Low-cycle fatigue behavior of 7075-T6 aluminum alloy at different strain amplitudes

Low-cycle fatigue (LCF) life and failure mechanism of 7075-T6 high strength aluminum alloys were investigated under MTS 809. The cycling stress response and the cyclic stress-strain relationships under different strain amplitudes were investigated. Using Manson-Coffin law, the three parameter exponential function equation and the damage function model of tensile hysteresis energy (Ostergren equation), the regression analysis of LCF test data was carried out, it was found that the fatigue life prediction results of the three parameter exponential function equation were better than the other two life prediction methods in terms of statistical analysis methods of standard deviation and dispersion band. Analysis of microstructure and fatigue failure fracture revealed that fatigue crack initiated at the interface of precipitations and alpha-phase aluminium substrate in surface or near surface of the sample.