The effect of hydrogen atoms on the screw dislocation mobility in bcc iron: A first-principles study

Hydrogen embrittlement I. Analysis of hydrogen-enhanced localized plasticity: Effect of hydrogen on the velocity of screw dislocations inα-Fe

“…This model was applied to bcc α-Fe to determine the kink-pair formation enthalpy at different applied stresses. The effect of hydrogen on the mobility of a screw dislocation in α-Fe was investigated [18] and it was found that hydrogen lowers the Peierls barrier when a hydrogen atom is trapped ahead of the screw dislocation on the slip plane. A hydrogen atom trapped behind the dislocation line can slow or stop the kink motion and decrease the dislocation mobility.…”

“…We base the present work upon some rather seminal recent papers [11,17,18] employing the density functional theory (DFT) to calculate (i) the interaction energy between a hydrogen interstitial and a screw dislocation, (ii) the kink-pair formation energy, and (iii) the kink migration energy; the latter two as functions of hydrogen concentration. These data were used to fit parameters to a line tension model [11,17].…”

“…A hydrogen atom trapped behind the dislocation line can slow or stop the kink motion and decrease the dislocation mobility. The softening effect of hydrogen atoms by promoting kink nucleation and the hardening effect by impeding the kink movement were both evaluated [18].…”

“…In order to overcome this limitation, we use a kinetic Monte Carlo (kMC) simulation of 1 2 [111] screw dislocations and track their glide in order to obtain a realistic description of the dynamics of a dislocation line over long time scales [19]. The advantage of this approach is that it replaces arbitrary assumptions about the nature of dislocation mobility with input based upon microscopic understanding and explicit quantum mechanical calculations [18].…”

Molecular Statics Simulation of the Effect of Hydrogen Concentration on {112}<111> Edge Dislocation Mobility in Alpha Iron

“…Atomistic simulations could be effective for clarification of the distinctive elementary process of dislocation motion under a hydrogen atmosphere; however, classical molecular dynamics cannot be used because of the long-time scale needed to calculate the dislocation motion and accompanying hydrogen diffusion. Therefore, molecular statics 13) and density functional theory 14) investigations have been conducted based on certain assumptions for the dislocation motion. Our previous studies 13,15,16) indicated an increase or decrease of the dislocation velocity depending on the applied stress conditions.…”