| 6061-T6 aluminum alloy has the advantages of high strength, corrosion resistance stability, which is widely used in shipbuilding, aviation, railway and other fields. This paper uses fiber laser welding of 6061-T6 aluminum alloy 4 mm thick to research on the fatigue crack growth in air by different welding process parameters and corrosion fatigue crack growth performance in artificial seawater.This paper use SE(B) three point bending crack growth test. Design loading device for SE(B) three point bending and the corrosion circulation system to provided experimental conditions for the study of fatigue crack growth performance. By observing the microstructure of welding joint, welding defects, hardness test of welding joint and fatigue fracture morphology, provided the theoretical analysis basis for the study of fatigue crack growth behavior.Study on the fatigue crack growth in parent mental, welding joint under different welding process conditions by the method of continuous decrease K.Through processing the experimental date to establish Paris formula in medium speed area of crack growth and calculate the threshold value under different welding process conditions, which can be concluded that a better welding technology parameter is 4 kW welding power, welding speed of 2 m/min, the fatigue crack propagation properties of the weld is better than the parent metal. Analysis the influence factors of welded joint fatigue crack growth: good welding forming, the weld microstrucure of tiny grains, the macroscopic and spherical gas hole at low speed area can improve the fatigue growth performance.Study on the fatigue crack growth in welding joint under the same welding process in air and artificial seawater. Through processing the experimental date to establish Paris formula in medium speed area of crack growth and calculate the threshold value, which can be obtained the corrosion fatigue growth rate is faster than in air in medium speed area of crack growth, but it is slower than in air in low speed area. Based on observation of fracture morphology characteristics, corrosion fatigue fracture mode is the intergranular fracture. It is one of main reason for the corrosion fatigue crack growth rate is faster than in air in medium speed area of crack growth that the crack tip seawater corrosion to produce the corrosion products. However, the corrosion products are stacked on fatigue crack growth point lead to stronger crack closure effect, the fatigue crack growth driving force decreases, so that the corrosion fatigue crack growth rate is less than in the air in the low speed region. |
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