Improved plasticity and corrosion behavior in Ti-Zr-Cu-Pd metallic glass with minor additions of Nb: An alloy composition intended for biomedical applications

The effects of minor additions of Nb (2, 3 and 4 at%) to the Ti40Zr10Cu38Pd12 alloy are discussed in terms of microstructure, thermal behavior, mechanical properties and corrosion resistance. The addition of Nb promotes the formation of nanocrystals, i.e., from a completely amorphous structure (when no Nb is added) to a mainly crystalline structure (for a 4% of Nb addition). The glassy alloy exhibits large hardness, relatively low Young's modulus and excellent corrosion behavior, although the plasticity is rather limited. A significant increase in compressive plasticity (total strain over 13%) is achieved in the sample with 3% of Nb without compromising the strength. Young's modulus of the as-cast alloy (around 100 GPa, as determined from acoustic measurements) increases only slightly when disperse nanocrystallites are embedded in the amorphous matrix. Improvement of the corrosion performance, with delayed pitting corrosion, is also observed for 3% Nb addition.