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Low-Cycle-Fatigue Performance of Stress-Aged EN AW-7075 Alloy

Sajadifar, Seyed Vahid
Krooß, Philipp
Krochmal, Marcel
Wegener, Thomas
Heidarzadeh, Akbar
Fröck, Hannes
Zavašnik, Janez
Kessler, Olaf
Niendorf, Thomas

The effect of a novel heat treatment, that is, aging under superimposed external stress, on the fatigue performance and microstructural evolution of a high-strength aluminum alloy (EN AW-7075) is presented. Stress aging, a combination of heat treatment and superimposed external stress, can enhance the mechanical properties of EN AW-7075 under monotonic loading due to the acceleration of precipitation kinetics. Scanning electron microscopy (SEM) and scanning transmission electron microscopy (STEM) reveal that a longer aging time and the presence of superimposed stress both promote the formation and growth of precipitates, that is, the precipitation of strengthening η´ precipitates. This is confirmed by differential scanning calorimetry (DSC) heating experiments of stressless and stress-aged states. Furthermore, stress aging leads to a reduction of dimensions of precipitate-free zones near grain boundaries. Cyclic deformation responses (CDRs) and half-life hysteresis loops are evaluated focusing on the low-cycle fatigue (LCF) performance of different conditions. A noticeable cyclic hardening seen in case of the specimens aged for a short time indicates the occurrence of dynamic strain aging (DSA). Eventually, stress aging allows for an enhancement of the monotonic mechanical properties of EN AW-7075 without degrading the cyclic performance in the LCF regime.

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Gefördert im Rahmen des Projekts DEAL
Citation
In: Advanced Engineering Materials Volume 25 / Issue 15 (2023-05-05) , S. ; eissn:1527-2648
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Namensnennung 4.0 International
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@article{doi:10.17170/kobra-202402229625,
  author    ={Sajadifar, Seyed Vahid and Krooß, Philipp and Krochmal, Marcel and Wegener, Thomas and Heidarzadeh, Akbar and Fröck, Hannes and Zavašnik, Janez and Kessler, Olaf and Niendorf, Thomas},
  title    ={Low-Cycle-Fatigue Performance of Stress-Aged EN AW-7075 Alloy},
  keywords ={600 and Aluminiumlegierung and Materialermüdung and Mechanische Eigenschaft and Gefüge },
  copyright  ={http://creativecommons.org/licenses/by/4.0/},
  language ={en},
  journal  ={Advanced Engineering Materials},
  year   ={2023-05-05}
}