Improved Fatigue Resistance of Al-Zn-Mg-Cu (7075) Alloys through Thermomechanical Processing.
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 thermomechanical treatments. Such a treatment was developed for Al-Zn-Mg-Cy (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 and alternating stress to cause failure in 10 to the 7th power cycles is more than 25% higher for commercial-purity 7075TMT and almost 50% higher for high-purity 7075TMT. The results emphasize the importance of microstructural control when high fatigue resistance is required. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 01, 1971
- Accession Number
- AD0732267
Entities
People
- Friedrich Ostermann
Organizations
- Air Force Research Laboratory