Nearly two decades have passed since the introduction of high entropy alloys, which can be synthesized using solid, liquid, or gas methods. This study focuses on the solid-state method of mechanical alloying to create high entropy alloy AlCoCuFeNi and examines the properties of the material at various stages of synthesis. The solid-state method of mechanical alloying was utilized in this research to synthesize a high entropy alloy, with samples taken at regular intervals of 10, 20, 30, 40, and 50 hours. X-ray diffraction (XRD) was used to characterize the alloys, with further XRD analysis performed to determine crystallite size and lattice strain. In this study, high entropy alloys were successfully synthesized as two-phase solid solutions with a two-phase crystal (FCC) structure. The resulting alloy had a crystallite size of 8.4 nm and a residual strain of 1.7%. Elemental mapping image revealed that after 50 hours of mechanical alloying, all elements in the high entropy alloy were dissolved into each other with nearly identical atomic ratios, a finding confirmed by XRD analysis. The solid solution alloys synthesized in this research exhibited an intriguing phase separation phenomenon at the nano scale. The observation of two phases with different lattice constants highlights the versatility of high entropy alloys and their potential for diverse applications.