The behavior of fatigue crack initiation and propagation in AA2524-T34 alloy

With the help of a four-point-bend fatigue rig, high-cycle fatigue tests were carried out on an AA2524 Al alloy at room temperature, 15 Hz and R = −0.1 in ambient air. Optical microscopy (OM) and scanning electron microscopy (SEM) were employed to capture a detailed view of the fatigue crack initiation and propagation of the samples as well. The fatigue strength is 70 pct of their yield strength. Fatigue cracks were found to be always initiated from the second phase particles or the interface between the second phase particles and matrix. And grain orientation may be the key factor controlling the micro-crack deflection.