Secondary orientation regulating dendrite growth behavior in single crystal blades by dendrite growth path and solute distribution

The dendrite growth behavior in DD3 single crystal blades under different secondary orientations was investigated. Microstructural analysis revealed a significantly smaller primary dendrite arm spacing (PDAS) in the blade body for the [210] orientation compared to the [100] orientation. For [210] orientation single crystal blades, the angle between the heat flow and the secondary dendrite arms was larger than the [100] orientation blades, causing a more complex dendrite growth path. Furthermore, melt flow induced lateral dendrite growth, promoting higher-generation branching during solidification. In addition, when the angle between the solute diffusion direction and temperature gradient changed, severe solute segregation occurred in [210] orientation, further leading to changes in the local undercooling and freezing range, which resulted in a decrease in PDAS. In other words, compared to [100] orientation, the decrease in PDAS of single crystal blades with [210] orientation was attributed to the synergistic effects of the dendrite growth path and solute element distribution during solidification process.