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

Abstract

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,τc. Differences between the core structures and glide planes of the screw dislocation for the two potentials do not affectτc 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 affectsτc 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 ofτc on void size and spacing follows an equation first found by modelling the Orowan process inthe approximation of linear elasticity.