Novel Multi-Class Grain Size Model for UDIMET720LI: Topical Collection: EuroSuperalloys 2026

The aim of this work is to present a workflow for the application of a multi-class grain size model, which describes the microstructure evolution during dynamic and post-dynamic recrystallization in forged UDIMET720LI components. In a first step, the distribution of the local microstructure in the as-received condition is characterized, which serves as an initial condition for the multi-class model. The recrystallization kinetics is analyzed through thermo-mechanical compression tests on a Gleeble ^® 3800 simulator and large-area electron backscatter diffraction analysis providing recrystallized fractions and size distributions. A finite element approach is used to translate the global test parameters to the local strain history of the samples during thermo-mechanical testing. Subsequently, the results from experimental characterization and simulated Gleeble tests are utilized to calibrate a semi-empirical Avarami-type recrystallization model. Finally, the application of the multi-class model is demonstrated by predicting the grain size distribution for two different thermo-mechanical processing routes.