Study on formability and microstructure evolution of hot deep drawing manufactured 7005 aluminum alloy sheet metal

Abstract

The hot deep drawing process with an in-die heating system was proposed on the forming of 7005 aluminum alloy to improve the formability due to the limitation of ductility during severe plastic deformation at room temperature. The feasibility of hot deep drawing AA7005 sheet (only 0.8 mm) was investigated and evaluated by Swift cup tests from RT to 450 °C. The priority of main process parameters, namely temperature, blank holder force, and stamping speed, on sheet metal forming limit were discussed by analysis of range and variance. Experimental results indicated that elevating the temperature could fundamentally improve the deep drawing performance of the alloy, which is manifested by the revolutionary change in sheet metal behavior — from the failure of deformation at lower temperatures (RT-200 °C) to achieving a limiting drawing ratio of 2.19 at 450 °C. The optimal process parameters under HDD conditions are given as drawing temperature of 400 °C∼450 °C, BHF of 3 kN, and punch speed of 15–20 %. The thickness variation increases with rising temperature corresponding to the formability enhancement during the process within acceptable limits. DRV and DRX are the flow softening mechanism under the high temperature and large strain in HDD process obtained from the analysis of microstructure and texture evolution. The elongation and rotation of grains further substantiated the interrelationship between drawing performance and microstructure evolution. Improving the deep drawing performance through HDD process can provide practical guidance for the application of AA7005 sheet metal.