Numerical and experimental investigation of the formability of AA6013-T6

TLDR: In this article, the experimental formability of AA6013 is characterized from room temperature to 250°C through limiting dome height (LDH) tests with a Nakazima hemispherical punch and in-situ stereoscopic digital image correlation (DIC) strain measurement.

Abstract: AA6013 is an age-hardenable, aluminum alloy with the potential for structural applications in weight-sensitive automotive components. The alloy is at peak strength in the T6 temper, but exhibits relatively low room temperature formability. In an effort to avoid costly post-forming heat-treatments, warm forming of the AA6013 in the T6 temper is investigated in the current work. The experimental formability of the alloy is characterized from room temperature to 250°C through limiting dome height (LDH) tests with a Nakazima hemispherical punch and in-situ stereoscopic digital image correlation (DIC) strain measurement. A forming limit diagram (FLD) is generated from the application of a curvature-based necking criterion to the elevated temperature LDH test results. The evolution of the strain distribution prior to necking is explored using models of the plane strain LDH tests at room temperature and 200°C. At 200°C, strain rate effects are explored relative to the local temporal strain evolution. Modelling efforts include development of a Barlat Yld2000 yield surface to capture the anisotropy of the alloy and use of experimentally obtained isothermal flow-stress curves. The effects of different tensile gage lengths on flow-stress and yield surface calibration for warm tensile testing are discussed. The room temperature model was found to accurately depict the thinning strain distribution consistent with the "safe" thinning strain distribution at room temperature. At 200°C, it is shown that the temporal strain evolution is strongly influenced by strain-rate effects.