Insight into the Role of Mo Content on the Microstructure and Impact Toughness of X80 Thick-Walled Low-Temperature Pipeline Steel

In this manuscript, the effects of Mo content on microstructure and impact toughness X80 thick-walled low-temperature pipeline steel were studied. Two test steels with different (0.25% 0.40%) prepared by thermo-mechanical control process. The properties measured at −45 °C, evolution was observed via an optical microscope (OM), a scanning electron (SEM), back-scattered diffraction (EBSD), transmission (TEM). Each showed formation mixed consisting polygonal ferrite (PF), granular bainite (GB), lath (LB). Increasing resulted in rise LB expense PF GB. At same time, morphology martensite/austenite (M/A) constituents changed from blocky to slender. dislocation density matrix around M/A enhanced increase content. This also led microstrains constituents. Also, number fraction high angle grain boundary (HAGB) (MTA > 15°) decreased addition more Furthermore, 0.25% 0.40%, 206 57 J. Both slender decrease HAGB deteriorated steel.