Vacancy and Interstitial Cluster Production in Neutron-Irradiated α Iron

Abstract

Vacancy cluster and interstitial cluster production in α iron was computed by simulating atomic collision cascades on a computer. Each collision was determined by the Erginsoy‐Vineyard interatomic potential for α iron. The computed densities of displacement spikes produced by primary knock‐on atoms with energies above 3 keV correlated qualitatively with the degrees of irradiation hardening observed by Harries et al. in ferritic steel specimens for five different neutron energy spectra. The computed total displaced atom densities did not correlate with the degrees of irradiation hardening observed by Harries et al. Annealing simulations indicated that displacement spikes produced by primary knock‐on atoms with energies below 2.5 keV should not contribute importantly to irradiation hardening in specimens irradiated at the temperature (∼60°C) adopted by Harries et al. The volume of collided atoms involved in a collision cascade usually exhibited a marked orientation along 〈110〉 directions as did the associated displacement spike. Spikes are therefore oriented in the primary slip planes of α iron and each could serve in toto as a barrier to dislocation motion.