Crack propagation behavior of dual-phase steel at low temperature

In this work, the crack propagation behavior and mechanism of dual-phase steel were studied under low temperature environment. The results show that the strength of dual-phase steel increases from -20 degrees C to -60 degrees C, and the fracture toughness presents the opposite trend. When the crack began to extend at low temperature, the size of plastic zone at the crack-tip is reduced, inducing the opening displacement rate, strain rate and temperature-strain parameters are reduced, which shows the extreme sensitivity to ambient temperature. More importantly, the fracture of dual-phase steel presents the transgranular fracture along {1 0 1} and {1 1 1} crystal planes, due to the accumulation of dislocation density. Therefore, the crack propagation of dual-phase steel at low temperature is caused by the dislocation accumulation and movement behaviors.