Morphological instability of lamellar structures in directionally solidified Ni-Ni3Si alloys
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.
- Publication:
-
Journal of Crystal Growth
- Pub Date:
- February 2018
- DOI:
- 10.1016/j.jcrysgro.2017.12.007
- Bibcode:
- 2018JCrGr.483..275W
- Keywords:
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- A1. Directional solidification;
- A1. Eutectics;
- A1. Morphological stability;
- A2. Bridgman technique