# Effect of Segregation on Deformation Behaviour of Nanoscale CoCrCuFeNi High-Entropy Alloy
The authors varied the laser scan speed, laser power, and unidirectional and reversing laser passes in a wide range during the MD simulations to adjust the conditions to produce HEAs with the desired characteristics. The MD method is widely used for the investigation of the mechanical properties of HEAs, for example, cyclic plasticity [35]. This method allows considering the influence of the temperature and twin boundaries on the features of the structure formation of the CoCrFeMnNi HEA. However, for studying large systems of atoms with comparably high accuracy, it is important to choose the correct modelling parameters [36]. One of the main features of Cantor HEAs is their high impact strength, which reaches a value of 230 kJ/m\({}^{2}\) at a temperature of 77 K, which is much higher than that of conventional alloys [37]. In works [38; 39], atomistic studies were carried out for the CoCrFeMnNi alloy. The authors observed the ductile behavior of this Cantor under tension at cryogenic temperatures. It was revealed that the plastic deformation scenario is determined by the contribution of several components such as the transformation of the FCC lattice into the HCP martensite and the twinning and plasticity of GBs. The deformation of the Cantor CoCrFeMnNi alloy at low temperatures proceeds with the transformation of the crystalline phase into an amorphous one, which is accompanied by the formation of the so-called \"amorphous bridge\" leading to a separation of the cavities from the center of the crack origin [39; 40]. This amorphization in the alloy occurs as a result of the formation of multi-dislocation compounds. The deformation mechanisms in these areas include partial dislocations of high-density Shockley, shear bands, and amorphous bridges, which are rarely found in conventional alloys at low temperatures. A detailed study on the effect of doping and diffusion processes at different temperatures on the evolution of HEAs' structures under various conditions is important for their mechanical design. Because of the compositional complexity of HEAs, there is a lack of clarity in current experimental and analytical studies regarding the effects of GB segregation on the deformation mechanisms of HEAs. For example, in some HEAs, GB segregation can lead to the formation of a \"soft skin\" region at the boundaries, where the atoms are less strongly bound and, therefore, more easily deformable. This can lead to enhanced plasticity and ductility, which can be beneficial for some applications [41]. On the other hand, GB segregation can also lead to the formation of brittle phases or precipitates, which can cause cracking or fracture under stress. In some cases, GB segregation can also influence the deformation mode of the material. For example, in a nanocrystalline HEA, GB segregation can promote deformation through grain boundary sliding rather than dislocation motion [42]. Overall, the effect of GB segregation on the deformation mechanisms of HEAs depends on a variety of factors, including the specific alloy composition, processing conditions, and the nature of the segregation itself [43]. Understanding the underlying mechanisms of GB segregation formation and their impact on the mechanical properties is an active area of research in the field of HEAs. In this regard, this work aims to study the effect of GB segregations on the shear and tensile deformation behavior of equiatomic nanoscale CoCrCuFeNi HEA at room (300 K) and cryogenic (100 K) temperatures. The elemental GB segregation of each element type in the HEAs is considered. The mechanical characteristics of the nanoscale CoCrCuFeNi HEA with and without segregations are compared.