β-Ti-based alloys for medical applications

Abstract

Titanium alloys have been used for medical purposes for over 60 years. They are used in the manufacture of artificial heart valves, stents of blood vessels, endoprostheses of bones and joints (shoulder, knee, hip, elbow), for auricle reconstruction, in facial surgery, and also as dental implants. In first-generation materials (such as commercially pure titanium or VT6 alloys), the matrix consisted of the α-Ti phase or α-Ti and β-Ti mixture. Unfortunately, implants made of first-generation materials require replacement after 10–15 years of usage. This is due to the degradation of implants and loss of contact with the bone. Recently, these materials have been replaced by β-Ti alloys. These second- generation materials make it possible to exclude the harmful effect of aluminum and vanadium ions released during the gradual implant corrosion, and their elastic modulus is closer to the values for living bone than those for α and α+β alloys. Important areas in the development of β-Ti alloys include increasing their mechanical strength, fatigue strength, corrosion resistance and biocompatibility. New methods for the production and thermo-mechanical processing of titanium alloys arise and develop such as additive technologies or severe plastic deformation. Expensive alloying elements (such as tantalum, zirconium or niobium) are quite successfully replaced with cheaper ones (for example, chromium and manganese). As a result, the properties of titanium implants are gradually getting closer to that of the human bone, and their service life is steadily increasing. Therefore, this paper describes a comparative analysis conducted in relation to β-titanium-based alloys for medical applications.