Influence of different parameters on fluidity and mechanical properties of a high pressure die casting AlSi10MnMg alloy

AlSi10MnMg alloy is the preferred alloy for producing large automotive castings owing to its high fluidity, while the quantitative relationship between fluidity and high-pressure die casting (HPDC) parameters remains insufficiently understood. In this work, the influence of HPDC parameters, including shot speed and die temperature, on the microstructure and fluidity of AlSi10MnMg alloy was investigated. The results reveal that reducing the slow-shot speed from 0.3 m·s −1 to 0.12 m·s −1 increases the size of externally solidified crystals (ESCs), while simultaneously allowing for an extended vacuum time that significantly reduces porosity. Consequently, only a slight decrease in flow length is observed, accompanied by a minor deterioration in mechanical properties. With an increase in the fast-shot speed from 1.04 m·s −1 to 2.08 m·s −1 , the average size of the ESCs decreases from 22.53 µm to 13.50 µm, and the porosity drops sharply from 1.13% to 0.04%. Accordingly, the flow length increases significantly from 1,238 mm to 1,450 mm, and the mechanical properties are markedly enhanced. Although an elevated die temperature reduces melt viscosity and prolongs the flowing time, it simultaneously promotes the pronounced coarsening and increases volume fraction of ESCs, thereby escalating flow resistance. Under the competing influences of thermodynamic benefits and microstructural resistance, the flow length marginally increases from 1,258 mm to 1,283 mm as the die temperature is raised from 120 °C to 150 °C. However, when the die temperature is further increased to 180 °C, the adverse effect of ESC coarsening completely offset the benefits of the elevated temperature, resulting in a virtually unchanged flow length. In addition, both excessively low and excessively high die temperatures increase casting porosity, leading to a subsequent decline in mechanical properties.