This study comprehensively investigates the impact of unsteady-state heat flow regime solidification on the thermal behavior and mechanical properties of the multicomponent Al-5Cu-5Si-5Mg-5Zn-1Zr (wt.%) alloy. The alloy was solidified in the unsteady-state heat flow regime at a cooling rate range of approximately (0.88–2.77 °C/s) using a custom-built solidification furnace equipped with eight thermocouples. Eutectic spacing (λ) decreased from 20 µm to 6 µm with increasing cooling rates, directly correlating with enhanced mechanical properties. The highest microhardness (HV=177.5 kg/mm²), compressive strength (σc=556.9 MPa), and compressive yield strength (σy=385.5 MPa) were achieved at the fastest cooling rate (2.77°C/s). These findings underscore the critical role of cooling rate optimization in achieving superior mechanical performance for aerospace and automotive applications.