Dislocation loops in irradiated iron

Abstract

Dislocation loops have been observed in iron foils irradiated with protons or Fe⁺ ions of energy 150 kev. Those produced by irradiation with Fe⁺ ions are shown to lie on {100} planes and to be pure edge in character. They are normally square, with the sides in the corresponding directions, and are formed by the condensation of interstitial atoms. It is believed that the loops are formed because of the excess concentration of interstitial atoms resulting from the direct insertion of atoms on bombardment. It is shown that either a homogeneous or a heterogeneous nucleation mechanism can account for the loop density observed. Finally, an estimate is made of the strain energy of various modes of condensation of point defects in iron. The most favoured are ½[111] (110), ½[111] (111), and [100] (100).