Observation of Ag-rich Precipitates on Ti-12Nb-1Ag Alloy

Objectives: Ti and Ti alloys have been applied widely because of favorable mechanical properties, corrosion resistance and biocompatibility. However, excessive modulus of Ti and Ti alloys may cause the phenomenon called stress shielding effect which will lead to more failure on implant surgery. Therefore, βTi systems such as Ti-Nb, Ti-Mo, Ti-Ta, Ti-Zr and so on, have been researched recently. In addition, there are still some problems on clinical application such as insufficient antibacterial property and biocompatibility for long-term implantation. To solve the problems, Ag element has been coated on the surface of material by various methods to inhibit the growth of bacterial. However, the surface coating is limited to long-term use because of wear and abrasion.
Methods: Based on the above, bulk Ti-12Nb-1Ag alloy was designed, the result of corrosion resistance showed that the corrosion potential of Ti- 12Nb-1Ag(-0.254eV) was higher than Ti-6Al-4V alloy (-0.476 eV), and even outperformed G2 pure Ti(-0.255eV). In addition, the preliminary antibacterial result also indicated that Ti-12Nb- 1Ag alloy possess the best antibacterial property test. The present study focused on the microstructure of Ti-12Nb-1Ag alloy, analysis the microstructure of Ti-12Nb-1Ag after various heat treatments by TEM (transmission electron microscope).
Results: The results showed that α and α’phase were observed after 850°C solid solution, In addition, Ag-rich precipitates could be found after 400°C aging treatment, and the particle size was about 20 nm.
Conclusions: Additionally, owing to diffusion of Ag elements, the size and shape of Ag-rich precipitates turned into 50~100 nm polygon particles with the increase of aging treatment time or increasing aging temperature resulting to various antibacterial property.