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

Atomic processes and strengthening effects due to interaction between edge dislocations and voidsin α-iron have been investigated by means of molecular dynamics with a recently developedinteratomic potential (Ackland et al 2004 J. Phys.: Condens. Matter 16 S2629) and comparedwith 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 temperatureT≥100 K, thereby confirming the validity of the previous results. In particular, voids are relativelystrong obstacles because for large voids and/or low temperature, the initially straight edgedislocation is pulled into screw orientation before it breaks away at the critical shear stress,τ_c. Differences between the core structures and glide planes of the screw dislocation for the two potentials do not affectτ_c in this temperature range. The only significant difference between the dislocation–voidinteractions 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 the70°-mixed orientation with the (Ackland et al 2004 J. Phys.: Condens. Matter 16 S2629) potentialand is seen in the critical line shape at which the dislocation breaks from the void. It affectsτ_c for some combinations of void size and spacing. The effect on the line shape does not arisefrom anisotropy of the elastic line tension: it is due to the high Peierls stress of the70° dislocation. When this effect does not control breakaway, the dependence ofτ_c on void size and spacing follows an equation first found by modelling the Orowan process inthe approximation of linear elasticity.