Effect of Nb content on corrosion behavior of Ti-based bulk metallic glass composites in different solutions

Abstract

The effect of Nb content on the corrosion behavior of in-situ (Ti0.45Zr0.31Be0.17Cu0.07)100−xNbx (x = 4, 6, 8, 10, and 12) was evaluated in 0.5 mol/L H2SO4, 0.6 mol/L NaCl, and 1 mol/L NaOH solutions. A dual-phase microstructure which composed of an amorphous matrix and dendrites was observed. Electrochemical measurements in each corrosion medium showed the same trend. The corrosion resistance first increased and then decreased with the addition of Nb content from 4 to 12 at.%. The results show the best corrosion resistance in terms of × = 8 for the alloys. Notably, Nb addition improved the pitting-corrosion resistance of samples in a chloride-containing solution, whereas spontaneous passivation occurred in chloride-free solutions. A preferential solution was observed in the amorphous matrix region in NaCl solution, but a part of dark spots and dents appeared on the surface after the polarization in chloride-free solutions. X-ray photoelectron spectroscopic measurements showed that Nb addition promoted the formation of metal oxide on the surface film, thus inducing a superior corrosion resistance for the bulk metallic glass matrix composites.