Various solidification conditions of processing alloys have a strong influence on microstructure development, often leading to extended solid-state solubility. In this study, the solubility of Mg in the α-Al solid solution was investigated by varying the solidification conditions of the AlMg5 alloy. Two different casting methods were employed: a conventional technique (gravity casting) and a non-conventional one (melt-spinning), using a self-design device. The variations in Mg solubility were assessed by EDS analysis, revealing a value of 5.20wt% for the sample obtained through gravity casting into a metallic die, and complete solubility of all alloying elements in the sample produced by melt-spinning. Although the XRD patterns confirmed the formation of a fully supersaturated solid solution after rapid solidification, the hardness of the material did not exhibit a significant increase, with values around 90 HV. These findings suggest that while melt-spinning enhances solubility at the microstructural level, additional mechanisms may be required to achieve substantial improvements in mechanical properties.