Fig. 1 Hot rolling schedules of three experimental steels

Fig. 2 SEM images of the microstructure of R1 a, R2 b, R3 c

Fig. 3 Elemental mapping of main alloy elements of R3. The color scale indicates increasing concentration from blue to red

Fig. 4 TEM bright field images of R1 a, b, R3 c, d, SAED pattern of point ① e, ② f

Fig. 5 Inverse pole figure (IPF) maps a-c and average grain size d of three samples

Fig. 6 Grain boundary distribution of R1 a, R2 b, R3 c, grain misorientation distribution d and measured grain boundary length densities e

Fig. 7 KAM maps of R1 a, R2 b, R3 c, distribution d

Fig. 8 Stress-strain curves of three samples in air and simulated marine atmosphere

Fig. 9 Yield and tensile strength a and ductility b of three samples

Fig. 10 Loss percentage of ductility of various samples in simulated marine atmosphere compared with that in air

Fig. 11 Surface morphologies of the fractures of R1 a, b, R2 c, d, R3 e, f in air and simulated marine atmosphere. a, c, e Fracture images in air and b, d, f corresponding ones in atmosphere

Fig. 12 Lateral morphologies of the fractures of R1 a, b, R2 c, d, R3 e, f in air and simulated marine atmosphere. a, c, e Images in air and b, d, f corresponding ones in atmosphere

Fig. 13 Cross-sectional morphologies of the fractures of R1 a, R2 b and R3 c, d in simulated marine atmosphere. The images in red boxes are magnified ones in white boxes

Fig. 14 Schematic of microstructural features and SCC initiation mechanism of R1 a, R2 b, R3 c