Microstructure and mechanical properties of a high-oxygen core-shell network structured Ti6Al4V alloy

Fully dense core-shell (CS) structured Ti-6Al-4V (Ti64) compact was synthesized by spark plasma sintering (SPS) from oxidized Ti64 powder. Microstructure characterization and compositional analyses show that the shell is with near single α phase and the core is composed of α lamellae packed by β phase with a continuous β phase in between. Phase transformation from (α+β) phase to a near single α phase in shell is attributed to oxygen penetration, thereby forming such a novel CS structure. The CS Ti64 compact exhibits a yield strength of about 1260 MPa and a fracture elongation of 13%. Such excellent mechanical properties are attributed to solid strengthening of oxygen and the unique core-shell structure. The mechanical properties can be further enhanced by manipulating the microstructure in core and shell via heat treatment.