The Migration Stage of Divacancies in Quenched Pure Aluminium, Dilute Aluminium Alloys, and Pure Copper Studied by Positron Annihilation

It is found that the line-shape parameter h increases and subsequently decreases in the initial region of Stage III, that is below −60°C in quenched pure aluminium and below −40°C in quenched AlTi dilute alloys, respectively. In addition, it is shown that divacancies seem to play an important role on the formation and collapse of small vacancy clusters. It is found that the line-shape parameter h increases remarkably from about −85°C in the initial region of Stage III in quenched pure copper. It is thought that the change in h parameter in this temperature region corresponds to the migration of a more mobile vacancy-type defect, which may be rather a divacancy, than a monovacancy.