Hot workability characteristics of low-density Fe–4Al–1Ni ferritic steel

The hot-working behavior of a low-density Fe–4Al–1Ni ferritic steel at the deformation temperature in the range of 700–950 °C and the strain rate in the range of 0.01–10 s-1 was studied on a Gleeble-3800 thermomechanical simulator by means of a compression test. The hot-working behavior of the experimental steel was in accord with a material with intermediate stacking fault energy. The deformation mechanism is controlled by the glide and climb of dislocations. The constitutive equations were established to predict peak stress. The apparent deformation activation energy of experimental steel was about 347.5 kJ/mol. Electron backscatter diffraction was applied to study the microstructure after deformation. The experimental results showed that both continuous dynamic recrystallization and discontinuous dynamic recrystallization could occur, and increasing deformation temperature and strain rate is conducive to the occurrence of discontinuous dynamic recrystallization behavior. According the dynamic materials model, the processing maps of the experimental steel were established. Combined with the microstructure results, the power consumption efficiency of continuous dynamic recrystallization, discontinuous dynamic recrystallization and dynamic recovery decreases gradually. There are two flow instability domains, which are related to mischcrystal microstructure caused by partial dynamic recrystallization. The optimum deformation parameters for industrial processing are as follows: deformation temperature 750–900 °C, strain rate 10 s-1.