Effect Of Ce On Microstructure And Performance Of Fe-27Cr-7Al Alloy

Series alloys of Fe-27Cr-7Al-0.2Ce and Fe-27Cr-7Al were prepared in Non- from consumes the vacuum arc furnace, and alloy foils with a thick of 3 mm were obtained through forging, hot roll and heat treatment . The effect of adding small amounts of Ce(0.2%wt) to Fe-27Cr-7Al on the microstructures in different temperatures were studied by Optics microscope; The effect of adding small amounts of Ce(0.2%wt) to Fe-27Cr-7Al on surface morphology and phase transition of alumina scale at 1000℃were investigated by X-ray and SEM. Oxidation kinetics of Fe-27Cr-7Al and Fe-27Cr-7Al-0.2Ce alloys at 1000℃were also investigated by TGA. The result suggests that:(1) Adding small amounts of Ce(0.2%wt) has a modifying effect to fine grain size of Fe-27Cr-7Al alloy at row temperature.(2) Adding small amounts of Ce(0.2%wt) can prevent (Cr,Fe) ₂₃C₆ from separating out from the Ferrite of Fe-27Cr-7Al alloy.(3) When Fe-27Cr-7Al alloy is oxidized in the air at 1000℃, the oxidized dynamics curve basically conforms to the parabola rule. In early stage, Fe-27Cr-7Al-0.2Ce alloy has a much lower rate of oxidation than Fe-27Cr-7Al alloy does. In later period, Fe-27Cr-7Al-0.2Ce alloy has a little lower rate of oxidation than Fe-27Cr-7Al alloy does.(4) Adding small amounts of Ce(0.2%wt) favors the formation ofθ-Al₂O₃ film in early stage of oxidation at 1000℃, and it favors phase transformation fromθ-Al₂O₃ toα- Al₂O₃ too. After 24 hours , Fe-27Cr-7Al-0.2Ce alloy has a single Oxide-film ofα- A1₂O₃. In early stage of oxidation, Fe-27Cr-7Al alloy can not form a complete oxide-film to cover alloy surface. After 24 hours, Fe-27Cr-7Al alloy has a two-layers oxide-film composed ofα-Al₂O₃ andθ-Al₂O₃.(5) After 96 hours oxidation at 1000℃, oxide-film of Fe-27Cr-7Al alloy begins to flake off, while Fe-27Cr-7Al-0.2Ce alloy has a smoother surface morphology than Fe-27Cr-7Al dose.