Grain structure and texture evolutions during single crystal casting of the Ni-base superalloy CMSX-4

The solidification grain structure and texture evolutions during single crystal (SX) casting of the advanced Ni-base superalloy CMSX-4 have been investigated. In order to understand the development of the solidification grain structure, SX casting experiments were carried out with a specially designed grain selector in a Bridgman directional solidification (DS) furnace. In addition to casting trials, the SX casting process was simulated by a 3-D cellular automaton-finite element (CAFE) model. The predicted solidification grain structure and the texture evolutions were validated by comparison with the microstructural observation and the electron back scattered diffraction (EBSD) results. It was shown that the overall grain structure, crystallographic texture evolution, and the location where the final selection of the single crystal occurs can be predicted well by the present CAFE model. The axial texture evolution of the single crystal was found to be significantly influenced by the grain density at the chill surface. The CAFE predictions also revealed that the geometry of the grain selector plays a significant role in the final selection of the single crystal.