LAUSR

Abstract The purpose of this paper is to examine the effect of hydrogen on the crack tip mechanism of an Al single crystal. A ( 121 ) [ 1 1 ¯ 1 ] (plane/front) crack system model with a varying hydrogen concentration was investigated based on a molecular dynamics (MD) framework employing an angular-dependent interatomic potential (ADP). The incipient crack tip event was analyzed using a mixed-mode displacement solution for mode-I and mode-II crack tip fields. The critical stress intensity factor for the onset of the crack tip deformation event was evaluated. A detailed description based on a von Mises atomic shear strain analysis revealed that the presence of hydrogen near a crack tip significantly inhibited the activities of emitted partial dislocations. The hydrogen locking of dislocations near a crack tip was found to facilitate the local amorphization of the crack tip, which considerably reduced the critical stress intensity factor for the onset of crack growth. The effect of the loading mode on the atomic-scale mechanism of the hydrogen embrittlement (HE) was further analyzed, and the explicit dependence of in-plane shear loading was observed.