Combined Effect of Melt Shearing and Mold Vibration on Morphology of Si and Mechanical Properties of Rheo-gravity Die Casting of A339 Al Alloy
摘要
This study investigates the combined effect of the cooling slope process and mold vibration on the morphology of primary silicon grains of A339 hypereutectic alloy. Subsequently, the study evaluates how different casting conditions influence the alloy’s density, porosity, and mechanical properties. The alloy was poured from the inclined plate with an angle of 45° and a length of 500 mm at two different pouring temperatures (580 °C and 590 °C) with and without mold vibration (30 Hz). For comparisons, conventional casting was done for the same process parameters. The microstructure, phase transformations and facture behaviour were analyzed using X-ray diffraction (XRD), optical microscopy, and scanning electron microscopy. The results indicate that the combination of melt shearing from the cooling slope and mold vibration significantly refines the primary and eutectic Si particles. When the pouring temperature decreased from 590 °C to 580 °C at specific mold vibration (30 Hz), the average grain size of primary Si particles decreased from 65 to 52 µm, and the average aspect ratio decreased from 3.23 to 2.98. The refined and uniformly distributed primary grains of Si (52 µm) (cooling slope process and mold vibration) resulted in improved mechanical properties, with the highest tensile strength (192 MPa), ductility (4.92%), hardness (82 BHN), density 2.73 gm/cm3 and lowest porosity 2.5% at 580 °C pouring temperature. Fracture behavior analysis reveals that fracture mode moves toward ductile from brittle in hypereutectic alloy. These findings demonstrate that the cooling slope process combined with mold vibration is an effective method for enhancing the microstructure and mechanical performance of A339 alloy.