Irradiation creep produced by the effect of stress on the nucleation of dislocation loops

Abstract

A general expression for the creep strain produced by a distribution of dislocation loops is derived and applied to the nucleation (assumed subject to Boltzmann statistics) of prismatic loops in b.c.c. and f.c.c. metals and alloys subjected to neutron irradiation. The nucleation of the loops is considered to take place in several stages, viz., an initial growth of small platelets of atoms on {110} planes (b.c.c. metals) or Frank loops on {111} planes (f.c.c. metals), followed by unfaulting and then conservative rotation to the pure edge orientation. The equations for the creep strain for low applied stresses explicitly contain terms relating to the various stages involved in the nucleation of the loops and show, inter alia, that rotation to the pure edge orientation does not cancel the strain produced by prior unfaulting.