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Improved fatigue resistance of Al-Zn-Mg-Cu (7075) alloys through thermomechanical processing

  • Mechanical Behavior
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Abstract

To decrease the accumulation of damage during long-life low-stress cyclic loading, microstructures must accommodate inelastic deformation by homogeneous or “dispersed” slip rather than by localized slip concentrations. In age-hardening aluminum alloys this requirement can be met by introducing a dense and uniform dislocation forest through suitable thermo-mechanical treatments. Such a treatment was developed for Al-Zn-Mg-Cu (7075) alloys, involving a process cycle of solution annealing, partial aging, mechanical working and final aging. The fatigue properties (S-N curves) of commercial and high-purity 7075TMT are compared with conventional 7075-T651 properties; with zero mean stress the alternating stress to cause failure in 107 cycles is more than 25 pct higher for commercial-purity 7075TMT and almost 50 pct higher for high-purity 7075TMT. The results emphasize the importance of microstructural control when high fatigue resistance is required.

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Author notes

  1. F. Ostermann

    Present address: Leichtmetall-Forschungsinstitut, Vereinigte Aluminum-Werke A.G., Bonn, Germany

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    1. F. Ostermann
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    F. OSTERMANN, formerly with Air Force Materials Laboratory, Wright-Patterson Air Force Base, Ohio.

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    Ostermann, F. Improved fatigue resistance of Al-Zn-Mg-Cu (7075) alloys through thermomechanical processing. Metall Trans 2, 2897–2902 (1971). https://doi.org/10.1007/BF02813269

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    • DOI: https://doi.org/10.1007/BF02813269

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