Oxidation induced amorphous stabilization of the subsurface region in Zr-Cu metallic glass

In the present study, we demonstrate that selective surface oxidation of Zr70Cu30 metallic glass can stabilize the amorphous structure in the subsurface region of the matrix. The oxidation proceeds by selective oxidation of Zr, forming monoclinic ZrO2 layer on the surface, and the subsurface layer becomes Cu-enriched due to back diffusion of Cu atoms from the oxide layer. Interestingly, in this system, the composition change in the subsurface region leads to enhancement of glass stability, forming of a double layered surface structure consisted of inner amorphous layer and outer monoclinic ZrO2 layer even when the remaining matrix is completely crystallized. (C) 2014 AIP Publishing LLC.