Carbon rejection triggered by lattice contraction at low-temperature making nano-bainitic steel toughener

In the steel industry, enhancing the toughness of the material often reduces strength. This study employs shallow cryogenic treatment on high-carbon nano-bainitic steel, inducing lattice shrinkage via cryogenic contraction stress. At low temperatures, this process facilitates the diffusion of carbon atoms in bainitic ferrite and reduces the dissolved carbon content within the bainitic ferrite. The bainitic ferrite matrix is successfully toughened, leading to a substantial improvement in material toughness. Results show that shallow cryogenic treatment slightly enhances hardness while significantly improving impact toughness (∼70%) and fracture toughness (∼12%). This study offers a novel approach to enhance the toughness of steel.