Superplastic Properties of Ultrafine-Grained AA6061 Alloy Fabricated by Cyclic Expansion-Extrusion
DOI:
https://doi.org/10.3849/aimt.02075Keywords:
AA6061 aluminum alloy, ; cyclic expansion-extrusion, ultrafine grains, severe plastic deformation, superplastic properties, superplastic formingAbstract
This paper investigates the superplastic behavior of AA6061 aluminum alloy processed by cyclic expansion-extrusion, a severe plastic deformation method producing ultrafine-grained structures. Cylindrical specimens underwent up to four cyclic expansion–extrusion cycles at room temperature. The average grain size decreased from ~100 μm (annealed state) to 5–6 μm after four cycles, with nearly 75 % higher and more homogeneous microhardness. The refined microstructure fulfils conditions for superplasticity dominated by grain boundary sliding at elevated temperatures. Tensile tests showed a maximum elongation of ~330 % at 530 °C and strain rate 10−3s−1, with a low maximum flow stress of 9.5 MPa. The results confirm cyclic expansion–extrusion as an effective route to enhance microhardness and enable superplastic forming of lightweight AA6061 alloys.
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