Abstract The morphological instability of lamellar structures in Ni–Ni3Si eutectic and hypereutectic alloys directionally solidified at low growth rates was investigated. The first instability in large lamellar structures was zigzag instability, which formed curved lamellae. A zigzag pattern was first displayed in three dimensions. The diffusion-limited growth of the Ni3Si phase decreased phase width and spacing, consequently causing zigzag instability. The reduced spacing was observed at λ/λave = 0.9. After zigzag instability, the microstructure of the eutectic alloy turned into a labyrinth structure and lamellar fragmentation. However, in hypereutectic alloys, shape transition from lamellae to rods occurred, in turn, by the broken lamellae or elongated rods to dumbbell-shaped rods, peanut-shaped rods, and circular rods.

中文翻译：

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定向凝固 Ni-Ni 3 Si 合金层状结构的形态不稳定性

摘要 研究了在低生长速率下定向凝固的 Ni-Ni3Si 共晶和过共晶合金中层状结构的形态不稳定性。大型层状结构的第一个不稳定性是锯齿形不稳定性，它形成弯曲的层状结构。锯齿形图案首先以三个维度显示。Ni3Si 相的扩散限制生长减小了相宽度和间距，从而导致锯齿形不稳定性。在 λ/λave = 0.9 处观察到减小的间距。锯齿形失稳后，共晶合金的显微组织转变为迷宫结构和层状破碎。然而，在过共晶合金中，从片晶到棒材的形状转变依次发生在片晶断裂或细长棒到哑铃形棒、花生形棒和圆形棒的过程中。