Serrated Flow and Surface Markings in Aluminum Alloys

Abstract

Serrated flow and associated progressive surface markings severely restrict the application of some aluminum sheet alloys for automotive body exteriors. This paper attempts to approach the phenomenon from the localization theory of continuum mechanics as well as from the classical atomistic and dislocation considerations. Plane strain tension tests were conducted for a commercial Al-Mg alloy (5182-O) at different strain rates and temperatures, and the local temperature changes were measured by an infrared thermal imaging system. Continuum mechanics analysis provided the insight into the myth that band surface markings never appear under biaxial tension strain states. In addition, continuum mechanics analysis shed light on the observation that PLC bands were not seen on the surface of plane strain tension specimens even though the stress-strain curves exhibited serrations. Finally, it is emphasized that only by combining the efforts of continuum mechanics at the macroscale and materials science at the microscale, can a complete understanding of the phenomenon be reached.