<p>With the development of aero-engines toward high performance, lightweight design, and integration, the integrated manufacturing of turbine disks and single-crystal blades has become a critical technical challenge. This study proposes a casting system and process optimization method for dual-alloy precision casting of turbine disks, tailored to the characteristics of the Ni-based K447A high-temperature alloy (K447A) and DD412 single-crystal alloy (DD412). The method involves pre-placing DD412 blades in the mold, followed by casting molten K447A into the mold to achieve solid–liquid bonding at the interface between the turbine disk and the single-crystal blades. Such a metallurgical bonding process occurs through mutual melting at the interface, which leads to the formation of common metallic bonds and consequently results in a continuous, compact, and robust interfacial bonding layer. Based on finite element numerical simulation, the study investigates the parameters of the heat-controlled solidification process, revealing their effects on the solidification process, melt filling behavior, defect formation, and mechanisms of grain nucleation and growth. Combined with the Taguchi optimization method, the optimal process parameters for controlling solidification behavior and minimizing casting defects are determined, establishing a process framework suitable for precision casting of dual-alloy-integrated turbine disks. Experimental results show that, under the optimized process, the turbine disk exhibits a uniform and refined microstructure, and the bonding interface between the single-crystal blades and the turbine disk achieves high-quality metallurgical bonding. This research provides theoretical support and experimental evidence for the process optimization and practical application of dual-alloy-integrated turbine disk manufacturing.</p>