Synthesis, structure and electrochemical behavior of a beta Ti-12Mo-5Ta alloy as new biomaterial

Abstract

We have synthesized a new Ti-based alloy that combines Ti with the non-toxic elements Ta and Mo. Ingot of composition Ti-12Mo-5Ta was prepared by melting pure elements in an arc-melting furnace. The alloy was annealed at 950 °C for one hour under high vacuum and quenched in water at room temperature. The alloy was characterized by X-ray diffraction, observed by microscopy and found to have a body-centered-cubic structure (β-type). We have measured the Young's modulus of Ti-12Mo-5Ta by ultrasonic technique and found a lower value (about 74 GPa) than the classical α + β Ti-6Al-4V alloy (120 GPa). As long-term stability in biological environment is required, we have evaluated the electrochemical behavior of both alloys. Experiments, i.e. measurements of open-circuit potential (OCP) versus time and the observation of linear and cyclic potentiodynamic polarization curves, were carried out in simulated body fluid (Ringer's solution) for two immersion times. Under these conditions both titanium alloys exhibit spontaneous passivity and high corrosion resistance. The excellent electrochemical properties combined with low elastic modulus make the new beta-type Ti-12Mo-5Ta alloy suitable for use as a bone substitute.