Transition from Intergranular Corrosion to Intergranular Stress Corrosion Cracking in AA2024-T3

The transition of intergranular corrosion (IGC) to intergranular stress corrosion cracking (IGSCC) in\nAA2024-T3 was studied using microfocal X-ray radiography, scanning electron microscopy (SEM), and\nelectrochemistry. A constant potential was applied in 1 M NaCl solution, and a fixed elastic tensile displacement\nwas applied in the transverse direction using a modified ASTM G49 jig. In this orientation, IGC grows primarily\nalong the elongated grain boundaries in the longitudinal and transverse directions, parallel to the applied stress. SEM\nand X-ray radiography provided insightful images of the transition to IGSCC. Linking of the individual IGC sites\noccurred at the edges of the elongated grains, resulting in transition of the IGC sites into IGSCC that was nominally\nnormal to the applied stress. This coalescence process was discontinuous in nature, as evidenced by arrest marks on\nthe fracture surface and oscillations in the measured current.