Improvement of the Oxidation Behavior of Yb-Gd-Si Ternary Alloys at Low Temperatures via Ti Addition

Abstract To improve the oxidation behavior of Yb-Gd-Si, 0.5 and 1 at% of Ti-containing Yb-Gd-Si (denoted as YGTS-0.5 and YGTS-1, respectively) were fabricated by arc melting. The oxidation behaviors of both YGTS specimens were evaluated by oxidation tests performed in a temperature range of 600–1200 °C for 1, 2, 4, and 8 h in air. Additionally, thermogravimetric analysis (TGA) was conducted at the abovementioned temperature range in air and steam. Oxidation tests at 1200 °C revealed no significant changes in the oxidation rate. Moreover, the oxidation tests revealed that Yb-Gd-Si and YGTS-0.5 became powdery after oxidation, whereas YGTS-1 maintained its form. Detailed microstructural observations indicated that the formation of TiO2 and other oxides in the Yb-Ti-O phase and oxide-containing Yb, Gd, Ti, and Si suppressed the formation of Yb2O3, which caused drastic oxidation at intermediate temperatures (600–900 °C). These results indicated that the addition of 1 at% of Ti to Yb-Gd-Si was effective in improving its oxidation behavior.