Glass formation and properties of Ti-based bulk metallic glasses as potential biomaterials with Nb additions

Ti47Cu38-xZr7.5Fe2.5Sn2Si1Ag2Nbx (x=0, 1, 2; at%) bulk metallic glasses (BMGs) with superior bio-corrosion resistance were synthesized by copper mold casting. Although the minor addition of Nb to the Ti-Cu-Zr-Fe-Sn-Si-Ag BMG slightly decreases the glass-forming ability (GFA), the Nb-bearing Ti-based alloys could be casted in a bulk glassy rod form with diameters up to 3mm. It is found that partial substitution of Cu with Nb is effective on enhancing the bio-corrosion resistance of the Ti-based BMG. Potentiodynamic polarization measurements show that Nb addition to Ti-based BMG leads to higher open-circuit potential and pitting potential as well as lower passive current density in Hank's solution. Electrochemical impedance spectroscopy (EIS) results indicate that with Nb content increasing, the charge transfer resistance values of the Ti-based BMGs become larger, demonstrating that the surface oxide films are more protective. The Nb-bearing Ti-based BMGs also exhibit good in vitro biocompatibility comparable to that of Ti-6Al-4V alloy. The enhanced bio-corrosion resistance, excellent in vitro biocompatibility and good mechanical properties of the Nb-bearing Ti-based BMGs are favorable for biomedical applications.