Enhancement of drawability of cryorolled AA5083 alloy sheets by hydroforming

Abstract

In this paper, an attempt has been made to enhance formability of cryorolled AA5083 alloy sheets (annealed at 275 °C for 15 min) in deep drawing of flat bottom square cup-shaped parts by hydroforming. Numerical simulations based on finite element method have been carried out to study the effect of important process parameters (fluid pressure and sealing force) on formability. The minimum corner radius and the maximum depth that can be achieved without failure and the maximum percentage thinning at the corners have been considered as measures of formability. The results have been compared with conventional deep drawing. The simulation results have also been validated with experimental work in both hydroforming and conventional forming. A process window with optimum combination of peak sealing force and peak pressure has been identified to form the cups up to full depth of the die without failure at die entry or bottom corners. Lubrication between the die and the blank reduced the minimum possible corner radius to nearly 16 mm with thinning less than 6%. In conventional forming only 70% of the full depth could be obtained before failure with 16 mm punch corner radius due to much higher thinning at the corners. This work demonstrates that, by hydroforming, formability of high strength cryorolled Al alloy sheets can be enhanced due to lower thinning and more uniform strain distribution and hence this process route (cryorolling followed by hydroforming) is a potential technique to produce complex parts from lightweight high strength Al alloy sheets due to enhanced formability. Keywords: Aluminum alloy, Cryorolling, Formability, FEM, Deep drawing, Hydroforming