In this study, the effect of cooling rate under unsteady-state heat flow conditions on the microstructural evolution and phase formation of a freely solidified Al-5Cu-5Si-5Mg-5Zn-1Zr multi-component aluminum alloy was investigated. Solidification experiments were conducted using a specially designed experimental setup to achieve different cooling rates along the sample. The microstructure and phase composition of the solidified alloy were comprehensively characterized using optical microscopy, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD). The results indicated that cooling rate significantly impacts the microstructure and intermetallic phase formation. As the cooling rate increased, dendritic structures became finer, and eutectic spacings decreased. Additionally, various intermetallic phases such as Al₂Cu, Mg₂Si, MgZn₂, and Al₃Zr were observed within the α-Al matrix phase depending on the cooling rate. At high cooling rates, intermetallic phases were more finely and homogeneously distributed, while at low cooling rates, a coarser and irregular distribution was observed. These findings suggest that solidification under unsteady-state heat flow conditions is an effective method for controlling the microstructure of multi-component aluminum alloys, and consequently, their mechanical properties. The results of this study could provide guidance for the development of new multi-component aluminum alloys and the improvement of the performance of existing alloys.