Improved Fatigue Resistance of Al-Zn-Mg-Cu (7075) Alloys through Thermomechanical Processing.

摘要

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-T651properties;with zero mean stress and alternating stress to cause failure in 10to 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)