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Methods of Ex Situ and In Situ Investigations of Structural Transformations: The Case of Crystallization of Metallic Glasses
Published on: June 7, 2018
Solidification velocities in deeply undercooled silver
Wai-Lun Chan1, Robert S Averback, David G Cahill
1Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA. wlchan@uiuc.edu
Physical Review Letters
|April 28, 2009
Summary
Researchers measured silver solidification velocity using ultrafast laser experiments. Velocity peaked at 0.85Tm, then plateaued, contradicting simple models but aligning with simulations.
Area of Science:
- Materials Science
- Solidification Physics
- Nanoscale Phenomena
Background:
- Understanding the kinetics of phase transitions, such as solidification, is crucial for materials processing and predicting material behavior.
- Existing models for crystallization velocity often rely on simplified assumptions about atomic interactions and transport phenomena.
Purpose of the Study:
- To experimentally determine the solidification velocity of pure silver (Ag) across a wide range of undercooling temperatures.
- To compare experimental findings with theoretical predictions, specifically collision-limited models and molecular dynamics simulations.
Main Methods:
- Utilized ultrafast, pump-probe laser experiments to measure solidification velocity.
- Employed optical third harmonic generation to determine the thickness of the liquid layer during solidification.
- Performed molecular dynamics simulations to model the crystallization process.
Main Results:
- Solidification velocity of pure Ag was measured from the melting point (Tm=1235 K) down to 0.6Tm.
- Observed a maximum solidification velocity at approximately 0.85Tm.
- The velocity remained nearly constant with further undercooling, a finding inconsistent with simple collision-limited models.
Conclusions:
- Experimental results agree well with molecular dynamics simulations.
- The crystallization velocity of silver exhibits weak temperature dependence over a broad undercooling range (0.85Tm to ~0.1Tm).
- Findings challenge simplistic models and highlight the importance of atomistic simulations for understanding solidification dynamics.
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