THE EFFECT OF MICROSTRUCTURE ON THE STRAIN LOCALIZATION IN COARSEGRAINED AA5754 SHEETS

Abstract

<p>AI-Mg sheets (5xxx series) for body-in-white (BIW) application are mostly<br />used for automotive structural parts due to their specific combination of<br />formability and strength. The limiting behavior for the wide application of AA5754<br />sheets is strain localization. The effect of microstructure inhomogeneties on<br />strain localization have recently been attracting a great deal of interest but not<br />fully understood. In this present work, the effect of grain-level microstructure<br />inhomogeneties in AA 5754 sheets is investigated.<br />Uniaxial tensile experiments combined with two 2-dimensional Digital<br />image correlation (DIG) techniques have been performed on coarse-grained<br />specimens to evaluate the deformations of individual grains. Grain orientations<br />and their evolution were measured by the electron backscattered diffraction<br />(EBSD) technique, and surface features such as slip traces were observed by<br />optical microscopy.<br />The regions of high local strain ('hot spots') within coarse-grained samples<br />nucleate at a very early stage of deformation and most of them continuously<br />grow throughout most deformation stages. 'Hot spots' are correlated with 'soft'<br />grains (i.e. grains with high Schmid factors) and soft-evolution grains (i.e. grains<br />with the <101> direction close to tensile axis).</p>