Potassium Clusters in Tungsten Grain Boundaries: Formation Mechanism and Strengthening Effect
Journal of nuclear materials(2023)
Abstract
We systematically studied the solution and aggregation behavior of Potassium (K) in the symmetrical tilt Tungsten (W) grain boundary (GB) Ʃ5(310)/[001] through first-principles simulations. The lowest-energy substitutional sites are the nearest neighbor sites of GB (V1) in the W-GB, instead of the GB sites themselves, which can be understood by the charge redistribution between the K and W atoms. Interestingly, our simulations show that segregation of multiple K atoms in W GB will form a cluster structure around the GB, which is well consistent with previous experimental reports. Electronic analysis reveals that previously trapped K atoms adjust the electronic densities around them to be more suitable for trapping more K atoms. Due to the greater binding energy of K-K over W-W at the GB, incorporation of K atoms leads to a slight increase in the fracture energy of the GB structure.
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Key words
Tungsten grain boundary,Potassium clusters,Segregation and aggregation,Ab initio molecular dynamics simulation
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