## 1 Introduction
The results showed that using PVTi-coated tungsten carbide end mills allows for effective machining of HEA without the need for coolant, while keeping tool wear within a steady-state wear region. In contrast, conventional cutting tool materials cannot be effectively applied to HEA, as excessive heat is generated during the machining process, severely limiting tool life. In terms of machinability, HEA performs approximately 59% better than stainless steel. Chemical analysis of the chip surface revealed that both HEA and 304 stainless steel exhibit a strong tendency to oxidize, and the analysis indicated that the material's microstructure changes during the machining process. Microhardness measurements show that material inhomogeneity or the self-hardening effect caused by cutting forces is one of the reasons for chip fragmentation. [PERSON] et al. [19] investigated the effects of spindle speed, feed rate, and cutting depth on surface roughness and morphology during ultra-precision cutting of Al\({}_{80}\)Li\({}_{5}\)Mg\({}_{5}\)Zn\({}_{5}\)Cu\({}_{5}\) HEA using diamond tools and PCBN tools. Ultra-precision cutting experiments were conducted using Al\({}_{80}\)Li\({}_{5}\)Mg\({}_{5}\)Zn\({}_{5}\)Cu\({}_{5}\) HEA rods, and the machined surface quality was collected using a white light interferometer. A microscope was used to observe the three-dimensional topography and the microstructural morphology of the HEA machined surface. Under scanning electron microscopy, two different crystalline phases were observed to form on the tool surface. The results show that when cutting with PCBN tools, greater compressive and frictional forces were generated between the tool and the HEA surface, promoting the refinement and diffusion of the eutectic phase, which the hardness of the finished surface was increased to 218 HV. In contrast, when using diamond tools, the hardness was decreased to 190 HV, primarily due to the influence of shear forces on the diamond tool. Shear force was also one of the reasons for the lower surface roughness observed. As the ultra-precision process parameters were increased, the surface roughness of Al\({}_{80}\)Li\({}_{5}\)Mg\({}_{5}\)Zn\({}_{5}\)Cu\({}_{5}\) HEA was increased. The feed rate has the greatest influence on surface roughness, followed by cutting depth, while spindle speed has a smaller effect. Furthermore, when using diamond tools, the surface roughness (Ra) shows little variation, whereas when using PCBN tools, the Ra was increased significantly. [PERSON] et al. [20] investigated the machinability of selective laser melting CoCrFeMnNi HEA through various processing methods, including milling, grinding, wire electrical discharge machining (wire EDM), and electropolishing (EP). Surface morphology, roughness, microhardness, residual stress, and subsurface quality were measured. Additionally, the effects of different machining processes on surface and subsurface quality were analyzed. The results show that milling and grinding may smooth the surface and enhance microhardness but introduce tool marks and compressed residual stresses due to microstructural deformation. Mechanical polishing, using low-pressure loose abrasives, creates an ultra-smooth surface without subsurface damage. Furthermore, wire EDM as a thermal processing method can flatten the surface but generates a heat melt layer, increasing tensile residual stress and surface microhardness. EP may smooth the surface, releases residual stresses, and removes subsurface damage, but it cannot achieve micron-level surface roughness from a very rough initial condition. Combining mechanical and electrical processes can yield better surface quality. In terms of elemental composition, the elements of CoCrFeMnNi HEA remain stable after mechanical and electrical treatments, but copper introduced by wire EDM alters its composition. There is an interrelation between microhardness, residual stress, and subsurface defects. Microstructural deformation leads to subsurface defects, which in turn increase microhardness and residual stress.