Microstructure characterization and property tailoring of a biomedical Ti-19Nb-1.5Mo-4Zr-8Sn alloy

A biomedical β titanium alloy (Ti-19Nb-1.5Mo-4Zr-8Sn) was designed and prepared by vacuum arc self-consumable melting. The ingot was forged and rolled to plates, followed by quenching and ageing. Microstructure evolution and its influence on mechanical properties of the alloy were investigated, using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, tensile and hardness tests. Results show that a two-phase structure featured with a dispersed nano-sized α′ phase and a supersaturated solid solution β phase (βsss) forms immediately after quenching from β-phase region. The quenched alloy exhibits an extremely low Young's modulus of 39 GPa, with an ultimate tensile strength above 930 MPa and an elongation of 10%, showing good promises for biomedical implant applications. The precipitation sequence during isothermal ageing at different temperatures was determined as, for Tageing=673-723 K, βsss+α′→α+α″+β→ω+α+α″+β→α+β, and for Tageing=773-873 K, βsss+α′→α″+α+β→α+β. The tensile strength, elongation, and elastic modulus of the alloy can be tailored easily through controlling the phase transition during ageing.