Investigation of defects (migration and formation) in metals by positron annihilation lifetime

In the present work a discussion of the possibilities to study defect in so lids is presented. Generally, positron behavior in metals is simpler than i n insulators. Migrations and formations of defects (point defects, dislocat ion) in metals have been studied in detail by using position annihilation l ifetime technique. Samples of Pb, Bi, Al, Mg, Ag. and Cu were deformed to 2 0% thickness reduction then annealed at different temperature 1 h before qu enched lair cooling). In each pair of samples, lifetime spectrum was accumu lated, as a function of the annealing temperature and measured at room temp erature. For each metal, two stages were observed with a minimum at T=(0.52 -0.62)T-m. This seems to be due to the compensation of two different proces ses; one for recovery and the other for defect formation. This observation of two processes is clear only on the metals have face center cubic structu re such as (Al, Pb, Ag and Cu). (C) 1999 Elsevier Science B.V. All rights r eserved.