Defect structure development in electron-irradiated Cu-based Si, Ge and Snbinary alloys

Systematic experiments of 1 MeV electron irradiation were made on Cu-based binary alloys above 300 K using a high-voltage electron microscope in order to study the effects of solute atoms on defect structure development. The solute elements examined were Si (+5.08%), Ge (+27.77%) and Sn (+83.40%), t he volume size factors of which are given in parentheses; the amounts of th ese were 0.05, 0.3 and 2at.% respectively. Interstitial-type dislocation lo ops and stacking-fault tetrahedra (SFTs) were formed in pure Cu and all the alloys. In pure Cu, the temperature dependence of the loop number density had a 'down peak' (i.e. loops hardly formed) around 373 K; below this tempe rature the majority of the loops shrank and disappeared during irradiation, while all the loops grew larger above it; and SFTs were unstable and repea ted the formation and disappearance. In the alloys, the loop number density decreased monotonically with increasing temperature (no down peak was obse rved); loop formation was greatly enhanced except for complete suppression above certain temperatures in Cu-Ge and Cu-Sn alloys; and stable SFTs forme d up to higher temperatures. The mechanisms for these effects were proposed , taking into account the trapping of point defects by solute atoms, the ra diation-induced segregation of solute elements, and the bias effect on poin t-defect absorption at defect clusters owing to the segregated solute eleme nts.