Oxidation mechanism of three Fe-Al alloys with and without addition of 0.1 at% yttrium at 800 °C

• Published in: Journal of rare earths Vol. 38; no. 10; pp. 1126 - 1130
• Main Authors: Xu, Xunhu, Wei, Hua, Xiang, Junhuai, Wang, Ling, Liu, Mingfeng, Zhang, Honghua, Men, Dandan, An, Jiangshan
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.10.2020
• Subjects: Fe–Al alloy; Isothermal temperature oxidation; Nodular oxide; Rare earth effect; Fe–Al alloy; Nodular oxide; Rare earth effect; Isothermal temperature oxidation
• ISSN: 1002-0721; 2509-4963
• DOI: 10.1016/j.jre.2019.10.007

The isothermal oxidation behavior of Fe-10Al, Fe-15Al, Fe-20Al alloys with and without the addition of 0.1 at% Y was studied at 800 °C under 1 × 105 Pa of flowing pure O2 for 24 h. The oxidation of three Fe-Al alloys can be divided into transient state and steady state oxidation stages. The oxidation of each stage is approximately in accordance with the parabolic law. The addition of 0.1 at% Y changes the oxidation behavior obviously and leads to a significant increase of the weight gain of Fe-10Al and Fe-15Al. The scale grown on Fe-10Al is much thicker and more complicated than that grown on Fe-20Al, which is composed of an exclusive thin layer of Al2O3 protective film. Due to the formation of a large number of nodules, the scales grown on Fe-15Al cannot provide full protection for the alloy. Scale microstructure of the three Fe-Al-0.1Y alloys is similar to their corresponding Fe-Al alloys. However, nodules with very small size still appear on the surface of Fe-20Al-0.1Y alloy. The critical Al concentration to form an exclusive Al2O3 protective layer for Fe-Al binary alloy is on the borderline between 15 at%–20 at%. For Fe-Al-0.1Y alloy, the presence of 20 at% Al is not enough to inhibit the growth of nodules. The oxidation behavior of the alloys with a higher Al content has rarely been investigated systematically. We examined the isothermal oxidation behavior of Fe-Al alloys with a higher Al content (10 at%–20 at% Al) to expand their field of application, with special attention on the role of the addition of rare earth element Y. Compared with the Fe-Al alloy without Y, the addition of Y not only significantly accelerates the oxidation of the Fe-Al alloy, but also promotes the growth of the nodule oxides. Therefore, the addition of 0.1 at% Y has a negative influence on the oxidation of the Fe-Al alloy. [Display omitted] •The oxidation behavior of Fe-Al alloys with a higher Al content (10 at%–20 at% Al) was evaluated.•The effect of Al content on the growth of nodules oxides was discussed.•The effect of Y on the high temperature oxidation resistance of high Al content Fe–Al alloy was discussed.