INFLUENCE OF LI IN DEFORMED AL-LI ALLOYS

Positron-annihilation Doppler-broadening and lifetime measurements are used to study the influence of Li on the defect behavior in deformed Al-0.2 at. % Li and Al-9.9 at. % Li samples. Deformations were perform ed at low temperature (77 K) and at room temperature. For the low-temp erature deformed sample the migration and subsequent clustering of vac ancies is seen in a stage between 200 and 350 K. The temperature depen dence of the positron trapping rate at voids is seen. Above this annea ling stage the only remaining defects are dislocations that anneal out above room temperature. In the dilute alloys it is seen that these di slocations are pinned by the Li atoms. In the concentrated alloy trapp ing of positrons at the delta' particles is observed. In the room-temp erature deformed dilute alloys vacancy-Li complexes and dislocations a re formed. These defects anneal in two distinct stages.