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The paper presents the results of laboratory homogenization investigations of the 6082 grade alloys, differing in Mg and Si content. At the first stage, the microstructure of alloys was analysed after homogenization finished with water quenching. SEM/EDS investigations and DSC tests were applied to evaluate the dissolution of the Mg2Si particles and concentration of the main alloying additions in the grains interiors, depending on soaking conditions. In the case of alloy with lower Mg and Si content, homogenization the temperature of 535ºC for 8h is sufficient for significant Mg2Si particles dissolution. For the alloy with higher Mg and Si content, after homogenization the temperature of 550ºC for 8h, the amount of undissolved Mg2Si particles decreases visibly, compared to homogenization at 535ºC for 8h. However, an unfavourable tendency of dispersoids growth is observed and these soaking conditions are not found to be recommended. At the second research stage, the influence of homogenization cooling rate on the size and distribution of the Mg2Si particles observed in the alloys microstructure was analysed. The ability of the Mg2Si particles, precipitated during various homogenization coolings, to rapid dissolution was estimated. For this purpose, the hardness after solution heat treatment with short annealing and ageing was determined and the DSC tests were performed. It was found, that cooling after homogenization at 315ºC/h is sufficient for precipitation of fine Mg2Si particles, which dissolve during subsequent rapid heating. Cooling at 40ºC/h, causes precipitation of Mg2Si phase in the form of large particles, unable for further fast dissolution.

In the paper, the influence of homogenization parameters on the microstructure and properties of the 5019 alloy DC-cast billets was analysed. At the first stage, the microstructure of the alloy in as-cast state was investigated using SEM/EDS technique. Additionally, a DSC test and hardness measurements were performed. In the as-cast material, the presence of the dendritic microstructure with a pronounced microsegregation of magnesium in the dendrites cross-section was found. Subsequently, the specimens were subjected to laboratory homogenization experiments, with different soaking conditions and water quenching. The microstructural effects of the investigated variants of homogenization were evaluated using the same techniques as in the case of the as-cast alloy. It was found that after homogenization, with soaking at the temperature of 530 °C for 6 hours, the microsegregation is eliminated and the concentration of magnesium in the grains centres is over two times greater than in the dendrites cores before annealing. The solidus temperature rises by about 12 °C in comparison to the as-cast state. Neither extending the soaking time nor rising the temperature contributes to a further increase of the solidus temperature, or the magnesium concentration in the grains interiors. However, the tendency of dispersoids to grow and the change of Fe-bearing constituents chemical composition were observed after the high temperature, or prolonged annealing variants.

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