Abstract
The aim of the thesis at hand was to improve the bending properties of the aluminium alloy EN AW–6016. In particular, two variants with different Mg content were used. For this purpose, heat treatments were carried out in an oxygen-containing atmosphere for varying lengths of time. Oxidation as well as evaporation during annealing should decrease the magnesium content near the surface of the material and thus increase its formability. It was shown that only annealing temperatures up to 575 °C are feasible, since higher temperatures lead either to local melting or to an inadmissible grain growth, depending on the material. Numerical simulation was used to approximate the theoretically expected Mg concentration profiles. The results were compared with concentration values obtained by X-ray and optical emission spectrometry. Furthermore, thermogravimetric measurements were performed to evaluate the oxidation behavior. Plate bending tests according to VDA 238–100 were used to determine the maximum bending angles. For the alloy with the lower Mg content an improvement in bendability can be achieved by slightly extending the solution heat treatment. A further increase through longer annealing times was not observed. For the alloy with the higher Mg content, in contrast, short annealing times do not result in a clear improvement in bendability, even though a decrease in the Mg content of the peripheral zone is noticeable. After a longer annealing time, however, the Mg concentration at the surface rises again, which is due to a pile-up of Mg atoms beneath the oxide layer, which is now becoming denser. A direct influence on the bending capacity cannot be seen here either. However, it has been repeatedly shown that very long heat treatments may result in an extremely strong increase in the bending angle. This result cannot be related to the Mg content of the alloy, since no such improvement was observed in samples with a comparable surface Mg content at shorter solutionizing times.
Translated title of the contribution | Influence of the surface composition on the bending properties of an Al–Mg–Si alloy |
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Original language | German |
Qualification | Dipl.-Ing. |
Awarding Institution |
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Supervisors/Advisors |
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Award date | 23 Oct 2020 |
Publication status | Published - 2020 |
Bibliographical note
embargoed until 01-10-2025Keywords
- bending properties
- aluminium
- aluminum
- Al-Mg-Si alloy
- 6xxx
- 6016
- automotive
- magnesium
- oxide layer