Assessing aluminium casting quality: a novel analytical approach for early-stage evaluation of alloy feedstock purity and integrity

A novel in-situ vacuum Reduced Pressure Test (RPT) device was developed to evaluate intrinsic ingot quality prior to remelting in aluminium casting processes. Five alloys (primary A356, secondary A356, secondary A225, secondary A413 and secondary A380) were analysed through solidification under 80 mbar vacuum in an argon atmosphere. Bifilm index, total defect area, density measurements and three-dimensional X-ray computed tomography (CT) were used to characterise bifilm-related defects. A strong positive correlation (R2 = 0.840) was observed between the cross-sectional bifilm index and the cumulative pore diameters obtained from CT analysis, confirming that sectional measurements can represent bulk defect burden. Remelting increased bifilm population due to oxide entrainment during charging, whereas controlled degassing reduced defect levels. A dimensionless two-parameter Ingot Quality Index (IQI), integrating cumulative bifilm length and total defect area, was proposed to classify feedstock integrity. The proposed framework enables upstream screening of feedstock and supports process control before casting.