This study successfully designed and prepared the Al-13.6Cu-6Si alloy, and its mechanical properties and thermal conductivity were enhanced by Sr modification. The Al-13.6Cu-6Si alloy exhibited significant enhancements in thermal conductivity, ultimate tensile strength, and elongation, with values of 130.1 W/(m·K), 322 MPa, and 4.6%, respectively, as per the performance test results. These improvements were achieved through a 0.3% Sr modification. These values were 10%, 19%, and 53% higher than those observed in the alloy without Sr modification. A comprehensive analysis using OM, SEM, EDS, XRD, and CA-CCTA was conducted to examine the microstructures. It was noticed that the inclusion of Sr caused a refinement in the α-Al dendrites and eutectic Si phase, causing a change in the eutectic Si phase from a plate-like structure to a fine and uniform coral-like shape. The direct confirmation of the cooling curve thermal analysis results showed that the addition of Sr resulted in additional constituent overcooling, which increased the nucleation rate of heterogeneous nucleation and led to the reduction in the grain size of α-Al.
