Corrosion Fatigue of High-Strength Aircraft Structural Alloys

Results of corrosion fatigue characterization of AA7075-T6 and AF1410 steel under different simulated marine environments and loading conditions are presented. In comparison with baseline tests conducted in laboratory air, corrosion fatigue experiments performed at 1-Hz frequency in the presence of 1% NaCl environment indicated a substantial reduction in fatigue lifetime in the case of AA7075-T6, whereas AF1410 corrosion fatigue life was found to be statistically unaffected at 1-Hz frequency in the presence of 1% and 3.5%NaCl. However, a reduction of frequency to 0.5 Hz significantly reduced the lifetime of AF1410 steel. On the other hand, Cd-plated AF1410 tested to study fatigue characteristics in a hydrogen-rich metal surface environment yielded minimal change in the lifetime. Atomic force microscope analysis was performed to discern features in fracture surface morphology leading to changes in lifetime of AF1410 and AA7075-T6 alloys.