Recycling of secondary aluminium alloys is energetically and financially more favorable than the production of primary aluminium, whereas only about 5 % of the total energy is consumed when recycling in comparison with energy consumed for the production of primary aluminium. This is also the reason that the amount of recycled aluminium has increased over the past few decades, and currently about one third of all aluminium products are made by using secondary alloys. Despite numerous advantages of aluminium recycling, the use of aluminium scrap revert for the production of high-quality alloys is a demanding process, whereas the attention is primarily paid to ensuring adequate chemical composition with as few inclusions and impurities as possible.
In order to analyze the influence of different aluminium scrap revert types on solidification of AlSi10Mg(Fe) alloy, we made four experimental samples. The first sample was made only from AlSi10Mg(Fe) alloy ingot, while the other samples were made from an ingot and different scrap revert type in a ratio of 1:1. The types of scrap revert that we used in the production of experimental samples were scrap castings, casting residue in a casting cavity and elements of casting systems. Firstly, we melted the samples and recorded the cooling curve using simple thermal analysis. We determined and characterized the characteristic solidification temperatures from the cooling curve. On all experimental samples we made chemical analysis, from which the results were used for simulation of the equilibrium and non-equilibrium solidification course using ThermoCalc program. Furthermore, we also calculated the equilibrium phase diagrams. We compared the results of the simple thermal analysis and equilibrium calculations and analyzed the influence of the scrap revert types on the solidification course of AlSi10Mg(Fe) alloy. With differential scanning calorimetry we determined the melting and cooling enthalpy, whereby we also confirmed the characteristic temperatures during melting and solidification of the samples. We analyzed the microstructure of the experimental samples with optical microscope, focusing primarily on the shape, distribution and amount of microstructural components.
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