High temperature oxidation behavior of directionally solidified Fe(Al,Ta)/Fe₂Ta(Al) eutectic composite

It is well known that Fe-Al intermetallic compounds have broad application prospects at high temperatures. The performance of Fe(Al,Ta)/Fe₂Ta(Al) eutectic composite prepared by Bridgman directional solidification technology has been further improved as compared with that of Fe-Al intermetallic compounds. In this paper, high-temperature oxidation behaviors of directionally solidified Fe(Al,Ta)/Fe₂Ta(Al) eutectic composite in static air were studied by isothermal oxidation test. The oxidized surface and cross section of directionally solidified Fe(Al,Ta)/Fe₂Ta(Al) eutectic composite were characterized by scanning electron microscopy, X-ray diffraction and energy dispersive spectroscopy. The mechanism of high-temperature oxidation was analyzed from the point of view of kinetics and thermodynamics studies combined with the data of the Ellingham-Richardson diagram. The oxidation weight gain of the Fe(Al,Ta)/Fe₂Ta(Al) eutectic composite at the same solidification rate is increased with temperature and Al₂O₃ is formed at the beginning of oxidation. However, a dense oxide film is not formed due to the small content of Aluminum, and the final oxide film for Fe(Al,Ta)/Fe₂Ta(Al) eutectic composite after 100 hours′ oxidation is composed of Fe₂O₃ and Al₃Fe₅O₁₂.