Compositionally gradient Ti-Ta metal-metal composite with ultra-high strength

Conventional lamellar-structured metallic composites usually have discontinuous interfaces with limited diffusion in between two metals. Here, for the first time, we fabricated a bulk Ti-Ta metal-metal composite containing Ti-enriched, Ta-enriched and obvious interfacial diffusional zones by using powder metallurgy technique. After hot swaging, all the three zones are lamellar-like along the radial direction. The metal-metal composite possesses ultra-high strength (σUTS = 1570 MPa) and low elastic modulus. It was found that the high strength was mainly caused by precipitation strengthening of fine α phase inside the Ti-enriched zones and fine grain-size in the Ta-enriched zones. Furthermore, the stress-induced martensitic transformation inside the diffusional zone can further strengthen the interface. The bonding force of the lattice structure was reduced by the solution of Ta element, and thus, leading to the low modulus. This exceptional microstructure provides a novel approach to obtain ultra-high strength and low modulus Ti-based biomaterials.