Fig. 1 Typical corrosion morphologies of samples a A, b B, c C, d D after IGC tests

Fig. 2 Typical corrosion morphologies of samples a E, b F, c G, d H after IGC tests

Fig. 3 Potentiodynamic polarization results of samples A, B, E, F

Fig. 4 Precipitates and dislocation structures on grain boundaries of samples a A, b B, c C, d D, e line scanning analysis at yellow line position of sample B, f composition at yellow line position in e

Fig. 5 Secondary phases and dislocation structures within the grain interiors in the solution-treated series Al-Cu-Mg alloys. a sample A, b sample B (inset shows the SAED pattern of the T-phase), c sample C, d sample D (inset shows the SAED pattern of the matrix), e composition of the T-phase shown in a

Fig. 6 S-phase precipitates and dislocations on grain boundaries of retrogression-treated series Al-Cu-Mg alloy: a sample E, b sample F, c dislocations near the grain boundaries of sample F, d composition of the S-phase shown in a, e sample G, f sample H

Fig. 7 Line scanning analyses on grain boundaries of sample F: a, b S-phase positions; c, d spacing positions between adjacent S-phases

Fig. 8 Dislocations and secondary phases in grain interiors of retrogression-treated series Al-Cu-Mg alloy: a sample E, b sample F, c S-phase in grain interiors of sample F (inset shows the SAED pattern of the S-phase), d composition of S-phase shown in (c), e sample G, f sample H

Fig. 9 Coherent relationship between S-phase and Al matrix in sample F: a morphology of S-phase, b composition of S-phase shown in a, c HRTEM of S-phase shown in a, d partially enlarged view of c, e FFT results of S-phase in c, f FFT results of Al matrix in c

Fig. 10 XRD test and analysis results of the alloys with retrogression treatment, 30-70% cold rolling deformation and natural aging: a XRD test results, b fitting result of sample F, c fitting result of sample G, d fitting result of sample H