Speaker
Description
Due to increasing operating temperatures in low-pressure turbine discs of next-generation geared turbofan engines, materials with superior high-temperature capabilities beyond those of alloy 718 are necessary. Among the promising candidates, UDIMET720LI offers excellent mechanical and environmental resistance properties; however, its narrow processing window poses significant challenges during industrial manufacturing. To reduce the need for costly thermomechanical treatments such as isothermal forging while still ensuring specification-compliant microstructures and mechanical properties throughout the component, robust process design strategies are essential. To address these challenges, a finite element method (FEM) coupled multi-class grain size model, originally developed for alloy 718, has been further adapted and extended for UDIMET720LI. The multi-class approach enables the prediction of heterogeneous grain size distributions arising from billet inhomogeneities and incomplete recrystallization processes. Furthermore, a thermo-kinetic mean-field model capable of accurately describing the γ′ precipitate evolution has been integrated to improve the prediction of local microstructures and resulting mechanical properties. The models were parameterized using extensive laboratory-scale compression experiments covering a broad range of temperatures, strain rates. To validate the developed framework and process design methodology, prototype forgings with varying process parameters were manufactured on industrial-scale equipment and characterized through certified testing laboratories, including microstructural analysis and mechanical property evaluation. The results demonstrate very good agreement between simulations and experiments, confirming the high predictive capability of the coupled modeling approach. The developed framework therefore represents a powerful tool for the robust and efficient design of future UDIMET720LI turbine disc manufacturing processes.