Development of a process chain for multi-stage sheet metal forming of high-strength aluminium alloys

Abstract

The high-strength aluminium alloys EN AW-6082 and -7075 are characterized by low density and high strength but also limited cold formability and pronounced springback behaviour in the ultra-high-strength T6 state. In order to exploit their lightweight design potential, temperature-supported process routes such as warm or hot forming are applied. Alternatively, there is the possibility of cold forming preconditioned semi-finished products at the expense of the initial material properties. Common to all variants are complex interrelationships due to linked plant periphery resulting from up- and downstream heat treatments. In addition, occurring heat transfers in temperature-supported process routes or strain hardening effects during cold forming lead to reduced formability. Especially for multi-stage forming processes, as they are required for complex components, the above-mentioned process routes reach their limits. The different requirements of the four single-stages (deep drawing, blanking, collar drawing and upsetting) for the production of a demonstrator geometry with adapted wall thicknesses make a new type of temperature control necessary. This paper shows that the combination of temperature-supported and multi-stage forming contributes to a significant increase in formability. The temperature-controlled forming tool used for this purpose enables an inline heating of the components during the process, so that an industrially feasible and economical overall process chain for the fabrication of the demonstrator geometry out of those alloys is convertible.