Positron experiments on the formation and growth of Guinier-Preston zones in AlZn alloys

Positron studies of vacancies and guinier‐preston zones in AlZn and AlZnMg alloys

“…Above 220 K the vacancies disappear and a t R T most of the positrons are trapped by defect-free GP zones. I n alloys with 4.5 at.% Zn or more all positrons are trapped hy these zones (DLUBEK et al 1981). …”

Positron Annihilation in Internally Oxidized Copper

“…In some cases the study of precipitation in metals by positron annihilation technique is also possible [3].…”

A positron lifetime study of cellular precipitation in Al-22 at.% Zn alloy

“…In dilute alloys at all ageing temperatures, and in concentrated alloys at low ageing temperatures, the precipitation of p-Zn occurs predominantly through continuous reactions such as spinodal decomposition and Guinier-Preston (GP) zone formation, while in concentrated alloys at high ageing temperatures the precipitation occurs through discontinuous reactions such as cellular decomposition and eutectoid reactions (Lorimer 1978). Phase separation in this alloy has been primarily investigated by small-angle X-ray and neutron scattering (Gerold and Kostorz 1978) and transmission electron microscopy (TEM) (Vijayalakshmi, Seetharaman and Raghunathan 1982). Small-angle scattering has been used in the study of the kinetics of the early stages of spinodal decomposition and GP zone formation and for direct comparison with theoretical models of phase separation in quenched alloys (Gunton, San Miguel and Sahni 1983).…”

“…Positron annihilation spectroscopy (PAS) is an established method for the study of electronic structure and defect properties in metals and alloys (West 1973, Hautojarvi 1979, Brandt and Dupasquier 1983. The method has been particularly successful in the study of vacancy clustering phenomena in solids (see for example Gopinathan (1984, 1987)).…”

“…These studies have confirmed that positrons are trapped at Zn-rich GP zones and that the annihilation characteristics are similar to those in bulk Zn. Isochronal annealing studies on the quenched samples have established the temperature range over which GP zones form and dissolve (Dlubek, Kabisch, Brummer and Loeffler 1979, Dlubek, Brummer, Yli-Kauppilla and Hautojarvi 1981, Alam, West and highly 1982. Furthermore, PAS has also been used to study the kinetics, of formation of GP zones in quenched and reverted A1-3-5wt%Zn alloy (Panchanadeeswaran, Plichta and Byrne 1984).…”