Atomistic process on hydrogen embrittlement of a single crystal of nickel by the embedded atom method

A molecular dynamics (MD) simulation by the embedded atom method (EAM) was conducted on hydrogen embrittlement (HE) at a crack tip of a single crystal of nickel composed of {1 0 0} planes under uniaxial tension along the [1 0 0] direction perpendicular to the crack plane at room temperature. A three-dimensional (3D) crack-tip model with 16,632 nickel atoms and from 2 to 653 hydrogen atoms segregated in the notched area was designed and the EAM potentials proposed by Baskes and co-workers were used for the simulation. The hydrogen-free specimen showed good ductility associated with a significant blunting of the crack tip. In the hydrogen-charged specimen, the elongation at the fracture decreased with increasing hydrogen content due to the suppressed and localized plastic deformation. Fracture occurred macroscopically on the (1 0 0) plane perpendicular to the tensile direction. Twin deformation associated with the fracture was formed in the specimen with 653 hydrogen atoms, corresponding to a thin layer of hydride at the notched area, while no twin deformation was formed in the other hydrogen-charged specimens or the hydrogen-free specimen. The simulation results were in good agreement with published experimental results.