5th International Conference on Advances in Solidification Processes (ICASP-5) 5th International Symposium on Cutting Edge of Computer Simulation of Solidification, Casting and Refining (CSSCR-5)

Low pressure turbine blades (LPT) made by centrifugal casting from titanium aluminides require demanding process control, as to achieve desired solidification microstructures. The columnar-to-equiaxed transition (CET) and the related texture are of special interest. In the joint European Project “GRADECET” they were investigated in μg, 1g and hyper-g conditions. Solidification experiments of the alloy Ti-46Al-8Nb in EAS’s Large Diameter Centrifuge (LDC) show that with increasing angular velocity the equiaxed grain formation is promoted, while also depending on alloy’s composition and solidification pathway. Our numerical model handles thermal radiation and conduction in the entire furnace, the transient steps of melting and columnar solidification coupled with thermo-solutal flow. Furthermore, to understand the observed asymmetric CET event and distinct scenarios about the origin of equiaxed grains, motion of nuclei with flow under centrifugal condition was modelled by the Lagrangian approach. Taken together the simulation results reveal that the centrifugal and Coriolis forces affect the pattern and magnitude of the flow thus changing the growth conditions including undercooling, temperature gradient and nucleation ahead of the columnar front. When the angular velocity in the LDC increases, CET conditions based on Hunt’ model are met more early, which is in good agreement with experimental observations.