Facing the Issues of Sheet Metal Equal-Channel Angular Pressing: A Modified Approach Using Stacks to Produce Ultrafine-Grained High Ductility AA5083 Sheets

A new approach for equal-channel angular pressing (ECAP) of thin AA5083 sheets using two different orientations is investigated to address the issues of sheet metal ECAP. The method includes the deformation of a stack of 6 individual sheets supported by bulk material pieces placed on both sides of the stack. An excess length of the support materials and their pre-deformation during an early stage of processing allows a buckling-free deformation of the thin sheets for one of the investigated orientations. Multiple ECAP passes (up to N = 4) at room temperature following route C and microstructural analyses by electron back-scatter diffraction are performed. Two passes of ECAP already result in considerable grain refinement with equiaxed grains, pronounced substructures and in an increased tensile strength at room temperature. At elevated temperatures (250 degrees C) a comparatively large elongation to failure (>130%) is found for the fine-grained sheets. Diffusion-controlled deformation mechanisms likely contribute to the deformation behavior of the investigated material. Scanning electron microscopy of the tensile specimens after testing reveals the formation of elongated and large cavities. These results highlight the suitability of the modified experimental method to produce (ultra)fine-grained thin aluminum sheets with distinctly increased strength and ductility.