The effect of yttrium addition on the air oxidation behavior of Zr-Cu-Ni-Al bulk metallic glasses at 400-500 °C

Zr53.8Cu29.1Ni7.3Al9.8 bulk metallic glass (ZCNA-BMG) and Zr52.8Cu29.1Ni7.3Al9.8Y1 bulk metallic glass (ZCNAY-BMG) were taken to elucidate the kinetic mechanism for the improvement in oxidation resistance upon the addition of yttrium over the temperature range of 400-500 °C. The oxidation kinetics of two BMGs both followed a multiple-stage parabolic-rate law, wherein ZCNAY-BMG exhibited a lower kp and thinner scales consisting of t-ZrO2, m-ZrO2, CuO, AlNi3, Y2O3 and some Al2O3 at T  ≥ 450 °C. The Al2O3 phase was only observed in the scale of ZCNAY-BMG at 450 °C due to the crystallization, and resulted in the much lower oxidation rate.