In this master's thesis, the effects of homogenization annealing on the formability of the aluminium alloy EN AW-7020 were investigated. The aim of the research was to determine the optimum homogenization temperature and time that provide a favourable combination of microstructure and mechanical properties for further plastic deformation.
The experimental work involved the homogenization of cast alloy samples at 470 °C and 490 °C for a period of 3 to 10 hours. The prediction of the microstructural composition was carried out using Thermo-Calc software. The solidus temperature was defined using differential scanning calorimetry. Microstructural changes were analysed by optical and scanning electron microscopy, while individual phases were identified by energy dispersive X-ray spectroscopy. The grain size was quantified according to ASTM E112. Formability was assessed by compression tests using the physical simulation system Gleeble 3500-GTC, from which flow curves were obtained and yield strengths defined.
The results showed that both the solidus temperature and the yield strength increased with longer homogenization times and higher temperatures, but this also led to undesirable grain growth. The optimum homogenization regime was found to be 490 °C for 5 hours, as it allowed adequate phase dissolution, achieved a suitable solidus temperature and maintained a fine microstructure and results in low stress during deformation, all of which contributed to conditions most favourable for the formability of the alloy EN AW-7020.
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