Abstract：In order to study the microscopic mechanism of the influence of hydrogen atoms on the fracture of metallic materials, this paper builds a model of crack - dislocation interaction under the influence of hydrogen atoms infiltrating at the crack tip within multiple grains based on the discrete dislocation theory. On the basis of this model, the influence of hydrogen atoms on the dislocation distribution on the slip planes in grains is considered. Further, the effects of hydrogen atoms on the dislocation penetration at the grain boundaries and the initiation of wedge cracks at the grain boundaries are obtained. This model is applicable to both body centered cubic (BCC) and face centered cubic (FCC) crystals.
Through calculations, the influence of different hydrogen infiltration concentrations and ranges at the crack tip on the dislocation distribution in front of the crack is analyzed. It is found that hydrogen atoms at the crack tip can promote dislocation emission and increase the driving force for dislocation movement on the slip planes, making it easier for dislocations to penetrate the grain boundaries. The relationship between the initiation of wedge cracks at the grain boundary and hydrogen atoms at the crack tip is presented. It is found that when the grain boundary angle is large, an increase in the hydrogen infiltration concentration and range at the crack tip makes it easier for wedge cracks to initiate at the grain boundaries.
The influence of hydrogen infiltration at the crack tip on the shear stress in the dislocation - free zone in front of the main crack is analyzed. It is found that an increase in the hydrogen infiltration range and concentration at the crack tip will enlarge the dislocation - free zone in front of the crack, thereby reducing the shielding effect of dislocations on the crack and making it easier for the main crack to propagate.
This model effectively demonstrates how hydrogen atoms at crack tip influence dislocations in crystals, providing a foundation for studying metal fracture in hydrogen environments.
2025, Vol. 46 
