对高温合金单晶叶片铸件中条纹晶起源处的微观组织进行了观察分析，提出了这种晶粒缺陷的产生机理。通过微观检测确认了条纹晶的出现是由于铸件表面单个枝晶主干在糊状区内被撕断，但又被残余液体焊合，呈现出明显的起点。导致这种撕裂的主要原因是型壳粘连引起的枝晶收缩严重受阻或是由夹杂切割引起的枝晶强度严重受损，从而形成了条纹晶缺陷产生的2种主要机制。撕裂后的枝晶会发生一定程度的整体偏转，在基体组织上形成一个由小角度晶界封闭而成的狭长晶粒。比较了条纹晶与其它晶粒缺陷的相似和不同之处，并讨论了减少条纹晶缺陷应该采取的工艺措施。

In the casting components of superalloys with increasing content of the refractory elements the occurrence of sliver defects becomes rather frequent. In comparison to the other grain defects such as stray grains and freckles, the sliver defect was less well understood and its formation mechanism is still unclear. In the present work, the origins of the sliver defects in the single crystal (SC) castings were investigated. In the metallographic detection, sliver grains can be identified to be miss-alignments of isolated, individual primary dendrite on the SC matrix. The sliver defects originated from the tearing of the existing dendrite stems in the mush zone, revealing a clear starting point of sliver defect. The cracks of the dendrites were filled by the interdendritic residual melt, which finally solidified into γ′-stripes. The tearing of some existing dendrite stems can be attributed to the adhesion of shell mold that hinders the shrinkage of the columnar dendrites on the casting surface. The second reason for the dendrite tearing is the insertion of oxide residues which significantly weakens the strength of the dendrite stems. Due to the support of the neighboring columnar dendrites, the tilting of the broken dendrites is limited, so that the grain boundary between a sliver and the matrix structure has normally a low angle. The structure and formation mechanisms of sliver defects were discussed in comparison with other defects such as stray grains, freckles and low angle grain boundaries. The corresponding methods were proposed to avoid sliver defects in production of SC superalloy castings.