Atomistic Study of the Effect of Hydrogen on the Tendency toward Slip Planarity in Bcc Iron.

Abstract

H-enhanced slip planarity is generally explained in terms of H-reducing stacking fault energy in fcc systems. Here, we showed that H-decreasing dislocation line energies can enhance the tendency toward slip planarity in bcc Fe through systematically studying the interaction between H and 1/2 <111> {110} dislocations using the EAM potential for Fe-H systems. It was found that the binding energy of H, the excess H in the atmosphere, and the interaction energy of H increased with edge components, leading to larger decrements in the line energies of the edge and increased mixed dislocations than those of a screw dislocation. The consequence of such interaction patterns is an increment in the energy change in the system when the edge and mixed dislocations are converted to screw dislocations as compared to the H-free cases. The cross-slip in bcc Fe is thus suppressed by H, increasing the tendency toward slip planarity.