Temperature dependence of positron annihilation characteristics in Al-8·5 wt% Zn

Abstract

Abstract Specimens of Al-8·5 wt% Zn given a variety of heat treatments have been studied using measurements of the annihilation lineshape parameter between 100 and 300 K. A mild temperature dependence of the lineshape parameter Iv , was observed for all the samples quenched from the supersaturated solid solution. The temperature dependence becomes stronger with progressive reversion at temperatures above the metastable miscibility gap. The observed temperature dependence is explained as arising from the competition between several trapping sites for positrons. Small clusters of two or three solute atoms are believed to be shallow traps and large clusters, GP zones and dislocation loops are identified as deep traps. For temperatures above 220 K a simple application of the positron trapping model yields a binding enthalpy of a zinc atom to a GP zone of 0.07 eV.