Abstract
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.

Key words
antimony, hypereutectic Al-Si-Zr alloy, modification mechanism, mechanical properties, electrical conductivity

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