Warm-forming of pre-aged Al-Zn-Mg-Cu alloy sheet

Abstract

Aluminium alloys of the 7xxx series are attracting the attention of automakers due to their high specific strength. However, widespread use of 7xxx series alloys for the production of car parts from sheet metal has so far been prevented due to their low formability at room temperature and the fact that conventional automotive paint-bake cycles are not suitable for aging the material to peak strength. Here we present an economic process chain for the deep-drawing of automotive parts from pre-aged AA7075 sheet at 180–250 °C that combines good formability with improved paint-bake response. The produced parts achieve roughly 95% of the peak-aged strength of AA7075. Precipitation during the production process is studied by differential scanning calorimetry and transmission electron microscopy.

Keywords

• Aluminium
• Automotive
• Retrogression
• Paint-bake
• Deep-drawing
• Transmission electron microscopy