3XXX series aluminum alloysAluminum alloy are valued in heat exchange applications for their corrosion resistance, thermal stabilityThermal stability, and good brazability. However, their commercial use is primarily limited to wrought and machined products, as conventional Al–Mn alloys are difficult to cast due to hot cracking and brittleness. Additionally, their relatively low strengthStrength restricts structural applications. This study aims to develop a castable Al–Mn–Mg alloy with enhanced mechanical performance by leveraging nanotechnology-promoted microstructureMicrostructure control. A small volume percentage of nanoparticles (0.5 vol.%) was introduced to control Al₆Mn phase growth, while Mn and Mg contents were systematically optimized to balance strengthStrength and ductility. Results show that nanoparticle addition not only improves mechanical propertiesMechanical properties but also delays the ductility loss typically observed at high Mn levels. The optimized composition demonstrates superior strengthStrength compared to commercial AA3004 while maintaining castability, offering a promising route to low-cost, high-performance aluminum alloysAluminum alloy for thermal management applications.