Fatigue properties and crack growth behavior of 7N01 and 6N01 aluminum alloys

In this study, the fatigue properties, microstructure, and surface damage tolerance of the 6N01 profile, 7N01 profile, and 7N01 plate aluminum alloy were studied. The fatigue test results show that the fatigue limit of the 7N01 profile was the highest and the 7N01 plate was the lowest. More importantly, most fatigue specimens failed in the safe life area provided by the Kitagawa-Takahashi line diagram, which indicates that there is a "short-notch effect" in the fatigue behavior of the pre-cracked aluminum alloys. For the sake of safety, according to the Kitagawa-Takahashi line diagram corrected by the fatigue test results, the effective harmless notch sizes a(0,eff) of 6N01 profile, 7N01 profile, 7N01 plate is 23.92, 10.81, 24.32 mu m, respectively, and their effective fatigue notch propagation threshold Delta k(eff,th) is 0.81, 0.39, 0.77 MPa m(1/2), respectively. These corrected values reestablished the fatigue tolerance of the three materials and provided the critical data reference for the practical application. Combined with this study and the analysis of the literature, it can be concluded that the short-notch effect of the three materials should be related to the microstructure, crack closure mechanism, internal defects.