Abstract
A novel approach towards the design of coarsening-resistant nanoprecipitates in structural alloys was investigated by kinetic Monte Carlo (KMC) simulation. The approach is motivated by recent experimental results in Cu-Nb-W alloys showing that room temperature ion irradiation resulted in W nanoprecipitation, leading to exceptional stability of W-rich-core/Nb-rich-shell nanoprecipitates formed following thermal annealing (Zhang et al., 2013 [11]). Here, image simulations of atomically resolved scanning transmission electron microscopy are performed to establish that these W nanoprecipitates are highly ramified. Thermal precipitate coarsening in an A-B-C ternary alloy similar to Cu-Nb-W is then studied by KMC simulations, where the highly immiscible and refractory C solute atoms are initially distributed into fractal nanoprecipitates, or cores, which become coated by a shell of B atoms during elevated temperature annealing. Compared with nanoprecipitates generated by compact C cores, the ramified nanoprecipitates result in exceptionally high trapping efficiency of B solute atoms during thermal coarsening, and the efficiency increases with the cluster size. The KMC results are analyzed and rationalized by noting that, owing to the Gibbs-Thomson effect, when the curvatures of the shell of the precipitates are zero or negative, the microstructure is coarsening-resistant. Such morphology can be realized by facets, or by dynamic balance within positive, negative and zero curvatures.
Original language | English (US) |
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Pages (from-to) | 37-46 |
Number of pages | 10 |
Journal | Acta Materialia |
Volume | 79 |
DOIs | |
State | Published - Oct 15 2014 |
Keywords
- Copper alloys
- Core/shell structure
- Ion irradiation
- Monte Carlo techniques
- Precipitation
ASJC Scopus subject areas
- Ceramics and Composites
- Metals and Alloys
- Polymers and Plastics
- Electronic, Optical and Magnetic Materials