| Summary: | Aluminium is considered a green metal due to its environmental responsive characteristics.
The 7475-T7351 aluminum alloy is extensively used in automotive and aerospace applications due to
its light weight and high strength. In the present work, the effects of the corrosive environment on the
high cycle fatigue (HCF) behaviors of the 7475-T7351 aluminum alloy was investigated. The aqueous
solution of sodium chloride was used for solution treatment. The HCF test was performed on
pre-cracked specimens using a servo-hydraulic universal testing machine, Instron 8800. The fractured
specimens were characterized using a scanning electron microscope. It was observed that the crack
propagation occurred through anodic dissolution at high stress and a significant crack tip blunting and
crack extension occurred. However, no appreciable change in crack growth was noticed over the lower
frequency range of 0.1 to 0.9 Hz. The slower growth rate envisages oxide debris formation between
the cracked faces. When the alloy was treated under corrosive environments, the HCF tests depicted
that the fatigue life reduces up to two orders of magnitude. The corrosion pits induced the crack
initiation in stage-I at lower alternating stress; however, the fatigue crack growth rate (FCGR) was
increased in the corrosive environment. The transition from stage-I to stage-II occurred at a lower
stress intensity range (∆K) level; it was due to the combined effects of corrosion, hydrogen
embrittlement, active path dissolution, and stress concentration. The corrosion fatigue test at low
frequency also depicted a slower FCGR as compared to its moderate frequency counterpart and showed
an irregular crack growth behavior.
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