A new approach to enhance the efficiency of local squeezing during high pressure die casting of aluminum alloys

• New approach to squeeze pin parameters enhances queezing efficiency in high pressure die casting. • The stroke of the squeeze pin provides details of solid fraction in the squeezed region. • Squeeze pin velocity is more important than the delay time for EN AC 46000 alloy during squeezing. • Reduced squeeze velocity can provide stable mechanical properties independent of delay time. High Pressure Die Casting (HPDC) produces near-net-shape components with varying wall thicknesses, leading to heterogeneous solidification conditions. These effects led to inhomogeneities, which significantly affect mechanical properties. Local squeezing is a standard approach for minimising shrinkage porosity. We applied local squeezing at the industrial standard and at two magnitudes lower speeds: 27.5 mm/s and 0.7 mm/s. We varied the delay time, a typically used parameter in industrial practice, between 0.0 and 3.0 s. During the intervention, we recorded the complete motion curve of the squeezing pin. We took a sample from the squeezed volume and characterised its porosity distribution by density measurements, computed tomography, and scanning electron microscopy. The tensile strength of the squeezed volume was also measured. From the results, we concluded that the squeeze pin movement speed has a much stronger effect on the success of squeezing, i.e., the reduction of porosity. Based on microstructural examinations, we showed that the key to successful squeezing is selecting the optimal melt-to-solid ratio, which correlates with the maximum distance the squeeze pin travels. These results contribute significantly to the development of a monitoring system that can increase squeezing efficiency by orders of magnitude compared to current industrial practice.