UBC Theses and Dissertations
Anisotropy of strength and fracture behavior in Al-Mg-Si-(Mn) extrusion alloys Kordmir, Setareh
Aluminum 6xxx extrusion alloys are attractive candidates for use in automotive applications to decrease vehicle weight. In this study, Al-Mg-Si alloys, and especially variants of AA6082 with two different Mn contents were extruded into 3 × 90mm strips on a pilot scale extrusion press with processing conditions designed to produce either recrystallized or unrecrystallized microstructures. The objectives of the study are to i) characterize the important microstructural features in the two alloys and ii) examine the relationship between orientation dependence of mechanical properties measured from uniaxial tensile and VDA bend tests with the microstructure. The characterization of microstructure and crystallographic texture was done using scanning electron microscopy and electron back scatter diffraction. The mechanical anisotropy was measured by tensile and VDA bend testing conducted at 0, 45 and 90o to the extrusion direction. The characterization analysis shows presence of crystallographic anisotropy, morphological and topological anisotropy of second phase particles in the studied alloys. It was found that the strength and fracture anisotropy in tension and bending were significantly affected by the microstructure. A linear correlation between the tensile true strain to fracture and the maximum bend angle prior to substantial damage was observed for the samples tested at 0 and 90o to the extrusion directions for the two alloys. However, the results for samples taken at 45o to the extrusion direction did not follow this trend.
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