Influence of alloy composition and lubrication on the formability of Al-Mg-Si alloy blanks

The formability of 1.0 mm-thick Al-Mg-Si alloy blanks with different Si and Mg contents was numerically and experimentally investigated using two deep drawing tools: (i) a cross-shaped tool with open die and (ii) a complex-shaped panel tool with closed die. For the cross-shaped tool, forming velocity and blankholder force were constant and the formability was characterized based on the maximum drawing depth at crack initiation. For the complex-shaped panel tool the forming velocity and the drawing depth was constant and the formability was characterized based on the maximum blankholder force at crack initiation. Two types of commercial lubricants were applied on the blank surfaces. In order to investigate critical forming conditions, numerical models of both deep drawing processes were built using the AutoForm finite element (FE) software. Parameters required as input for these models were experimentally determined. The flow curve and the anisotropy of each of the aluminum alloys were determined using uniaxial tensile tests. Based on the results of pin-on-plate tests an advanced friction model which considers different contact pressures and sliding velocities was created using the TriboForm software. Good agreement between deep drawing simulations and experiments was achieved in terms of forming force, local thinning and strains. Experiments and simulations confirmed that the maximum drawing depth or blankholder force, respectively, tended to increase with increasing Si and Mg contents. However, the influence of lubrication on the formability of the Al-Mg-Si alloy blanks was much more significant than the influence of the alloy composition.