Low modulus and high strength in a β Ti alloy exhibiting near-linear deformation behavior and TRIP/TWIP effect for potential biomedical applications

Possessing the lowest possible Young's modulus and yet sufficiently high yield strength simultaneously is important and highly desirable for biomedical Ti alloys used for orthopedic applications but achieving this modulus-strength trade-off relationship is generally challenging in single-phase metal materials. Here, alloy design strategies of a low electron-to-atom (e/a) ratio, Goss texture and oxygen solute strengthening effect were considered and the achieved findings are that an incipient Young's modulus of 33.5 GPa together with a yield stress of 650 MPa was achieved in the present solution-treated (900 degrees C/30 min) Ti-Nb-Sn-O bulk alloy having a single beta phase. The low Young's modulus in this study was because of the combined roles of a low e/a ratio (4.16), the nonexistence of omega phase, and a predominant (110)(beta)[001](beta) Goss texture on reducing Young's modulus effectually. Additionally, a near-linear deformation behavior before yielding (similar to 2.3 %) was also observed in the present alloy probably caused by the considerable nanodomains with preferential orientation in the Goss textured beta matrix but was neither owing to the stress-induced beta to alpha" martensitic transformation nor owing to the omega/alpha" phases. A good strength-ductility balance also was achieved in this study owing to the combined transformation-induced plasticity (TRIP) and twinning-induced plasticity (TWIP) effects. The studied beta Ti-Nb-Sn-O alloy simultaneously possessing low Young's modulus existing toward that in human bone and high yield strength as well as large elongation appears to be a promising metal material for orthopedic implants.