Oxidation Behavior of Zr56Al16Co28 Metallic Glasses

The oxidation behavior of Zr56A16Co28 bulk metallic glass was studied in synthetic air 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 673K to 923K. Cobalt oxides precipitated on the topmost oxide layer of the metallic glass during oxidation. The observations on their morphologies show that the size and amount of these precipitations both increased with elevated temperature. A high resistance against oxidation in Zr56Al16Co28 bulk metallic glasses was observed below crystallization temperature: Only about 2 m-thickness scale formed after oxidation for ten hours at 773K. The oxidation is accelerated dramatically at 823K. However, the oxidation resistance was enhanced at a further increased temperature, 923K, which was likely attributed to the formation of large amounts of Al2O3 and m-ZrO2.