Casting Al-Cu-Mn alloy has the characteristics of low density, high specific strength, high hardness, good processability, and high-temperature performance. Therefore, it is one of the preferred lightweight structural materials and has been widely used in various fields such as aerospace, and transportation, such as aircraft rib and wing components, and automobile wheels. [1][2][3] In previous studies, adding rare earth elements such as Zr, Y, and La to Al-Cu-Mn alloys for microalloying treatment has become the main means of improving the comprehensive performance of alloys. [4][5][6] Rare earth elements can not only purify the melt and refine grain structure but also activate the aluminum alloy. However, the use of trace rare earth element Sc for aluminum alloy microalloying in the study of casting Al-Cu-Mn alloy is not common. As the working environment and green environmental requirements of materials become increasingly stringent, the application of traditional Al-Cu-Mn alloys is becoming more and more restricted. [7] Therefore, improving the comprehensive properties of Al-Cu-Mn alloys is an urgent problem to be solved.Sc is currently one of the most effective rare earth elements found to optimize the performance of aluminum alloys. Research on adding Sc to 2000 series Al-Cu alloys has been widely recognized. Wu et al. [8] found that Sc can improve the yield strength (YS) and pitting corrosion resistance of Al-2.5Cu alloys, and can promote the precipitation of θ 0 precipitates at different positions under different grain sizes. The smaller the grain size, the stronger the effect of Sc microalloying. Zhang [9] quantitatively described the effects of scandium and silver on the grain size and precipitation phase of Al-Cu alloys, as well as the contributions of grain refinement and precipitation strengthening to the YS. The results showed that the addition of Sc refined the grain size, and θ 0 precipitation increased the YS, tensile strength, and elongation (EL) of Al-Cu alloys to 314.2, 410.6 MPa, and 6.31%, respectively.In addition, adding Sc to Al-Cu alloys can form Al 3 Sc precipitate phases. The dispersed Al 3 Sc precipitates in the matrix play an important role in improving the mechanical properties of the alloy, as they can pin grain boundaries and dislocations, preventing grain slip and restricting the motion of grain boundaries, thereby significantly improving the resistance to deformation

This study investigated the effect of Sb additions (0, 0.4, 0.8, 1.2, 1.6, and 2.0 wt.%) on the microstructure, mechanical properties, and thermal conductivity of hypereutectic Al-20Si-0.3Zr alloy. The aim was to refine and homogenize the Si phases to improve the alloy's thermal conductivity, casting fluidity, and mechanical properties. Various techniques, including SEM, EDS, XRD, DSC, a universal testing machine, and a conductivity tester, were used to analyze the as-cast specimens. The results showed that adding Sb up to 1.6 % significantly refined the morphology of primary Si, reducing its average size by 87.2 % from 376.17 to 48.30 µm, and modified the eutectic Si structure from seagrass-like to vane-like. This refinement and homogenization led to an increase in optimal elongation (El) by 183 % from 1.2 to 3.4 % and the ultimate tensile strength (UTS) by 29.4 % from 132.1 to 170.9 MPa. Furthermore, the addition of 1.6 % Sb improved the alloy's thermal conductivity and conductivity while also reducing its solidification temperature range from 442.2 to 328.5 K, improving casting fluidity. These findings suggest that Sb modification can be a useful method to improve the thermal conductivity, casting fluidity, and mechanical properties of Al-20Si-0.3Zr alloy.