Effects of Ta and Zr contents on microstructure, tensile properties and elastic modulus of Ti-Nb-Ta-Zr system alloys

Effect of Ta content on mechanical properties of Ti-30Nb-XTa-5Zr alloys and effect of Zr content on mechanical properties of Ti-30Nb-10Ta-XZr alloys were investigated. Ti-30Nb-10Ta-5Zr, which is the simplified compositional alloy of Ti-29Nb-13Ta-4.6Zr developed for biomedical applications, has been selected as the basic alloy composition. Tensile tests and elastic modulus measurements and microstructural observations were carried out on those alloys. Microstructures of Ti-30Nb-XTa-5Zr alloys containing Ta less than 10 mass% show the mixture of β and ω phases. Microstructures of Ti-30Nb-XTa-5Zr alloys containing 10 mass%Ta or greater than 10 mass%Ta show single β phase. The tensile strength and elongation of Ti-30Nb-XTa-5Zr alloy show a great change with changing Ta content. The threshold of Ta content for the changing exists between 5 mass% and 10 mass%Ta. The tensile properties of Ti-30Nb-10Ta-XZr alloys are affected by the change of deformation mechanism of β phase. The tensile strength of Ti-30Nb-10Ta-XZr alloys increases with increasing Zr content. The elongation of these alloys decreases with increasing Zr content. The tendency of tensile properties of Ti-30Nb-10Ta-XZr alloys is also caused by the change in deformation mechanism of β phase. From the point of view of stress-strain curves obtained by tensile tests and variation of elastic modulus with changing Zr content, Zr found to act as β stabilizer in Ti-Nb-Ta-Zr system alloy. Ti-30Nb-5Ta-5Zr, Ti-30Nb-10Ta and Ti-30Nb-10Ta-3Zr have relatively lower elastic moduli and greater elongation. Thus, these three Ti-Nb-Ta-Zr system alloys have potential to be used for biomedical applications.