Relatively low Nb and Ta additions balance corrosion and passive-film performance in Ti–Zr medium-entropy alloys

Relatively low additions of niobium or tantalum provided a better balance of corrosion resistance, passive-current response, high-potential film stability and early cell adhesion in Ti–Zr-based medium-entropy alloys tested in phosphate-buffered saline (PBS), according to the study abstract. The research is an experimental materials-science study using in vitro electrochemical, surface-characterization and early cell-adhesion assessments; it does not establish clinical benefits for biomedical implants.

The investigators fabricated Ti–Zr–Nb and Ti–Zr–Ta alloy series with different niobium and tantalum contents by vacuum arc melting. Commercially pure titanium and Ti–6Al–4V served as reference materials. X-ray diffraction and electron backscatter diffraction were used to examine phase constitution and microstructure, while electrochemical measurements assessed corrosion behavior and passive-film responses in PBS. Gibbs free energy analysis and early cell-adhesion assessments were also performed, as summarized in the abstract.

Increasing the Nb or Ta content promoted a change from α′/α″/β multiphase structures toward β-dominated matrices, with Nb showing the stronger β-stabilizing effect. Corrosion resistance did not improve monotonically with increasing alloy content. Ta5 had the lowest corrosion current density among the investigated alloys, at 1.13 × 10−6 A cm−2, whereas Nb4 had the lowest passive current density among the designed alloys, at 2.60 × 10−5 A cm−2. Nb10 and Ta10 showed higher interfacial impedance near the open-circuit potential, but they also had higher corrosion and passive current densities and an earlier rise in current during anodic polarization. These measurements indicate that high interfacial impedance near open-circuit potential did not necessarily correspond to stable anodic passivation.

X-ray photoelectron spectroscopy identified passive films based on TiO₂ and ZrO₂ that also contained Nb- or Ta-containing oxide species. The reported Gibbs free energy analysis indicated that formation of the high-valence oxides was thermodynamically favorable. Overall, the abstract reports that relatively low Nb or Ta additions produced a better combined balance of the evaluated corrosion, passivation and early cell-adhesion properties than higher additions. Because the supplied evidence is an abstract rather than the full article, the precise protocols, uncertainty estimates, statistical results and detailed limitations of the cell-adhesion assessment are not available here; the findings should not be interpreted as evidence of implant performance or patient outcomes.

Subject of Research: Experimental evaluation of Nb and Ta alloying effects on corrosion, passive films and early cell adhesion in Ti–Zr medium-entropy alloys

Article Title: Effect of Nb and Ta alloying on corrosion behavior and passive film chemistry of biomedical Ti–Zr-based medium-entropy alloys in PBS solution

Article References: Hu, S., Wei, P., Liu, Y., Chen, Z., & Liu, D. (2026). Effect of Nb and Ta alloying on corrosion behavior and passive film chemistry of biomedical Ti–Zr-based medium-entropy alloys in PBS solution. Journal of Materials Science, 61(43), 34147-34172. https://doi.org/10.1007/s10853-026-13760-2

Image Credits: AI Generated

DOI: 10.1007/s10853-026-13760-2

Keywords: Ti–Zr medium-entropy alloys, niobium alloying, tantalum alloying, corrosion behavior, passive films, electrochemistry, XPS, cell adhesion, Effect, alloying, corrosion, behavior