Mechanical and Electrochemical Corrosion Behavior of Porous Ti-10Zr-xNb Alloys Processed via Powder Metallurgy for Biomedical Implants

Titanium alloys are widely used for biomedical implants due to their favorable mechanical properties, corrosion resistance, and biocompatibility; however, their high stiffness relative to bone can lead to stress shielding. This study developed porous Ti-10Zr-xNb alloys (x = 5, 10, 15, 20 wt %) via powder metallurgy using 600 MPa cold compaction, followed by high-vacuum sealed sintering to reduce stiffness through controlled porosity. All alloys exhibited a biphasic α + β microstructure, with the β phase fraction increasing with the Nb content. The Ti-10Zr-20Nb alloy achieved the highest mechanical performance, with a compressive strength of 844.70 ± 20.92 MPa and an elastic modulus of 32.51 ± 1.52 GPa, within the modulus range of cortical bone. Electrochemical tests (OCP, EIS, PDP) conducted in simulated body fluid revealed a gradual decline in corrosion resistance with the increasing Nb content despite nearly constant porosity levels. This behavior is attributed to Nb-induced β phase stabilization and its likely influence on passive film defect chemistry, which may promote defect-assisted charge transport and reduce the barrier effectiveness of the passive film under porous conditions. Among the compositions, Ti-10Zr-5Nb exhibited the highest corrosion resistance, with <i>E</i>_corr = -0.0361 V and <i>I</i>_corr = 17.24 μA/cm², whereas alloys with a higher Nb content showed more negative corrosion potentials and elevated corrosion currents. Overall, Ti-10Zr-20Nb offers the best mechanical compatibility for orthopedic load-bearing implants, whereas Ti-10Zr-5Nb provides favorable electrochemical stability for dental environments.