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

Abstract

A molecular dynamics simulation was conducted on hydrogen embrittlement at a crack tip of a single crystal of α-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 threedimensional 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 α-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.

Molecular Dynamics Simulation of Hydrogen-Edge Dislocation Interaction in BCC Iron

“…Finally, the present calculations demonstrate that beneath the influence of hydrogen on cavity nucleation and growth, as already simulated using MD simulations [29], the magnitude of the interaction between hydrogen and dislocations is of prime importance for understanding the mechanical properties of hydrogen charged iron and steel.…”

Atomistic study of hydrogen embrittlement of grain boundaries in nickel: II. Decohesion

“…Although experiments clearly demonstrate embrittlement, the microscopic 5 processes are not established nor does a comprehensive and predictive theory for this phenomenon yet exist. Atomic-scale simulations are thus increasingly being used to test possible embrittlement concepts [7,8,9,10,11,12,13,14,15,16], within the limitations of such modeling. Since embrittlement is often accompanied by a change from ductile fracture to intergranular cleavage, mechanisms involving H segregation at grain boundaries would seem to be of particular importance.…”

Simulation of Hydrogen Embrittlement at Crack Tip in Nickel Single Crystal by Embedded Atom Method

“…The uniaxial tensile displacement perpendicular to the (100) crack plane was then enforced on the two ends of the model in the X-axis. The displacement-boundary conditions for these two ends with S X preset using a kind of smooth loading method 21) to avoid the influence of sudden tensile loading after sufficient relaxation are shown in Fig. 3.…”

“…12) The three-dimensional (3D) crack tip model on the nanometer scale, which was originally proposed by our group 21) to study HE of iron, was used in the simulation to reveal the influence of hydrogen on the fracture. The simulation results are discussed in comparison with published experimental results.…”