Lightweight design using high‐strength aluminum alloys has gained importance due to the continuing need for weight reduction and increasing crash safety requirements in the automotive industry. There are various manufacturing processes available for processing high‐strength aluminum alloys. Herein, the production of high‐strength aluminum parts by roll forming and stamping based on the example of an AA7075‐T6 hat profile is compared. Roll forming represents a continuous manufacturing process, while stamping is a discontinuous process. Different process routes (T6, W‐Temper and O) for roll forming as well as for stamping (T6, W‐Temper, O and hot forming) are in focus of the investigation. Fundamental differences of the forming processes and the tempering condition are observed and criteria for the choice of the manufacturing process and process route are presented. The temperature‐supported process routes improve the poor cold formability of AA7075 alloy and thus enhance the process window. Potential is offered for both manufacturing processes by applying tailored properties achieved through targeted quenching.

The impacts of various thermo-mechanical process routes in forming of EN AW 7075 alloy on mechanical properties, microstructure and corrosion resistance were investigated. A simulated forming process of two very different conditions, i.e., T6 and W-Temper is the focus of the present study. Irrespective of soaking time and pre-deformation, specimens quenched in water exhibited superior mechanical properties compared to air-cooled ones. A shorter solution heat-treatment soaking time in the pre-deformed condition, i.e., T6-Temper, caused a drop in the elongation at fracture. Microstructural analysis revealed, regardless of pre-deformation and soaking time, a high fraction of fine η′ strengthening precipitates with stoichiometry close to MgZn upon artificial ageing in the specimens quenched in water. Mechanical properties and microstructural evolution indicate that pre-deformation of solution heat treated specimens before the ageing treatment, i.e., W-Temper, leads to dislocation multiplication and, eventually, further nucleation sites for precipitation. Thus, forming the W-Temper condition caused very similar resulting mechanical properties and microstructure compared to that of the T6 condition. However, W-Temper forming was found to be detrimental for stress corrosion cracking. Corrosion behaviour of air-cooled specimens was found to be very poor in general. Results obtained in the present work can facilitate the development of thermo-mechanical process routes for EN AW 7075 to eventually tailor mechanical properties, corrosion behaviour and microstructure.

High-strength aluminum alloys, such as the AA7075 alloy, offer great potential for lightweight construction thanks to their high specific strength. However, high strength and low ductility are a challenge for processing these materials. In our study, three different process routes (T6, W-Temper, O) for roll forming of a hat profile are investigated experimentally and in an FE-simulation. Since the targeted production of the hat profile is hindered due to material failure in T6-condition, inline induction heating and subsequent water spray quenching is used to bring the material to the W-Temper state before roll forming. As a third option, a pre heat treatment is applied to a soft annealed (O) material state. The experimental results show fundamental differences of the forming processes, depending on the tempering condition. The FE-simulation involves the roll forming process for the production of a hat profile and shows a high agreement with the experiments. Finally, the experimental results demonstrate how inline solution annealing by induction heating for the W-Temper process affects the properties and the quality of the profiles produced.

The present study provides an overview of previous studies on the welding of the AA7075-T6 aluminum alloy, followed by an investigation of the influence of short-time solution annealing on the mechanical properties of the weld. Conventional laser welding of Al-Zn-alloys leads to a low weld strength, which makes a post weld heat treatment (PWHT) favorable. The PWHT includes solution annealing, quenching and subsequent aging. For solution annealing, different holding times and cooling rates are investigated in this study. The focus of the investigation is on a short solution annealing time, which on the one hand is ecological and economically favorable and on the other hand offers great potential for inline heat treatments. The shortest solution annealing time of 10 s shows a significant increase in weld strength (joint efficiency of 72%), compared to the non-heat treated weld (joint efficiency of 52%). The microstructural analysis reveals that the cooling rate after solution heat treatment affects the formation of precipitates in the microstructure of the welded AA7075 alloy. Moreover, the enhancement of mechanical properties is related to the formation of Mg-Al-Cu and Mg-Zn rich precipitates.

The presented paper provides a modelling strategy for roll forming of a high strength AA7075 aluminum tube. Roll forming allows the cost-effective production of large quantities of long profiles. Forming of high strength aluminum brings challenges like high springback and poor formability due to the low Young’s modulus, low ductility and high yield strength. Forming processes with high strength aluminum, such as the AA7075 alloy, therefore require a detailed process design. Three different forming strategies, one double radius strategy and two W-forming strategies are discussed in the paper. The paper addresses the question whether common roll forming strategies are appropriate for the challenge of roll forming of a high strength aluminum tube. For this purpose, different forming strategies are investigated numerically regarding buckling, longitudinal strain distribution and final geometry. While geometry is quite the same for all strategies, buckling and strain distribution differ with every strategy. The result of the numerical investigation is an open tube that can be welded into a closed tube in a subsequent step. Finally, roll forming experiments are conducted and compared with the numerical results.

Aufgrund ihrer geringen Kaltumformbarkeit werden hochfeste Aluminiumlegierungen in temperaturunterstützten Prozessrouten umgeformt. Bei mehrstufigen Prozessen führt dies zu komplexen und störanfälligen Prozessfolgen. Eine Umformung im W-Temper-Zustand vereinfacht die Temperaturführung und steigert die Robustheit. Die hierbei möglichen Prozessführungen sowie die Einflüsse der relevanten Prozessparameter (Zeit und Abschreckmethode) sind Inhalt dieses Beitrags.   Due to their low cold formability, high-strength aluminum alloys are formed in temperature-supported process routes. This leads to complex and failure-prone process sequences in multi-stage processes. Forming in the W-Temper state simplifies temperature control and increases robustness. This paper deals with the possible process control as well as the influences of the relevant process parameters (time and quenching method).