Variation of crystal orientation during epitaxial growth of dendrites by laser deposition

doi:10.1016/j.jmst.2017.05.002

Abstract

Abstract:

A nickel-based superalloy was deposited onto a single crystal substrate based on epitaxial laser metal forming (E-LMF). The microstructure development in two depositions has been researched. For the first time, the crystal orientation of dendrites varying beyond 20° was found when the dendrites deflected in deposition. In addition, a new grain boundary was found between different orientation dendrites in a grain, and the detected grain boundary angle was 23°. The result shows that flowing field in laser pool is responsible for this phenomenon.

Key words: Crystal orientation, Epitaxial growth, Laser deposition, Single crystal, Dendrite growth

Guowei Wang, Jingjing Liang, Yizhou Zhou, Libin Zhao, Tao Jin, Xiaofeng Sun. Variation of crystal orientation during epitaxial growth of dendrites by laser deposition[J]. J. Mater. Sci. Technol., 2018, 34(4): 732-735.

Figures/Tables 4

Fig. 1. Schematic diagram showing the laser deposition process.

Fig. 2. Optical micrograph of microstructures for (a) sample A and (b) sample B. The yellow dashed curves present the melted traces. The white dotted rectangles are joint zones between right and left melted traces. The deflection angles of dendrite growth direction at red points (C1, D1, E1, C2, D2, E2) were measured. Microstructures of joint zones for (c) sample A and (d) sample B. The deflections of dendrite growth direction at melting traces were signed with black meander-line.

Fig. 3. EBSD map for (a) sample A and (b) sample B. In the white dotted rectangles (F1, G1, H1, F2, G2, H2), the variations of crystal orientation were measured as inverse pole figures. The white rectangles are joint zones between right and left melted traces.

Fig. 4. Calculation results of flowing field for (a) sample A and (b) sample B. (c) Dendrites deflecting toward upstream direction. (d) Deflective growth of dendrites in melting pool. (e) A sketch to explain the zig-zag pattern. (f) A sketch to explain the deflection trend.

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