Simulation of hydrogen embrittlement at crack tip in nickel single crystal by embedded atom method : Advances in computational materials science and engineering II

A molecular dynamics simulation by the embedded atom method was conducted to investigate hydrogen embrittlement of a nickel single crystal, which is composed of 163311 nickel atoms on the nanometer scale and has a [011]-oriented notch under uniaxial tension along the [100] direction at room temperature. The hydrogen-free specimen showed good ductility associated with pronounced blunting of the crack tip. Hydrogen influence was most serious in the specimen that had been hydrogen-charged in the notched (100) planes ahead of the crack tip. In the specimen that had been hydrogen-charged in the notched area, a hydrogen-assisted fracture occurred macroscopically on the (100) plane perpendicular to the tensile direction and the elongation at failure decreased with increasing hydrogen content. A low hydrogen content caused strain localization only, while a high hydrogen content caused microvoid formation in the notched area as well. The specimen containing a thin layer of hydride fractured and exhibited brittleness due to significant microvoid formation and subsequent microvoid growth and linkage at the early stage of deformation. The simulation results show good agreement with the published experimental observations.