Effect of Pouring Temperature on Microstructure Characteristics and Properties of Semi-Solid Near-Eutectic Al–Si Alloy

Near-eutectic Al–Si alloys attracted significant interest in automotive, aerospace, and other industries owing to their superior strength and high-temperature resistance. However, the alloy’s narrow solid–liquid temperature range presents challenges in semi-solid processing. In this study, an Enclosed Cooling Slope Channel was used to prepare near-eutectic Al–12Si–4Cu–2Ni–0.8Mg–0.1Gd alloy semi-solid slurry. We investigated the impact of liquid squeeze casting (LSC) and rheo-squeeze casting (RSC) on the alloy’s microstructure characteristics and properties of the alloy were explored. Findings indicate that the average size of primary α-Al decreases first and then increases with the rising pouring temperature. Through the RSC process, the ultimate tensile properties of the material are significantly improved, achieving optimal tensile properties at the pouring temperature of 605 °C, with ultimate tensile strength and elongation of 247 MPa and 2.66%, respectively. Compared with LSC samples, the ultimate tensile strength and elongation increased by 44.4% and 116.3%, respectively. This enhancement in properties is credited to the notable reduction in porosity and the spheroidization of primary α-Al. Regarding high-temperature performance, the alloy’s tensile strength at a test temperature of 200 °C stands at 194.6 MPa. marking only a only 21.2% decrease from the room temperature result. The precipitation of the thermally stable phase and the solid solution effect of Gd elements effectively hindered the reduction of high-temperature tensile properties. Graphical Abstract