Segregation and aggregation of rhenium in tungsten grain boundary: Energetics, configurations and strengthening effects

We have investigated the segregation of rhenium (Re) atoms in a tungsten (W) Σ5(310)/[001] symmetrical tilt grain boundary (GB) as well as their influences on the mechanical properties of W using a first-principles method. It is found that the W Σ5(310)/[001] GB can serve as a strong sink for a single Re atom with the lowest segregation energy of −0.57 eV. The stability of Re in the W GB is directly related to the Re-occupied position and the bond lengths of Re with neighboring W atoms. Interestingly, it is clearly observed that the segregation of multiple Re atoms in the W GB will form the distinct planar structures, in a good agreement with previous experimental studies. Such planar segregation of Re can be rationalized by the strong site-dependent attraction of Re-GB and the weak repulsion of Re–Re. Further, we demonstrated that both a single Re and Re clusters have the significant strengthening effect on the W GB owing to the obvious increase of charge density between two grains, and this influence will be enhanced with the increasing of Re numbers. Our calculations provide a good reference to understand the behavior of Re in W and evaluate the performance of the W-PFM in future fusion reactors.