β-Ti-Based Alloys for Medical Applications

Abstract

Titanium alloys have been used for medical purposes for over 60 years. They are employed in the manufacture of artificial heart valves, blood vessel stents, and endoprostheses of bones and joints (shoulders, knees, hips, and elbows); for the reconstruction of auricles; in facial surgery; and as dental implants. In first-generation materials (such as technically pure titanium or VT6 alloys), the matrix consisted of α-Ti phase or a mixture of α and β phases. Unfortunately, implants from first-generation materials require replacement after as early as 10–15 years of usage. This is due to the degradation of the implants and loss of contact with the bone. Recently, these materials have been replaced by β-titanium alloys, second-generation materials that make it possible to exclude the harmful effect of aluminum and vanadium ions released during the gradual corrosion of the implant, and their elastic modulus is closer to the values for living bone than those for α and α + β alloys. Important directions in the development of β-titanium alloys include increasing their mechanical strength, fatigue strength, corrosion resistance, and biocompatibility. New methods for the production and thermo-mechanical processing of titanium alloys, such as additive technologies or severe plastic deformation, are created and developed. Expensive alloying elements (such as tantalum, zirconium, or niobium) are very successfully replaced with cheaper ones (for example, chromium and manganese). As a result, the properties of titanium implants are gradually getting closer to those of human bone, and their service life is steadily increasing. In this regard, we have carried out a comparative analysis of β-titanium-based alloys for medical applications.