The individual and synergistic effects of ferrite and vanadium addition on the tensile strength and impact toughness of two Mn–Si–Cr bainitic steels (22Mn2SiCrV and 22Mn2Si2Cr) are systematically investigated. Two heat treatment routes—annealing–bainite‐based quenching–tempering (A‐BQ‐T) and annealing–intercritical bainite‐based quenching–tempering (A‐IBQ‐T)—were applied to the two steels, yielding four conditions: A‐BQ‐T, A‐BQ‐T‐V, A‐IBQ‐T, and A‐IBQ‐T‐V. Among these, the A‐IBQ‐T‐V samples exhibited the best mechanical properties, achieving a tensile strength of 1538 MPa and an impact toughness of 83.2 J. The results indicated that the combined effects of ferrite and vanadium carbide precipitates (VCs)‐induced microstructural refinement are the key factors responsible for the superior combination of high strength and adequate toughness. Such austenite/ferrite interfaces and VCs provide more nucleation sites for A‐IBQ‐T‐V samples. Furthermore, transmission electron microscopy and electron backscatter diffraction observations revealed that these features promote multi‐directional growth, resulting in refined final microstructures and high fraction of high‐angle misorientations. Besides, it is also noted that while the Ac 1 and Ac 3 temperatures are raised by vanadium addition, the martensite start temperature and the critical cooling rate to obtain full martensite remain largely insensitive to vanadium content.
Luo et al. (Fri,) studied this question.