Fig. 1 Schematic diagram of thick plate position division and sampling

Fig. 2 OM and SEM micrographs of the near fracture surfaces of the 1/4 T and center tensile samples of the test steel: a, c 1/4 T; b, d CSZ; e energy spectrum map of inclusion in d

Fig. 3 EBSD micrographs of 1/4 T and center samples of test steel. a, d IPF maps; b, e misorientation distribution maps; c, f KAM distribution maps; g statistical figure of large and small-angle grain boundary distribution; h KAM value distribution statistical maps. a, b, c 1/4 T; d, e, f CSZ

Fig. 4 EBSD band slope analysis results of CSZ in test steel: a band slope map; b bcc phase map that conforms to band slope data; c multiphase structure distribution map

Fig. 5 Element distribution maps in the CSZ

Fig. 6 a, b TEM micrographs of the precipitated particles, c HRTEM images of the white circle in b, and SAED pattern

Fig. 7 SEM micrographs of the tensile fracture of the test steel; a, c 1/4 T; b, d center; e energy spectrum map of inclusions in d

Fig. 8 EBSD maps of the fracture longitudinal section voids of the center sample: a IPF map; b misorientation distribution map; c KAM distribution map

Fig. 9 a-e SEM micrographs of cracks in the CSZ; f energy spectrum map of inclusions

Fig. 10 EBSD maps of fracture section crack in CSZ: a IPF map; b phase map; c KAM map

Fig. 11 a Hollomon model, b modified C-J analysis

Fig. 12 a Taylor factor map, b GND distribution map

Fig. 13 a Distribution map of sub-grain boundaries; b Taylor factor map; c changes in misorientation along line 1 in b; d changes in misorientation along line 2 in b

Fig.14 Crack propagation path and microstructure distribution in CSZ