Fig. 1 Schematic diagram of the experimental procedure

Fig. 2 Microstructural evolution of the experimental steels annealed at different temperatures: a-c orientation imaging maps; d-f grain orientation spread maps; g-i phase maps; j-l grain size distribution

Fig. 3 EBSD analysis of grain boundary characteristics of the experimental steels annealed at different temperatures: a-c grain boundary maps; d-f misorientation angle distribution. a, d AT700; b, e AT800; c, f AT1100 (The red, green and blue lines indicate the low-angle grain boundaries with an orientation difference of 2°-15°, the high-angle grain boundaries with an orientation difference of > 15°, and the Σ3 grain boundaries, respectively)

Fig. 4 Microstructure and element distribution of the experimental steels annealed at different temperatures: a AT700; b AT800; c AT1100

Fig. 5 Oxidation kinetics curve of the experimental steels at 800 °C in air for 8 h: a mass gain curves; b relationship between square of mass gain and exposure time

Fig. 6 SEM morphologies of the surface oxidation products for the experimental steels oxidized at 800 °C for 8 h: a, d AT700; b, e AT800; c, f AT1100

Fig. 7 XRD patterns of high-temperature oxidation products of the experimental steels

Fig. 8 Cross-sectional morphology of the experimental steels after oxidation for 8 h at 800 °C: a AT700; b AT800; c AT1100

Fig. 9 Cross-sectional morphology and element distribution of oxide layer after oxidation for 8 h at 800 °C: a AT700; b AT800; c AT1100

Fig. 10 Potentiodynamic polarization curves of the experimental steels in 3.5 wt% NaCl solution

Fig. 11 EIS of the experimental steels in 3.5 wt% NaCl solution under OCP condition: a Nyquist plot; b Bode plot. The inset in a is the equivalent electric circuit model used to fit the EIS data

Fig. 12 Surface morphologies of the experimental steels after electrochemical corrosion: a, d AT700; b, e AT800; c, f AT1100

Fig. 13 Surface morphologies of the experimental steels after immersion in 3.5 wt% NaCl solution