Interaction of an edge dislocation with voids in α-iron modelled with different interatomic potentials

Atomic processes and strengthening effects due to interaction between edge dislocations and voids in alpha-iron have been investigated by means of molecular dynamics with a recently developed interatomic potential (Ackland et al 2004 J. Phys.: Condens. Matter 16 S2629) and compared with those obtained earlier with an older potential (Ackland et al 1997 Phil. Mag. A 75 713). Differences between the interactions for the two models are insignificant at temperature T >= 100 K, thereby confirming the validity of the previous results. In particular, voids are relatively strong obstacles because for large voids and/or low temperature, the initially straight edge dislocation is pulled into screw orientation before it breaks away at the critical shear stress, tau(c). Differences between the core structures and glide planes of the 1/2 < 111 > screw dislocation for the two potentials do not affect tc in this temperature range. The only significant difference between the dislocation-void interactions in the two models occurs at low temperature in static or pseudo-static conditions (T <= 1 K). It arises from the influence of the dislocation segment in the 70 degrees-mixed orientation with the (Ackland et al 2004 J. Phys.: Condens. Matter 16 S2629) potential and is seen in the critical line shape at which the dislocation breaks from the void. It affects tc for some combinations of void size and spacing. The effect on the line shape does not arise from anisotropy of the elastic line tension: it is due to the high Peierls stress of the 70 degrees dislocation. When this effect does not control breakaway, the dependence of tau(c) on void size and spacing follows an equation first found by modelling the Orowan process in the approximation of linear elasticity.