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The need to reduce or contain a weight increase in new automobile designs is leading to the use of more and more aluminum and, in particular, to the adoption of aluminum outer body panels in a number of volume production vehicles. This has been made possible by improvements in the properties of heat treatable aluminum sheet materials and also from a better understanding of the issues related to part design and manufacturing. The alloy AA6111 has become the material of choice due to its unique combination of formability and paint bake strengthening and is used, for example, in the deck lids of the current Ford Crown Victoria, Grand Marquis and Taurus/Sable models. A modified process for this alloy has now been developed which significantly increases its paint bake strengthening and can be used either to obtain even better dent resistance or to reduce the gauge and hence obtain cost and weight savings.

A Knowledge Based CAD System has been developed to investigate various aspects of press tool design, and to assist with the introduction of stamped aluminum into automobile structures. Knowledge based design “rules” which have been derived directly from: material properties, FEM parametric studies, deformation mechanics, simple heuristics, and various geometric features, are demonstrated.

The influence on properties of various alloying elements in the principal aluminum alloys used for external auto body components has been studied and from the results an alloy with improved characteristics has been devised. The properties evaluated were strength, formability, age-hardening response and corrosion resistance. The fabrication practices were also examined and the best procedures to maximize properties were developed. The alloy has been formulated to provide the necessary formability requirements encountered in the production of body panels, while still obtaining a high yield strength after paint bake for good denting resistance. The result is a sheet alloy with slightly reduced yield strength but better formability and less susceptibility to spring back than 2036, 2038 and 6010 in the T4 temper and with an excellent response to paint bake treatments. The corrosion resistance of the new alloy is superior to that of 2036 and 2038 and is comparable to that of 6009 and 6010.