Possible mechanism of homogeneous nucleation, growth and annealing of interstitial-type dislocation loops in pure FCC metals

By the molecular dynamics technique (MDT) it is shown that tri-interstitials with orthogonal orientation of the dumbbell axes ar nuclei for interstitial type dislocation loops. These nuclei occur uniformly throughout the whole volume, grow and then form large loops with an a/3<111> Burgers vector. It is concluded that under irradiation loops cannot be generated above the annealing temperature of a tri-interstitial. At approx. 0.5 Tsub(melt) the loops transform into octahedra limited by Shockley stacking faults and by stair rod dislocations with the a/6<110> and a a/6<002> Burgers vectors. Emission of single interstitials is not observed up to 0.7 Tsub(melt). (author)