Numerical and Experimental Design of a Step HPDC Mould for Process–Microstructure Correlation in Lightweight Component

The increasing demand for lightweight and energy-efficient components has strengthened the use of high-pressure die casting (HPDC) for thin-walled aluminium parts, often produced from recycled alloys. However, HPDC components are still affected by microstructural heterogeneity and defect formation, such as shrinkage porosity and gas entrapment, which are closely related to melt flow and solidification conditions. In this study, a dedicated step-casting geometry was developed to reproduce, within a single casting, solidification conditions representative of industrial HPDC components with varying thickness. The design was supported by numerical simulations to control filling and thermal evolution. Experimental HPDC trials were performed under industrial conditions, followed by microstructural characterization in terms of porosity, Secondary Dendrite Arm Spacing (SDAS) and skin layer thickness. Comparison with a complex industrial demonstrator component confirmed that the step casting reliably reproduces both average microstructural features and their variability. The proposed numerical–experimental approach provides a robust framework for process HPDC design and optimization for lightweight cast components.