Effects of Porosity on Mechanical Properties of Castings in High-Pressure Die-Casting Process

With recent trends toward lightweight designs, the integration and enlargement of aluminum-based automotive body parts have accelerated. These large-scale casting processes primarily rely on high-pressure die casting (HPDC). To improve the formability of large body components and increase their strength through heat treatment, it is crucial to control the gas porosity defects, which are a major drawback of the HPDC process. In this study, to control gas porosity defects, computed tomography (CT) was used to classify different types of porosity. The results clarified how porosity forms and evolves in both conventional and vacuum die-casting processes, as well as the effects of heat treatment on the porosity and mechanical properties of the castings. Sphericity was used to distinguish blowholes (sphericity >= 0.4) from shrinkage defects (sphericity < 0.4) via X-ray CT analysis. As the solution treatment time increased, the tensile and yield strengths increased, whereas the elongation decreased. Under the same heat treatment (500 degrees C + 1.5 h), the elongation ranged from 8.60 to 6.20%, with greater elongation observed when blowholes were more prevalent and the pore size and volume were smaller.