Due to its low density, good corrosion resistance and many other properties, aluminium is versatilely useful. It is crucial in transport, civil engineering, packaging and food industry. Production of aluminium with electrolysis of alumina (Al2O3) is very energy consuming, which encourages industry towards recycling.
The main aim of diploma work was to study recycling of secondary aluminium, which is polluted with varnish based on TiO2 and increase of titanium concentration in alloy EN AW-1070. We melted three series of slugs made from examined alloy. The first series without varnish was our comparative sample, the second one was coated with one layer of varnish and the third one with five coats of varnish. We used the following examination techniques: a simple thermal analysis (ETA), a differential scanning calorimetry (DSC), an X-ray fluorescence analysis (XRF) and an optical microscopy. We also calculated the thermodynamic equilibrium with compositions after casting, using the Thermo-Calc Software.
After the use of the X-ray fluorescence analysis and the Thermo-Calc Software we were able to find out which phases in fact occurred in the microstructure of a material. The results of the simple thermal analysis showed that the sample, containing five layers of varnish, solidified within the shortest time frame. However, the sample without any varnish took the longest time to solidify. After comparing the DSC curves we concluded that both, heating and solidification enthalpy decreased as more titanium was added. Finally, with the help of the optical microscope we managed to measure the components of the microstructure and prove the refinement effect of the titanium.
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