Improvement of Solidification Structure Uniformity in Al-Cu Alloy Casting Process

Aluminum–copper alloys are core lightweight materials in aerospace applications; however, their casting is prone to grain size imbalance and Al₂Cu phase segregation. To address these issues, this study focused on an Al–6.07 wt.% Cu alloy and employed a three-factor, three-level orthogonal experimental design using squeeze casting. The effects of pouring temperature, forming pressure, and holding time on solidification uniformity were investigated using metallographic microscopy, SEM, and EPMA. The results indicated that the optimal process parameters were a pouring temperature of 730 °C, a forming pressure of 170 MPa, and a holding time of 13 s, combined with aging at 120 °C for 4 h. Under these conditions, the grain size standard deviation (GSSD) of the surface and core was reduced to 7.3 μm and 13.5 μm, respectively, while the Al₂Cu phase segregation degree decreased to 0.14. Consequently, the tensile strength reached 342 MPa, with a microhardness of 120 HV. The study confirms that the proposed “pressure–temperature–solute” coupling mechanism effectively suppresses segregation, providing both theoretical insight and process guidance for the mass production of high-load-bearing alloy components.