Characterization of hot deformation behavior and processing map of FGH4096-GH4133B dual alloys

The dual superalloys FGH4096-GH4133B were joined by the electron beam welding. Isothermal compression tests were carried out on electron beam weldments FGH4096-GH4133B alloys at the temperatures of 1020-1140 °C (the nominal γ′-transus temperature is about 1080 °C) and strain rates of 0.001-1.0 s−1 with the height reduction of 50%. The results showed that the true stress-true strain curves are greatly affected by deformation temperature and strain rate. There is an intrinsic and necessary connection between the flow stress and thermal-dynamic behavior, which can be indicated by the true stress-true strain curves. The power dissipation maps at different strains exhibit that true strain has a great effect on processing maps. Processing maps under different strains were constructed for evaluation of the flow instability regime and optimization of processing parameters. When the true strain is 0.69, the optimum processing condition is around 1090−1130 °C/0.1−1.0 s−1 with the peak efficiency of 0.58. The dynamic recrystallization mechanism and microstructure evolution in the welding seam of the studied dual-alloys have been discussed. High temperature and low strain rate are instrumental to dynamic recrystallization. The size of dynamically recrystallized grain decreased with the increase of strain rate and increased with the increase of deformation temperature. Based on the established combine processing map and microstructures, hot deformation process should be carried out under the condition of 1100−1120 °C/0.3−1.0 s−1 with high strains to obtain homogeneous and fine microstructure.