What Are Biomedical Titanium Alloys and Their Uses?

Biomedical titanium alloys are used in implants and medical devices because they combine biocompatibility, corrosion resistance, useful strength, and relatively low density. Commercially pure titanium and Ti-6Al-4V are established materials, while lower-modulus β alloys are being studied to reduce stiffness mismatch with bone. Their uses and material choices are compared below.

What Is a Biomedical Titanium Alloy?

Biomedical materials interact with biological systems to diagnose, treat, repair, or replace tissues and organs or to improve their function. They include medical metals, polymers, and ceramics. Metals are especially important in orthopedic and cardiovascular products. Titanium has a favorable biological response, good compatibility with tissue, and no inherent magnetic behavior, supporting extensive medical use.

Biomedical titanium alloys combine biocompatibility, mechanical performance, corrosion resistance, and low density. High strength and a relatively low elastic modulus can reduce stress shielding and support bone healing. Titanium is bioinert and corrosion resistant in physiological environments. Its density is about 56% that of stainless steel, reducing implant weight. Development has progressed from commercially pure titanium and Ti-6Al-4V to modified alloys and low-modulus β titanium alloys.

Classification and Mechanical Properties

Biomedical titanium alloys are classified by microstructure as α, α+β, or β alloys. Commercially pure titanium and Ti-6Al-4V remain widely used clinically. Lower-modulus β alloys with improved biocompatibility are a major research focus.

Second- and third-generation alloys generally have lower elastic modulus and use increasing amounts of niobium. Ti-35Nb-7Zr-5Ta and related Ti-Nb-Ta-Zr systems are among the lowest-modulus materials tabulated here. The listed elastic modulus is 55 GPa for Ti-35Nb-7Zr-5Ta, compared with approximately 30 GPa for bone. Ti-Nb superelastic β alloys are particularly well studied.

New β alloys include Ti-Nb, Ti-Mo, Ti-Zr, and Ti-Ta systems. Potentially harmful V, Al, Ni, and Cr are increasingly replaced by biocompatible Nb, Zr, Ta, Sn, Pt, and Mo. Ti-Nb alloys offer low elastic modulus, avoid aluminum and vanadium, and are widely studied as medical metals.

Biomedical Performance

High Specific Strength

Titanium alloys have a density near 4.51 g/cm³, about 60% that of steel. Pure titanium approaches ordinary steel strength, while high-strength titanium alloys exceed many structural steels. Their high strength-to-density ratio enables strong, stiff, lightweight components. Conventional medical α alloys can cause stress shielding because of their higher elastic modulus. Alloying, plastic deformation, and solution treatment can modify crystal structure and reduce implant modulus.

Corrosion Resistance

Titanium alloys outperform stainless steel in humid air and seawater and resist pitting, acid attack, and stress corrosion. They also resist alkalis, chlorides, chlorinated organics, nitric acid, and sulfuric acid, although performance is poorer in some reducing or chromate media.

1. Ti-39Nb shows corrosion-degradation behavior in physiological saline comparable with pure titanium and performs substantially better in fluoride-containing environments.
2. Ti-10Nb-10Zr performs well in 3.5% NaCl and artificial saliva, with a particularly low degradation rate in artificial saliva.
3. Ti-26Nb-4Zr-3Mn and Ti-26Nb-4Zr-5Mn show high corrosion potentials and low current densities in Hank’s solution, indicating good corrosion resistance.