Processing map of GH4169 alloy during hot plastic deformation

Based on the stress-strain data of thermal simulation compression tests, the processing maps of the annealed GH4169 alloy with coarse grains were established according to the dynamic materials model (DMM). Combined with the optical microscopy (OM) observations and the electron backscatter diffraction (EBSD) technique analysis, the stable and instable regions of the annealed GH4169 alloy with coarse grains were determined and the mechanisms of deformation under different conditions were investigated. The suggested processing parameters of the annealed GH4169 alloy with coarse grains were also studied. The results show that the flow instability of the annealed alloy with coarse grains occurring at the strain rates of 10 ^-0.25~1 s ^-1 and the temperatures of 950~1100°C is mainly related to the cracking induced by the local plastic flow. Three classic zones of dynamic recrystallization for GH4169 alloy with coarse grains are found in the region with moderate and low strain rates. The maxium energy dissipation efficiency occurring at the strain rate of 10 ^-3s ^-1 and the temperature of 950°C is closely associated with the promotion of dynamic recrystallization due to the δ phases precipated along the grain boundaries as well as the local nucleation of dynamic recrystallization inside the grain. Comprehensively considering the energy dissipation efficiency, elongation and microstructure, the process parameters of the starting forging for the alloy with coarse grains are suggested to be the strain rates of 10 ^-2.7~10 ^-1.5 s ^-1 and temperatures of 1087.5~1100°C, and those of the final forging are suggested to be the strain rates of 10 ^-2.5~10 ^-1.5 s ^-1 and temperatures of 1000~1065°C.