The Effect of Shot peening on Corrosion Fatigue Properties of 6063-T5 Aluminum Alloy in Sea Water

In the current study corrosion fatigue properties of 6063-T5 alloy were studied via standard test methods and the results were compared with the fatigue properties of the specimens at the same conditions. Results revealed that shot peening process caused a considerable increase on fatigue life of alloy. But on the other hand that presence of an aggressive environment around the alloy concurrent with applying a cyclic stress, Significantly reduced the fatigue life of the alloy. Further studies showed that the fatigue cracks initiate and propagate both from specimen external surface and internal bulk, while in shot peened specimens, these cracks initiate from underneath external surface. Furthermore, in propagation step, these cracks experience an evidence deviation from their expected direction or branch formation in case of facing to an impurity, phase or precipitation i.e. Mg 2Si. microstructural studies on Corrosion Fatigue fracture surfaces showed the occurrence of hydrogen embrittlement phenomenon. Furthermore, there was a significant different between the fatigue fracture surfaces compare to corrosion fatigue fracture surface. Dimensions, and crack propagation of fatigue specimens were completely different from corrosion fatigue cracks.