Deciphering the Three-Dimensional Relationship between Dendrite Orientation and Platform Configurations during the Directional Solidification of Single-Crystal Superalloys

Dendrite orientation plays a critical role in governing the expansion growth of nickel-based single-crystal superalloys within the platform region. The three-dimensional relationship between the dendrite orientation and platform configurations needs to be deciphered. This work aims to address this problem by systematically investigating how the orientations of the primary arm and secondary branches affect the dendrite growth behavior in the platform region. The results indicate that both primary arm inclination and secondary branch deviation enhance dendrite asymmetry at the platform bottom, increase the proportion of higher-order branches, promote the convergence interface among the high-order branches, and amplify misorientation and grain boundary formation. The initial orientation of secondary branches exerts a more pronounced effect on their growth behavior in the platform region. The larger deviation angles of the primary/secondary branches and the greater curvature of the solid–liquid interface contribute to an enhanced tendency for dendrite deflection during the directional solidification. This mechanism provides a rationale for the observed dendritic morphological asymmetry, nonuniform distribution, and grain boundary formation in the platform region. This work provides a comprehensive 3D understanding of dendrite growth and grain boundary formation during platform solidification in single-crystal turbine blades, thereby providing theoretical guidance for manufacturing high-quality single crystals.