Evaluation of the properties of AA7020 tubes generated by a heat treatment based hydroforming process

Evaluation of the properties of AA7020 tubes generated by a heat treatment based hydroforming process

Jonas Reblitz, Ricardo Trân, Verena Kräusel, Marion Merklein

download PDF

Abstract. Energy efficiency and sustainability are getting more and more relevant in society and industry. Especially energy-intensive sectors offer a high potential for power savings. Thus, different lightweight strategies are applied in the automotive sector. In this context, high strength profile components are used as crash structures. As an example, these profiles are deployed to protect the battery of electrically powered vehicles. Therefore, high strength aluminum alloys of the 7xxx series are suitable for compensating the high battery weight partly. Compared to steel, this material is characterized by a high strength-to-weight ratio as well as an increased thermal conductivity. However, one challenge in forming high strength aluminum alloys is the limited formability at room temperature. For this purpose, heat treatment based process routes for tube hydroforming are investigated within this research work. By the combination of W-temper forming and hydroforming complex part geometries can be generated. A subsequent artificial ageing process realizes the required high strength of the profiles. Using AA7020 tubes, the properties of a demonstrator geometry are compared to the initial state T6 of the semi-finished parts. For this purpose, the wall thickness distribution and the grain structure are evaluated. Thereby, the influence of forming and heat treatment on the geometrical and microstructural properties is to be analyzed. For the evaluation of the achievable hardening of the aluminum alloy, the mechanical properties are investigated by tensile tests. This investigations provide an assessment of the process route under industry-related conditions.

Heat Treatment, Hydroforming, Tubes

Published online 3/17/2023, 8 pages
Copyright © 2023 by the author(s)
Published under license by Materials Research Forum LLC., Millersville PA, USA

Citation: Jonas Reblitz, Ricardo Trân, Verena Kräusel, Marion Merklein, Evaluation of the properties of AA7020 tubes generated by a heat treatment based hydroforming process, Materials Research Proceedings, Vol. 25, pp 221-228, 2023

DOI: https://doi.org/10.21741/9781644902417-28

The article was published as article 28 of the book Sheet Metal 2023

Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.

[1] Information on https://www.eea.europa.eu/ims/total-greenhouse-gas-emission-trends, (October 1, 2022).
[2] Information on https: https://www.destatis.de/Europa/EN/Topic/Environment-energy/CarbonDioxideRoadTransport.html, (October 1, 2022).
[3] Information on https://transport.ec.europa.eu/news/efficient-and-green-mobility-2021-12-14_en, (October 1, 2022).
[4] Information on https://www.cargroup.org/wp-content/uploads/2021/02/Aluminum-Battery-Enclosures-Constellium-February-2021-FINAL.pdf, (October 1, 2022).
[5] Information on https://www.audi-technology-portal.de/en/download?file=1946, (October 1, 2022).
[6] N. Rigas, H. Schmid, M. Merklein: Comparison of different forming methods on deep drawing and springback behavior of high-strength aluminum alloys, Mater. Sci. Eng. 1157 (2021) 012048. https://doi.org/10.1088/1757-899X/1157/1/012048
[7] E. Sáenz de Argandoña, L. Galdos, R. Ortubay, J. Mendiguren, X. Agirretxe: Room temperature forming of AA7075 aluminum alloys: W-temper process, KEM 651 (2015) 199-204. https://doi.org/10.4028/www.scientific.net/KEM.651-653.199
[8] Hebbar, S., Kertsch, L., Butz, A.: Optimizing Heat Treatment Parameters for the W-temper Forming of 7xxx Series Aluminum Alloys, Metals 10 (2020) 1361. https://doi.org/10.3390/met10101361
[9] R. Trân, J. Reblitz, R. Haase, V. Psyk, V. Kräusel, M. Merklein: Hydroforming of High-Strength Aluminum Tubes with Thermo-Mechanical Manufacturing Processes, Eng. Proc. 26 (2022) 13. https://doi.org/10.3390/engproc2022026013
[10] F. Ostermann: Anwendungstechnologie Aluminium. 3rd edn. Springer Vieweg, Berlin, Hei-delberg (2014). https://doi.org/10.1007/978-3-662-43807-7
[11] Z.-C. Sun, L.-S. Zheng, H. Yang, Softening mechanism and microstructure evolution of as-extruded 7075 aluminum alloy during hot deformation, Mat. Charact. 90 (2014) 71-80. https://doi.org/10.1016/j.matchar.2014.01.019
[12] M. Fujda, R. Misicko, L. Rusnakova, M. Sojko, Effect of Solution Annealing Temperature on Structure and Mechanical Properties of EN AW 2024 Aluminium Alloy, Journal of Metals, Materials and Minerals 17 (2007) 35-40.
[13] J. Reblitz, S. Wiesenmayer, R. Trân, M. Merklein, Investigation of geometrical and microstructural influences on the mechanical properties of an extruded AA7020 tube, WGP 2022 LNPE (2023) 1-12.
[14] S. Lotz, E. Scharifi, U. Weidig, K. Steinhoff, Effect of Combined Forming and Aging Processes on the Mechanical Properties of the Precipitation-Hardenable High-Strength Aluminum Alloys AA6082 and AA7075, Metals 12 (2022) 1250. https://doi.org/10.3390/met12081250
[15] M. Merklein, J. Degner, Influence of pre-strain and simulated paint-bake on mechanical properties of high strength aluminum alloy AA7020, AMM 805 (2015) 115-122. https://doi.org/10.4028/www.scientific.net/AMM.805.115
[16] S. Krishnanunni, R. K. Gupta, G. Ajithkumar, V. Anil Kumar, Optimization of Heat Treatment Cycles and Characterization of Aluminum Alloy AA7010, JMEP 28 (2019) 776-787. https://doi.org/10.1007/s11665-019-3861-9
[17] A. Deschamps, F. Livet, Y. Bréchet, Influence of predeformation on ageing in an Al-Zn-Mg alloy-I. Microstructure evolution and mechanical properties, Acta mater. 47 (1999) 281-292. https://doi.org/10.1016/S1359-6454(98)00293-6