Anisotropy and inhomogeneities in thin sheets of commercial aluminium alloys submitted to simple shear

Two commercial non heat-treatable aluminium alloys (3004 and 5182) previous ly heavily cold-rolled have been submitted to in-plane shear tests in vario us directions with respect to the initial rolling direction. The macroscopi c mechanical behaviour, the dislocations microstructure and the global crys tallographic texture have been analysed. Both alloys presented before the s hear tests similar geometrical characteristics: dislocation patterns, morph ology of the granular structure and of the distribution of precipitates, cr ystallographic texture. They differed mainly by their solid solution, leadi ng to a wavy slip character for the 3004 alloy and to a planar slip charact er for the 5182 alloy. The shear stress-shear strain curves were significantly different for the t wo alloys. In 3004 alloy a stress saturation occured after about ten percen t of strain, whereas the 5182 alloy appeared harder, with a positive harden ing until the maximum stress, obtained after more than 40%. In both alloys, the ductility during shear test was hardly dependent on the direction cc o f shear with respect to the initial rolling direction. Shear strains larger than 100% could be obtained for alpha = 0 degrees in 3004 and for alpha = 0 degrees-15 degrees and 90 degrees-105 degrees in 5182. Fracture occurred very early for the other a values, and these features was correlated to the development of shear bands in the gauge length from the corners of the sam ples. The spatial distribution of the shear bands was sharply localised in case of low ductility, whereas diffuse spreading of shear banding permitted high ductility. The T.E.M. observations showed elongated cells in the shear direction in 30 04 alloy, and, after sufficient strain, microbands formation in 5182 alloy, consistently with the expected slip character. However, inside the shear b ands, similar microstructure composed of highly elongated cells or bundles of microbands was observed in both alloys. The global crystallographic texture evolution was low in 3004 alloy due to the low ductility except for alpha = 0 degrees, and to the partly stability of the textured for alpha = 0 degrees. In 5182 alloy, more noticeable text ure changes were pointed out, but the cases of large ductility corresponded to initial textures containing large volume fraction of stable torsion com ponents, or when these components are easily obtained during shear.