Formation of Dislocation Loops at Low Temperatures in Quenched Aluminum

Abstract

Formation of dislocation loops in aluminum below room temperature down to -90°C is studied by the two step aging method after quenching. The beginning stage of the vacancy clustering is similar to that around room temperature, that is the small vacancy clusters growing to dislocation loops have a fairly wide range in their size of weak bindings and a well defined nucleus of dislocation loop does not exist. It is concluded that the main part of the beginning stage of the clustering is played by quenched-in di-vacancies, especially at low temperatures. Two kinds of influences of impurity atoms are found. The major influence is to enhance the formation of the loops, but the increase in the stability of vacancy clusters by impurity is not enough to make well defined stable nuclei of dislocation loops.