α_p and α’. This activated a large number of geometrically necessary dislocations (GNDs) near the interface, mostly with <c+a> components, contributing significantly to the alloy's extraordinary work-hardening abilities. Strengthening of Ti6Al4V alloy was mainly attributed to the formation of hierarchical nanotwins and solid solution of Al elements in α_p and α′, effectively impeding dislocation motion. These results open up possibilities for obtaining Ti6Al4V with high strength and ductility synergistically, with potential applicability to other materials.