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Glass transition by gelation in a phase separating binary alloy.
1Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
Physical Review Letters
|August 29, 2014
Summary
Glass transition in amorphous alloys occurs via gelation, forming a stiff atomic network. This network, similar to polymer gels, enhances mechanical properties and halts structural coarsening.
Area of Science:
- Materials Science
- Condensed Matter Physics
- Computational Chemistry
Background:
- Amorphous alloys exhibit unique properties due to their disordered atomic structure.
- Understanding the glass transition mechanism is crucial for designing advanced materials.
- Phase separation in alloys can lead to complex microstructures and properties.
Purpose of the Study:
- To investigate the mechanism of glass transition in a model phase-separating amorphous alloy, Cu50Nb50.
- To elucidate the role of local atomic packing in the glass transition process.
- To compare the observed glass transition phenomena with gelation in other soft matter systems.
Main Methods:
- Utilizing molecular dynamics (MD) simulations to model the behavior of Cu50Nb50.
- Analyzing atomic configurations and local packing during the simulated glass transition.
- Tracking the formation and evolution of percolating networks.
Main Results:
- The glass transition in Cu50Nb50 was found to occur through a gelation-like process.
- A mechanically stiff, percolating network with icosahedral local packing formed at interfaces.
- This network effectively arrested the coarsening of the phase-separated structure and provided shear resistance.
Conclusions:
- The glass transition in this amorphous alloy is analogous to gelation in polymeric and colloidal systems.
- The formation of an icosahedral-rich network is key to the mechanical stiffening and stability of the amorphous alloy.
- This study provides a new perspective on the fundamental mechanisms governing the behavior of amorphous alloys near their glass transition.
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