A Comparative in vitro Study on Biomedical Zr-2.5X (X = Nb, Sn) Alloys

Nb and Sn are major alloying elements in Zr alloys. In this study, the microstructure, mechanical properties, corrosion behavior, cytocompatibility and magnetic resonance imaging (MRI) compatibility of Zr-2.5X (X = Nb, Sn) alloys for biomedical application are comparatively investigated. It is found that Zr-2.5Nb alloy has a duplex structure of α and β phase and Zr-2.5Sn alloy is composed of α phase. Both separate addition of Nb and Sn can strengthen Zr but Nb is more effective in strengthening Zr than Sn. The studied Zr-2.5X (X = Nb, Sn) alloys show improved corrosion resistance compared to pure Zr as indicted by the decreased corrosion current density. The alloying addition of Nb enhances the pitting resistance of Zr, whereas the addition of Sn decreases the pitting resistance of Zr. The extracts of Zr-2.5X alloys produce no significant deleterious effect on fibroblast cells (L-929) and osteoblast-like cells (MG 63), indicating good in vitro cytocompatibility. The Zr-2.5X (X = Nb, Sn) alloys show decreased magnetic susceptibility compared to pure Zr and their magnetic susceptibility is far lower than that of pure Ti and Ti-6Al-4V alloy. Based on these facts, Zr-2.5Nb alloy is more suitable for implant material than Zr-2.5Sn alloy. Sn is not suitable as individual alloying addition for Zr because Sn addition decreases the pitting resistance in physiological solution.