Microstructure Evolution and Properties of Additive-Manufactured Ti-6Al-4 V Alloys via Three-Stage Heat Treatment

A novel three-stage heat treatment method was applied to study the microstructural evolution and properties of additive-manufactured Ti-6Al-4 V alloys. An ultrafine α phase was obtained via the αʹ →α + β hase transformation after the three-stage heat treatment. The distribution of low-angle grain boundaries near the secondary phase was highly uniform. After the three-stage heat treatment, the density of geometrically necessary dislocation increased, while the maximum texture intensities of the α phase decreased. The nanoindentation load–displacement curve analysis revealed that the load value increased from 511.3 to 579.0 mN after the three-stage heat treatment. Tensile tests revealed that the three-stage heat treatment sample has the highest stain of 11.86%. All the samples fracture mode was ductile fracture. Additionally, an increase in the secondary α phase content could improve the corrosion performance.