The Effect of Microstructural Variables on the Surface Roughening of 5XXX Series Aluminum Sheet in Biaxial Tension

The investigation into reducing overall vehicle weight by replacing conventional steel sheet metal with lightweight materials has been initiated. However, implementation of these lightweight alloys, specifically those that are Albase, has been slow due to both a limited knowledge of material behavior and a lack of experience in the sheet forming process. By obtaining a better understanding of the material characteristics (e.g., surface roughening, friction, biaxial strain limits, and springback) during biaxial stretching, these materials can be more readily utilized for complex stamped components. Along these lines, the free surface roughening of a model aluminum alloy in the 5XXX series was studied as a function of biaxial straining using the modified Marciniak in-plane stretching test. Through the use of neutron and x-ray diffraction techniques, the change in crystallographic texture of the sheet was determined as a function of the strain level. Modification of the surface topography was monitored through electron microscopy and surface roughness measurements. With increasing strain in the material, the development of a prominent component, represented as <220> parallel to the normal direction of the sheet, was observed. This coincided with a linear change in the surface roughness as the material was deformed. From these results, relationships between the strain level, relative change in crystallographic orientation, and surface roughening were discussed.