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The mechanical strength of the 7XXX series aluminum alloys can be improved through cold rolling due to the hardening, however, there is a reduction on ductility, thus requiring a later stage of annealing heat treatment. The present work is aimed on the evaluation of the effects of an annealing heat treatment at 500 °C for 15 minutes, on the microstructure and mechanical properties of a cold rolled 7475-T7351 aluminum alloy with 3 mm thickness. For this purpose, it was used microstructural characterization by scanning electron microscopy / X-ray Dispersive Energy Spectrometry, and uniaxial tensile tests. It was concluded that the annealing heat treatment, promoted the matrix recrystallization, providing a decrease of the tensile strength and yield strength, and increase of the ductility. The coarse precipitates evidenced are similar and possibly Al7Cu2Fe and Al2CuMg.

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Friction Stir Welding (FSW) promotes the joining of sheets due to localized plastic deformation and heating by displacing a non-consumable tool. This work aimed to verify the influence of an annealing heat treatment performed at 300 and 500 ºC with 15 minutes of soaking times, before and after the FSW of a 7475-T7351 aluminum alloy. The macrographs of the welded joint (top and cross section) and micrographs of the cross section was obtained by a stereoscope and optical microscope were analyzed and the mechanical behavior was characterized by uniaxial tensile tests. It was concluded that the annealing heat treatments did not influence significantly the nugget grain size, but there are indications that the realization of these before the FSW, provide a homogeneity in the mechanical properties of the welded joint and the base material.