On the dendrite deformation and evolution mechanism of Ni-based superalloy during directional solidification

Abstract

The dendritic growth in a novel casting with complex solidification path during directional solidification was investigated by experiment and simulation. The different dendrite deformations were found in the side strip and the corner, and the misorientation was measured by electron backscattered diffraction. The dendrite deformation in the local strip above each platform causes the cumulative deviation of dendrite direction in the whole strip, and this deformation is caused by the differential thermal shrinkage between upper and lower cross-sections. In addition, the dendrite with incomplete trunk concentrately deformed in the corner, and the deviation direction is consistent with its branches toward the platform, indicating that the deformation occurs before branching and thereby thermal concentrated stress is excluded. The simulation results confirm the occurrence of horizontal shrinkage stress in the mushy zone of the platform when the dendrites in the sidebar leave the platform, and also determine that the dendrite branches occur before the effect of the thermal concentration stress in the corner.