Phase stability of Yb-Gd-Si ternary alloys at elevated temperature

A ternary alloy with an Yb-Gd-Si composition was designed using thermodynamic calculation software. The ternary alloy with two different steady-state phases (Yb:Gd:Si = 25:18:57 and 19:23:58 at%) was successfully fabricated using arc melting. Oxidation tests were carried out at 1200 °C for 1, 2, 4, and 8 h in air. Thermogravimetric and microstructural analyses indicated that weight gain during oxidation at 1200 °C was suppressed compared with that for the Yb–Si alloy (Yb3Si5) owing to the formation of complex oxides in the Yb2O3–Gd2O3–SiO2 system. In addition, the phase stability of Yb-Gd-Si was higher than that of Yb3Si5 because the growth of a eutectic phase in Yb-Gd-Si during oxidation was prevented compared with Yb3Si5. The addition of Gd in Yb–Si alloy was effective in improving phase stability and oxidation behavior.