Improvement of microstructure and mechanical properties of 7050-T7451 aluminum by a novel double-sided friction stir processing

摘要

Recently, friction stir processing (FSP), as an effective method, has been employed to modify microstructures and mechanical properties of metal sheet. A novel technique of double-sided friction stir processing (FSP) was proposed in this study. A 7050-T7451 aluminum alloy sheet of 6.5mm in thickness was processed by FSP with 30% overlap in each side. The position deviation of the stir pin from the upper surface to the bottom surface is 35%. Significant grain refinement with an average grain size of 2.5μm from the as-received 50μm, can be obtained after double-sided FSP. In comparison with the conventional FSP, no HAZ (heat affected zone) or TMAZ (thermal mechanical affected zone) was formed between the adjacent stir zones of the aluminum alloy sheet. At a strain rate of 10~(-3) s~(-1), a maximum elongation of 29.8% and 327% in transverse direction of FSP passes have been achieved at room temperature and 400 °C, respectively.