Sliver is a common solidification defect in nickel-based single crystal superalloy castings. Earlier studies about the slivers believed that this kind of defect originates from the undercooled nucleation of dendrites, like stray grains. In recent years, however, more researches show that the occurrence of sliver defects may be caused by the orientation deviation or dendrite fractures. The specific generation mechanism and inducing factors have not yet reached a unified conclusion in the academic community.

Regarding the origin of sliver defects, we have done related research. First, we observed the morphology of sliver defects from multiple scales, as shown in Figure 1. In some castings, the sliver defects may have an advantage orientation, and even finally transform into large stray defects throughout the entire casting. Different from the stray crystal and freckles defects, lots of experimental results prove that the sliver crystal defects do not have a large orientation deviation angle from the matrix. Further research on the orientation defects of sliver defects has been carried out in this study and tried to prove the forming mechanism of sliver defects.