Influence of yttrium as a minority alloying element on the corrosion behavior in Fe-based bulk metallic glasses

The role of yttrium in corrosion behavior in an HCl solution was studied systematically by comparing bulk FeCrMoCB metallic glasses with and without yttrium. The corrosion resistance was very sensitive to minor yttrium addition. The material exhibits a detrimental effect on corrosion resistance at 0.5 at.% yttrium addition while a beneficial effect at more yttrium additions. Such effects are argued to be associated with variations of the semiconductor properties of passive film (i.e. defects concentration and band structure of passive film), induced by minority yttrium alloying element doping. It was shown that there exhibits a bi-layer structure of passive film on Fe-based metallic glasses. The outer layer with high valence cations is responsible for the dissolution behavior of the passive film, whereas the inner layer with doped oxides connects with the semiconductor properties. This result presents us an important hint that the corrosion resistance of metallic glasses can be improved by elaborately tailoring the defect structure of passive film via proper additions of minor alloying elements.