Abstract
The surface fatigue crack propagation behavior has been investigated under tension-tension cyclic stress at two different frequencies in 3 mass% NaCl aqueous solution for the 5052 and 5083 aluminum alloys, and 1100 commercially pure aluminum sheets with an artificial surface defect. While the fatigue life (number of cycles to failure) at low frequency is obviously longer than that at high frequency in 5083 alloy and 1100 aluminum, the fatigue life is almost independent of the frequency in 5052 alloy. The reduction of fatigue life is largest for 1100 aluminum containing almost no addition of Mg which generally improves corrosion resistance of an aluminum alloy. The fatigue life for 5083 alloy, which is assumed to have β phase more than 5052 alloy because of differences in Mg content and heat treatment, is lager than that for 5052 alloy. In the early stage of fatigue crack when propagation is governed by corrosion environment, surface crack propagation rate at low frequency tends to be slightly higher compared with that at high frequency for 5052 alloy. Further, the 5052 alloy exhibits the flatter front shape of fatigue crack at failure at the lower, because the surface crack propagation is more accelerated by corrosion effect.
