Microstructure Modeling as a Tool to Optimize Forging of Critical Aircraft Parts
Forging of high strength nickel base superalloys 720 and 718 for aircraft parts requires the usage of finite element simulations to ensure a proper thermo-mechanical treatment. Because of the strong mechanical requirements and narrow specifications of such parts not only a correct, defect free final geometry is necessary, but also a defined microstructure. The crucial point is therefore, to control all process parameters in a way to achieve the demanded properties. The typical forging processes like hydraulic, screw press and hammer forging imply a broad spectrum of strain rates. The influence of this different strain rates as well as forging temperature and strain on dynamic and post-dynamic recrystallization have been examined experimentally. Annealing tests at various temperatures and time periods have been performed, to investigate the grain growth behavior and dissolution processes in this before mentioned materials during heating periods. The obtained data was used to build phenomenological models, which were implemented into finite element code of a commercial special purpose finite element program. 2D and 3D Simulations of multiple step thermo-mechanical processes are compared with microstructure examinations of forged parts to show the usability and accuracy of such models as a tool to optimize complex forging processes of critical aircraft parts. In combination with systematic process data collection during production a stable processes and satisfactory mechanical product properties are guaranteed.
B. Bacroix, J.H. Driver, R. Le Gall, Cl. Maurice, R. Penelle, H. Réglé and L. Tabourot
M. Stockinger and J. Tockner, "Microstructure Modeling as a Tool to Optimize Forging of Critical Aircraft Parts", Materials Science Forum, Vols. 467-470, pp. 683-688, 2004