Laboratory-Scale Procedure for Evaluating the Flux Efficiency on Melt Cleanliness and Tensile Properties of Recycled Aluminum Alloys

The present study aims to develop a laboratory-scale procedure to evaluate the efficiency of melt-cleaning and drossing fluxes during aluminum alloy recycling, focusing on their effects on melt cleanliness and tensile properties of an AlSi9Cu3(Fe) alloy. X-ray fluorescence and diffraction, as well as differential scanning calorimetry, are used to characterize two different commercial fluxes. The molten metal is treated at 720 and 760 degrees C. Reference melts without flux treatment are also collected. The melt sampling procedure involves H2 concentration monitoring, reduced pressure test (RPT), and casting of tensile specimens. The composition of the generated dross is analyzed too. Differences are encountered in the chemical composition of the analyzed fluxes, while they exhibit similar melting temperatures. The RPT emphasizes the advantages of flux treatment on melt cleanliness. The tensile plastic properties, including ultimate tensile strength and ductility, are influenced by the flux treatment, while the elastic properties, such as yield strength, remain unaffected. The Weibull analysis allows us to discriminate the efficiency between the different processing conditions. Additionally, the three-parameter Weibull statistics highlights the significance of flux treatment and temperature monitoring to increase the threshold value. The dross analysis highlights the importance of flux treatment to minimize metal losses.