Oxidation Behavior of the Y₅₆Al₂₄Co₂₀ Bulk Amorphous Alloy Containing Crystalline Composites at 325-450°C

The oxidation behavior Of Y56Al24Co20 bulk metallic glass containing similar to 4.2% Y-rich particles was studied over the temperature range of 325-450 degrees C in dry air. The results showed that the oxidation kinetics of the alloy followed the parabolic rate law at T <= 375 degrees C, with rate constants generally increased with temperature. Conversely, para-linear kinetics were observed at higher temperatures (T >= 400 degrees C)). The scales formed on the Y-base amorphous composite were temperature dependent, consisting of exclusively yttrium oxides (Y2O3) at T <= 375 degrees C and of Mostly Y2O3 and alumina (Al2O3) at temperatures. No evidence of any cobalt-containing oxide was found in the scale.