Positron-annihilation studies of a superplastic Al-Ca-Zn alloy

Abstract
The Al‒(5 wt%)Ca‒(5 wt%)Zn alloy has been studied by positron annihilation and transmission electron microscopy. Positron trapping has been observed in specimens of Al‒(5 wt%)Ca‒(5 wt%)Zn from lifetime and Doppler-broadening measurements. The trapping has been attributed to incoherent matrix-precipitate interfaces and to grain boundaries. The results can only be interpreted if the grain boundary contains more than one kind of trap for positrons. This hypothesis is in agreement with the present knowledge of the grain boundary structure.