Oxidation behavior of Zr56Co28Al16 bulk metallic glasses

The oxidation behavior of Zr56Co28Al16 bulk metallic glasses was studied over the temperature range of 673–923 K. The oxidation kinetics of the metallic glass follows a two-stage or single parabolic rate law from 773 K to 923 K. Cobalt oxides precipitated on the topmost oxide layer during oxidation. Below the crystallization temperature, the scale formed after oxidation for ten hours was less than 2 μm-thickness. The oxidation was accelerated up to 823 K, but the oxidation resistance was enhanced at a further increased temperature 923 K. The oxidation process was governed by the inward diffusion of oxygen and the outward diffusion of Co.

The surface morphology of the sample showed that CoO granules were formed along the grinding grooves, meanwhile, the amounts of the CoO on the surface increased with increasing temperatures except at 823 K that nodules were randomly gathered.Figure optionsDownload as PowerPoint slideHighlights
► The oxidation kinetics of the BMG follows a single or two-stage parabolic law.
► CoO granules were formed on the surface.
► Cobalt was found segregated near the surface or the oxide-alloy interface.