Dependency of the corrosion properties of in-situ Ti-based BMG matrix composites with the volume fraction of crystalline phase

The chemical and electrochemical corrosion properties of in-situ Ti45(Zr-Be-Cu-Ni)55−xNbx BMG matrix composites, with x = 0, 5, 10, 15 at.% and containing different volume fractions of crystalline β-(Ti,Zr,Nb) phase, have been investigated in a hydrogenated 1 M H2SO4 + 2 ppm F− electrolyte at 80 °C. In comparison to monolithic Ti-based BMGs and Ti–6Al–4V alloy, the in-situ BMG matrix composite with ∼20% volume fraction of β-(Ti,Zr,Nb) phase exhibits a high corrosion resistance characterized by a low value of corrosion current density, a stable passivation behavior in both potentiodynamic and potentiostatic polarization and low weight loss during immersion tests. The enhancement of the corrosion resistance is attributed to Ti-, Zr- and Nb-rich oxide layers produced on top of both the dendrite and amorphous matrix. However, for the BMG composite with a large (∼41.5%) volume fraction of Nb-rich dendrites the corrosion resistance was reduced leading to the dissolution of the amorphous matrix during immersion tests.