Improvement of formability of 6xxx aluminum alloys using incremental forming technology

Aluminum sheet is becoming increasingly common as an automotive body panel material. The heat-treatable aluminum alloys of the 6xxx series are widely used as an outer panel material, due to their ability to precipitation harden during the paint-bake cycle, resulting in improved dent resistance. Increasing the formability of these alloys would allow for multiple parts of less complex geometry to be combined into a single more complex part, thereby avoiding the costs associated with any subsequent joining operations. Incremental forming is a process that can improve material formability through the use of short, recovery heat treatments applied between increments of deformation. The objective of this study was to investigate the incremental forming behavior of 6111-T4 an alloy, which is often used for exterior body panel applications. Interrupted tensile testing was used to simulate the incremental forming process. The effect of different heat-treatment parameters on mechanical properties was analyzed. The heat treat regimen developed for uniaxial testing was then applied to a series of plane strain tests using a hemispherical punch, to simulate the more complex states of stress found in forming operations.