The purpose of the master thesis was to investigate the problem of insufficient elongation and variations thereof at certain castings manufactured by the company Talum, d.d. For this, we further studied the obtained chemical composition of castings and their heat treatment. The pieces are cast by low-pressure casting technology and heat-treated under the regime of heat treatment T6. First they were solution annealed and then quenched in water and artificially aged. The theoretical part provides basic information on the casting of aluminum alloys, details about the group to which it belongs 3xx.x basis for preparing material and low-pressure die casting and heat treatment, with emphasis on the T6. In the experimental part the course of research that have been conducted within the framework of this master's thesis is presented. To carry out the research, we used eight castings of Talum, d.d. Two pieces remained in the as-cast state, two were examined in solution treated state, two after the full heat treatment in the company Talum, d.d., while two were checked after own heat treatment conducted in the Faculty of Natural Sciences. On the pieces we performed tensile tests, examination of the microstructure using light microscopy, chemical analysis using energy dispersive spectroscopy and tensile fractures review using scanning electron microscopy. After analyzing the results, we find that with our own heat treatment we succeeded to increase elongation, but the tensile strength and yield were both reduced, which did not achieve the values prescribed by the buyer. Furthermore, we find that all pieces of the chemical composition deviates from the prescribed, which may adversely affect the elongation. When analyzing the fracture surface, we found a porosity of tensile specimens, which also has a negative effect on elongation.
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