The effects of chromium addition and heat treatment on the microstructure and tensile properties of Fe-24Al(at.%)

Fe-24Al(at.%) base alloys containing 0–6 at.% Cr were elaborated by melting and casting under argon atmosphere. The ingots obtained were initially homogenized at 1000 °C for 5 h in air, then hot rolled at temperatures in the range 1000-800 °C. The hot rolled strips obtained were submitted to two heat treatments: 800 °C for 1 h, and 800 °C for 1 h plus 500 °C for 9 days. Tensile test specimens were machined from the hot rolled and heat treated strips. Samples for transmission electron microscopy and X-ray diffraction were taken from the as-rolled and annealed material for microstructural characterization. The best combination of ductility and yield strength is obtained for the alloy Fe-24Al-2Cr(at.%) heat treated at 800 °C for 1 h. The material heat treated at 800 °C for 1 h presents a partially recrystallized microstructure containing the α (disordered) and B2 (ordered FeAl) phases. The additional heat treatment at 500 °C for 9 days leads to a microstructure containing both α and DO3 (ordered Fe3Al) phases with degradation of the mechanical properties.