Hydrogen embrittlement of a single crystal of iron on a nanometre scale at a crack tip by molecular dynamics

A molecular dynamics simulation was conducted on hydrogen embrittlement at a crack tip of a single crystal of -iron composed of {100} planes under uniaxial tensile load along the 100 direction on a nanometre scale at 293 K. The modified Morse pair-potential function of Fe-Fe and the Morse potential function of Fe-H were used to calculate the interatomic action force. A three-dimensional model with 2618 iron atoms and from one to 260 hydrogen atoms segregated at the notched area was designed for the simulation. The general conclusion on hydrogen embrittlement of a single crystal of -iron could be described qualitatively as the processes of cavity nucleation, cavity linkage and, finally, fracture. Cavity nucleation occurs on the (100) plane in the notched area of the specimen with more than three hydrogen atoms at the early stage of the deformation and does not depend on the hydrogen content. The cavities are linked to each other and fracture occurs on the plane with progressing deformation. The deformation step of cavity linkage and fracture decrease logarithmically with increasing hydrogen content, while neither the cavity nor the fracture occur, even at the maximum total deformation of 50%, due to blunting of the crack tip in the specimen without hydrogen.