Characterization of the Melt Quality and Impurity Content of an Lm25 Alloy

The melt quality of an LM25 aluminum casting alloy has been examined using reduced pressure test (RPT) measurements, porous disc filtration analysis (PoDFA), and fatigue and tensile tests. The aim of this study was to determine the existing melt quality and thus to evaluate methods used with respect to monitoring and improving melt cleanliness. Special emphasis was given to the influence of oxides. It was found that the melt quality has varying degrees of effect on the tests used. The results indicate in particular that it was necessary to distinguish between “new” oxides (bifilms) and “hard” inclusions in the melt, as new oxides impact on porosity, whereas hard inclusions impact on ductility. Based on the results of this study, suggestions for the measurement of the melt quality have been proposed.