Influence of Treatment Time and Nitrogen Flow Rate on the Density Index and Porosity Potential of AA 380.0 Aluminum Alloy for High-Pressure Die Casting

A complete 3² factorial design was conducted with two replicates, totaling 18 experimental runs. The metallurgical quality was quantified by the Density Index (DI), determined by the hydrostatic method after a reduced pressure test (RPT). The DI reduced from 27.6 % (untreated bath) to 0.90 % after 720 s of degassing. Response Surface Methodology (RSM) modeling adjusted a second-order polynomial (R² = 98.54 %; adjusted R² = 97.94 %; predicted R² = 96.87 %), confirming statistical significance of time, flow, and time×flow interaction (p < 0.05). The thermodynamic analysis based on Sieverts’ Law showed a 36 % reduction in the equilibrium solubility of hydrogen due to the thermal drop of the bath (787 °C → 711 °C). The lowest experimental DI values were observed at T = 720 s and V ≈ 25 L/min.