Industrial production of products, such as strips, plates, and sheet from aluminium alloys starts with semi-finished product in a form of slabs. Slabs are made with direct chilled continuous casting process, which is very fast and does not allow solidification at equilibrium conditions. Negative effects of DC casting are eliminated with the process of homogenization annealing. Homogenized slabs are then hot rolled into strips with thickness of about 10 mm. Strips are then cold rolled to final thickness with possible intermediate annealing, which softens the strips and enables easier formation of the final product.
The main aim of the master thesis was enthalpy balance analysis of the aluminium alloys EN AW 5182 during entire process path of sheet production with EDT (electron discharge texturing) surface. Samples were obtained after every step of sheet production process path. Using Thermo-Calc computer program thermodynamic simulation of equilibrium and nonequilibrium solidification was made, whereas equilibrium phase diagram and the equilibrium phase fraction at certain temperatures was calculated. Differential scanning calorimetry (DSC) was made on every sample, whereas the melting and solidification characteristic temperatures and the melting and solidification enthalpies from the results were obtained. Optical microscopy and scanning electron microscope (SEM) with energy-dispersive X-ray spectroscopy (EDS) were used in order to analyze microstructure and microstructural components.
Using thermodynamic simulations, the phases that can appear in the microstructure and the influence of temperature during the different process on these phases were analyzed. Results of DSC analysis show that reaction enthalpy and melting temperatures of microstructural elements changes with every process in the process path. Figures from optical microscope reveal how each process affects the shape and size of the intermetallic phases. Figures and analysis of grain structure reveal how each process affects the size, texture, shape and number of αAl grains. Based on SEM and EDS results, differences in chemical composition of the intermetallic phases and in αAl grains, after each process, were observed. Based on all the results, we concluded that each step of the process, which includes different processing temperatures and deformation, has a significant effect on the reaction enthalpy and cannot be unambiguously described.