Convection-Induced Compositional Patterning at Grain Boundaries in Irradiated Alloys
G F Bouobda Moladje1, R S Averback1, P Bellon1
1Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana-Champaign, Illinois 61801, USA.
Physical Review Letters
|August 18, 2023
Summary
Radiation-induced segregation in alloys can form stable precipitate patterns at grain boundaries. These patterns resist coarsening due to solute advection dominating thermal diffusion, a novel finding in materials science.
Area of Science:
- Materials Science
- Nuclear Engineering
- Physical Chemistry
Background:
- Radiation-induced segregation (RIS) is a critical phenomenon in materials under irradiation.
- Precipitate stability at grain boundaries (GBs) influences material performance and longevity.
- Understanding precipitate coarsening kinetics is essential for predicting material behavior.
Purpose of the Study:
- To investigate the stability of precipitates formed by RIS at GBs in dilute alloys.
- To quantify the influence of grain size and GB misorientation on precipitate patterns.
- To identify novel regimes of precipitate stability and coarsening resistance.
Main Methods:
- Utilizing phase field modeling to simulate precipitate formation and evolution.
- Quantifying the effects of grain size and symmetric-tilt GB misorientation.
- Analyzing maps of the chemical Péclet number to understand transport phenomena.
Main Results:
- A novel regime was identified where GB precipitates resist coarsening over long timescales.
- Arrested coarsening occurs when solute advection dominates thermal diffusion at the precipitate-matrix interface.
- This mechanism prevents interfacial local equilibrium and overrides capillary-driven coarsening effects.
Conclusions:
- GB precipitate patterns formed by RIS can exhibit remarkable stability against coarsening.
- The dominance of solute advection over thermal diffusion is key to this arrested coarsening.
- This finding offers a new perspective on precipitate stability, distinct from behavior in liquid-solid systems.
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