# Effect of Segregation on Deformation Behaviour of Nanoscale CoCrCuFeNi High-Entropy Alloy
## 3 Results and Discussion
### Deformation at 100 K  
It is worth noting that modeling at 100 K did not reveal significant differences in the dynamics of the deformation-induced evolution of the structure compared to that at 300 K, as demonstrated in Figures 6 and 8. The primary distinction lies in the fact that at 100 K, the bicrystal containing copper segregation exhibited weaker plastic properties than at 300 K. The decrease in temperature from 300 K to 100 K caused the elongation of the bicrystal to drop by 3% before breaking. However, the deformation mechanism of the bicrystal in the presence of other types of atoms at GB segregation remained similar at both temperatures. demonstrate that GBs with segregations are unstable and relocate under shear deformation, with the presence of a segregated layer fixing one of the GBs. During deformation, the structure evolves due to the formation and migration of twins and the migration of GBs in the vicinity of the crack. The bicrystal with copper and chromium segregations exhibited the highest strength under shear deformation, and the maximum shear stress increased with an increase in the thickness of the segregation layer. Conversely, the bicrystal without segregation had the greatest plasticity. An increase in the thickness of the segregated layer from 3 A to 5 A in the bicrystal with the crack led to a decrease in its plasticity. Additionally, an increase in strength during stretching was observed for the bicrystal with chromium segregation, while an increase in the thickness of nickel and copper segregations at the GB of the bicrystal made it more ductile. The simulation results indicate that the mechanical properties of the studied bicrystal are similar at both 300 K and a cryogenic temperature of 100 K. Only a slight decrease in plasticity was observed at 100 K for the bicrystal containing the copper segregation. Future studies are required to investigate the contribution of cryogenic temperature to the formation of amorphous bridges with a higher number of segregations. Additionally, the impact of misorientation between GBs in the CoCrCuFeNi HEA containing cracks near the GBs on its mechanical properties is an important aspect that requires further investigation. Overall, our results provide important insights into the correlation between the structure and properties of new types of the nanoscale CoCrCuFeNi HEA demonstrating the potential to control the mechanical properties of HEAs through the manipulation of the thickness and type of segregations. Despite many experimental studies on the deformation behavior of various HEAs, to the best of our knowledge, there are few experimental results reporting on the influence of segregations at GBs on deformation mechanisms specifically in the CoCrCuFeNi HEA. Therefore, our results cannot be directly compared with experimental ones. However, the GB segregation of Cr in HEAs and its positive effect were discussed earlier in [51]. The authors reported that Cr has a strong self-bonding tendency leading to improved GB strength. Moreover, the strengthening effect of Cu atoms at the GBs of CoCrCuFeNi HEA was observed earlier in [52] using combined MD/Monte Carlo modelling. Similarly, we observed higher stress required for the plastic shear deformation of bicrystals with Cr and Cu at GBs compared with other cases. We believe that this study can be helpful for a better understanding of the effect of various GB segregations on the mechanical properties of HEAs. However, it should be noted that the impact of doping elements on HEAs' characteristics requires further deep investigations, as doping may lead to the formation of various phases with reduced physical and mechanical properties. Conceptualization, E.A.K. and R.I.B. ; methodology, A.M.K. ; software, A.M.K. and A.V.Y. ; data curation, A.A.K. ; writing--original draft preparation, A.M.K. ; writing--review and editing, E.A.K. ; visualization, E.Z.K. ; supervision, E.A.K. All authors have read and agreed to the published version of the manuscript.