The Acceleration of Phase Transformation and Strength–Toughness Match by Cerium Addition for Low‐Temperature Bainite

The engineering application of traditional nano‐bainite steel, also known as low‐temperature bainite steel, has been restricted due to its relatively low toughness and the prolonged isothermal transformation time during manufacturing processes. To address these limitations, this study investigates the effects of cerium (Ce) addition on the mechanical properties and phase transformation behavior of typical nano‐bainite steel. The samples are austenitized and followed by isothermal treatment at temperatures ranging from 230°C to 300°C. The results reveal that 0.015 wt% Ce addition significantly reduces the bainite transformation incubation period and accelerates transformation. Specifically, at an isothermal treatment temperature of 230°C, the incubation period is shortened from 22,500 to 11,353 s corresponding to a reduction of nearly 50%. This substantial decrease can be attributed to the reduction of activation energy for bainite phase transformation from traditional 55.94 kJ mol −1 without Ce to 44.92 kJ mol −1 with Ce. Furthermore, Ce addition can markedly enhance the impact toughness with a comparative 1500 MPa strength level for as‐employed samples. After isothermal treatment at 230°C, the impact energy reaches 47 J significantly higher than 26 J of samples without Ce. This improvement is primarily due to the combined effects of microstructural refinement and inclusion modification by Ce addition. Therefore, appropriate Ce addition simultaneously shortens processing time and markedly enhances the toughness of low‐temperature nano‐bainite microstructures.