Fatigue and Corrosion Behavior of Solid-State Recycled Aluminum Alloy EN AW 6082

Abstract

In this research, a solid-state recycling process of aluminum was performed. It consisted of aluminum EN AW 6082 alloy machining chip cold precompaction and hot extrusion followed by a combination of equal channel angular pressing (ECAP) and heat treatment. The main aim of this paper is to determine the fatigue and corrosion behavior of the recycled specimens. In order to determine the recycled specimen fracture mode after fatigue testing, fractography analysis was performed. The corrosion behavior of all specimens was investigated in 0.5 M NaCl solution using open circuit potential measurements, polarization and electrochemical impedance spectroscopy (EIS) methods. It was found that the corrosion resistance of the tested specimens is similar for reference and as-extruded recycled specimens, while it is increased for those which were additionally processed with equal channel angular pressing and heat treatment. Namely, the corrosion current decreased in the same order, while the polarization resistance increased. Impedance measurements have shown that the subsequent plastic deformation and heat treatment of recycled specimens facilitated passivation of tested materials and improved surface film properties, which is confirmed with scanning electron microscopy and energy-dispersive x-ray spectroscopy. Fatigue life was similar for recycled and reference specimens for the selected stress levels. However, fractography showed that multiple cracks appeared inside the recycled specimens which caused different crack propagation mechanisms compared with reference specimens.