<p>There has been a growing interest in modern metal alloys with exceptional mechanical and functional properties that can be used in many advanced technologies, including biomedicine, the aerospace industry, and electronics. One of the research directions is the development of magnesium-based alloys, such as Mg–Zn–Ca, characterized by lightness, high strength, and biocompatibility. The article discusses the synthesis process of the Mg₆₂Zn₃₀Ca₄Au₁Er₃ alloy using the mechanical alloying (MA) method, which allows for a unique microstructure, appropriate powder refinement, and characteristic thermal properties. This paper analyzes the effect of chemical composition and process parameters on the microstructure and thermal properties of the tested alloy. The powders were milled for 5, 8, and 13&#xa0;h. The effect of ball milling time on the morphology, phase, and thermal transformations of magnesium-based alloys was investigated by producing alloys of the same composition after different milling times. The morphology of the obtained powders and their chemical composition were verified using scanning electron microscopy (SEM) with energy-dispersive spectroscopy (EDS). The particle size distribution in the samples was determined using laser particle size measurement. Structural changes were examined using X-ray diffraction (XRD). The thermal characteristics of the alloys were studied using differential scanning calorimetry (DSC). After SEM analysis, it was observed that the powders, regardless of the milling duration, exhibit a spherical shape with irregular smooth surfaces, and their sizes are similar. The phases identified after the MA process include Mg₅₁Zn₂₀, CaEr₂O₄, and Ca₅Zn₃, a solid solution of αMg, and unreacted Au. DSC analysis revealed additional peaks corresponding to the MgZn₂ phase. The DSC analysis also disclosed the presence of multiple peaks associated with the phases present in the alloy.</p>