<p>To enhance the mechanical properties of Al-Si-Cu-Mg alloy systems and promote the application of cast aluminum alloys in high-load structural components, this study first prepared Al-5wt.% TiB₂ intermediate alloy using KBF₄, K₂TiF₆, and pure aluminum, then incorporated it into the base alloy using the intermediate alloy dilution method, and combined it with a vacuum die casting process to produce TiB₂/Al-7Si-1.2Cu-0.4Mg composite materials. The microstructure and mechanical properties of the composite material were studied using optical microscopy, scanning electron microscopy, and tensile testing. The results showed that TiB₂ particles could be uniformly and stably distributed throughout the composite material as an effective reinforcing phase, which was verified by repeated experiments. When the TiB₂ content is in the range of 0.1–0.3 wt.%, the tensile strength and elongation of the composite material show a trend of first increasing and then decreasing with increasing TiB₂ content. TiB₂ particles not only hinder dislocation movement but also alter the morphology of the eutectic Si phase, transforming it from a lamellar structure to a short rod-like or granular structure. Among these, when the TiB₂ content is 0.15 wt.%, the composite material exhibits optimal mechanical properties, with a tensile strength of 290 MPa, an elongation of 2.4%, and a hardness of 104.57 HBW in the as-cast state, representing improvements of 31.8%, 4.3%, and 2.7%, respectively, compared to the as-cast base material. The reason why the tensile strength (290 MPa) of the composite prepared in this study remains competitive despite the low silicon content lies in the combination of the strengthening mechanism of TiB₂ particles and the advantages of the adopted process. The uniform dispersion of TiB₂ particles achieves the dual effects of grain refinement and second-phase strengthening, which compensates for the insufficient contribution of low silicon content to the matrix strength. Furthermore, the high compactness ensured by vacuum casting further guarantees the full exertion of the strengthening effect, making the material properties superior to those of the die cast alloy with the same composition but without TiB₂ addition. The improvement in the strength and toughness of the composite material can be attributed to the combined effects of grain refinement, TiB₂ strengthening, and improved morphology of the Si phase.</p>