Effect of post-heat treatment on microstructure and properties of EH47 steel CGHAZ

To clarify the effect of post-heat treatment on the microstructure and mechanical properties of the coarse-grained heat-affected zone (CGHAZ) for EH47 steel, simulated CGHAZ specimens were subjected to post-heat treatment at 250°C for 1.0 h. The results showed that the microstructure of CGHAZ was composed of granular bainite (GB) and lath bainite (LB), and a large number of iron-carbon particles (∼81 nm) were precipitated after post-heat treatment. The relationship between dislocations, low-angle grain boundaries and iron-carbon particles was revealed by KAM values. The iron-carbon particles hindered the movement of sub-grain boundaries and dislocations, thereby increased the yield strength (∼120 MPa). The precipitation of iron-carbon particles caused the cracking of bainite ferrite and reducing the fracture toughness of CGHAZ.