Abstract
In this paper, the fatigue crack growth rates of A7N01 aluminum alloy welded joint in weld zone (WZ) and heat affected zone (HAZ) are compared under the stress ratio of 0.1. At the same time, the fatigue crack growth rate of WZ under different stress ratios is studied. The results show that the difference of microstructure leads to different fatigue crack growth rates in different areas of welded joints. The HAZ shows better fatigue crack growth resistance and slower fatigue crack growth rate. However, due to the burning loss of Zn element in the WZ, the precipitation of strengthening phase after solidification in the molten pool is less, and the fatigue crack propagation resistance is weak. After 60 days of natural aging, the number of precipitated phases in the WZ and HAZ increased, and the fatigue crack propagation resistance is improved compared with that in the welded condition. Compared with grain boundary strengthening, precipitation strengthening is more important. With the increase of stress ratio, the fatigue crack closure effect in WZ gradually weakens, and the fatigue crack propagation rate increases.
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