The effect of alloying additions on collision cascades in heavy-ion irradiated copper solid solutions

Abstract

Abstract Transmission electron microscopy (TEM) methods described in another paper (Stathopoulos 1981) have been employed in a comparative study of the effect of alloying with various types and amounts of solute atoms on the damage created by 30 keVCu+ and W + ions in copper. The irradiations were carried out on a series of high-purity Cu–Al and Cu–Ge and a selection of Cu–Si, Cu–Ni, Cu–Zn and Cu–Be single-crystal alloys at room temperature. The results demonstrate that the same cluster-formation mechanism operates in the alloys as in the pure metal, i.e. athermal collapse of vacancies in collision cascades to create small defect clusters, 8 → 100 Å diameter, in the form of simple and dissociated Frank loops, and stacking fault tetrahedra (s.f.t.). The type and concentration of the solute was found to influence strongly the final cluster geometry with the degree of loop dissociation increasing as the stacking fault energy of the alloy decreased. A large proportion of s.f.t. were found in the more concentrated alloys with the exception of Cu–10·1 Ni alloy where 2·5% of the loops had unfaulted to perfect loops. In all the alloy systems the efficiency with which cascades collapsed to produce visible vacancy clusters was higher than in copper depending on solute type and increased with increasing solute concentration. A correlation was found with the modulus of the solute-atom size factor suggesting the importance of dechannelling of ions and planarly channelled knockons in creating the extra defects. The effect of alloying on cluster size distributions was found to be complex in its dependence on the solute and ion species employed. The detailed variations are discussed in terms of the balance between the processes considered important in the creation and clustering of vacancies in the cascade.