Investigations on deformation behavior of AA5754 sheet alloy under warm hydroforming conditions

Material behavior of AA5754 was investigated under different forming process conditions, including two loading conditions (uniaxial tensile and biaxial bulge), several strain rates (constant strain rates at 0.0013 and 0.013/s, and variable strain rate profiles: increasing and decreasing profiles), and several temperature levels (ambient up to 260°C). Additional warm hydroforming experiments were conducted using a closed-die set up to understand the forming limits of AA5754. The results from tensile and hydraulic bulge tests as well as closed-die hydroforming experiments suggested that, in general, formability of AA5754 can be significantly improved with slow forming rates (<0.02/s), high forming temperature (<200°C), and biaxial loading (hydroforming) that can delay strain localization (necking). However, the effect of forming rate did not reveal any significant gain in formability for temperatures below 200°C. The effect of variable strain rate control was found to be significant only at elevated temperatures (>200°C), where increasing strain rate resulted in lower formability and decreasing strain rate improved the maximum attainable dome height at temperatures above 200°C. Finally, the material flow curves obtained from the tensile and bulge tests were shown to provide reasonably accurate predictions for cavity filling ratios (∼ 3-15 error) in finite element analyses.