On recoil-energy-dependent defect accumulation in pure copper - Part II. Theoretical treatment

Over the years, an enormous amount of experimental results have been report ed on damage accumulation (e.g. void swelling) in metals and alloys irradia ted under vastly different recoil energy conditions. Unfortunately, however , very little is known either experimentally or theoretically about the eff ect of recoil energy on damage accumulation. Recently, dedicated irradiatio n experiments using 2.5 MeV electrons, 3.0 MeV protons and fission neutrons have been carried out to determine the effect of recoil energy on the dama ge accumulation behaviour in pure copper and the results have been reported in part I of this paper (Singh et al., 2001, Phil. Mag. A, 80, 2629). The present paper attempts to provide a theoretical framework within which the effect of recoil energy on damage accumulation behaviour can be understood. The damage accumulation under Frenkel pair production (e.g. 2.5 MeV electr on) has been treated in terms of the standard rate theory (SRT) model where as the evolution of the defect microstructure under cascade damage conditio ns (e.g. 3.0 MeV protons and fission neutrons) has been calculated within t he framework of the production bias model (PBM). Theoretical results, in ag reement with experimental results, show that the damage accumulation behavi our is very sensitive to the recoil energy and under cascade damage conditi ons can be treated only within the framework of the PBM. The intracascade c lustering of self-interstitial atoms (SIAs) and the properties of SIA clust ers such as one-dimensional diffusional transport and thermal stability are found to be the main reasons for the recoil-energy-dependent vacancy super saturation. The vacancy supersaturation is the main driving force for the v oid nucleation and void swelling. In the case of Frenkel pair production, t he experimental results are found to be consistent with the SRT model with a dislocation bias value of 2%.