STUDY OF RECOVERY IN PLASTICALLY DEFORMED AL-LI-BASED ALLOY BY POSITRON-ANNIHILATION

Positron annihilation mean lifetime measurements have been performed o n two samples of the commercial alloy [(8090) Al-Li-Cu-Mg-(Zr)]. One s ample was deformed (37.5%) at room temperature and subjected to isochr onal annealing. The temperature was varied from 300K to 623K. The othe r one was homogenized at 823 K and subjected to isothermal annealing a t 873 K. The time of annealing varied from 0 to 12 h in steps of 2 h. Evidence of nonspurious lifetime component, in both cases, have been o bserved. The results of the plastically deformed samples (<(tau)over b ar> = 202 +/- 2 ps) are interpreted as trapping of positrons in disloc ations and Li-rich zones. On the other hand the results of the homogen ized sample (<(tau)over bar> = 183 +/- 2 ps) are interpreted as trappi ng of positrons in Li-rich zones only.