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

Highlights: • Adding 1 at.% yttrium into Zr-Cu-Ni-Al BMG partly provides a beneficial effect to reduce its oxidation rate at 400–500 °C. • The Al₂O₃ phase was detected in the scale of the BMG added yttrium, but absent in that of Zr-Cu-Ni-Al BMG at 450 °C. • The oxidation of the Zr-Cu-Ni-Al-Y BMGunderwent an initial formation of t-ZrO₂, CuO and Cu₂O, followed by m-ZrO₂ and Al₂O₃. - Abstract: Zr_53.8Cu_29.1Ni_7.3Al_9.8 bulk metallic glass (ZCNA-BMG) and Zr_52.8Cu_29.1Ni_7.3Al_9.8Y₁ 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 k_p 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.