Fig. 1 SEM cross-sectional micrographs of the alloys T6 aged for a 30 min, b 24 h, c 120 h. The observation plane is shown by the inset sketch

Fig. 2 DA alloys post-aged at 180 °C for a 10 min, b 30 min, c 48 h; at 150 °C for d 30 min, e 8 h, f 144 h; at 120 °C for g 1 h, h 60 h, i 120 h after immersion test. The observation plane is shown by the inset sketch

Fig. 3 a Combination of maximum corrosion depths and yield strength, b combination of uniform ductility and yield strength in samples treated with various conditions. All of the DA samples are peak-aged at different post-ageing temperatures as indicated in the images. The T78 results of the alloy were obtained in Ref. [22]

Fig. 4 TEM images of the T6 peak-aged samples: a matrix precipitates, b typical grain boundary feature

Fig. 5 TEM images of the DA samples post-aged a-d at 120 °C for 120 h, e at 150 °C for 8 h, f at 180 °C for 30 min recorded in a the side plane (side-view, the plane perpendicular to the transverse direction) and b-f the rolling plane (plane-view). The white arrows in c, e, f indicate the nano-sized precipitates

Fig. 6 HAADF-STEM images and the corresponding EDS mappings of the samples treated with different conditions: a T6 sample aged at 180 °C for 24 h, b DA samples aged at 180 °C for 30 min, c at 150 °C for 8 h, d at 120 °C for 120 h