Lamellar orientation modulation of Fe–Al alloys

Fe–Al intermetallic alloys, known for their superior oxidation and corrosion resistance, show broad application prospects in various industries. Among all Fe–Al phases and structures, alloys with a fully lamellar structure produced by the eutectoid transformation Fe₅Al₈(ε) → FeAl + FeAl₂ exhibit better resistance to cracking especially when the lamellar orientation is aligned parallel to the loading direction. To achieve Fe–Al alloys with parallel lamellar orientation, we analyze the interface between Fe₅Al₈ and FeAl₂ during phase transformation. The Bramfitt planar disregistry method is then used to quantitatively compare the differences between 0°- and 45°- oriented lamellae. The calculated disregistry is 46.2 % for 0°-oriented lamellae and 58.6 % for 45°-oriented lamellae, which demonstrates a controllable window for regulating lamellar orientation between 0° and 45°. Accordingly, directional solidification is employed to control the undercooling, as well as the nucleation and growth of lamellae with different orientations. The mechanical tests indicate that 0°-oriented lamellae exhibit better performance compared with both 45°-oriented lamellae and as-cast alloys. Thus, this fixed lamellar orientation could provide expanded opportunities for Fe–Al intermetallic applications.