About the predictability of microstructure evolution upon thermomechanical processing of nickel-based superalloys

International audienceHot-forging of aerojet turbine disks will be under focus in the presentation, with the aim of discussing the possibility of predicting the microstructure obtained after forging as a function of the applied thermomechanical parameters. In case of classical discontinuous recrystallization, with nucleation along the former grain boundaries and growth driven by stored energy, dynamic and post-dynamic microstructure evolutions can be predicted by using a quite mean field model, both for supersolvus and subsolvus conditions. on the other hand, critical grain growth sometimes occurs, a phenomenon that is clearly driven by local metallurgical conditions and topology. Full field models are then necessary for predicting such topological events. Another example of non-conventional evolution that remains difficult to model and thus to predict, is the heteroepitaxial recrystallization phenomenon recently reported in γ-γ' alloys where nucleation arises from a phase transformation process inside primary precipitates