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 3mm.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.
A large-sized CuZr-based bulk metallic glass(BMG) composite with enhanced mechanical properties is prepared successfully. With the addition of Ta to CuZr-based alloys, the critical composite size changes and the microstructure diversifies. The composite with 0.5 at.% Ta addition has the largest critical size with the microstructure of single CuZr(B2) phase uniformly dispersing in amorphous matrix. This composite exhibits good mechanical properties, i.e., large compressive plasticity and work-hardening ability, which should be attributed to the uniformly distributed CuZr(B2) phase. The increased critical size of CuZr-based BMG composite can be explained by the fact that proper Ta addition can suppress the precipitation of crystalline phases other than B2 CuZr phase during solidification. This study may be helpful for the fabrication of largesized BMG composites with excellent mechanical properties.
In the present study,high-zirconium ternary Zr-Al-Fe bulk metallic glasses(BMGs) with low Young's modulus and good plasticity were developed.Zr75 Al7.5 Fe17.5 BMG exhibits a low Young's modulus of 70 GPa and high Poisson's ratio of 0.403.Pronounced plasticity was demonstrated under both compression and bending conditions for the BMGs.Furthermore,the alloys show high corrosion resistance in phosphate buffered solution.The combination of desirable mechanical and chemical properties implies potential for biomedical applications.
