Corrosion fatigue crack propagation of 7XXX series aluminum alloys from key components of high-speed train

The corrosion fatigue cracks propagation behavior of A7N01P-T4 and A7N01S-T5 aluminum alloys in 3.5 wt.% NaCl solution and air were studied by single side notch corrosion fatigue tests (SNET). The crack growth rate (da/dN) was measured and the crack propagation mechanism was analyzed by scanning electron microscopic analysis. The results showed that the corrosion fatigue cracks growth rate of A7N01S-T5 alloy in air and 3.5 wt.% NaCl solution is faster than that of A7N01P-T4 alloy. The crack propagation follows a mixed intergranular and transgranular mode. The anodic dissolution and hydrogen embrittlement accelerate the propagation of corrosion fatigue crack of 7-series Al alloy in 3.5 wt.% NaCl solution. The corrosion resistance and fatigue crack propagation are related to the strength of the alloys and the density of grain boundaries.