• Liquid-solid compound casting successfully fabricates A356/6061 bimetallic composites with complete metallurgical bonding when a dense protective layer is applied via chemical zinc deposition and electroplating.
• The interfacial microstructure is characterized by equiaxed grains with eutectic silicon at grain boundaries, and the zinc plating thickness does not significantly affect the transition layer microstructure.
• Pouring temperature critically influences metallurgical bonding; higher temperatures increase transition layer thickness but slightly decrease interfacial shear strength, with a maximum shear strength of 68 MPa.
• The hardness of the bimetallic interface lies between the hardness of the constituent alloys, indicating a gradient property suitable for lightweight automotive applications.