Effect of Al on the hot deformation and recrystallization behavior of Fe-Ni-Al-Cr-Ti ferritic superalloy

The Fe-Ni-Al-Cr-Ti ferritic alloy exhibits excellent creep resistance, granting it significant application potential in critical components such as aircraft engines and ultra-supercritical thermal power equipment. In the case of Fe-Ni-Al-Cr-Ti ferritic alloy, it is necessary to systematically investigate its hot deformation behavior, to provide support for the formulation of reasonable hot working processes. To this end, two Fe-Ni-Al-Cr-Ti ferritic alloys with varying Al contents were made, and hot-compression tests were carried out using a Gleeble-3500 thermal simulator over a broad range of strain rates and temperatures. We created the constitutive equations and hot processing map, and determined the activation energy Q for hot deformation based on the stress-strain curves obtained during hot compression testing. Additionally, transmission electron microscopy (TEM) and electron backscatter diffraction (EBSD) were used to characterise the microstructures of the compressed specimens. The findings reveal that an increase in Al content from 4 wt.% to 6.5 wt.% results in a relative 400.92 kJ mol -1 increment in the hot deformation activation energy Q of the tested alloy. Moreover, the optimum processing domain for hot deformation transitions from the range of 1030–1150 °C and 0.01–0.11 s -1 to that of 1130–1150 °C and 0.01–0.12 s -1 . Microstructural characterization results reveal that the increase in Al content promotes the formation of a higher density of ellipsoidal B2-NiAl/L2 1 -Ni 2 TiAl composite precipitates. These particles exert a stronger pinning effect on grain boundaries, suppressing the dynamic recrystallization process, thereby resulting in significantly finer recrystallized grains in the 6.5 wt.% Al contained alloy.