Effects of solidification parameters on microstructures of Ni3Al based single crystal

Abstract A series of Ni3Al single crystal specimens were prepared by directional solidification with seeding technique and the influence of processing parameters such as heating temperature and withdrawal rate on the microstructure and segregation tendency were investigated. In this work, dendrite structure was observed while the ranges of parameters were adopted. As the withdrawal rate or heating temperature increased, the primary dendrite arm spacing decreased gradually. The results strongly indicated that the average size of γ’ precipitates in dendrite core was larger than the one in inter-dendrite area in Ni3Al based alloys. With the increasing withdrawal rate or heating temperature, the size of γ’ precipitates in both dendrite core and inter-dendrite area decreased, while the morphology became regulated from spherality to cube. The tendency of segregation of Mo and Re in inter-dendrite area became more intense with the increasing withdrawal rate. No obvious variation of the segregation of elements was observed at different heating temperature.