Numerical simulation of fluid flow, solidification and defects in high pressure die casting (HPDC) process

The high pressure die casting process is extensively used to manufacture light metal parts with high productivity. A major drawback of the process is the relatively high variability in mechanical properties and poor repeatability between casting cycles, limiting the achievement of weight reduction through lighter design. Although it has been established that mechanical properties are adversely affected by casting defects, the origin of the relatively high randomness in the HPDC process is not well understood. Numerical simulation is a powerful and cost-effective tool to address this question, as it gives access to quantities that are difficult to obtain experimentally. A numerical simulation approach based on the finite element casting software ProCAST has been developed. The model was applied to the casting of aluminium tensile test samples, which were used to measure the tensile properties of the alloy. Simulation permitted the study of fluid flow, solidification and defect formation during each stage of the HPDC process: pouring, injection and cooling. Air entrapment and porosity distribution in the cast part were predicted. The results were compared with temperature measurements, porosity observations and solid distribution in the sleeve prior to injection. Although the results are still very preliminary, some trends could be established between the level of turbulence of the melt during injection and reduced elongation.