Effect of Casting Pressure on Porosity, Microstructure, and Mechanical Properties of Large Die Casting Aluminum Alloy Parts

The application of casting pressure is a defining characteristic that distinctly differentiates the high-pressure die casting (HPDC) process from other conventional casting techniques. In this study, large and complex die casting aluminum alloy parts are prepared by vacuum-assisted HPDC process at three different dynamic casting pressures of 260 bar, 300 bar, and 390 bar. Combining X-ray computed tomography technique, tensile testing, and microscopic characterization, this paper analyzed the effect of different dynamic pressures on porosity and mechanical properties. The results show that increasing the dynamic pressure can significantly reduce the porosity. At near end, compared to parts produced at 266 bar and 300 bar, the yield strength of parts at 390 bar increased by 5.59% and 12.32%, respectively. The Weibull analysis substantiates that an increase in dynamic pressure enhances the consistency of elongation, thereby providing valuable insights for the assessment of process adjustments and the enhancement of mechanical properties. As the dynamic pressure increases, grains decrease in mean diameter and becomes more densely distributed. The sample fracture (390 bar) has a relatively small size of air pores and a dimpled morphology, especially in the central area. Thus, the tensile strength and plasticity of die casting alloys can be improved by using HPDC process. Thus, employing a high dynamic pressure-assisted HPDC process significantly enhances both the mechanical strength and ductility of die casting alloys.