Computer simulation of reactions between an edge dislocation and glissile self-interstitial clusters in iron

Abstract

Clusters of self-interstitial atoms (SIAs) are formed in metals by high-energy displacement cascades, often in the form of small dislocation loops with a perfect Burgers vector, b. Atomic-scale computer simulation is used here to investigate their reaction with an edge dislocation gliding in α-iron under stress for the situation where b is inclined to the dislocation slip plane. The b of small loops (37 SIAs here) changes spontaneously and the interstitials are absorbed as a pair of superjogs. The line glides forward at critical stress τ_c when one or more vacancies are created and the jogs adopt a glissile form. A large loop (331 SIAs here) reacts spontaneously with the dislocation to form a segment with b = 〈100 〉, which is sessile on the dislocation slip plane, and as applied stress increases the dislocation side arms are pulled into screw orientation. At low temperature (100 K), the 〈100〉 segment remains sessile and the dislocation eventually breaks free when the screw dipole arms cross-slip and annihilate. At 300 K and above, the segment can glide across the loop and transform it into a pair of superjogs, which become glissile at τ_c. Small loops are weaker obstacles than voids with a similar number of vacancies, large loops are stronger. Irrespective of size, the interaction processes leading to superjogs are efficient for absorption of SIA clusters from slip bands, an effect observed in flow localization.

Acknowledgements

This research was sponsored by (i) grant PERFECT (F160-CT-2003-508840) under programme EURATOM FP-6 of the European Commission, (ii) a research grant from the UK Engineering and Physical Sciences Research Council and (iii) the Division of Materials Sciences and Engineering and the Office of Fusion Energy Sciences, US Department of Energy, under contract DE-AC05-00OR22725 with UT-Battelle, LLC.