U-channel forming of an 7075-T6 in warm conditions

Abstract

The use of high mechanical strength aluminum coupled with the warm forming process makes it possible to replace certain steel parts in vehicles, thus reducing its mass and consequently greenhouse gas emissions. Warm forming of aluminum alloys requires heating the part between 150°C and 250°C to increase formability and reduce springback. In this study, a 7075-T6 alloy U-channel part was warm formed at 200°C in a short enough time to maintain the T6 state of the material. The process consisted of successively performing the heating by contact and stamping steps on the same mechanical press. From a thermomechanical characterization of the alloy in the temperature range between RT and 200°C and several strain rates, numerical simulations of the forming of the U-channel part were carried out using Abaqus. The experimental springbacks reduced with temperature were in agreement with the numerical simulations. An analysis of the conductivity and hardness of the material showed also that the 7075 keeps its T6 state until 10 s of warm forming.

Forming of a cylindrical cup in 7075-T6 under warm temperature conditions

“…Additionally, it is crucial to preserve the T6 state of these alloys, which has been found to exhibit optimal performance. In our previous study [8], we showed that warm temperature forming should last between 10s and 20s at 200 • C to maintain the T6 state. Prolonged heating can lead to the formation of precipitates which do not maintain the T6 state and then require additional heat treatment costs to recover them.…”

“…From results presented in [8], these material parameters are identified by tensile tests at RT and 200 • C for strain rates of 2 × 10 −4 , 2 × 10 −3 , 2 × 10 −2 and 0.2s −1 .…”