The effect of temperature and strain rate on the interaction between an edge dislocation and an interstitial dislocation loop in α-iron

The influence of temperature, T, and strain rate, , on the reaction between the edge dislocation line and a periodic row of 4 nm interstitial dislocation loops with Burgers vector in α-Fe has been investigated by means of molecular dynamics, using a potential developed recently for body centred cubic Fe (Ackland et al 2004 J. Phys.: Condens. Matter 16 1). A dislocation segment with b = [010] is formed by favourable reaction in all cases: it is sessile in the glide plane and leads to the formation of a screw dipole on the line under increasing stress. The mechanism controlling line breakaway and the corresponding critical stress depend mainly on T rather than . At high T (300 and 600K here) the length of the screw dipole is short (<10b) and the controlling mechanism is the glide of the [010] segment over the loop surface coupled with cross-slip of the short screws. The loop is totally absorbed on the line by transformation of b to . At low T, where thermal effects are negligible, a long (∼100b) screw dipole is drawn out and the controlling mechanism is annihilation of the dipole by screw cross-slip. This results in only partial absorption of the loop. By comparing the results with earlier ones obtained using an older interatomic potential, conclusions are drawn on the effects of interaction between edge dislocations and interstitial loops in iron.