Tensile Properties and Fracture Mechanism of Strain Rate Brittleness on Quenched Cold‐Rolled Carbon Steel

For metal materials, the corresponding mechanical indicators obtained by tensile experiments at different strain rates are different. Herein, after the quenching and cold‐rolling process, a deformed lath martensite structure is obtained in low‐carbon steel. A scanning electron microscope (SEM), transmission electron microscope (TEM), and 3D atom probe (3DAP) analyses are used in this research. The results show that measurement uncertainty exists and when the strain rate is 0.0021 s −1 at room temperature, the elongation is at its minimum value, which gets into an extreme point. C atoms segregate into the martensite boundary when the strain rate brittleness occurs from 3DAP analysis. This phenomenon indicates that the supersaturated C atoms in the steel undergo nonequilibrium segregation at the lath boundary during the elastic phase of stretching, which results in strain rate brittleness.