Accession Number : AD0732267

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

Descriptive Note : Final rept. Jun-Dec 70,

Corporate Author : AIR FORCE MATERIALS LAB WRIGHT-PATTERSON AFB OHIO

Personal Author(s) : Ostermann,Friedrich

Report Date : SEP 1971

Pagination or Media Count : 30

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)

Descriptors :   (*HEAT TREATMENT, ALUMINUM ALLOYS), (*ALUMINUM ALLOYS, FATIGUE(MECHANICS)), MECHANICAL WORKING, MICROSTRUCTURE, TENSILE PROPERTIES, ZINC ALLOYS, MAGNESIUM ALLOYS, COPPER ALLOYS

Subject Categories : Properties of Metals and Alloys
      Fabrication Metallurgy

Distribution Statement : APPROVED FOR PUBLIC RELEASE