Impact of Temperature Gradient on Crystal Selection in Spiral Separator: A Simulation Study

The grain growth of Ni-based high temperature monocrystalline DD4 alloy by directional solidification in spiral separator was mathematically formulated with CAFE model, theoretically analyzed and numerically simulated with software ProCAST. The influence of the temperature (T) gradient:including the large, intermediate and small ones (defined in a pulling rate of 1, 5 and 10 mm/min, respectively), on the preferential growth orientation was investigated. The simulated results show that the T-gradient significantly affects the growth orientation. For example, randomly oriented crystalline nuclei form on the chilling plate surfaces; as the distance from the chilling surface increases, the equiaxial grains turn into the columnar ones in the separator, and the < 001 > oriented grains can be selected. When it comes to crystal selection, the medium T-gradient outperforms the large and small ones.