Fig. 1. Equilibrium phase fraction (a) and C and Mn content in each phase (b) for the studied steel at different temperatures.

Fig. 2. Tensile properties of studied 10 Mn steel: (a) Engineering stress-strain curves of specimens warm rolled at the different temperatures with 50% reduction in thickness; (b) Engineering stress-strain curves of specimens warm rolled at 600°C and 650°C with either 50% or 63% thickness reduction.

Fig. 3. SEM images on the microstructures of specimens just after the warm rolling at 250°C (a), 400°C (b), 600°C (c) and 800°C (d) with 50% reduction in thickness, and at 600°C with 63% (e, f). The region marked in (e) is magnified in (f). 'γ' and 'θ' represent austenite and cementite, respectively.

Fig. 4. EBSD band contrast images overlapped by phase distribution on the microstructures of specimens warm rolled at 250°C (a), 600°C (b) and 800°C (c) with 50% reduction in thickness; and at 600°C with 63% (d). The green in images represent austenite; the ‘a’ represents martensite.

Fig. 5. SEM images on the microstructures after the IA for the specimens warm rolled at 250°C (a), 400°C (b), 600°C (c), 650°C (d), 700°C (e), 750°C (f) and 800°C (g) by 50% reduction in thickness, and at 600°C (h) and 650°C (i) by 63%. The 'a' and 'P' in images represent ferrite and pearlite.

Fig. 6. EBSD band contrast images overlapped by phase distribution on microstructures of specimens after the IA at 620°C for 5 h, when they were warm rolled at 250°C (a), 600°C (b), 650°C (c) and 750°C (d, e) by 50% reduction in thickness, or at 600°C (f, g) and 650°C (h) by 63%. (e) and (g) are the magnified views of marked regions in (d) and (f); (e1) and (e2) are the AES mapping of C and Mn concentrations in the marked region of (e). The green and the deep red represent austenite and cementite respectively.

Fig. 7. TEM images on microstructures of 600H specimen, which was warm rolled at 600°C by 63% reduction and then annealed at 620°C for 5 h.

Fig. 8. XRD spectra on 600H, 650 L and 650 L specimens examined along the transverse direction.

Fig. 9. Difference of Mn content in cementite particles and the matrix in 700 L (a, b) and 600H (c, d) specimens.

Fig. 10. EBSD band contrast maps overlapped by phase distribution on microstructures after the fracture of 600 L (a), 600H (b), 650 L (c, d), 650H (e, f) and 750 L (g) specimens. (f) is the magnified view of marked region in (e).

Fig. 11. Time-temperature-transformation (TTT) (a) and continuous-cooling- transformation (CCT) (b) diagrams for the decomposition of austenite in the studied steel, calculated on the basis of the composition and austenite grain size of studied steel using JmatPro 6.1 software; The employed warm rolling processes and the IA process are superimposed in (a).