Study on Fatigue Performance of 7075-T651 Aluminum Alloys

The fatigue life experiments of 7075-T651 aluminum alloy were conducted under different stress amplitude and S-N curves was gained from fitting the experimental data.An estimation of detailed fatigue limit result was 223MPa.The fractography of high stress amplitude and low stress amplitude using scanning microscope displayed that the crack initiation mostly derived from the interior flaw or inclusion,and crack propagation gone with the quasi-cleavage crack.The crack propagation regions under high stress amplitude was characterized by furrow and tyre patterns while lots of fatigue fringe together with the fatigue sidestep and secondary crack generated in the crack propagation regions of low stress amplitude.The tearing edge and equiaxial dimples existed in fatigue failure region of both high stress amplitude and low stress amplitude fracture surface.The bulky inclusion particles can be the crack initiation while dispersion of tiny precipitated phase has a positive influence on fatigue performance of 7075-T651 aluminum alloy.