On Serrated Plastic Flow in an AA5052-H32 Sheet

Temporal and spatial characteristics of serrated plastic flow or the so-called Portevin-Le Chatelier (PLC) deformation bands in a commercial $Al-2.5%Mg$ sheet metal due to dynamic strain aging effects were investigated experimentally under quasi-static uniaxial tension. It was found that the thickness and width of test coupons, applied loading conditions (machine stiffness and crosshead speed), and mechanical polishing had an observable effect on the temporal characteristics of the serrated plastic flow while short and long interruptions during the tensile tests with stress relaxation and even completely unloading show minimal effects on the subsequent serrated flow behavior. Serrations in axial load in AA5052-H32 were found to associate with the appearance of discrete narrow deformation bands in the tensile test coupons with the bands aligned $59±1deg$ with respect to the tensile loading axis. The detailed strain distribution across the deformation bands showed a bell-like instead of steplike shape, indicating that the formation of these deformation bands was controlled by a local nucleation and growth process at a cross section in the polycrystalline sheet.