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 (αp) and heterogeneous martensite (α′) microstructure, comprising fine martensite laths (FMLs) and coarse martensite laths (CMLs), we achieved an exceptional combination of strength σb∼1148.15 MPa and ductility ϵf∼24.32%. Detailed TEM analysis revealed variations in nanohardness between αp and α′ regions, strain partitioning between the two constituents, and a strain gradient from the αp/α′ interface to the grain interior of αp and α'. This activated a large number of geometrically necessary dislocations (GNDs) near the interface, mostly with 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 αp 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.