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Dendrite fragmentation in alloy solidification due to sidearm pinch-off
H Neumann-Heyme1, K Eckert1, C Beckermann2
1Institute for Fluid Dynamics, Technische Universität Dresden, 01062 Dresden, Germany.
Physical Review. E, Statistical, Nonlinear, and Soft Matter Physics
|January 15, 2016
Summary
Dendrite sidebranch detachment, a key alloy solidification process, is modeled to understand its dynamics. Pinch-off occurs within specific geometric and cooling rate ranges, bounded by other detachment mechanisms.
Area of Science:
- Materials Science
- Metallurgy
- Solidification Science
Background:
- Dendrite sidebranch detachment is a critical fragmentation mechanism in alloy solidification.
- This detachment occurs at the junction between a sidearm and its parent stem.
- The process is driven by capillarity but opposed by solidification.
Purpose of the Study:
- To model the essential dynamics of dendrite sidebranch development.
- To investigate the morphological transitions during sidebranch detachment.
- To identify the conditions and bounds for sidebranch pinch-off.
Main Methods:
- A simple numerical model of a single dendrite sidearm was employed.
- The model captured the dynamics of sidearm evolution and pinch-off.
- Analysis focused on geometrical parameters and solidification rates.
Main Results:
- Sidearm pinch-off occurs within limited ranges of geometrical parameters and cooling rates.
- Pinch-off is bounded by sidearm retraction and coalescence regimes.
- Pinching at the branching point is faster than the Rayleigh-Plateau instability.
Conclusions:
- The overall evolution of sidearm shape depends sensitively on initial geometry and solidification rate.
- Simple scaling relations define the bounds for the pinch-off regime.
- Numerical modeling provides insights into complex solidification fragmentation mechanisms.
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