Homogenization of twin-roll cast AA8079 aluminum alloy studied by in-situ TEM
(Faculty of Mathematics and Physics, Charles University, Ke Karlovu 3, 121 16 Prague 2, Czechia)
Abstract: AA8079 is a commonly used stock material for manufacturing thin packaging foils. The primary alloying elements Fe and Si can form binary and tertiary intermetallics. In-situ TEM simulating homogenization annealing process of the as-cast material was used to analyze the real-time changes of the shape, type, and distribution of these particles. They affect the mechanical properties of the final product and susceptibility of the material to the formation of pinholes and other macroscopic defects. Another set of as-cast samples were annealed in a regime simulating industrial treatment in combination with measurements of resistivity to validate the results of the in-situ experiment. The results show clear temperature intervals of recovery, matrix desaturation, and phase transformations occurring in several stages: spheroidization of the original particles above 450 °C, nucleation of new particles at 475 °C, particles coarsening above 525 °C, and an entire dissolution of the original particles above 550 °C.
Key words: aluminum alloys; in-situ annealing; homogenization; foil stock materials