The Low Temperature Impact Behavior and Ductile-Brittle Transition of Nano-cluster-Strengthened Steel

A series of impact tests within the temperature range of -180320 degrees C were applied to study the low temperature impact behavior and ductile -brittle transition of the 700 MPa nanocluster-strengthened steel. The results clearly demonstrated that temperature had a significant effect on impact properties. As the temperature decreased, the impact absorption energy and shear section ratio were correspondingly reduced, and the micro -morphology was changed gradually from ductile fracture to brittle fracture. The ductile -brittle transition temperature (DBTT) range of was between -80 degrees C and -160 degrees C. The fitting results of the Boltzmann function for the ductile -brittle transition curve were in good agreement with the experimental observations. Specifically, the DBTT was determined to be -110 << 1 degrees C, which suggested good low -temperature impact toughness. The outstanding low -temperature impact toughness of the test steel is mainly due to its low C content and high Ni content, fine effective grain size (EGS), and a large number of Cu -rich nanoscale precipitates. Furthermore, the effect of temperature on dislocation movement plays a major role in the ductile -brittle transition.