Heat treatment of Al-Si-Mg alloy with addition of Li

Namen magistrske naloge je bilo opazovanje vplivov različnih parametrov toplotne obdelave, to sta čas in temperatura raztopnega žarjenja in umetnega staranja, na razvoj mikrostrukturnih sestavin in vpliv le teh na trdoto zlitin AlSi7Mg in AlSi7Mg z dodatkom Li. Kot primerjalni vzorec smo opazovali vpliv prej omenjenih parametrov na zlitino AlSi7Mg, ki je bila izpostavljena enakim pogojem toplotne obdelave kot zlitina AlSi7Mg z dodatkom Li. Vzorci obeh zlitin so bili uliti v dve merilni celici, croning in grafitno merilno celico, ki predstavljata dve različni ohlajevalni hitrosti. V prvem koraku smo pripravili talino zlitine AlSi7Mg ter zlitino enake sestave, ki smo ji dodali 1 mas. % Li. V primeru croning merilnih celic smo le te opremili s termoelementom tipa K pri čemer smo spremljali potek strjevanja s pomočjo enostavne termične analize – ETA. Vsaka zlitina je bila strjena z dvema različnima ohlajevalnima hitrostma. Pripravili smo serijo 24 vzorcev, kjer je vsaka zlitina imela 6 vzorcev za pripadajočo ohlajevalno hitrost. Osnovno, izhodiščno stanje so bili vzorci v litem stanju, ostale vzorce pa smo nato glede na plan kombinacij toplotne obdelave in/ali raztopno žarili na temperaturi 530 °C v trajanju 8 ur in/ali umetno starali na temperaturi 160 °C v trajanju 4 in 8 ur. Po končani toplotni obdelavi smo za vsak vzorec opravili po 6 meritev trdote po metodi Vickers. S pomočjo rezultatov termične analize in posnetkov mikrostruktur pod svetlobnim mikroskopom smo lahko dokazali prisotnost posameznih faz ter določili potek strjevanja.The purpose of the master\u27s thesis was to observe the effects of various heat treatment parameters i.e., time and temperature of solution annealing and artificial aging, on the development of microstructural components and the effect on the hardness of AlSi7Mg and AlSi7Mg alloys with Li addition. As a comparative sample, we observed the influence of the parameters on the AlSi7Mg alloy, which was exposed to the same heat treatment conditions as the AlSi7Mg alloy with Li addition. Samples of both alloys were cast in two measuring cells, a croning and a graphite measuring cell, representing two different cooling rates. In the first step, we prepared a melt of the AlSi7Mg alloy and an alloy of the same composition, to which we added 1 wt. % Li. In the case of croning measuring cells, equipped with a K-type thermocouple, we monitored the solidification with the help of a thermal analysis - ETA. Each alloy was solidified at two different cooling rates. We prepared a series of 24 samples where each alloy had 6 samples for the corresponding quench rate. The basic starting state were the samples in the cast state, and the other samples were then, according to the plan of heat treatment combinations, solution annealed at a temperature of 530 °C for a duration of 8 hours and/or artificially aged at a temperature of 160 °C for a duration of 4 and 8 hours. After finishing the heat treatment, we performed 6 hardness measurements for each sample according to the Vickers method. Using the results of thermal analysis and images of microstructures, we were able to prove the presence of individual phases and determine the course of solidification