Grain selection during solidification in spiral grain selector

A macro-scale ProCAST and a meso-scale Cellular Automaton Finite Element model (CAFE) are used to simulate the competitive growth and grain selection during solidification in spiral grain selector, which is widely used in industry to produce single crystal turbine blades. The macro-model ProCAST calculates the macroscopic heat transfer and fluid flow and the calculated thermal profiles are then used as input in the meso-scale CAFE model to predict grain structures and grain orientations. Competitive growth and grain selection in the selector has been analysed with emphasis on the shape of the spiral. It is found that the spiral becomes more effective as a grain selector, when it has a smaller "take-off" angle. However, the grain orientations cannot be optimised during the selection event in the spiral. To validate the modelling results, spirals with different shapes were cast in a fully instrumented industrial directional casting furnace and the grain structure and orientations in the spirals were analyzed.