Formation and biocorrosion behavior of Zr-Al-Co-Nb bulk metallic glasses

Ni- and Cu-free Zr-Al-Co-Nb glassy alloys with different Nb and Co contents were synthesized by melt spinning and copper mold casting. The effects of Nb addition to partially replace Co in the Zr₅₅Al₂₀Co₂₅ glassy alloy on the glass-forming ability, thermal properties, in-vitro biocorrosion behavior and surface wettability of the metallic glasses were investigated. Although addition of Nb up to 5 at.% slightly decreased the supercooled liquid region and the glass-forming ability (GFA), the alloys could be casted in a bulk glassy rod form with diameters up to 3 mm. The Zr-Al-Co-Nb glassy alloys were spontaneously passivated with low passive current densities in phosphate buffered saline and Hanks’ solution. Substitution of “toxic” Co by Nb is effective in improved the corrosion resistance of the Zr-Al-Co glassy alloy. Water contact angle measurements showed that Nb addition increased the hydrophilicity of the glassy alloys, which may enhance cell adhesion of the alloys in biomedical applications.