Effect of Bactericidal Elements Addition on the Microstructure and Mechanical Properties of Ti34Nb Alloy

The functionalization of β-Ti alloys by the addition of small amounts of bactericidal elements is interesting for biomedical applications. Thus, alloying pure titanium with highly biocompatible elements such as Nb or Ta, stabilizes the β phase of the resulting alloy although they can also include difficulties during the fabrication process due to their refractory nature. This work studies the effect of small additions of Ag and Cu (1.5 to 3 wt.%) on the microstructure and mechanical properties of the Ti34Nb (wt.%) alloy processed by powder metallurgy. The blend elemental powders were mixed (30 rpm during 30 min). The samples were compacted at 600 MPa and sintered at 1250 oC during 3 hours. The microstructure was analyzed by X-Ray Diffraction (XRD) and Field Emission Scanning Electron Microscope with X-Ray Spectroscopy (FE-SEM/EDS). The mechanical properties were obtained by bending tests; the elastic modulus was measured by ultrasonic methods and the porosity by Archimedes test. Cu addition generates the appearance of α phase sheets inside the β phase grains. Cu also decreases the open porosity and increases the closed porosity of the material. On the contrary, Ag addition does not influence the stabilization of the β phase and it does not modify the density, thus the total porosity of the resulting material. With respect to the influence of the alloying elements on the elastic modulus (E) of the alloys, the E of the Ti34Nb (76.8 GPa) increases with the Cu addition (92.6 GPa) and decreases with the Ag one (68.9 GPa). Therefore, silver addition, which does not modify the microstructure and slightly decrease the mechanical properties of the Ti34Nb, can be considered a good alloying element to provide antibacterial features to the titanium alloy without losing performance.