Enhanced corrosion resistance of a ZrCuNiAl bulk metallic glass in simulated groundwater by minor crystallization

Understanding the corrosion behaviors of bulk metallic glasses (BMGs) in practical working environment is essential for the applications of BMGs as corrosion resistance materials. The present work investigated the corrosion behaviors of Zr_50.7Cu₂₈Ni₉Al_12.3 (at. %) BMG and also its heat treated alloys with different volume fraction of crystalline phase in a solution simulating groundwater. It was shown that the corrosion of the present ZrCuNiAl alloy is induced by pit etching and Cu would be aggregated at the corrosion positions in a form of Cu²⁺ ions. Zr, Ni and Al would inversely be dissolved by the simulated groundwater and so were lack at the corrosion positions, and they are probed as form of Zr⁴⁺, Ni²⁺ and Al³⁺ ions on the corrosion surface, which supports the formation of metal oxides ZrO₂, CuO, NiO and Al₂O₃. The experimental results discover a corrosion resistance trend first enhancing and then reducing with increasing crystalline phase volume fraction, proving that minor crystallization in fact also improve corrosion resistance in this BMG system, but large volume fraction of crystalline phases would deteriorate the anti-corrosion performance of BMGs. Thus the amorphous state itself improves corrosion resistance of the studied alloy.