THE EFFECT OF EXFOLIATION CORROSION ON THE FRACTURE AND FATIGUE BEHAVIOR OF 7178-T6 ALUMINUM

The effect of pre-existing exfoliation corrosion on the fracture tough ness and fatigue crack growth of a high-strength structural aluminium alloy (7178-T6) is considered. The material tested is in sheet form an d the toughness of the alloy is measured using the R-curve approach. B efore testing, exfoliation corrosion is introduced in the crack tip re gion of the toughness specimens and ahead of the notch in the fatigue specimens using a solution recommended for accelerated corrosion testi ng. The toughness of the alloy is shown to be only slightly reduced by the presence of exfoliation corrosion at the crack tip, and this slig ht reduction is modelled by thinning of the material at the crack tip. Fatigue experiments show that the presence of exfoliation corrosion e nhances the fatigue crack growth rate at intermediate Delta K values.