Hot deformation behavior and constitutive model modification of PM superalloys based on DMM theory

Powder metallurgy (PM) superalloys are highly favored in the application of hot-end components of aero-engines due to their uniform composition and microstructure as well as excellent properties. Meanwhile, their unique defects such as the prior particle boundaries and the requirements for fine grain size also bring difficulties to the optimization of its hot working process. In order to guide the hot working process more accurately, in the present study, the processing maps applicable to any type of stress-strain rate curves are used in combination with microstructure analysis to determine the suitable processing range of the PM alloy. Moreover, the Arrhenius constitutive model is modified based on the DMM (Dynamic Material Model) theory, and the HIPed-FGH4096 superalloy is taken as an example for illustration. Using these revised processing maps, compared with those based on the power-law assumption, the low strain rate region that would cause coarse and irregular grains has been successfully excluded from the suitable processing range. The suitable processing range was finally determined as 1070 °C-1100 °C and 0.01 s -1 -0.1 s -1 . In addition, after the constitutive equation is modified based on the DMM theory, its AARE (Average Absolute Relative Error) was reduced from 17.4 % to 3.6 %, and the characteristics of microstructure evolution indicated by the processing maps are restored. These findings are expected to contribute to the microstructure optimization and hot working process of PM superalloys