An Evaluation of the Capability of the Reduced Pressure Test to Assess Liquid Metal Damage in Aluminum Alloy Castings

A systematic study was conducted to determine correlations between reduced pressure testing metrics and tensile results in aluminum alloy castings. The metrics investigated are the density and bifilm indices that have been traditionally used in industry, as well as three other metrics obtained from computed tomography scans. Analysis has shown that reduced pressure testing does not yield reliable results on the quality of aluminum alloy castings. Both density and bifilm indices provide high levels of α- and β-errors, well above those in traditional acceptance sampling plans. There is wide scatter in tensile results at the levels of both indices that are considered to represent “good” melts. The results of the CT scan metrics are similar. Possible reasons for these results and their implications are discussed.