Serrated Flow Behavior in Commercial 5019 Aluminum Alloy

Serrated flow effects are visible on a metal surface even after coating. Thus, they are undesirable to manufacturers and product users. To meet the expectations of the industry, research on the conditions for serrated flow occurrence in 5019 aluminum alloy was carried out and the results were collected in the current paper. Thus, the influence of the alloy initial microstructure due to different tempers as well as plastic deformation conditions, i.e., strain rate and temperature, on the alloy stress–strain behavior was determined. Two tempers were considered: the as-fabricated F-temper and the W-temper (i.e., quenched in water after annealing at 500 °C). The synergic influence of these tempers and their tensile test conditions on the serration behavior of the stress–strain curves, i.e., the stress drop and reloading time, were also determined and categorized. Structural and X-ray diffraction studies rationalized the stress–strain characteristics according to dynamic strain aging models with positron annihilation lifetime spectroscopy providing insight into the role of lattice defects (i.e., dislocations and vacancies). The map of the serrated flow domain allowed us to obtain the activation energy of the onset of the Portevin–Le Chatelier effect equal to 56 kJ/mol. It is close to the activation energy for the pipe diffusion mechanism, obtained by applying the model formulated originally for Type B stress serration.