Tailored Heat Treatment Strategy for the Orbital Forming of Functional Components from EN AW-7075

Abstract

The application of forming operations instead of conventional cutting processes is a practical approach to increase material efficiency and functional integration, thus addressing lightweight design. In this context, the innovative process class of Sheet-Bulk Metal Forming is presented, which combines the advantage of bulk and sheet metal forming. One of the assigned processes for the manufacturing of functional components with different form elements is orbital forming. Within previous investigations, the major challenge could be identified as a control of the material flow. Since process parameters, like an increased forming force, are not sufficient to avoid process failures in form of wrinkles, other measures have to be taken into account. Especially when applying precipitation hardenable aluminum alloys, one possibility is the application of a local short-term heat treatment. By locally reversing the hardening effect of the precipitation clusters, the interaction between softened and still hard areas can be used to attain the desired material flow. Although this procedure is established for conventional sheet metal forming processes and was furthermore investigated for the orbital forming of components from the aluminum alloy EN AW-6016, the influence on the forming of high-strength aluminum from the 7xxx-series is still content of current research. Especially due to a reduced formability at room temperature, this alloy is predominantly formed at elevated temperatures. By introducing the established method of a local short-term heat treatment on 7xxx alloys, a contribution towards a possible forming at room temperature is made. Therefore, this work focuses on the development of a tailored heat treatment strategy to control the material flow during orbital forming. Specimens out of the high-strength aluminum alloy EN AW-7075 with a thickness of 2.0 mm in condition T6 are heat-treated and consequently cold formed. The results are quantified by a geometry-based analysis. The resulting strain distribution is used to verify the material flow proportions.