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

Abstract

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.

Coadsorption of CO and H2 on an Iron Surface and Its Implication on the Hydrogen Embrittlement of Iron

“…Storing hydrogen gas in metal containers leads to the manifestation of a well-known phenomenon called environmental hydrogen embrittlement. − The phenomenon of hydrogen embrittlement has been investigated intensively in the literature. − Most of the authors agree that atomistic hydrogen within the metal lattice migrates to a region in the lattice characterized with high strain. It is widely believed that driven by the stress, hydrogen concentration increases ahead of crack tips, leading to accelerated crack growth and materials failure. − …”

Traction–separation relationships for hydrogen induced grain boundary embrittlement in nickel via molecular dynamics simulations

“…For metallic systems with impurities, atomistic simulations including first principles methods have been used to study hydride precipitation, hydrogen segregation, and the embrittling potency of various elements [4,25,[34][35][36][37][38][39][40][41][42][43][44]. For example, ab initio methods have been used to study energetic aspects of the interaction between H and defects in metallic materials including: (i) the reduction in cohesive energy due to the presence of H in Ni [38], Al and Fe [37], (ii) the strong binding energy between H and dislocation cores, which could prevent dislocation cross slip and promote planarity of slip in Al [39] and α-Fe [25], and (iii) the reduction in stacking fault energy in Zr [4,40], enabling enhanced plasticity as confirmed by larger scale atomistic simulations [4].…”

Density Functional Theory study of the hydrogen storage in a vacancy zone of an iron–nickel cell

“…In pure nickel, a low hydrogen content caused strain localization only, while a high hydrogen content caused microvoid formation as well. The specimen contains a thin layer of hydride fractured and exhibited brittleness [4].…”