An electron back-scattered diffraction study on the microstructural evolution in large-grained iron aluminides during superplastic deformation

Microstructures in large-grained Fe3Al and FeAl alloys after superplastic deformation at 850 °C with a strain rate of 1.25×10−3 s−1 and at 1000 °C with a strain rate of 2.08×10−2 s−1, respectively, have been studied. Scanning electron microscope–electron channeling contrast observations indicate that the initial large grains were refined from about 50 to 100 μm to about 10–20 μm in Fe3Al alloy and from above 350 μm to about 20–30 μm after deformation in FeAl alloy. Electron back-scattered diffraction analysis revealed that the density of sub-grain boundaries and low angle grain boundaries increased with the elongation in both alloys, clearly indicating that dislocation sliding and climbing are important processes during deformation, and this is supported by transmission electron microscopy observations. The experimental results support our previous model of continuous recovery and recrystallization for the mechanism of superplastic deformation in large-grained iron aluminides.